600M.W.PLANT Electric Course

March 12, 2018 | Author: knx175 | Category: Magnetic Field, Electrical Components, Electricity, Electric Power, Manufactured Goods

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600M.W. PLANT ELECTRIC COURSE...

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NAGARUNA THERMAL POWER PROJECT UNITS-#1&2

Contents Chapter Ⅰ

Generator Proper................................................................................. 1

1.1 Basic Knowledge.................................................................. 错误！未定义书签。 1.1.1 Working Principle ............................................................................................... 1 1.1.2 Magnetic Field and Magnetic Potential............................... 错误！未定义书签。 1.1.3 Synchronous Generators................................................................................... 7 1.2 Proper Structure ................................................................... 错误！未定义书签。 1.2.1 Basic Structures .................................................................. 错误！未定义书签。 1.2.2 Cooling Mode..................................................................................................... 9 1.2.3 Stator.................................................................................................................. 9 1.2.4 Rotor ................................................................................................................ 16 1.2.5 Ventilation System ........................................................................................... 18 1.3 Normal Operation .............................................................................................. 20 1.3.1 Rated Condition ............................................................................................... 20 1.3.2 Operation under Non-rated Conditions............................................................ 21 1.3.3 Active Power Regulation and Static Stability ................................................... 23 1.3.4 Safe Operation Limit ........................................................................................ 24 1.3.5 Reactive Power Regulation ............................................................................. 26 1.3.6 Normal Operation and Monitor ........................................... 错误！未定义书签。 1.4 Abnormal Operation .......................................................................................... 32 1.4.1 Capability of overload ...................................................................................... 32 1.4.2 Asymmetric Operation ..................................................................................... 32 1.4.3 Operation on Loss of Excitation...................................................................... 34 1.4.4 Operating at Leading Power Factor................................................................. 35 1.4.5 Operation in Air ................................................................................................ 36 1.4.6 Torsion Stability ................................................................... 错误！未定义书签。 1.5 Technical Data ................................................................................................... 38 ChapterⅡExcitation System ..................................................................................... 45 2.1 Introduction to UNITROL 5000 System............................................................. 46 2.1.1 Excitation Transformer..................................................................................... 46 2.1.2 Excitation Regulator......................................................................................... 47 2.1.3 SCR.................................................................................................................. 47 2.1.4 Excitation and De-excitation Unit..................................................................... 47 2.1.5 UN5000 Excitation System Performance ........................... 错误！未定义书签。 2.2 Operation and Adjustment of Excitation System.................. 错误！未定义书签。 2.2.1 Control and Display Unit .................................................................................. 49 2.2.2 Remote Control................................................................... 错误！未定义书签。 2.2.3 Local Control....................................................................... 错误！未定义书签。 2.2.4 Startup of Excitation System............................................... 错误！未定义书签。 2.2.5 Shutdown of Excitation System .......................................... 错误！未定义书签。 2.3 Automatic Control and Protection ........................................ 错误！未定义书签。 2.3.1 Switching between Main Channels.................................................................. 55 1

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2.3.2 Auto/Mannual Switching of Main Channels ........................ 错误！未定义书签。 2.3.3 Emergency Spare Channel................................................. 错误！未定义书签。 2.3.4 SuperimposedControl ......................................................... 错误！未定义书签。 2.3.5 PSS .................................................................................................................. 58 2.3.6 Rotor Earthing Protection ................................................................................ 58 2.3.7 Limiter ................................................................................. 错误！未定义书签。 2.3.8 De-excitation and Overvoltage Protection ....................................................... 62 2.3.9 PT Fault Inspection .......................................................................................... 62 2.3.10 Rotor Temperature Measurement.................................................................. 62 2.3.11 Overcurrent Protection ................................................................................... 63 2.3.12 Protection for Loss of Excitation (P/Q) .......................................................... 63 2.3.13 Overexcitation Protection (V/Hz Relay) ......................................................... 64 2.3.14 Excitation Transformer Temperature Measurement ...................................... 64 2.4 Technical Specifications ....................................................... 错误！未定义书签。 Chapter Ⅲ Generator Hydrogen Control System ................................................... 68 3.1 Description of System and Equipment.............................................................. 68 3.1.1 Principle of Work.............................................................................................. 68 3.1.2 Cooling Channels of Rotor and Core............................................................... 69 3.1.3 Operation Control of Hydrogen System........................................................... 70 3.1.4 Cooling of Hydrogen ........................................................................................ 70 3.1.5 Generator Gas Replacement........................................................................... 70 3.1.6 Gas Replacement Work Issues Requiring Attention ....................................... 71 3.1.7 Attention Points in Pperation............................................................................ 71 3.2 Systems Equipment and Their Principle of Work.............................................. 72 3.2.1 Hydrogen Gas Control Unit.............................................................................. 72 3.2.2 CO2 Gas Control Unit ...................................................................................... 73 3.2.3 Purging Control Valves .................................................................................... 73 3.2.4 Gas Replacement Plate................................................................................... 73 3.2.5 Hydrogen Purity Detector ................................................................................ 73 3.2.6 Hydrogen Dryer................................................................................................ 73 3.2.7 Hydrogen System Special-purpose Circulating Blower................................... 77 3.2.9 Temperature and Humidity Transmitter ........................................................... 77 3.2.10 Generator Hydrogen Leakage on-line Tester ................................................ 77 3.3 Technical Specifications ....................................................... 错误！未定义书签。 Chapter Ⅳ Generator Sealing Oil Control System .................................................. 79 4.1 Description of System and Equipment.............................................................. 80 4.1.1 Oil Smoke Purifier............................................................................................ 83 4.2 Operation of Sealing Oil System ....................................................................... 84 4.2.1 Work Process of Sealing Oil System............................................................... 84 4.2.2 Work Mode of Sealing Oil System ...................................... 错误！未定义书签。 4.2.3 Attention Points in Operation ........................................................................... 85 4.3 Technical Specifications ....................................................... 错误！未定义书签。 Chapter Ⅴ Stator winding Cooling Water System ................................................... 91 5.1 Description of System and Equipment.............................................................. 91 5.1.1 Equipment Configuration of Stator winding Cooling Water System ................ 91 5.1.2 Main work flow as follow: ................................................................................. 92 2

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5.1.3 Control Requirements on Water Temperature................................................. 93 5.1.4 Control Requirements on Water Quality.......................................................... 93 5.1.5 Operation and maintenance ............................................................................ 94 5.2 Introduction to Local and Remote Control Equipment ...................................... 95 5.2.1 Water Tank ....................................................................................................... 95 5.2.2 Water Pump ..................................................................................................... 95 5.2.3 Cooler............................................................................................................... 96 5.2.4 Demineralizer and Its Use ............................................................................... 97 5.2.5 Water Filter....................................................................................................... 98 5.2.6 Temperature Regulator Valve and Pressure Regulator Valve........................ 98 5.2.7 Instruments ...................................................................................................... 99 5.2.8 Loss of Stator Winding Cooling Water............................................................. 99 5.3 Technical Specifications ....................................................... 错误！未定义书签。 Chapter Ⅵ Synchronizing Equipment.................................................................... 101 6.1 Summarize ...................................................................................................... 101 6.1.1 Technical Data............................................................................................... 101 6.2 Front Panel and Dimensions........................................................................... 102 6.3 Working Mode ................................................................................................. 103 6.4 Definition Terminal............................................................................................112 Chapter Ⅶ Generator Relay Protection ...................................... 错误！未定义书签。 7.1 Relay Protection Configuration ........................................... 错误！未定义书签。 7.1.1 Configuration Features of Protection.................................. 错误！未定义书签。 7.2 Composition of Generator Protections .............................................................116 7.2.1 Generator Differential Protection ....................................................................116 7.2.2 Generator 95%-Stator Earth Fault Protection.................................................116 7.2.3 Generator 100%-Stator Earth Fault Protection...............................................116 7.2.4 Generator Reverse Power Protection.............................................................116 7.2.5 Generator Low Forward Protection ................................................................117 7.2.6 Generator Low Impedance Protection............................................................117 7.2.7Generator Under Frequency Protection& Generator Over Frequency Protection 118 7.2.8 Generator Overvoltage Protection ..................................................................118 7.2.9 Generator Overload Protection.......................................................................118 7.2.10 Generator Loss of Excitation Protection .......................................................118 7.2.11 Generator Back-up Overcurrent Protection(Voltage Controlled) ..................119 7.2.12 Generator Unblanced Load Protection ........................................................ 120 7.2.13 Generator Pole Slipping Protection ............................................................. 120 7.2.14 Generator Interturn Protection ..................................................................... 120 7.2.15 Generator Rotor Earth Fault Protection....................................................... 121 7.2.16 Generator Cooling Water Loss .................................................................... 121 7.2.17 Generator Rortor Overload Protection......................................................... 121 7.2.18 Turbine Stearm Valve Closed ...................................................................... 121 7.2.19 Generator Overexcitation Protection ........................................................... 121 7.3 Composition of Excitation Transformer Protections........................................ 121 7.3.1 Excitation Transformer Overcurrent Protection ............................................. 121 7.3.2 Excitation Transformer Overload Protection.................................................. 121 Chapter Ⅷ Microcomputer Dynamic Recorder for Generator-transformer Unit.... 122 3

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1. 2. 3. 4. 5. 6.

Contents

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Introduction...................................................................................................... 122 Technical Characteristics................................................................................. 122 Technical Parameters...................................................................................... 123 Hardware Illustration ....................................................................................... 127 Recorder Monitor Software Illustrations.......................................................... 128 Analysis Software............................................................................................ 135

Chapter Ⅸ Esp Control System ............................................................................ 143 1. The main features of EPIK series controller: .................................................. 143 1.1 The EPIK main functions:................................................................................ 144 2 The Computer controlled communication system........................................... 146 2.1Displaying screen............................................................................................... 146 2.2T/R sketch map.................................................................................................. 146 2.3Comparing diagram of the Current .................................................................... 147 2.4The record table of T/R state. ............................................................................ 147 2.5Rapping running................................................................................................. 148

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Chapter Ⅰ Generator Body

1.1 1.1.1

The generators used are QFSN-600-2-22F three-phase synchronous generators jointly manufactured by Dongfang Electrical Machinery Co., Ltd. and HITACHI in the usage of technologies introduced from the latter. The cooling mode of the generator is water-hydrogen-hydrogen. Static excitation with self-excitation in side of generator is used. UNITROL 5000 micro-computer digital silicon controlled rectifier (SCR) excitation system manufactured by ABB is used (imported at bulks and assembled by Dongfang Electrical Group). Basic Knowledge Working Principle A generator consists mainly of a stator and a rotor, between which there is an air gap. The working principle is shown in Figure 1-1. There are three-phase windings, AX, BY and CZ on the stator, which in space have a difference of 120° angle and each of them has equal number of coils.The rotor pole (main pole) is installed with exciter windings. Excitation is produced by direct current, the direction of flux comes from Pole N of Rotor, which enters Pole S of rotor to form a circuit through air gap, stator core and air gap, as shown by the dashed lines in the figure. to drive the generator to rotate in the counterclockwise direction with prime mover, the Figure 1-1 Working principle of synchronous generator magnetic line of force will cut the conductor of stator winding. It can be learnt from the law of electromagnetic induction that alternating potential will be induced in the stator conductor: e = Bmlvsinωt = Emsinωt Bm is the maximum value of sine wave flux density, l is the length of conductor cut by magnetic line of force, v is the linear speed of cutting and ω=2πf, f is the frequency of potential. As the three-phase windings of the generator stator Figure 1-2 Three phases potential curve have a difference of 120° in physical spatial arrangement, the magnetic line of force of the rotor field will cut Phase A, B and C in turn. As such, the induced potentials of the three phases are equal in amplitude and have a difference of 120° in phase angle. Suppose the maximum value of the phase potential is Em, the initial phase angle of Phase A potential is 0, then the transient values of the three phase potentials are: eA = Emsinωt eB = Emsin(ωt-120˚) eC = Emsin(ωt-240˚) If a generator has p pairs of poles and the rotating speed of a rotor is n/min, the rotating speed of the rotor in second will be n revolutions/60, the induced potentials will be alternated pn/60 times per second, i.e., the frequency is f=pn/60. As there are one pair of poles in steam 1

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1.1.2

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turbine, so in case of n=3000r/min, f=50Hz. Magnetic Field and Magnetic Potential The fluxes of AC generator are divided into two parts, one in simultaneous interlinkage with both stator and rotor windings, called air gap flux and serving as the media for conversion of mechnical and electric energy in generator; the other part is in interlinkage with stator winding or rotor winding, called leakage flux. The route of air gap fluxes is: from stator yoke to rotor through stator teeth and air gap, then through air gap and stator teeth to stator yoke, forming a closed magnetic circuit. The air gap flux can be established by stator magnetic potential or rotor magnetic potential. When current exists in both stator and rotor windings of generator, it will be jointly established by stator magnetic potential and rotor magnetic potential. 1) No-load operation of synchronouse generator

Fig. 1-3 No-load magnetic field of salient pole synchronous generator When the synchronous generator is driven to synchronous speed by prime mover, the rotor winding is fed with DC excitation current while stator winding is opened, the status is called no-load operation. The magnetic circuits in no-load operation are shown in Figure 1-3. At this time, the stator armature current is 0, in the air gap of generator there are only magnetic potential Ff and magnetic field independently produced by rotor current, which are called excitation magnetic potential and excitation magnetic field. The fluxes in interlinkage with rotor and stator through air gap are called main flux, i.e., the air gap flux in no-load (Φ0), or also called excitation flux. While the fluxes in interlinkage with only exciter winding other than stator winding are called leakage flux (Φfσ), which are not involved in energy conversion process in generator. When the rotor is rotating at the synchronous speed of n1, the main fluxes are cutting stator winding to induce three phase fundamental wave potentials at frequency of f=(pn/60), the effective value of which is: E0=4.44fN1kN1Φ0. As such, the main flux of Φ0 can be changed by chaning the excitation current If, when the value of no-load potential E0 will also be changed. It can be learnt from the calculation formula of magnetic circuit that when the sizes and material of cores are determined, the magnetic features thereof are determined as well.

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Figure 1-4 shows the time-space vector diagram in case of synchronous generator no-load operation, wherein Ff1 is the fundamental wave of excitation magnetic potential, Bf1 is fundamental wave of air gap flux density, both of which are in same phase and their positive wave amplitudes are in the positive Figure 1-4 Time-Space vector diagram of synchronous direction of rotor axis and generator in no-load rotating with the rotor at synchronous speed of (ω1=2πf). The flux at flux density wave of Bf1 in interlinkage with any phase of stator is a time variable, represented by Φ0. The potential of Φ0 induced by this phase is represented by E0, which is lagged behind Φ0 by 90°. 2). Synchronous generator symmetric load operation When the stator is connected with symmetric load, a second magnetic potential, armature magnetic potential, is created by the load current. The armature magnetic potential will interact with the excitation magnetic potential to form a combinted magnetic potential in air gap in case of load, and establish air gap magnetic field in case of load. Therefore, the so-called armature reaction in case of symmetric load is the impace of fumdamental wave of armature magnetic potential on fundamental wave of main pole magnetic field. The fundamental wave of armature magnetic potential produced by three phase symmetric load current flowing through symmetric three phase coil is a rotating magnetic potential at a speed of n=60f/p, substitute with f=pn1/60, n=n1, showing that the speed of fundamental wave of armature magnetic potential is equal to that of excitation magnetic potential and entry are in same direction. It can be seen that the fundamental wave of armature magnetic potential have same speed and direction as excitation magnetic potential, always maintaining relative motionlessness in space. On account of this, their mutual relations are maintained unchanged and they jointly establish air gap magnetic field with steady values and produce average electromagnetic torque, realizing the energy conversion from mechnical to electric. This “relative motionlessness between stator and rotor magnetic potential” is a fundamental conditions for normal operation of all electromagnetic induction generators. The nature of armature reaction depends on the relative spatial locations between armature magnetic potential fundamental wave and excitation magnetic potential, mainly the phase phase difference from excitation magnetic potential E0 and armature current I, i.e., in relation to ψ (angle between E0 and I). a. Armature reaction when à and Ñ0 are in phase (ψ=0)

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Figure 1-5 Armature reaction when ψ=0 Figure 1-5 shows a principle diagram of a synchronous generator, in which each phase of armature coil is represented by an equivalent integral centralized coil, and only the fundamental waves of exciter winding and armature coil are considered. The diagram is made when the excitation potential of Phase A is at maximum. Excitation magnetic potential Ff1(excitation flux Φ0) is located on axis d of rotor, while the potential E0 produced by induction of rotating excitation magnetic field in stator three phase coils is located on axis q 90° behind axis d, so is the fundamental wave Fa of armature magnetic potential combined by three phase currents. As such, when I and E0 are in phase, the axis line of armature magnetic potential Fa is always 90° different from the rotor pole axis line (axis d) and coincides with the quadrature axis of rotor (axis q). Therefore, this type of armature reaction is called quadrature axis armature reaction, and the armature magnetic potential Fa at this time is called quadrature axis armature magnetic potential Faq. The air gap combined magnetic potential Fδ is a vector sum of Ff1 and Fa, while Bδ is the air gap flux density wave produced by Fδ. It is clear that the quadrature axis armature reaction reverses the combined magnetic field axis location a sharp angle from the direct axis at no-load, as well the amplitude is increased. b.Armature reaction when à is behind Ñ0 at a sharp angle of ψ

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Figure1-6 Armature reaction when 0 0 , so, when δ of the generator is within dδ

the range of 0°~90°, the operation is steady; if in the range of 90°~180°, the operation is not steady. But in practice to improve the reliability of power supply, the rated operation point of generator should be maintained at a certain distance from the limit of stability, rendering the limit power larger by certain times than the rated power, the power angle of δ for normal operation is 30°~45°. 1.2.9

Safe operation limit 1)Safe operation limit Under steady operation conditions, the safe operation limit of generator is dependent on the following four conditions: a. Output power limit of prime mover b.Rated capacity of generator, i.e., the safe operation limit determined by heating of stator windings and core. Under a given voltage, the allowable value for stator current is determined. c.The maximum excitation current of generator, usually determined by the heating of rotor. d.Stability of leading phase operation. When the power factor of generator is smaller than 0 (current leading voltage), the generator turns to leading phase operation, the active power output of magnetic potential generator is limited by the conditions for static stability. In addition, the internally cooled generator may be limited by the end heating. The above conditions determine the allowable operating range of generator. 2). Generator P-Q curve For a generator operating in the power system, under certain voltage and current, the reactive power of such generator will increase and the active power will decrease as the power factor decreses; as the power factor increases, the reactive power needs to be decreased and the active power needs to be increased so that the output capacity will not exceed the allowable value. The P-Q curve of generator shows the relation of allowable active power P and reactive power Q under various power factors, which is also called safe operation limit of generator.

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Figure 1-21 Steam turbine generator P-Q curve 实际稳定限制：Actual stability limit;原动机输出限制：Prime mover output limit;定子发热限制：Stator heating limit;转子发热限制：Rotor heating limit P-Q curve of generator is drawn when the generator terminal voltage, cooling medium temperature are certain under various hydrogen pressure conditions. The voltage, electromotive force and power are all indicated in per unit value. The basic steps in drawing include: a.Take Point O as the center and take stator rated current of IN as the radius, draw the arc. b.On left of Point O of horizontal axis, take a segment OM equal to

UN , which Xd

approximates to the short circuit ratio KC of the generator, in direct proportion to the no-load excitation current. c.Take Point M as the center, take

Eq as the radius (segment MC in Figure1-21, which Xd

is in direct proportion to the rated excitation current) to draw the arc. d.Draw a horizontal line HBG with the rated power of turbine parallet to the x-coordinate, representing the prime mover output limit. e.Draw a line MH from Point M perpendicular to the x-coordinate, with a corresponding δ=90°, representing the theoretically static stability limit. Considering that the generator may possibly be subject to overload, proper leeway shall be reserved for the actual static stability limit so that the generator may withstand sudden overload without changing the excitation current. (BF curve in the above figure) The area enclosed by the above curves or segments (Area DCGBFD) is called the safe operation range or safe operation area of the steam turbine generator. The operation point of generator is in the area or on the boarder, when long term safe and steady operation of generator can be maintained.

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Figure 1-22 Generator P-Q diagram 1.2.10

Reactive power regulation When the generator is in parallel connection with system with infinite capacity, if the active power output remains unchanged, the reactive power can be regulated by adjustment of excitation current. 1)No load characteristics When adjusting the excitation current, the electromotive force of generator will change accordingly as per its no load characteristics. When measuring the no load characteristic curve, as the remanence in rotor magnetic circuit varies, two different curves, one asending and one descending, will be obtained if the excitation current If changed from 0 to a maximum value and changed from such value to 0. The magnetic hysteresis is reflected in magnet material. Es1 and Es2 in the diagram represent Figure 1-23 No load characteristics under the remanence potentials when If=0 under two situations. difference remanence The no load characteristics may be drawn on basis of 26

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actual value or per unit value (take rated voltage UN as the base value for potential and excitation current If0 for the base value of excitation current). 2). Short circuit characteristics

Figure 1-24 Analysis of synchronous generator steady state short circuit 空载特性：No load characteristics; 短路特性：Short circuit characteristics Short circuit characteristics is the relation between short circuit current Ik and If in case of generator three phase steady state short circuit. The above diagram is the vector diagram of the generator in case of short circuit. In this case U=0, the factor limiting the short circuit current is just the internal impedance in the generator. The armature resistance of synchronous generator is far smaller than the synchronous reactance and the short circuit current can be considered as purely inductive, i.e.,ψ≈90°. So the armature magnetic potential at this time is basically a direct axis magnetic potential with pure function of de-excitation, i.e., Fa=Fad, the various magnetic potential vectors are one a line, with the resultant magnetic potential ' = - ' . The resultant potential E of air gap can be

Fδ F f Fad

δ

acquired using the no load characteristics. As U=0, so & = U& + & +j & ≈j &

Eδ

IRa

IX σ

IX σ

It can be seen from the above equation that the short circuit resultant potential is only equal to leakage reactance voltage drop, the corresponding air gap resultant flux is very small and the magnetic circuit of the generator is not satured, equivalent to Point C in the above diagram. As such, the resultant magnetic potential ' ∝ ∝I. So, the excitation magnetic potential

Fδ

Eδ

F f is in direction proportion to I. As such, the short circuit characteristics is a line. 3) Short circuit ratio Short circuit is data frequently used in design of synchronous generator. Originally short circuit means the ratio of short circuit current to rated current in case of three phase steady state short circuit under excitation current corresponding to no load rated voltage. As the short circuit characteristics is a line, thie definition is converted to the ratio of excitation 27

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required for generation of no load rated voltage and rated short circuit current.

Kc =

I k 0 I f 0(U =UN) 1 = = kµ * I N I fk(Ik=In) X d (不饱和）

不饱和：Unsaturated The above equation shows that the short circuit ratio is the inverse of direct axis synchronous reactance unsaturated value represented by per unit value multiplied by saturation factor kμ under no load rated voltage (usually kμ=1.1~1.25). The value of short circuit has great impact on generator. If the short circuit ratio is small, when the load changes the voltage of generator is significant and the stability of generator in parallel operation is poor, though the cost of generator is low; the short circuit ratio may be increased by increasing the air gap and thus decreasing Xd, the performance of generator is improved with higher cost, as more copper is required for excitation magnetic potential and rotor. In general, along with the increment of single unit capacity, the required value of short circuit is reduced to improve the utilization rate of material.

Figure1-25 Generator short circuit current and no load characteristics curve 4). Synchronous generator external characteristics

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Figure 1-26 External characteristics of generator under different power factors 滞后：Lagging; 超前：Leading The external characteristics shows the relation curve of terminal voltage U and load current I under the conditions of n=nN, If= constant and COSΦ=constant. In case of inductive load and pure resistance load, the external characteristics is descending and in case of capacitive load, it is ascending. It is clear that in order to make sure U=UN when I=IN under all power factors, a higher excitation current needs to be provided under inductive load, maing the generator operating under overexcitation state; while under the capacitive load, a smaller excitation can be provided when the generator is operating under underexcitation state. 5). V curve When the generator is under inductive load, the armature reaction shall have the nature of de-excitation. At this time, to maintain the terminal voltage of the generator, the excitation current must be increased. Therefore, the change of reactive power must depend on the regulation of excitation current. Below we will study then change of stator current when regulating excitation current under given output power P.

Figure 1-27 Phasor Diagram of Synchronous Generator a. As the E01 is rather high, the stator current outputs reactive power to the system for its lagging to the terminal voltage, and at this time the magnetizing current is relatively large and called as over excitation state for its large current. b. With the decrease of the magnetizing current, the E0 is decreased , the power angle θ and factor COSΦ are raised, and the stator current of the generator is decreased as well with 29

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the reduction of the reactive power. As the exicitation potential is dropped to E02, the COSΦ equals to 1 and the staotor current is up to minimum, such conditions are called as normal exciation. c. With conditinous decrease of the magnetizing current, the stator current bcomes more excessive than the terminal voltage, and so the generator begins to take the reactive power from the system at an underexcitation state. d. if further decrease of the mangeitzing current is performed, the potential E0 will reduce much more, and the power angle θ and factor COSΦ will go on increasing as well. Limit for the stable operation of the genearo will reach in case of θ=90°

Figure 1-28 Synchronous generator V curve 不稳定区：Unsteady area; 超前：Leading; 滞后：Lagging; 常数：Constant; 欠励： Underexcitation; 正常：Normal; 过励:Overexcitation We will use a test, maintaining the grid voltage and generator output active power unchanged, to change the excitation current If and measure the corresponding stator current I, thus obtaining the relation curve between the two: I=f(If). As this curve takes the shape of “V”, it is called V curve of synchronous generator. For each active power value a V curve can be drawn, the higher the power value is, the higher the curve moves. The lowest point of each curve represents COSΦ=1. Connect the lowest points of the various curves, a COSΦ=1 curve is obtained, on right side of which the generator is under overexcitation while on the left side the generator is under underexcitation. There is an unsteady area at left of the V curve (corresponding to θ>90°).

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Figure 1-29 Generator V curve 1.2.11

Normal operation and monitor 1). Rated operation mode During normal operation, the generator shall be operating according to the data shown on the nameplate (rated operation mode) or operating continuously for long term within the capacity limit curve (P-Q curve). As the long term operation output of generator is mainly affected by the heating of unit, so the parameters such as active power, reactive power, stator current, stator voltage, hydrogen pressure, purity, cold hydrogen and hot hydrogen temperature, stator winding temperature, 31

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Generator Body

1.3 1.3.1

core temperature, stator inlet and outlet water temperature and rotor winding temperature. 2). Speed with load Operation of generator within the capacity curve with any load is allowable, the load change rate of which shall in principle follow the turbine load curve. 3). Allowable scope of change for voltage and frequency Under rated load, the allowable scope of change for voltage and frequency of generator is as described before. 4). Generator shaft center elevation change As the generator and turbine are connected with rigid coupler, so the shafts must be aligned. During operation, if the centers are misaligned, the connection stress will be increased, the load distribution of bearing will be unreasonable and there will be more vibration, causing mechanical accident. The change of generator shaft elevation is a function of support part temperature, while the temperature is directly following the change of cooling hydrogen temperature. So, during the normal operation of generator, the cooling hydrogen temperature shall be maintained to the extent possible. Abnormal operation Capability of overload When the generator system has trouble, avoid the static stability of the grid being destroyed, over load operation of stator and over voltage operation of rotor in short time is allowed, but hydrogen parameter, cooling water parameter in stator winding and stator voltage should be at rated value. This operation condition can occur for not more than two times each year, and time interval can not be less than 30 minutes, detailed regulations are listed in the following tables:

1.3.2

Time(second)

10

30

60

120

Stator current / rated stator current (%)

226

154

130

116

Time(second)

10

30

60

120

Rotor voltage/rated rotor voltage (%)

208

146

125

112

Asymmetric operation 1). Asymmetric operation Asymmetric operation of generator is abnormal condition. It means an operating state when the three phase symmetric state of electrical components forming the power system is destroyed, such as three phase impedance asymmetry and three phase load asymmetry. While incomplete phase operation is a special condition of asymmetric operation, in which case the transmission line, transformer or other electrical equipment has one or two phases open. The degree of asymmetry is usually represented by the proportion of negative sequence I2 to rated current IN. 2). Hazard of negative sequence current on generator When the generator is in asymmetric operation, there is negative sequence current in the 32

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stator winding of generator in addition to the positive sequence current. Positive sequence current is produced by generator potential, which maintains a synchronous speed with the rotor in same direction. For purpose of rotor, it is static and at this time the heating of rotor is determined by the excitation current only. When negative sequence current appears, in addition to superimposition with positive sequence current which may make the winding phase current exceed the rated value, it will further cause additional heating of rotor and mechanical vibration. When negative sequence current flows in the stator three phase winding, the negative sequence magnetic field created will rotate in reverse direction to the rotor at synchronous speed, inducing current at double frequency in the excitation winding, damping winding and rotor proper and thus causing additional heating. Due to the skinning effect, these currents mainly flow in the thin surface, forming circular current along the circle at the rotor end. These currents flow the wedge and teeth of the rotor as well as a number of contact surfaces with the collars. These parts have high resistance and the heating is particularly significant. In additional to the above heating, the negative magnetic field produced by the negative sequence current will cause impulse torque at double frequency on the rotor, causing generator to emit vibration at 100Hz with noise and torsional oscillation on the shaft system.The steam turbine generator, as the rotor is non-salient, the windind is arranged in the slots with poor emission conditions, so the additional heating produced by the negative sequence current is often the main condition restricting the asymmetric operation. 3). Capability of unbalanced loading For generator’s normal operation, stator three-phase current should be equal; the generator should not be operated at any loads above nominal rating in normal operation mode. When three-phase currents are unbalanced, the negative phase sequence current (I2) can not exceed 10% of rating current (IN) in steady condition, and any one phase current shall not exceed the rating value. When non symmetrical fault occurs, the phase current will deviate from the ideal relationship of balanced load, and a negative phase sequence armature current is imposed on the generator, excessive unbalanced loading results in extra losses and temperature rise. The extra losses appear primarily on the surface of rotor. The permissible unbalanced load limits (I2, I22 t) are stated as follows (See Figure 1-30) I2/IN ≤8%

(I2/IN)2t ≤8 seconds

33

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Figure 1-30 Unblanced fault capacity Steam turbine generator asymmetric load allowable range is determined by the three conditions: a. The current of the phase with most load shall not exceed the rated current of the generator; b. The temperature of any point on the rotor shall not exceed the allowable temperature of rotor insulating material class and metallic material. c.The mechanical vibration in case of asymmetric operation shall not exceed the allowable range. The first condition considers that the heating of stator winding shall not exceed the allowable value, and the second and third conditions are intended for the hazards of negative sequence current in asymmetric operation. The asymmetric operation capability of generator is also termed negative sequence capability, which is usually represented by two technical parameters: a. Steady negative sequence capability for allowable long time operation, represented ; by allowable maximum negative sequence current per unit value

I 2∗ =

I2 IN

b.Transient negative sequence capability for allowable short time operation, represented by allowable short time 2 , meaning the maximum negative sequence heating for short

I 2 ∗t

time. The negative sequence capability of generator: steady I2( per unit value) ≥8%, transient 2 ≥8s.

I 2 ∗t

1.3.3

When the unbalanced negative sequence current of generator exceeds the allowable value, the unbalance current shall be minimized to the allowable value; if the allowable time for unbalanced current is reached, the generator shall be disconnected immediately. Operation on loss of excitation If the generator loses its excitation, it will function as an induction generator. In the case of that

34

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the field winding is short circuited or closed by discharge resistance, taking the following factors into consideration: a).The particular overheating and the cooling condition on the rotor surface. b).The overheating and cooling condition of stator end portion. After the generator loses excitation, it can still operate for 15 minutes with 40% of load , which is shown in Figure 1-31 However, if excitation circuit is open, an excessive high over voltage will be induced in the field winding due to the induction and endanger the field winding insulation.

1.3.4

Figure 1-31 Operation on loss of excitation Operating at leading power factor Allowable scope of generator’s leading phase operation is mainly limited by static stabilization of generator and heat of the stator core. The generator can be steadily operated at rating active power with the leading power factor (0.95). The Generator Curve in Figure1-32 Shows the details.

35

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Figure 1-32 Generator capability curve 1.3.5

Operation in air The generator is allowed to operate for a short time only during installation, adjustment and test run for dynamic mechnical inspection. The prerequisite conditions for operation in air are as follows: 1). No excitation current. 2). The air in the generator must be dry with a relative humidity 0.1 %; d. Line single phase quick reclosure shall not be subject to limit; e. Unit with excitation out of step, if the oscillation current and moment are smaller than the corresponding values of 0.6~0.7 output short circuit, the allowable operation time is 15~20 cycles. Technical data Serial number 1 2 3 4 5 6 7

Item Type Rated output sn Rated output pn Maximum permissible capactive Rated power factor cosΦN Rated voltageUN Rated current IN

Unit MVA MW MVA kV A

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Technical data QFSN-600-2-22F 706 600 208 0.85 22 18525

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Serial number 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

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Generator Body

Item Rated frequency fN Rated speed nN Rated field voltageUfN Rated field current IfN Field voltage of no load Field current of no load Stator winding connection Cooling mode Excitation type Dc resistance of stator winding(per phase) Dc resistance of field winding( at 15°C) Capacitance of stator winding A phase B phase C phase Inductance of stator winding Direct-axis synchronous reactance Xd Quadrature-axis synchronous reactance Xq Direct-axis transient reactance (Unsaturation)X′du Direct-axis transient reactance (Saturation) X′d Quadrature-axis transient reactance (Unsaturation) X′qu Quadrature-axis transient reactance (Saturation) X′q Direct-axis subtransient reactance (Unsaturation)X″du Direct-axis subtransient reactance (Saturation) X″d Quadrature-axis subtransient reactance (Unsaturation)X″qu Quadrature-axis subtransient reactance (Saturation)X″q Negative phase-sequence(Unsaturation)X2u Negative phase-sequence(Saturation)X2 Zero phase-sequence(Unsaturation)Xou Zero phase-sequence(Saturation)Xo Direct -axis transient open-circuit time constant T′do Quadrature-axis transient open-circuit time constant T′qo Direct -axis transient short-circuit time constant T′d Quadrature-axis transient short-circuit time constant T′q Direct -axis subtransient open-circuit time constant T″do Quadrature-axis subtransient

Unit Hz r/min V A V A

Technical data 50 3000 431 4727

YY H2O-H2-H2 Static Thyristor Excitation Ω

0.001456(at 15°C)

Ω

0.067715

pf pf pf H

243000 243000 243000 0.521

%

184.11

%

184.11

%

28.85

%

25.39

%

28.85

%

25.39

%

20.49

%

18.85

%

20.49

%

18.85

%

23.01

%

21.17

%

9.64

%

9.16

sec

8.446

sec

0.938

sec

1.187

sec

0.118

sec

0.047

sec

0.047

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Serial number 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83

Generator Body

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Item Unit Technical data open-circuit time constant T″qo Direct -axis subtransient short-circuit sec 0.035 time constant T″do T″d Quadrature-axis subtransient sec 0.035 short-circuit time constant T″q Deexcitation time constant Tdm sec 3.357 2 Inertia moment GD t.m 2 39 Short circuit ratio ≥0.5 Steady negative sequence current I2 % ≥8 Transient negative sequence ≥8 current I 22 t Allowable variation of frequency ±% -5~+3 Allowable variation of voltage ±% 5 Underexcitation asynchronous MW/min 240/15 operation capability Leading phase operation capability MW 600MW cosΦ=0.95(Leading) Leading phase operation time h Long term operation 120°, no more than 2 times; Mistake connection capability 180°, no more than 5 times; THF % ≤1 Voltage waveform sine distorsion % ≤3.0 rate Ku Sustained short-circuit current(3 % 151.9 phase) Initial transient short-circuit current (effective) Line-neutral % 633..7 Line-line % 437.8 3 phase % 463.5 Initial subtransient short-circuit current (effective) Line-neutral % 698.0 Line-line % 495.2 3 phase % 607.0 Three phase short circuit maximum % 790.21 current (DC component peak) Phase-phase short circuit maximum t.m 1587.0 electromagnetic torque Noise dB(A) ≤85 Peak regulation capability Time 10000 Generator service life Year ≥30 Vibration amplitude Critical speed First order r/min 982 Second order r/min 2671 Critical speed bearing/shaft vibration amplitude Vertical mm ＜0.08/0.15 Horizontal mm ＜0.08/0.15 Bearing/shaft vibration amplitude in case of overspeed Vertical mm ＜0.08/0.15 Horizontal mm ＜0.08/0.15 Bearing/shaft vibration amplitude in case of rated speed 40

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Generator Body

Serial number Item 84 Vertical 85 Horizontal Stator winding end vibration 86 frequency f v Stator winding end vibration 87 amplitude 88 Shaft torsional oscillation frequency 89 Stator winding copper loss Qcu1 90 Stator iron loss Qfe 91 Excitation loss Qcu2 92 Short-circuit supplementary loss QKd 93 Mechanical loss Qm 94 Total loss ΣQ 95 Effeiciency η 96 Insulation class 97 Stator winding 98 Field winding 99 Stator core 100 Limit of temperature 101 Stator winding 102 Field winding 103 Stator core 104 Stator winding outlet water 105 Structure part of stator end Pressure, flow and temperature of 106 cooling medium Inlet hydrogen temperature of 107 generator Outlet hydrogen temperature of 108 generator Inlet temperature of stator winding 109 water 110 Conductivity of stator winding water 111 Ph valve of stator winding water Inlet pressure of stator winding 112 water 113 Water quantity 114 Number of hydrogen coolers Inlet water temperature of hydrogen 115 cooler Outlet water temperature of 116 hydrogen cooler 117 Water quantity of hydrogen cooler 118 Rated H2 pressure 119 Maximum permissible H2 pressure 120 Hydrogen volume in generator 121 Hydrogen leakage 122 Purity of hydrogen Minimum permissible purity of 123 hydrogen) 124 Dew point of hydrogen Inlet temperature of bearing 125 lubricating oil Outlet temperature of bearing 126 lubricating oil

Unit mm mm

Technical data ＜0.025/0.076 ＜0.025/0.076

Hz

fv≤94 or fv≥115

mm

≤0.15

Hz kW kW kW kW kW kW %

≤45，≥55，≤95，≥110 1858.8 837.56 1883.0 1232.4 1105.79 6917.6 ≥98.8 F F F

°C °C °C °C °C

≤120 ≤115 ≤120 ≤90 120

°C

46

°C

62

°C

45±5

μs/cm

0.5~1.5 7.0~9.0

MPa(g) 0.1~0.2 t/h

96 4

°C

20~38

°C

≤48

t/h MPa(g) MPa(g) m3 Nm 3/24h

4×115 0.45 0.5 86 ≤14 ≥98% 95%

°C

-25~-5

°C

35~45

°C

≤70

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Serial number

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Generator Body

130 131 132

Item Quantity of steady bearing lubricating oil Inlet temperature of gland sealing oil Outlet temperature of gland sealing oil Quantity of gland sealing oil Number of sealing oil pumps Sealing pad temperature

133

Pressure of gland sealing oil

MPa

134 135 136 137 138

Inner diameter of stator core Do Outer diameter of stator core Da Length of stator core Li Gas gap(one side)g Number of stator slots Number of stator winding branches a1 Stator winding dimension Rigid m×h-wall thickness Rigid m×h Number of coil strands in each slot Hollow Rigid Stator current density J1 Stator line load As1 Stator slot main insulation single side thickness Weight of stator (The maximum lift,including trunnious、foots etc.) Transporting weight of stator (excluding trunnious、foots etc.) Transporting dimensions of stator(L×W×H) Weight of rotor Outside diameter of rotor D2 Body length of rotor Transporting length of rotor L2 Number of rotor slots Rotor slot dimension m×h Number of line turns in each slot of rotor Copper line dimension of each turnm×h Rotor current density J1 Rotor slot insulation single side thickness Air gap flux density Bs Thickness of insulation between turns of rotor Diameter of retaining ring Dk Length of retaining ring Lk Main materials and stress Type of silicon steel sheet for stator Thickness of silicon steel sheet Type of copper line

mm mm mm mm

127 128 129

139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169

Unit

Technical data

L/min

25

°C

35~45

°C

≤70

L/min Set °C

2×90 2 ≤90 Than hydrogen pressure 0.056±0.02Mpa 1312 2625 6731 94 42 2

mm mm

4.6×6.4-1.2 2.25×6.4

n n A/mm2 A/cm

28 28 10.36 1887.6

mm

5.85

t

266

t

258

mm

9200×3820×3850

t mm mm mm

67.5 1124 6909 14300 32 47.2(38)×150

mm

7 mm A/mm

13.16×44.6 2

9.86

mm

1.52

Gs

10208

mm

0.33

mm mm

1201 859

mm

50W310 0.5 Oxygen free annealed copper

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Serial number 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188

Item Type of material for shaft FATT Shaft yield limit σs Shaft safety factor K Rotor copper line type Rotor copper line yield limit σs Material type of retaining ring Retaining ring yield limit σs Rataining ring safety factor K Material type of rotor slot wedge Collector ring and brush Collector ring surface linear speed OD of collector ring Material of collector ring Allowable carrier density for brush Brush carrier density under rated condition Allowable excitation current for collector ring and brush Brush friction factor Brush resistivity

Serial Item number 1 Type 2 Quantity Grade of 3 accuracy 4 Capacity

NAGARUNA THERMAL POWER PROJECT UNITS-#1&2

Generator Body

Unit °C N/mm 2 N/mm 2 N/mm 2 k

m/s mm A/cm 2

Technical data 25Cr2Ni3MoV ≤-17 ≥580 2 Silver contained copper line ≥206 18Mn18Cr ≥980 ≥2 Ly12-Cz 54 343.5 T10A 10

A/cm 2 7.08 A

6193

μΩm

≤0.22 18

Table 1-1 Techncial data for bushing CT CT for metering gauge Protective CT and AVR Bushing Bushing 15 6

Active and reactive energy meter Bushing 3

5P20

0.5

0.2

200VA

200VA

100VA

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Generator Excitation System

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ChapterⅡExcitation System The power supply that feeds synchronous generator with excitation current and its attached systems at called excitation system, which usually consists of two main parts, excitation power unit and excitation regulator. The excitation power unit provides excitation current to the rotor of synchronous generator; and the excitation regulator controls the output of excitation power unit in accordance with the input signals and the given regulation rules. The excitation system of synchronous generator consists of mainly power unit and regulator (device) as shown in Fi.g 2-1:

Figure 2-1 Basic principle block diagram of generator excitation system 励磁功率单元：Excitation power unit；发电机：Generator；电力系统：Power system；励磁调节器：Excitation regulator；输入信号：Input signal；励磁系统：Excitation system Excitation system is an important part in generator, which has high influence on the safe and stable operation of power system and the generator itself. The main functions of excitation system include: 1). Regulate the excitation current according to the load of generator to maintain the terminal voltage at a given value; 2). Control the distribution of active power among the generators in parallel connection; 3). improve the static stability of generator in parallel connection; 4). improve the transient stability of generator in parallel connection; 5). deexcite in case of internal fault of generator to minimize loss; 6). maximum and minimum excitation limits on the generator according to operation requirements.

Figure 2-2 Excitation system category block diagram 45

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Generator Excitation System

励磁系统：Excitation system; 按供电方式分：Categorized accoding to power supply mode; 他励式励磁系统：Separately excited; 自励式励磁系统：Self excited; 按功率引取方式分： Categorized accoding to power lead mode; 按整流器是否旋转分：Categorized accoding to rotation of rectifier; 直流电机励磁系统（直流励磁机）：DC excitation system (DC exciter); 整流器励磁系统（交流励磁机）：Rectifier excitation system (AC exciter); 自并励系统：Self shunt excitation system; 自复励系统： Self compounded excitation system; 谐波励磁系统： Harmonics excitation system; 按复合位置分：Categorized according to compound position; 静止整流器励磁系统：Static rectifier excitation system; 旋转整流器励磁系统：Rotating rectifier excitation system; 交流侧复合的自复励系统：AC side compounded self compounded excitation system; 直流侧复合的自复励系统：DC side compounded self compounded excitation system There are a variety of excitation system forms for synchronous generator, which can be divided into two categories according to power supply mode, separately excited and self excited, as shown in Figure 2-2. The excitation system used in generator manufactured by us is end seld shunt excitation static excitation system, which is UNITROL5000 excitation system supplied by ABB. 2.1 Introduction to UNITROL 5000 excitation system The generator static excitation system controls the excitation current through the SCR bridge, fulfilling the purpose of regulation of voltage and reactive power of synchronous generator. It consists of four main parts: excitation transformer, SCR, excitation and de-excitation unit, as shown in Figure 2-3:

励磁变

励磁调节器

整流器

调节器

灭磁单元

RE

测量元件

~ Figure 2-3 Generator static excitation system schematic diagram 励磁变：Excitation transformer; 励磁调节器：Excitation regulator; 整流器：Regulator; 灭磁单元：De-excitation unit; 调节器：Regulator; 测量元件：Measuring element 2.1.1

Excitation transformer The excitation transformer system consists of three single phase dry transformer, with a capacity of 3×2400kVA and a transformation ratio of 22 kV /900V. Connected group: Y/d-11. Class F insulation, the windind conductor material is copper, natural cooling, with the operating ambient temperature at 0°C~＋50°C. The excitation transformer is provided with measuring devices for temperature, light gas and heavy gas as well as pressure release device. These 46

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devices are equipped with lead-out contacts for provision of remote signals. At the high voltage side, each phase is provided with 3 groups of CT with an accuracy of 5P20/5P20/0.5. Two groups are for protection and one group is for measurement. At the low voltage side, each phase is also provided with 2 groups of CT with an accuracy of 5P20/5P20, one group for protection and one group for measurement. 2.1.2

2.1.3

2.1.4

Excitation regulator Excitation regulator (AVR) is of digital microprocessor based type, with reliable performance and having characteristics of fine adjustment and improvement of generator transient stability.The excitation regulator is provided with units such as overexcitation limit, overexcitation protection, underexcitation limit, PSS, V/HZ limiter, rotor overvoltage protection and PT broken conductor block protection; the additional functions include rotor earthing protection, rotor temperature measurement, serial communication module, crowbar, DSP smart current equalizer, shaft voltage spike absorption devices. The AVR has two identical but independent automatic excitation regulators in parallel operation, which may automatically trach each other. When one regulator channel is faulted, it may automatically switch to the other channel for operation and give alarm. When a regulator is in independent operation, the various operation conditions of the generator may be satisfied, the automatic and manual circuits may mutually and automatically track each other; when the automatic circuit is faulted, it will automatically switch to manual. The AVR has the functions of automatic regulation of reactive power and power factor. The automatic excitation regulation device is capable of operating continuously under the ambient temperature of -10°C~+40°C and an ambient with an average monthly minimum temperature of 25°C and an average monthly maximum relative humidity of 90%. The air cooled SCR is capable of operating continuously in an ambient temperature of -10°C~+40°C. The AVR panel is by means of natual or forced draft and the normal operation of AVR can be maintained in case of fan fault. SCR When one power cabint of the power rectifier quits, the operation requirements that generator force excitation and 1.1 times of rated excitation current. When two power panels quit operation, the excitation capacity reauired for rated condition of generator may be provided. The design value of SCR element junction temperature (forced air cooling): 90°C. Each power element of the rectifier device is equipped with quick fuse so as to clear the short circuit elements in time and detect the fuse as well as give signals. The cooling fans of the rectifier device has 100% standby capacity, which may come into operation automatically in case of insufficient air pressure or volume. The ventilation power supply of the rectifier device has two circuits and may switch automatically. In case of fault on any rectifier panel or cooling power supply, warning signals will be given. The fault free service hours of fan is 50,000 hours with a redundancy of 2×2, with 10 years mean time between failure. The SCR bridge is in the redundant configuration of n-2. The rectifier device shunt elements are all equipped with current equalizers, the coefficient of the rectifier element shall be no less than 0.9. Excitation and deexcitation unit In the static excitation system (usually called self shunt excitation or end excitation system), the power supply for excitation is fed from the generator end. The excitation current of synchronous generator is fed from excitation transformer, magnetic field switch and SCR bridge. In usual conditions, when the excitation starts, the excitation energy of the generator 47

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is from the residual voltage of the generator. When the input voltage of SCR increases to 10V~20V, the SCR bridge and excitation regulator may be put into normal operation and the soft start process will be completed under the control of AVR.. If the residual voltage of generator can not meet the excitation requirement due to long time shutdown, 220V DC power supply may be used. When the voltage of generator increases to the specified value, the excitation circuit will release automatically. Then the SCR bridge and the excitation regulator may be put into normal operation and the soft start process will be complted under the control of AVR. The curve of soft start process of excitation system is shown in Figure 2-4: UG

So

fts

ta

rt

100%

Field flashing

Softstart time (Ex. 5s)

t

Figure 2-4 UN5000 excitation system soft start process curve

2.1.5

After connection with grid, the excitation system will be operating under the mode of AVR, regulating the terminal voltage and reactive power of generator, or operating under the mode of superimposed regulation (including constant power factor regulation, constant reactive power regulation and grouped regulation that may accept dispatching orders). The function of deexcitation equipment is to open the magnetic field circuit and release the energy of the magnetic field as soon as possible. The deexcitation circuit consists of mainly magnetic field switch, deexcitation resistor, SCR jumper and relevant trigger elements. UN5000 Excitation System Performance 1). When the excitation voltage and current of the generator do not exceed 1.1 times of its rated excitation current and voltage, the excitation system is ensured to operate continuously. 2). The excitation system has short time overload capability, which is greater than the short time overload capability of the generator rotor windinds. 3). The force excitation times of the excitation system shall be no less than 2 (static excitation system, even when the stator voltage drops to 80% of the rated value), the allowable force excitation time is 20s. 4). The excitation system has a high initial response characteristics, within 0.1s the excitation voltage increases to the maximum voltage and 95% of the rated voltage. 5). The response ratio of the excitation system, i.e., the voltage increase speed, shall be no less than 3.58 times/s. 6). The steady gain of the excitation system ensures that the voltage static error ratio of the generator is ≤.5%. 7). The dynamic gain the excitation system ensures that when the voltage of the generator suddenly drops, the SCR bridge opens to the maximum allowable value. 48

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Generator Excitation System

8). The regulation range of the automatic excitation regulator: in case of no load, it shall be capable of regulating smoothly within 20-110% of the rated voltage, with resolution of the setting voltage not exceeding 0.2%~0.5% of the rated voltage. In case of no load of generator, the manual voltage regulation range is 10%-130%UN. 9). The voltage frequency characteristics: when the generator no load frequency change is within ±1% and the SCR regulator can be used, the change of terminal voltage shall not exceed 0.25% of the rate value. 10). When the generator is operating under no load, the voltage regulating speed of the automatic excitation regulator may be set. The setting at delivery shall not exceed 1% rated voltage/s, and no smaller than 0.3% rated voltage/s. 11). The rotor circuit of the generator is equipped with overvoltage protection, the dispersity of operation voltage shall be no more than ±10%. The silicon parts or the SCR parts of the excitation device and other equipment may withstand the operating conditons such as DC side short circuit fault and asynchronous operation of generator. 12). The forced outage rate of generator caused by fault of excitation system shall be no more than 0.25 time/year, the forced clearance rate of excitation system shall not exceed 0.1%. 13). The availability of AVR (including PSS) shall not be lower than 99.9%. 14). The exciation system shall meet the requirement of 125% of terminal voltage in case of turbine generator short circuit and no loat test. 2.2 Operation and Adjustment of Excitation System The UNITROL5000 excitation system is a complete set installed in power plant. The generator static excitation system consists of 9 panels, arranged in a line by the generator at turbine house 13.7m platform. The arrangement of the panels is as shown in Table 2-1 (front view): Table 2-1 Arrangement of UNITROL5000 excitation system panels ＡＶＲ panel

2.2.1

Deexcitation panel

DC outgoing line panel

Rectifier panel

Rectifier panel

Rectifier panel

Rectifier panel

Rectifier panel

AC excitation incoming line panel

The UNITROL5000 excitation system has the following main control methods: a. Remote control by key pad orders in the control room. These orders are given through the excitation system in binary signals. b. Remote control by scree monitor control orders in the control room. These orders are given through the excitation system in binary signals or through the Field bus. c. Local control by local control unit (local control panel) integrated in the excitation system. In normal conditions the excitation system is operated by the control system through remote control. The local control panel installed on the front panel of the exciation system is only optional in case of commissioning, test or emergency. The operators must be familiar with the design of system control and display elements, the functions of the orders of the excitation system as well as the use of control and display units. Control and display unit The available remote control and local control orders are given in Table 2-2. The right column 49

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Generator Excitation System

(feedback indication) shows whether the feedback indication is displayed in the control room: Table 2-2 List of available remote and local control orders Order Remote Local Feedback indication Excitation circuit switch on Χ Χ Χ Excitation circuit switch off

Χ

Χ

Χ

Excitation on

Χ

Χ

Χ

Excitation off

Χ

Χ

Χ

Channel 1 in operation

Χ

Χ

Χ

Channel 2 in operation

Χ

Χ

Χ

Operation mode-auto

Χ

Χ

Operation mode-manual

Χ

Operating regulator given point up Operating regulator given point down Reactive power regulator in service Reactive power regulator out of service PSS in service

Χ

Χ

Χ Max.

Χ

Χ

Max.

Χ

Χ

Χ

Χ

Χ

Χ

Χ

Χ

PSS out of service

Χ

Χ

Control mode...Local

Χ

Control mode...Remote

Χ

Test of indicator lamp

Χ

Release

Χ

Excitation switch on

Χ

Χ

Χ Χ The shaded area in the above table gives the local control orders, indicating that they are only effective when the ENABLE key is pressed on the local control panel. Before the excitation system is put into service, it must be ensured that all the required power supplies are in place to maintain safe startup, and the following inspections must be done: 1). Maintenance of the system is completed 2). The control and power cabinets are ready and properly locked 3). The generator delivers no load and the temporary earthing wires are removed 4). The control power supply of the deexcitation switch and the power supply of he regulator are energized 5). There are no alarm and fault signals 6). The excitation system is switched to remote control mode 7). The excitation system is switched to automatic operation mode 8). The generator reaches rated speed (check the speed shown on the display instrument) Remote control Many control orders and feedback indications may achieve the effective remote control of the excitation system in the control room. When the excitation system switch is placed at Excitation switch off

2.2.2

Χ

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2.2.3

Generator Excitation System

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REMOTE mode, the orders given from the control room are effective. The orders of the excitation system and the generator and their functions are detailed as below: 1). Excitation switch on/off As long as there is no trip signal, the ON order may close the excitation switch. After the closure, the excitation may be put into service. The OFF order may open the excitation switch and make the excitation quit, switching the deexcitation resistor to parallel connection with the rotor windings. As such the deexcitation of the generator is quickly completed through the rectifier and the deexcitation resistor. When the main switch of the generator is opened (generator operating under no load), the excitation switch may be opened by remote control. 2). Excitation on/off The EXCITATION OFF order is used to immediately cut off the excitation of the generator. At the same time, the rectifier of the excitation system is coverted to AC inversed operation (magnetic field energy feedback), and the deexcitation resistance is switched parallel connection with the rotor windings so that the generator discharges quickly through the rectifier inversion and deexcitation resistance. At the same time the excitation off order is given, the excitation switch is opened. After 60 seconds the trigger pulses applied on the rectifier are blocked, and the entire excitation system is fully blocked and cut off. The EXCITATION ON order is used to put the excitation of the generator into service. The excitation system feeds to the generator rotor and the voltage of the generator can be quickly established to the rated value. As long as the trip order is in function, the excitation on order is null. When the excitation on order is given, if the excitation is still in open position, it will close automatically. Only the deexcitation switch is closed the excitation will be initiated and the excitation current starts to flow. The following conditions must be ensured for a successful start of excitation: The excitation switch must be in ON position. There are no open orders and trip signals. The speed of the generator shall be above 90% of the rated speed. If the excitation transformer is directly powered by the generator terminal, the initial excitation power system is required for the excitation system. Local control

8-lines display

Keys for panel operation

Keys for local operation of excitation system

Figure 2-5 UN5000 excitation system local control panel

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The arrangement of the local control panel on the regulator cabinet is shown in Figure 2-5, which includes 16 special system display and control keys with LED, 10 operation mode and internal function control keys as well as an LCD monitor with 8 lines × 40 characters. The basic control of the excitation system may be achieved by 16 keys with status information. The alarm information and analogue values may be displayed on the LCD. It has a good man-machine interface, used for local control and monitor of the excitation system.The LCP has the following functions: 1). The display resolution is 240×64, which may at the same time display 8×40 characters. The LCP may at the same time display 8 analogue value signals, or 4 analogue value signals in the form of bar chart (with the range of 0% to 120%). The setpoint display signals have as many as 32 points. The display mode can be set through the function keys. The display signals can be searched through page roll key and selected by cursor. 2). Signal and alarm In case of excitation system alarm, the alarm signals will prevail over the measurement signals. The alarm conent includes alarm number and the textual description of the alarm in 40 characters. The LCP may chronologically display alarm messages at the same time, if there are more, the remaining ones may be displayed through roll key. The capacity of the alarm messages is 80. The alarm indicator lamp is located on the upper right corner of the alarm key, which will blink upon occurrence of alarm. After pressing the acknowledge key, if the alarm still exists, the indicator lamp changes from blinking to constant on, and the lamp will be off after the alarm disappears. 3). Local operation control The LCP has 16 membrane keys with status indicator lamps, which are used for local control of the excitation system. Digital and bar display: after initialization, 8 defined analogue values will be displayed. When pressed, 8 analogue signals with channel number, signal description, value and unit will appear, and the yellow LED is on. More analogue signals will show using roll key. When pressed, first 4 analogue signals with channel number, signal description, value and unit as well as combined bars will appear. At the same time, the yellow LED is on. More analogue signals will show using roll key. The 8 analogu values are listed in the table below: Table 2-3 List of analogue values of generator excitation system Channle number

Value

Unit

Value 1

Generator voltage

kV

Value 2

Generator current

kA

Value 3

Active power

MW

Value 4

Reactive power

Mvar

Value 5

Excitation current

A-dc

Value 6

Setpoint of automatic channel

kV

Value 7

Setpoint of manual channel

A-dc

Value 8

Actual voltage value of generator

%

Fault display: there are a variety of alarm and trip signals that indicate the faults of the excitation system.

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When presses, if there is any fault (red LED on), up to 8 fault messages will appear. The first fault always shows in the first line, and the subsequent faults will show in turn according to the falut numbers. More subsequent faults will show using the roll key. These fault messages may be grouped into excitation alarm, protection switching and trip. For the first fault message, the control panel automatically switches to display the corresponding fault message. The first fault will show in the first line and subsequent faults show in the following lines. In addition, when the first fault is reported, the LED on the RESET key blinks. The fault messages are removed: All the alarm messages are stored in the control panel. In addition, the specified alarm messages are also stored in the microprocessor; these may only be reset by pressing the RESET key and held for a period. When pressing the RESET key for a short time, if the alarm stored in the microprocessor operates, the LED change from blinking to constant on. If new fault alarm appears, the LED will again begin to blink. This may eliminate the fault display stored in the control panel. If there is no alarm operation, the LED on the key will be off. When pressing the RESET key for more than 1s, if there is still alarm operation, the LED will change from blinking to constant on. If new fault alarm appears, the LED will again begin to blink. This may reset the alarm stored in the control panel and reset the alarm stored in the microprocessor. If there is no alarm operation, the LED on the key will be off. Display and print control:

# Cursor key

Press the cursor key to display the 1-8 lines or 1-4 lines on the screen. The current line is the hightlighed channel number with reverse contrast indication. When the last line is shown, it will jump to the first line. The cursor key is only active when analogue signals are displayed (digital or bar display).

Roll key When analogue signals are displayed (digital or bar display), press the roll key, the displayed (indicated by reverse contrast) channel number and its analogue value will change accordingly. When fault messages are displayed, press the roll key to show all the fault messages at all lines 2-8 or move up or down. The first fault shown in the first line maintains its position. Page change key When this key is pressed, the channel number changes 10 positions or the fault number changes 6 positions. The other functions are similar to the roll key. Print key When the print key is pressed, the analogue values of lines 1-8 are transferred to the printer (if connected) through RS-232 serial interface. If the fault messages are active, these messages are transferred to the printer as well. If the data are transferring and the printer has received them, the yellow LED will be on. If the yellow LED blinks, it indicates the buffer of thr printer is full for the moment. To extend the service lif of LCD, the display and background light thereof do not need any key, which will be off and disappear after 60 minutes. Afterwards, if press one of the 10 function keys on the local control panel or if a fault message occurs, the LCD of the local control panel 53

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Generator Excitation System

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will be active again. Startup of excitation system Table 2-4 Sequence of startup of generator excitation system Operation 1

Excitation switch on

2

Excitation system into service

Display Control Indicator lamp Excitation switch already on ON on Indicator lamp Voltage established in ON on 5-20s

⇒ Generator operation under no load 3

4

Excitation system ready to operate under low load. Use up/down keys to adjust the voltage of generator to the grid level. When the generator voltage is synchronized with the grid voltage, close the main circuit switch of the generator.

Voltage of generator adjusted to the setpoint. The reactive power of the generator approximates to 0.

⇒ Generator operation under low load

5

2.2.5

Adjust the voltage of the generator and the generator will produce certain reactive power.

Use up/down keys to set the reactive power of the generator to the operation limit

Shutdown of excitation system Table 2-5: Sequence of shutdown of generator excitation system Operation

Display

1

Disconnection of generator from the grid: decrease the reactive power through the voltage setpoint of the generator. –decrease the active power through the turbine regulator. –open the generator main circuit switch

2

Excitation system out of service, excitation switch open

Control

The voltage of generator Indicator lamp decreases to 0 within OFF on several seconds.

The sequence chart of the generator excitation system startup and shutdown is shown in Figure 2-14. 2.3 Automatic control and protection There are a variety of configuration types for the automatic control of the UNICTROL 5000 excitation system, the selected type by us is 2 AVR+2 FCR+2 BFCR, i.e., the double channel system with manual emergency spare channel (as shown in Figure 2-6). This is the top configuration of the UNICTROL 5000 excitation system at the time.

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Figure 2-6 Double channel system with manual emergency spare channel 2.3.1

2.3.2

Switching between main channels This excitation system has two totally independent regulators and control channels (Channel I and Channel II). The two channels are identical, as such either of them can be selected as operating channel. The spare channel (the one not in operation) always tracks the one in operation. Basically, switching between the channels can be carried out at any time except the following conditions: If any fault is detected on the channel in operation, it will be automatically switched to the second channel as an emergency response. Afterwards, it is only possible to switch back to the active automatically. If any fault occurs on the spare channel, the switching from the active one to the spare one can not be done. If fault occurs on one channel, the voltage of generator at the same time experiences dynamic disturbance, it will be automatically switched to the spare channel immediately, which will not follow the dynamic disturbance of the generator voltage. To prevent this condition, the spare channel will in a relative slow manner follow the voltage of the generator with a certain time delay. Auto/mannual switching of main channels This excitation system is such featured that each main channel has an automatic regulator (automatic) and a manual regulator (manual). In the automatic mode, the voltage of the generator is regulated, as such a constant voltage is generated at end of generator. While in the manual mode, the excitation of generator (magnetic field current) maintains constant, along with the change of generator load, the excitation of generator (setpoint of magnetic field current) must be regulated manually to maintain the voltage of the generator unchanged. Basically, as the spare regulator is always following the active regulator, at any time the switching between auto and manual modes is possible. However, special attentions shall be paid to the following: 1). If any fault is detected in the automatic mode (→switched to manual mode as emergency response), it will automatically be switched back to auto mode after the fault is eliminated. 2). If any fault occurs in the manual mode, the switching from auto mode to manual mode will be stopped. 3). If the generator may operate at the limit of the automaci mode but in the allowable operation range, which has exceeded the alloable operation range of the manual mode. In this case, the manual regulator may stop to follow the automatic regulator. The feedback indication allows the manual regulator to follow inspection and verification. 55

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Note

2.3.3

2.3.4

Generator Excitation System

NAGARUNA THERMAL POWER PROJECT UNITS-#1&2

4). It is possible that switching from auto to manual and then back to the operation mode before occurrence of fault as a result of fault. Therefore, the follow up control of manual regulator has the function of delaying and correspondingly slowing down the change of excitation current. 5). During switching from auto to manual mode, the characteristics of relative slow follow up of the manual regulator must be considered. It will direcly follow the change of excitation current and the switching will have a very short delay (waiting message: AUTO/MANUAL READY). So, the switching without disturbance under any circumstance can be maintained. The manual mode as a special regulator (as spare regulator) has only the function of regulating excitation current (without the function of regulating generator voltage). In manual mode, the excitation of generator must be under supervision of skilled operators. As long as the signals of generator voltage and CT exist, in manual mode the underexcitation limiter may also prevent the hazardous low excitation of generator. In extremet conditions, the low excitation will result in pole slipping. In addition, under no load and low speed, the V/Hz limiter will decrease the excitation current to prevent the generator and the transformer connected therewith from oversaturating. The variables of operation such as generator voltage, current and reactive power must be monitored by the operators, which, in case of necessity, may be regulated through change of settings of the excitation current.

Emergency spare channel In addition to the two main channels, the excitation is also provided with two emergency spare channels. The emergency spare channels, which have similar manal mode as the main channels, are equipped with an excitation current regulator. In addition to the excitation current regulator, the emergency spare channels are also provided with overvoltage protection and trigger pulse controllers independent of the main channels. The overvoltage protection inserted into the main channl functions as standby protection. The function of the emergency spare channels is the same as that of the main channels, i.e., the emergency spare channels may only regulate the excitation current other than the voltage of the generator. The excitation current regulator of the emergency spare channels automatically follows the main channels. Therefore, in faulted condition of the main channels, automatic switching without disturbance will be done. The manual switching from main channels to the emergency spare channels may only be performed by specially authorized operators. The follow up regulation of the two regulators ensures that switching back to the main channels is possible. Superimposed control If automatic mode is selected and the generator is connected to the grid, it may be switched to 56

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the reactive power regulator (Q)/power factor regulator (cosΦ). The reactive power regulator (Q)/ power factor regulator (cosΦ) are the upper regulators of voltage regulator and may only function slowly in operation. Therefore, the short time fault of grid will not affect the upper regulator, which will remain functional. All the limiters in auto mode are same functional as before. The voltage regulators, including upper regulators, may be controlled by the limiters if necessary.

Figure 2-7 Superimposed control schematic block diagram The reactive power regulator/power factor regulator has the feature that it may set the setpoint of its own (setpoint integrator). When the upper regulator is opened, the setting of the setpoint always follows the actual value (the current reactive power Q/ current power factor). This means that the operation point of generator will not take function immediately after transferring from voltage regulator to upper regulator. Only after the setpoint of the upper regulator is regulated by the HIGHER / LOWER order, the reactive power Q /power factor will change accordingly. HIGHER / LOWER (↑/↓) order: the (↑/↓) order in the control room may control the operation modes of AUTO, MANUAL / AUTO, MANUAL and the setting of setting value of the upper regulator. If an operation mode is activated, the setpoint may only be regulated by these orders. 1). In auto mode In the auto mode, the setpoint of the generator voltage is regulated by the order of ↑/↓. In case of operation under no load, the setpoint is changed to regulate the voltage of the generator; in case of operation under load, the setpoint is changed to regulate the reactive power. In case of operation up to the limit of the generator stator and/or the rotor, the corresponding limit regulators will in the proper direction interfere with and stop the functioning of ↑/↓ order. If the setpoint of generator voltage reaches its minimum or maximum setting value, the “Active regulator MIN-POS / MAX-POS” message will appear. If at the same time the orders of ↑ and ↓ are given, the setpoint will not be regulated. When the excitation is connected, the setpoint of the generator voltage will automatically set to its rated value. 2). In manual mode In the manual mode, the setpoint of the exciation current is regulated by the order of ↑/↓. In case of operation under no load, the setpoint is changed to regulated the voltage of the generator; in case of operation under load, the setpoint is changed to regulate the reactive power. In the manual mode, on the underexcitation limiter (to prevent pole slipping of generator) and V/Hz limiter (to prevent saturation of magnetic circuit) are available. The ↑/↓ order is not as in auto mode prevented from exceeding its limit by limiter. Therefore, it must be ensured that the operation limit of the rotor and generator will not be exceeded in accordance with the power diagram. 57

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2.3.5

2.3.6

Generator Excitation System

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If the setpoint of the excitation current reaches its minimum or maximum setting value, the “Active regulator MIN-POS / MAX-POS” message will appear. If at the same time the orders of ↑ and ↓ are given, the setpoint will not be regulated. When the excitation is connected and the main switch of the generator is at the open position, the setpoint of the excitation current will automatically set to its no load excitation current value. PSS PSS is a standard software function of MUB of the UNITORL 5000 excitation system. By introducing additional feedback signals, the PSS suppresses the low frequency oscillation to improve the stability of the grid. The control algorithm of PSS is based on the double input PSS model, and the additional feedback signals are the accerlation power signals of the units, integrated from power signals and rotor angle frequency signals. When the active power of the generator reaches a setting value, the PSS can be manually put into service (must be carried out the professionals), as such the voltage of generator is limited within the given range (such as 90-110% UGN). The PSS may at any time be taken out of service, and, it will quit operation automatically when the active power and the voltage of the generator exceed their setting values or the generator is disconnected from the grid. Rotor earthing protection The rotor earthing protection device UNS 3020 is an independent protection relay. It is used as the earthing fault protection of the entire rotor circuit (including the power SCR and excitation transformer secondary side) of the generator. Its features include: 2 sections of structures (one for alarm and two for trip), the setting value and time delay of each section may be reagulated separately. Figure 2-8 shows the schematic diagram of wiring for earthing protection relay of ABB UN5000 excitation system. The protection is superimposed AC voltage measurement admittance bridge type, CK1 and CK2 are block coupling capacitors, CR is the equivalent capacitor of the generator excitation circuit to earth, CK1, CK2 and the excitation circuit equivalent capacitor CR are in series, connected at the mearuing arm of the AC bridge. The to earth capacitance of excitation circuit of large units is great, only the to earth capacitance of the excitation winding will be as high 1~2μF, if the additional voltage

•

U0

has a

frequency at 50Hz, the to earth capacitive reactance is only 1.6~3.2kΩ. It can be seen that for hydrogen cooled units, the to earth capacitive reactance is far smaller than the to earth insulation resistance (usually at megohm class). Therefore, the superimposed AC voltage one point earthing protection has low sensitivity, to improve which the AC bridge is used. The superimposed AC voltage one point earthing protection has simple wiring and has no dead zone. The earthing sensitivity of any point on the entire excitation winding is more or less the same, and the protection may be used as the earthing fault protection of the entire rotor circuit of the generator (including the power SCR and excitation transformer secondary side). But the balance of bridge is easily affected by the rotor brush and the shaft earthing brush contact resistance; the requirement on frequency of the superimposed AC power supply is strict; the measuring arm is complex arm, therefore it is complicated to regulate the balance of bridge.

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Figure 2-8 Rotor earthing protection principle 2.3.7

Limiter The limiter is intended to maintain the safe and stable operation of the generator and avoid abnormal outage due to operation of the protection relay. Figure 2-9 shows the typical power diagram of salient pole synchronous generator and the corresponding operation limit position at rated terminal voltage. It can be seen from the diagram that two overexcitation limiters of maximum excitation current and inductive stator current are provided in the overexcitation area; three underexcitation limiters of capacitive stator current, reactive power limiting (P/Q limiting) and minimum excitation current limiters are provided in the underexcitation area. The working principle of limiter is: each limiter has its limiting quantity and limiting value, when the value of the limiting quantity reaches the limiting value, the corresponding limiter will generate a deviation signal between the limiting quantity and the limiting value. After operation of the limiter in the overexcitation area, the excitation current will be decreased to a maximum allowable level; while after the operation of limiter in the underexcitation area, the excitation current will be increased to the required minimum level. In normal operating conditions, the operation of the generator is within the allowable range of the power diagram and the input of the PID controller is the deviation signal of the terminal voltage, i.e., the main deviation signal. If the change of operation condtion makes that the deviation signal of the overexcitation limiter inferior to the main deviation signal, the priority thereof will be higher than the main deviation signal. As such, the PID controller will obtain the minimum value of the various deviation signals. This principle applies also to the underexciation limiter, just in opposite direction. 1). Limitation of excitation current The maximum excitation current limiter is used to prevent the rotor circuit from overheating, the design of which has the characteristics of inverse time limit. The limiter has two limiting values: one force ceiling current limiter, the other is the allowable overheating limiting value for continuous operation. The two control parameters in relation to the overheating limiting value are the rotor equivalent heating time and rotor equivalent cooling time. During normal operation of synchronous generator (without operation of limiter), the limiting value of the maximum excitation current limiter is the force excitation ceiling current limiting 59

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value Imax, the AVR may provide force excitation ceiling current when necessary. When system fault occurs and force excitation is required to eliminate such fault, if the actual value of the excitation current exceeds the overheating limiting value, the regulator will start a residual power integrator, integrating the current deviation value △i2(wherein △i=Ifield-Itherm) to time, the result of which is in direct proportion to the heating energy of the excitation winding. If the excitation current continues to remain higher than the overheating limiting value, the output of the integrator ∫△i2dt=△E will increase. When the output of the integrator exceeds △Emax, the limiting value of the maximum excitation current limiter will be decreased from Imax to Itherm. The above work is done by the overheating detector. When the excitation current drops below the normal value, the residual power integrator will start the reverse cooling intergration, reducing the output according to the cooling time constant Tcooling.

Figure 2-9 Salient pole synchronous generator typical power circle diagram 欠励区域：Underexcitation area; 过励区域：Overexcitation area; 容性定子电流限制： Capacitive stator current limit; 有功：Active power; 感性定子电流限制；Inductive stator current limit; 最大汽机功率：Maximum turbine power; 无功功率（P/Q 限制）：Reactive power (P/Q limit); 最大励磁电流限制：Maximum excitation current limit; 最小励磁电流限制：Minimum excitation limit; 无功：Reactive power If the system fault continues to occur and again force excitation is allowed, when the cooling time is not over yet, the time required for the remaining energyto reach △emax (the allowable time for operation under such force excitation current) will be shorter than the first time. If the cooling time is over (the limiter in reset position), the limiter will allow the excitation current to maintain at the ceiling level during the nomal period allowed by the force excitation. External signals may be used to interfere with the overheating limiting value Itherm, such as the temperature signal representing the cooling gas of generator, which may be added to the overheating limiting value Itherm. The maximum excitation current limiter has two limiting characteristics under different situations, as shown in Figure 2-10.

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If [A ] p r o s p e c t iv e v a lu e o f f ie ld c u r r e n t If m a x ( 1 ,6 * If n )

C ase 1 C ase 2

I f th e r m ( 1 ,0 5 * If n )

T e q u iv (1 0 s )

t [s ] t

Figure 2-10 Two limiting characteristics of mamximum excitation current limiter The main task of minimum magnetic field current limiter to prevent loss of excitation. This function is often applied in water turbine generators, which may perform in-depth leading phase operation at the underexcitation side of the power diagram, i.e., operating close to the zero excitation current. In this case, the minimum excitation current limiter ensures that the excitation current is no smaller than the minimum limiting value. This limiting value is a must to maintain the normal operation of converter and it may prevent the rotor shoe from overheating. The minimum magnetic field current limiter has only one minimum limiting value, instant operation. 2). Limitation of stator current The limiter is used to prevent the generator stator from overheating, which is effective at both the overexcitation and underexcitation sides. Its working principle is similar to that of the maximum excitation current limiter. The main difference lies in the fact that the stator current limiter does not have a definite maximum stator current limiting value. When the time tends to zero, the limiting value theoretically may be infinite (Imax=∞), which may be set by proper parameters and the inverse time limit characteristics close to the stator winding maximum allowable thermal energy. The stator current limiter is divided into two parts at underexcitation and overexcitation sides, the limiting quantities of which are both average values of the stator current. When the generator is overexcited, the stator current limiter at the underexcitation side will close, and vice versa. By detecting the power factor of the load, it can be ensured that bidirectional operation (overexcitation and underexcitation) of the stator current limiter is correct. It is obvious that the stator current limiter may not affect the active current component of the generator. If the active current component of the generator is higher than the limiting value of the stator current limiter, the limiter will automatically regulate the reactive power of the generator to zero to avoid misoperation. 3). P/Q limiter The P/Q limiter is in nature an underexcitation limiter, used to prevent the generator from entering the unsteady operation area. The limiting curve of this limiter is determined by five reactive power setting values corresponding to five active power points (P=0%, P=25%, P=50%, P=75%, P=100%). The curve is related to the voltage level of the stator and deviates following the change of such voltage.

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2.3.8

Generator Excitation System

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Deexcitation and overvoltage protection The trigger unit of part of static deexcitation device (jumper), having a number of independent discharge silicon controlled circuits, as shown in Figure 2-11. U N S 00 17

3 4

X 1

1 2

5 6 7

Figure 2-11 Principle diagram of deexcitation circuit The controlled deexcitation circuit of the generator may be duplicated, connected at the same time as the trip coil of the deexcitation switch. In addition, a voltage detection circuit is provided, which will automatically trigger the controlled silicon if the excitation voltage exceeds its preset value. Therefore, the controlled silicon bridge and the magnetic field winding is protected from impact by dangerous peak voltage as the jumper is used as the independent overvoltage protection device. 2.3.9 PT fault detection The detection of PT fault is achieved by comparison of the measured values of generator terminal voltage and excitation transformer secondary voltage. If the difference between the two voltages exceeds the setting value (15% of the rated value of the generator terminal voltage), the logic controller will initiate the switching: if two channels share one CT, the mode will be switched from auto to manual, if two channels use their independent PT and disconnection of PT occurs on the active channel, the auto mode of the active mode will be switched to the auto mode of the spare channel. If two groups of PT have fault, the mode will be switched to manual. 2.3.10 Rotor temperature measurement The measurement of rotor temperature is achieved by the calculation of resistance of the excitation winding, as expressed below:

T1 =

Td 0 ′ Tdl

Wherein: Uf=magnetic field voltage If=magnetic field current Lf=excitation winding inductance UB=brush voltage drop RB=brush resistance RL=resistance of the main circuit conductor between measuring point of magnetic field and brush T1=equivalent time constant 62

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Td0’=magnetic field time constant Td1=load time constant (between Td’ and Td0’) P= Laplacian According to the calculation result of the winding resistance, the temperature is calculated as per the following expression:

Rf Tf =

−1

Rf 0 α

Wherein: Tf=rotor temperature Rfo=0°C rotor excitation winding resistance α=resistance temperature coefficient of excitation winding material [1/°C] The measurement result of the rotor temperature may be displayed locally and/or remotely, and may be used for alarm. 2.3.11 Overcurrent protection The overcurrent protection is divided into inverse time limit overcurrent protection and transient overcurrent protection. The characteristics of the overcurrent protection is similar to that of the described maximum excitation current limiter, only that the curve is higher. 2.3.12 Protection for loss of excitation (P/Q) When the operating point of the generator exceeds its stability limit, protection for loss of excitation will operate to trip the generator. The protection curve is set using the five points in the power circle diagram (see chapter 11 for details), and the curve is similar to the limiting curve of the P/Q limiter. But the P/Q protection curve moves left by 5% to 10% based on the limiting curve of P/Q. As the stability limit of the synchronous generator is related to the terminal voltage, the P/Q protection curve is also corrected in direct proportion to the terminal voltage of the generator. When the operating point of the generator exceeds the protection curve, the timer will be triggered and the order to trip the generator will be given after a settable time delay. The timer delayed startup signal may also be used for alarm.

Figure 2-12 Principle diagram for loss of excitation protection of generator

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2.3.13 Overexcitation protection (V/Hz relay)

Figure 2-13 Principle diagram for overexcitation protection of generator This is used to prevent excessive flux of synchronous generator and transformer.The overexcitation protection at first calculates the current allowable value of the terminal voltage based on the generator frequency and setting value. If the actual voltage of the generator exceeds the allowable value, the timer delay will be triggered. Before the time delay is over, if the voltage fails to return to the allowable value, the tripping signal will be given. 2.3.14 Excitation transformer temperature measurement The UNITROL 5000 software may through the PTC or PT100 sensors embedded at the position of the excitation transformer secondary coil with maximum temperature measure the temperature of the winding. If PTC is used, two sensors will be used for each phase and connected in series then to the two analogue value input points of the FIO. The regulator will detect whether the temperature of the current excitation transformer reaches the setting value of the two sections of temperature. The alarm will be activated if the section 1 setting value is exceeded and the trip of excitation system will be activiated if the section 2 setting value is exceeded.

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Figure 2-14

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ON/OFF time sequence of excitation for generator

Superimposed regulation

MANUAL

Q/cos ϕ Off

Q/cos ϕ On

Exc. Off

Exc. On

FCB Off

FCB On

No fault no alarm

ON OFF

ON OFF

ON OFF

ON OFF

ON OFF

Perm. reset to 90% Ifo

1

2

Reset to 100%

3

4

By operating personnel

5

6

Load operation (on network)

By operating personnel

Compensation to AUTO-Regulator

Synchron. system

Voltage

7

Perm. reset to 90% Ifo

Reset to 100%

8

9

Generator Excitation System

*) Remote operation: Enable via external locking functions

Higher/lower

Reference value change

ON / OFF

Superimposed Regulation

ON / OFF

Machine breaker

ON / OFF

Excitation

Enable excitation *)

Remote Local control control

r.p.m.

On / off cycle for generator application (Standard application without additional application program, no fault or alarm present)

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2.4 Technical specifications Table 2-6

Generator Excitation System

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Main technical data of generator excitation system

Type of excitation Type Rated excitation voltage Ceiling voltage of excitation system (at 100% Ugn)

UNITROL 5000 431V 1000V

Rated continuous excitation current Celing voltage (for 20s )

4727 A 8986 A

Response time

80ms

Excitation mode Total power consumption of excitation cabinet

DC220V 58 kW

Protection class

IP54

2. Excitation transformer Type Rated capacity

Dry transformer 3*2400 kVA

Number of phase Group of wiring

3 Y/d-11

Rated frequency Rated voltage:

50Hz 22/0.9

HV side LV side Time that the HV side may withstand 1.3 times of rated voltage of the generator

22kV 900V 1 min.

Time that the HV side may withstand 2 times of rated 20s current Protection class Cooling mode BIL Power frequency withstand voltage Partial discharge Insulation class

IP22 Self cooling+fan 170kV 70kV (1 min) >’key：It is used to choice the proposed bit, the selected bit will flicker. ‘ENTER’key：It is used to confirm the proposed information or confirm modification. 1.a.9 Parameter explanation： The parameter besides the described parameters in 4.2.4 ,still have two settings as following: Factory parameter setting: If wants to set all sync channel parameters to factory setting values (factory setting reference 4.2.4 parameters explanations), may reference the following method to operate: When inquires the software edition number, demonstrates C0：0601，presses ‘> >' key and ‘+' key to revise 0601 to 1234, then presses ‘ENTER’ to change all sync channel parameters to factory setting values. Password revision: The equipment password is empowered to revise the sync parameter and demarcate the device’s measurement parameter. The factory password is 1111, please safekeeping and unforgotten the revised password. To revise password can reference the following method: When appearing PP：

（the next ‘P’ flashes），presses ‘ENTER’ key（no longer flashes），

presses ‘ENTER’ key again, shows PP：0000，then presses ‘>>’ key and‘+’ key to revise password, at last, presses ‘ENTER’ key to confirm the revised password. 1.a.10 Setting ranges of parameters Software guaranteed all input parameters are in the permission scope, the concrete parameter permission scope sees 4.2.5.

b) . Sync working mode 1.b.1 Mode introduction The normal working mode is SID-2SL-A main working pattern, may control TJJ outputs according to system side and generator/line side sync parameters, guarantee the sync closing breaker operation correctly execute. Simultaneously may inquire system side and generator/line side voltage, frequency, phase-displacement and so on, also may inquire the current sync channel parameter. 1.b.2

How to enter

Accessing power or reset operation to directly start up SID-2SL-A. The device selects a sync channel first and displays --：---- , it flashes and waits an input signal to choice the sync channels, 107

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then can enter into nominal working mode after selecting successfully. If the select channels signal have been selected before start up the device, then waiting about 0.5 second and enter. After entering into nominal working mode, if the select channels signal alters or disappears, the device will automatically select a channel again. Success selecting will enter into nominal working mode again and no manual intervention to ensure that the final choice of synchronization parallel automatically.

1.b.3

Display and operation explanation

In working mode, the nixietube and synchroscope (composed of 36 highlight LED) and other lights are shown to be effective. The synchroscope displays the phase-displacement of system side and generator/line side, the degree of two adjacent LED is 10°.When generator/line frequency is higher than system side, the display is clockwise rotation (namely fast direction), and vice versa. When a difference between both sides’ voltages excesses max voltage deviation, the left LED light, and it flashes red when generator/line side voltage is lower than system side’s, on the contrary, the left lamp flashes green. The lamp will go out just at the value within allowable voltage deviation. When a difference between both sides’ frequencies excesses max frequency deviation, the right LED light, and it flashes red when generator/line side frequency is lower than the system side’s , on the contrary, the right lamp flashes green. The lamp will go out just at the value within allowable frequency deviation. Closing light shows TJJ state action, when TJJ closed the LED light (red), when TJJ opened the LED extinguishes. 6 eight-segment highlight digital tubes display parameters at three Display modes. They are: automatic display mode, measure parameters inquiries mode, sync parameters inquiries mode. Three display mode through the 'PARA' key switching cycle. Automatic display mode: After entering into the normal mode is the automatic mode. It automatic displays voltage deviation, frequency deviation and phase-displacement. When the voltage deviation of both sides exceeds the setting value, it displays UC：±XX.X， which indicates both sides voltage deviation percentage, the max value is 99.9（Only showed 99.9 even more than 99.9% ），and the generator/line side is the high side which means positive(not shown positive sign), the system side of high means negative (minus sign indicates ‘-’).

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When the system side and the generator/line side voltage deviation is in the setting scope and the frequency difference is over setting, shows FC：±X.XX，indicates both sides frequency deviation, the max value is 9.99，and the generator/line side of high means positive(not shown positive sign), the system side of high means negative (minus sign indicates ‘-’).

When the voltage and frequency deviation are all in setting range, shows JC：XXX.X，indicates both sides phase-displacement, 0-359.9°scope. Note that satisfy any of the following conditions, the phase-displacement would be set 180 ° directly.

l

Frequencies of system side or generator/line exceed 35-65Hz scope.

l

Frequency deviation exceeds 5Hz（both positive and negative).

l

Voltages of system side or generator/line lower 10V.

The three parameters automatic display, when the system side and the generator/line side inputs change, the display item automatically change without control button.

In this mode, ‘PARA’ is used to switch other display modes, the keys of ‘>>’, ‘+’ and ‘ENTER’ are invalid.。

Measure parameters inquiries mode：Presses ‘PARA’ key can switch to this mode, circle displays system side voltage, generator/line side voltage, voltage deviation, system side frequency, generator/line side frequency, frequency deviation and phase-displacement in turn.

System side voltage：To display SU：XXX.X，the unit of V； Generator/line side voltage：To display gU：XXX.X，the unit of V； Voltage deviation：Same as automatic mode;

System side frequency：To display SF：XX.XX，the unit of Hz；

Generator/line side frequency：To display gF：XX.XX，the unit of Hz；

Frequency deviation：same as automatic mode； Phase-displacement：same as automatic mode. 109

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In this mode, ‘PARA’ key is used to switch other display modes, ‘>>’ key is used to inquire above parameters in turn, the keys of‘+’ and ‘ENTER’ are invalid. Sync parameters inquiries mode：Presses ‘PARA’ key can switch to this mode, circle displays 7 sync parameters of the selected sync channel in turn. They are system side rating voltage, generator/line side rating voltage, system side TV’s aux turn angle, difference frequency lockout angle, same frequency allowance power-angle, allowance voltage deviation and allowance frequency deviation. System side rating voltage：To display Sn：XXX.X，the unit of V，n=1-9、A、b、C indicates the present sync channel serial number, followed by 1-12, the following are similar; Generator/line side rating voltage：To display gn：XXX.X，the unit of V； System side TV’s aux turn angle：To display dn：XX.X，the unit of °； Difference frequency lockout angle：To display Ln：XX.X，the unit of °； Same frequency allowance power-angle：To display hn：XX.X，the unit of °； Allowance voltage deviation：To display Un：XX，the unit of %； Allowance frequency deviation：To display Fn：0.XX，the unit of Hz. In this mode, ‘PARA’ key is used to switch other display modes, ‘>>’ key is used to inquire above parameters in turn, the keys of‘+’ and ‘ENTER’ are invalid. 1.b.4

TJJ action logical specification：

TJJ action conditions set by the logic of action, as described below:

a). condition decision：there are following 12 action logical specifications. (1). Frequency deviation higher：generator/line side frequency is higher than system side frequency and frequency deviation is larger than setting value;

(2). Frequency deviation lower ： generator/line side frequency is lower than system side frequency and frequency deviation is larger than setting value;

(3). Voltage deviation higher：generator/line side voltage percentage is higher than system side voltage percentage and voltage deviation is larger than setting value;

(4). Voltage deviation lower：generator/line side voltage percentage is lower than system side 110

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voltage percentage and voltage deviation is larger than setting value;

(5). Same frequency/difference frequency paralleling category judgment input：correlative input signal connection is same frequency paralleling, correlative input signal disconnection is difference frequency paralleling;

(6). Phase-displacement over limit：phase-angle difference of both sides is larger than setting value (difference frequency sync is difference frequency lockout angle, same frequency sync is same frequency allowable power-angle);

(7). System side non-voltage：system side voltage is less than system side rating voltage 20%;

(8). Generator/line side non-voltage：generator/line side voltage is less than generator/line side rating voltage 20%;

(9). System side alive-voltage：system side voltage is larger than system side rating voltage 70%;

(10). Generator/line side alive-voltage：generator/line side voltage is large than generator/line side rating voltage 70%;

(11). One side non-voltage confirm input signal：input judgment，one side non-voltage confirm input signal connect and both sides non-voltage input signal disconnect;

(12). Both sides non-voltage confirm input signal：input judgment，both sides non-voltage confirm input signal connect and one side non-voltage input signal disconnect.

b). action logical： (1). TJJ closing logical：Meet any of the following conditions TJJ are closed (‘&&’means fore-and-aft conditions come together, ‘！’means conditions dissatisfied) .

u

（one side non-voltage confirm input signal）&&（system side non-voltage）

&&（generator/line side alive-voltage）； 111

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u

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Synchronizing Equipment

（one side non-voltage confirm input signal）&&（system side alive-voltage）

&&（generator/line side alive-voltage）； u

（both sides non-voltage confirm input signal）&&（system side non-voltage）

&&（generator/line side non-voltage）； u

（！frequency deviation higher）&&（！frequency deviation lower）&&（！

voltage deviation higher）&&（！voltage deviation lower）&&（！phase-displacement over limit） &&（system side alive-voltage）&&（generator/line side alive-voltage）. (2). TJJ opening logical：If not satisfied with any of the above conditions then TJJ opened.

2.17 Definition terminal All terminals are accessible from the rear, the definitions are as show as below：

l

Definitions of JK1 socket pins:

1

2

3

4

5

6

7

8

9

10

11

12

13

14

syste

syste

Gener

Generat

V

#1

#1

#2

#2

Alar

Alar

Vac

powe

powe

m

m

at

ac

loc

lock

loc

lock

m-

m+

a

r

r

side

side

sourc

sourc

TV’s

TV’s

e

e

A

B (N)

（-）

（+

phase

phase

or/line

or/line

side TV’s

an

side

B

cy

TV’s A

phase

(N)

k out-

out +

k

out+

out-

phase

Auxiliary voltage is supplied from 110 to 220VAC/DC

l

Definitions of JK2 socket pins:

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Synchronizing Equipment

1e

2

3

4

5

6

7

8

9

10

i #3lock g out -

#3lock

#4lock

#4lock

#5lock

#5lock

#6lock

#6lock

#7lock

#7lock

out +

out -

out +

out -

out +

out -

out +

out -

out +

11

12

13

14

15

16

17

18

19

20

#8lock

#8lock

#9lock

#9lock

#10lock

#10lock

#11lock

#11lock

#12lock

#12lock

out -

out +

out -

out +

out -

out +

out -

out +

out -

out +

Sync lockout contact uses a MOSFET relay with high-power optoelectronic isolator, its output divide into positive polar and negative polar. Please note that polar when connecting. MOSFET relay contact contains 600VDC/6A, which could drive the circuit breaker to close directly. Not only do the relay comb-out the time lag of the electromagnetic type synchronism-check relay and inductive electric potential disturbance, but also entirely exterminate the abuse of long operation frequently of the electromagnetic type synchronism-check relay that lead to fatigue and damage. 1

2

3

4

5

6

7

8

Sele

Sele

9

Sele

Sele

Sele

Select

Sele

Select

ct

ct

Select

ct #1

ct #2

ct #3

#4

ct #5

#6

#7sy

#8sy

#9

sync

sync

sync

sync

sync

sync

nc

nc

sync

chan

chan

chan

chann

chan

chann

cha

cha

chann

nel

nel

nel

el

nel

el

nnel

nnel

el

10

11

12

13

14

15

16

17

18

NonSele

Sele

Sele

volta

ct

ct

ct

Non-voltag

ge

#10

#11

#12

e verify in

verify

SF/DF

Remote

Spare

Public

sync

sync

sync

one side

in

select

rest

input

input

chan

chan

chan

one 113

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nel

nel

Synchronizing Equipment

nel

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side

Inputs adopt DC110V or DC220V，Please specify when ordering.

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Generator Relay Protection

Chapter Ⅶ Generator Relay Protection Generator is the most important equipment in power system. Large capacity units play a critical role in a system, as such how to maintain the safe operation of generator in power system is highlighted. As direct cooling technologies are often used for large capacity units, the volume and weight are not increasing in direct proportion to the capacity. Therefore, the parameters of large generators are significantly different from those of small and medium sized generator. In this case the characteristics of faults and unsafe operation are also different, which poses complexity for protection. Compared with small and medium generators, the large ones have the following main features: 1). The short circuit ratio is decreased and the reactance is increased. The short circuit ratio of large generator is used reduced by about 0.5 and all the reactances are bigger than those of the small and medium generators. Therefore the short circuit level of large generators is lower, which is undesired for relay protection. As Xd is increased, the static stability reserve coefficient of generator Kch is decreased, therefore the static stability is easily lost in case of system disturbance or loss of excitation of the generator. As parameters such are Xd", Xd' and Xd are increased, the average asynchronous torque is greatly reduced, roughly from 2-3 times of the rated value for small and medium generators to the rated value. As such the slip during asynchronous operation after loss of excitation is increased, the allowable load and time for asynchronous operation are smaller and shorter. On the other hand, more active power needs to be absorbed from the system, therefore it is very bad for stable operation of the system. 2). The time constant is increased. The stator circuit time constant Ta and the ratio Ta/Ta' are singnificantly increased. In case of short circuit, the attenuation of stator acylic current is slow and the entire short circuit current is deviating at a side of the time axis for a number of power frequency cycles, making that the CT more easily saturated and the correction operation of protection is greatly affected. 3). The inertia time constant is decreased. The volume of large generators does not increase in direct proportion to the capacity, in which the utilization rate of material is higher and thus the directe effect of lower inertia contant H is caused. The inertia time constant of 600MW generator is at about 1.75, and the unit is more likely to experience oscillation under disturbance. 4). The thermal capacity is reduced. Another effect of higher utilization rate of material is that the thermal capacity of generator (WS/°C) is significantly reduced compared to copper loss and core loss.For example, the stator winding symmetric overlaod capability of 200MW generator and lower is 1.5 times of rated current, with an allowable operating time of 120S, the rotor winding overload capacity is 2 times of rated excitation current, with an allowable operating time of 30S; while for 600MW steam turbine generator, the stator winding overload capacity is specified to be 1.5 times of rated current with a time of 30S, and the rotor winding overload capability is 2 times of rated excitation current with a time of 10S. The rotor surface capability of withstanding negative sequence overload I 2t , for small and medium generators 2

(indirect cooling mode) it is 30S and for 600MW (directing cooling mode) generator it is 10S. 2.18 Relay protection configuration 2.18.1 Configuration features of protection Two complete electrical quantity protections are provided, either using different groups of CT and PT and having separate output trip circuits. 115

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In addition to the UN5000 excitation system of ABB, the rotor earthing protection of generator is also achieved by the separate protection. The rotor earthing protection is provided with one earthing point, with the first time limit for alarm and the secone for trip. 2.19 Composition of Generator Protections The device for generator protections are 7UM6225 and 7SJ602 produced by Simens Co., Ltd. 2.19.1 Generator Differential Protection The numerical current differential protection of the 7UM62 is a high speed selective short-circuit protection for generator。Differential protection systems operate according to the principle of current comparison and are therefore also known as current balance protection systems. They utilize the fact that in a healthy protected object the current leaving the object is the same as that which entered it。Any measured current difference is a certain indication of a fault somewhere within the protected zone. The protected zone is limited by the CTs in the neutral point of generator and the CTs at the terminal side. 2.19.2 Generator 95%-Stator Earth Fault Protection The stator earth fault protection detects earth faults in the stator windings of three phase machines. The criterion for the occurrence of an earth fault is mainly the emergence of a displacement voltage. This principle makes possible a protected zone of 90 % to 95 % of the stator winding. The displacement voltage UE can be measured either at the machine starpoint via voltage transformers or neutral earthing transformers or via the e-n winding (broken delta winding) of a voltage transformer set 2.19.3 Generator 100%-Stator Earth Fault Protection The 100 % stator earth fault protection detects earth faults in the stator windings of generators which are connected with the network via a unit transformer. This protection function, which works with a 20 Hz injected voltage, is independent of the network frequency displacement voltage appearing in earth faults, and detects earth faults in all windings including the machine starpoint. The measuring principle used is not influenced at all by the generator operating mode and allows measurements even with the generator at standstill. The basic principle is shown in the following figure. An external low frequency alternating voltage source (20 Hz) injects into the generator starpoint a voltage of max. 1% of the rated generator voltage. If an earth fault occurs in the generator starpoint, the 20 Hz voltage drives a current through the fault resistance. From the driving voltage and the fault current, the protective relay determines the fault resistance. The protection principle described here also detects earth faults at the generator terminals, including connected components such as voltage transformers.

2.19.4 Generator Reverse Power Protection Reverse power protection is used to protect a turbo-generator unit on failure of energy to 116

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Generator Relay Protection

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the prime mover when the synchronous generator runs as a motor and drives the turbine taking motoring energy from the network. This condition leads to overheating of the turbine blades and must be interrupted within a short time by tripping the network circuit-breaker. For the generator, there is the additional risk that, in case of a malfunctioning residual steam pass (defective stop valves) after the switching off of the circuit breakers, the turbine-generator-unit is speeded up, thus reaching an overspeed. For this reason, the system isolation should only be performed after the detection of active power input into the machine. The reverse power protection of the 7UM62 precisely calculates the active power from the symmetrical components of the fundamental waves of voltages and currents by averaging the values of the last 16 cycles. The evaluation of only the positive phasesequence systems makes the reverse power determination independent of current and voltage asymmetries and rresponds to actual loading of the drive end. 2.19.5 Generator Low Forward Protection The machine protection 7UM62 includes an active power supervision which monitors whether the active power falls below one set value as well as whether a separate second set value is exceeded. Each of these functions can initiate different control functions. When, for example, with generators operating in parallel, the active power output of one machine becomes so small that other generators could take over this power, then it is often appropriate to shut down the lightly loaded machine. The criterion in this case is that the "forwards" power supplied into the network falls below a certain value. In many applications it can be desirable to issue a control signal if the active power output rises above a certain value. The device calculates the active power from the positive sequence systems of the generator currents and voltages. The computed value is compared with the set values. 2.19.6 Generator Low Impedance Protection Machine impedance protection provides backup protection functions to the main protection of generator. Pickup is implemented as overcurrent pickup and can be optionally supplemented by an undervoltage seal-in circuit. After numeric filtering, the currents are monitored for ver-shooting of a set value. A signal is output for each phase where the set threshold has been exceeded. These pickup signals are considered for choosing the measured values. The pickup is reset when 95% of the pick-up threshold is undershot, unless maintained by the undervoltage seal-in feature. For calculating impedance only the currents and voltages of the faulty (shorted) phase loop are decisive. Accordingly the protection, controlled by the pickup, evaluates these measurement values Loop Selection • The corresponding phase-earth loop is used for a 1-pole pickup • With a 2-pole pickup, the phase-phase loop with the corresponding phase-tophase voltage is used for impedance calculation. • With a 3-pole pickup, the phase-phase loop with the highest current value is used and with equal current amplitudes Since the impedance protection is multi-stage, the protected zones can be chosen such that the first stage (ZONE Z1, T-Z1) covers faults in the generator and the lower voltage side of the unit transformer, whereas the second stage (ZONE Z2, ZONE2 T2) covers the network. It should be noted that high voltage side 1-pole faults cause impedance measurement errors due to the star-delta connection of the unit transformer on the lower voltage side. An 117

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Generator Relay Protection

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unwanted operation of the stage can be excluded since the fault impedances of power system faults are modeled too high. 2.19.7 Generator Under Frequency Protection& Generator Over Frequency Protection The frequency protection detects abnormally high and low frequencies of the generator. If the frequency lies outside the admissible range, appropriate actions are initiated. Frequency protection consists of the four requency elements f1 to f4 (47Hz,48Hz,49Hz51Hz),theses stages are used alternatively for frequency decrease or increase separately. The frequency can be determined as long as at least one of the phase–to–phase voltages is present and of sufficient magnitude. If the measurement voltage drops below a settable value Umin, frequency protection is blocked because precise frequency values can no longer be calculated from the signal. 2.19.8 Generator Overvoltage Protection Overvoltage protection serves to protect the electrical machine and connected electrical plant components from the effects of inadmissible voltage increases. Overvoltages can be caused by incorrect manual operation of the excitation system, faulty operation of the automatic voltage regulator, (full) load shedding of a generator, separation of the generator from the system. The setting of limit values and time delays of the overvoltage protection depends on the speed with which the voltage regulator can regulate voltage variations. The protection must not intervene in the regulation process of the faultlessly functioning voltage regulator. For this reason, the two-stage characteristic must always be above the voltage time characteristic of the regulation procedure. 2.19.9 Generator Overload Protection The thermal overload protection prevents thermal overloading of the stator windings of the machine being protected. The device calculates the overtemperature in accordance with a single-body thermal model .When an initial settable overtemperature threshold is reached, an alarm is issued for load reduction measures. If the second overtemperature threshold is reached, the protected equipment is disconnected from the network. 2.19.10 Generator Loss of Excitation Protection The loss-of-field protection protects a synchronous machine from asynchronous operation in the event of faulty excitation or regulation and from local overheating of the rotor. Furthermore, it avoids endangering network stability by underexcitation of large synchronous machines. To assess underexcitation the device processes all three terminal phase currents and all three terminal voltages for the stator circuit criterion. It also processes the excitation voltage for the rotor circuit criterion . For the stator circuit criterion the admittance is calculated from the positive sequence currents and voltages . The admittance measurement always produces the physically appropriate stability limit as the figure shows:

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Generator Relay Protection

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The underexcitation protection in the 7UM62 makes available three independent,freely combinable characteristics. it is possible to model static machine stability by means of two partial characteristics with the same time delays (T CHAR. 1 = T CHAR 2). The partial characteristics are distinguished by the corresponding distance from the zero point (1/xd CHAR. 1) and (1/xd) CHAR. 2) as well as the corresponding inclination angle α1 andα2. If the resulting characteristic (1/xd CHAR.1)/α1; (1/xd CHAR.2)/ α2 is exceeded (in the following figure on the left), a delayed warning or a trip sign al is transmitted.A further characteristic (1/xd CHAR.3 /α3 can be matched to the dynamic stability characteristic of the synchronous machine. Since steady operation is impossible if this characteristic is exceeded, immediate tripping is then required (time stage T CHAR 3).

2.19.11 Generator Back-up Overcurrent Protection(Voltage Controlled) The inverse-time overcurrent protection is used as back-up protection for the machine short-circuit protection (differential protection and/or impedance protection). In generators where the excitation voltage is taken from the machine terminals, the short-circuit current subsides quickly in the event of adjacent faults (i.e. in the generator or unit transformer region) due to the absence of excitation voltage. Within a few seconds it sinks below the pick-up value of the overcurrent time protection. In order to avoid a dropout of the pickup, the positive-sequence component is monitored additionally. This component can influence the overcurrent detection in this ways: If the value falls below a settable voltage threshold, an overcurrent stage with a lower pick-up value is enabled.

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Generator Relay Protection

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2.19.12 Generator Unblanced Load Protection Unbalanced load protection detects unbalanced loads of three-phase induction motors. Unbalanced loads create a counter-rotating field which acts on the rotor at double frequency. Eddy currents are induced at the rotor surface leading to local overheating in rotor end zones and slot wedges. Another effect of unbalanced loads is overheating of the damper winding. The unbalanced load protection of 7UM62 uses numerical filters to dissect the phase currents into their symmetrical components. It evaluates the negative-phase sequence current I2. If the negative phase-sequence current exceeds a parameterized threshold value, the trip time starts. A trip command is transmitted as soon as this trip time has expired. Warning Stage: If the value of the continuously permissible, negative phase-sequence current I2> is exceeded, after expiry of a set time T WARN a warning message „I2> Warn“ is issued。 Thermal Characteristic:The heating up of the object to be protected is calculated in the device as soon as the permissible unbalanced load I2> is exceeded. In this context, the current-time-area is calculated constantly to ensure a correct consideration of various load cases. As soon as the current-time-area ((I2/IN)2 · t) has reached the K asymmetry factor, the thermal characteristic is tripped. Definite Time Tripping Stage:High negative phase sequence currents can only be caused by a two-pole power system short circuit which must be covered in accordance with the network grading plan. For this reason, the thermal characteristic is cut by a selectable, independent negative phase-sequence current stage. 2.19.13 Generator Pole Slipping Protection Depending on power network conditions and feeding generators, dynamic occurrences such as load jumps, short-circuits not disconnected quickly enough, auto-reclosure or switching actions, may cause system swings. Such power swings endanger power network stability. Stability problems often result from active power swings which can lead to pole-slipping and generator overloading. The out-of-step protection is based on the well-proven impedance measurement and evaluation of the complex impedance vector trajectory. The impedance is calculated from the positive sequence fundamental frequency components of the voltages and currents 2.19.14 Generator Interturn Protection The interturn protection detects faults between turns within a generator winding (phase). This situation may involve relatively high circulating currents that flow in the short-circuited turns and damage the winding and the stator. The protective function is characterized by a high sensitivity. The figure shows the basic principle of measurement. The displacement voltage is measured at the open delta winding by means of 3 two-phase isolated voltage transformers. So as to be insensitive towards earth faults, the isolated voltage transformer starpoint has to be connected to the generator starpoint by means of a high-voltage cable. In the event of an interturn fault, the voltage in the affected phase will be reduced

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Generator Relay Protection

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causing a displacement voltage that is detected at the broken delta winding. The sensitivity is limited rather by the winding asymmetries than by the protection device. 2.19.15 Generator Rotor Earth Fault Protection Rotor earth fault protection is used to detect earth faults in the excitation circuit of synchronous machines. An earth fault in the rotor winding does not cause immediate damage; however, if a second earth fault occurs it constitutes a winding short-circuit of the excitation circuit. The resulting magnetic imbalances can cause extreme mechanical forces which may destroy the machine. The rotor earth fault protection in the 7UM62 uses an external system frequency auxiliary voltage of approximately 36 to 45 V AC, This voltage is symmetrically coupled to the excitation circuit and simultaneously connected to the measurement input UE of the device provided for this purpose. The coupled voltage drives a small charging current (normally a few mA) through the coupling unit, as the case may be the brush resistance and the capacitance to earth of the excitation circuit. This current IRE is measured by the device. The rotor earth fault calculation calculates the complex earth impedance from the auxiliary AC voltage URE and the current IRE. The earth resistance RE of the excitation circuit is then calculated from the earth impedance. The earth resistance supervision has two stages. Usually an alarm is issued if an initial stage is undershot. If the value falls below the second low-resistance stage, tripping will be initiated after a short time delay。 2.19.16 Generator Cooling Water Loss 2.19.17 Generator Rortor Overload Protection The same as the generator overload protection. 2.19.18 Turbine Stearm Valve Closed 2.19.19 Generator Overexcitation Protection Overexcitation protection is used to detect inadmissibly high induction in generator. An increase in induction above the rated value very quickly saturates the iron core and causes large eddy current losses. The protection must intervene when the limit value for the protected object is exceeded. The overexcitation protection feature servers to measure the voltageU/frequency ratio f, which is proportional to the B induction and puts it in relation to the BN nominal induction. Overexcitation protection includes two staged characteristics,The first stage results alarm and excitation reduction,the second stage results trip. 2.20 Composition of Excitation Transformer Protections 2.20.1 Excitation Transformer Overcurrent Protection 2.20.2 Excitation Transformer Overload Protection

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Microcoputer Dynamic Recorder for Generator-transformer Unit

NAGARUNA THERMAL POWER PROJECT UNITS-#1&2

Chapter Ⅷ Microcomputer Dynamic Recorder for Generator-transformer Unit 1.

Introduction LBD-MGR-8000 is based on the hardware of original recorder. It is new generation of embedded dynamic recorder with independent intellectual property. They are mainly applied for recording voltage, current and relay protection device’s action sequence under different fault states in power system, to help operators analyzing the failure cause correctly.

2.

Technical Characteristics 2.1 High Performance Design with Embedded Hardware Platform It can accomplish calculations of kinds of initiate mode in a short time to judge the fault rapidly and accurately for the sample and calculations are performed by 32-bit floating DSP that is low consumptive and powerful in calculation. EXT embedded main board without fan is in charge of data processing. The main board is low consumptive, stabile, reliable and tailored arbitrarily according to actual demand to design kinds of I/O mode. The stability and reliability are improved greatly because of the application of large scale of programmable logic device, craft of SMD and 6 layers PCB. 2.2 Stabile and Efficient Design with Embedded Software Platform We adopt multitask real-time embedded operating system used by international military. The system has many efficient characteristics, such as simplify the program, tailor the program according to actual demand, run in junior embedded system and occupy less computer resource. The use of embedded system avoids computer virus and despiteful attack on the net, it ensures that user′ mistake or virus would not damage or paralyze the system. 2.3 High-speed Data Acquisition The maximum sampling frequency is up to 20 kHz and the resolution of digital event channels is 0.05ms. It provides high quality data source for analyzing fault, distance-measurement, monitoring operating state in detail; It is helpful discover the limitation of the new device and the hidden problems of the device operating for years for operators; It is useful to reoccur fidelity fault wave, reflect the quality of power support truly, discover the abnormality of operating device. 2.4 Humanity Visual Self-diagnostic Warning Function The self-check on main surface mount chip is necessary because of redundant design of hardware. The error display visually if chip is damaged, avoiding the defect that the serviceman can not maintain when the network interrupt or the back computer fail; It also can be reported by remote 122

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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dispatching or transmitted to analyze station. 2.5 Independent Operation in Safe Mode The set adopts 6U panel design and has perfect ability to protect the set from disturbance. It is convenience to install, maintain and debug. Create running and operating log automatically and record the operation status in detail for reference. To output and display wave analysis, the set configures with large screen TFT liquid crystal display. 2.6 Transient, Steady-state Data Adopt Independent Double Channel Storage, Transmission Technology Transient data and steady-state data store and transmit independently. It has steady-state record function to record data in normal system, including electric parameters, such as voltage, current, active power, reactive power, frequency etc. The set begins to record consecutively when it starts normally, it goes on when something abnormal happen to the system or it records transient data because of fault start. It ensures that the data in the whole procedure of per disturbance can be recorded completely when long-time disturbance (pollution of system for example) happen to the power network consecutively for many times. 2.7 Security Storage of Large Volume Data The set adopts advanced hardware design to save record data directly to disk. For large capacity of storage medium have the ability to record consecutively, the volume of memory has no effect on the volume of the record data. Backup data dually ensure the security against the influence of network and power down. 2.8 Network Function Support TCP/IP communicate protocol; Support IEC 870-5-103 communicate protocol; Support Ethernet; Support multiple communicate modes such as double cord, coaxial cable, optic fiber, phone line. It is convenience to communicate and combine network with other management system. 2.9 Electrical Test Function Exciter no-load test: Generator short test; Generator no-load test; Main exciter load test while generator no-load ; Main exciter load test when generator short; Generator no-load excitation-loss test; Excitation system step response test; Generator zero-initial voltage boosting test; Main transformer zero-initial voltage boosting test; Network incorporated synchronically test; self-defined test etc. 3

Technical Parameters 3.1 Maximum Sampling Frequency: 20kHz； 123

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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Modular Transforming Precision: 16 bits; Resolution of Digital Event Channels: 0.05ms； The Highest Harmonic Resolution Ratio: 99 times. 3.2 Data Recording Mode The mode is classified into steady record and transient record, the data is marked with absolute time. 3.2.1

Steady Record

It records electric parameters consecutively, such as voltage, current, active power, reactive power, frequency etc. The interval of the data can be set as 0.02s or 1s. 3.2.2

Dynamic Record

3.2.2.1 Mode of Dynamic record: Dynamic record was divided into A, B, C and D to record consecutively. The set starts to run automatically when disturbance happen to power network, it records as follow： A : data before disturbance, the record time can be set as 40ms to 500ms. B : data after disturbance, the record time can be set as 100ms to 1000ms, the frequency can be set as 20/10/5/2kHz. C :data after disturbance, the record time can be set as 1s to 20s, the frequency can be set as 1/0.5 kHz. D: If concussion happen to the system, the record time can be set as 10 to 30 minutes, the sampling frequency can be set as 50/10/1Hz. 3.2.2 .2 Start Condition The first start: Start automatically and run sequentially as A-B-C when any start condition is satisfied. Repeat start: run repeatedly when new start conditions appears. Halt automatically when recording finishes. 3.3 Rated Parameters: AC voltage: Un=57.7V, 100V; 2*Un: Long time running; AC current: In=5A, 1A; 2*In: Long time running; 124

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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Lasting 10s when 20 times overload; Lasting 1s when 40 times overload; High frequency signal:-10V～+10V, -5V～+5V; Non-electric parameters: sensor output such as temperature, pressure and so on; Digital：Normally open, normally closed passive dead contact. 3.4 Power Source: AC: 220V, accepted deviation: -20%~+10%; Frequency: 50Hz ± 0.5Hz, accepted deviation: -5%~+5%; DC: 220V or 110V, accepted deviation: -20%~+10% 3.5 Start Mode: It includes analog start, digital start and manual start mode. 3.5.1 Analog Start 1). Positive-sequence component start: It includes positive-sequence over-voltage start and low-voltage start 2). Negative-sequence component start: It includes negative-sequence voltage start and current start. 3). Zero-sequence component start: It includes zero-sequence voltage components start and zero-sequence current component start. 4). Oscillation start: It starts while the current fluctuates for 10% in 1.5s. 5). Frequency difference start and frequency change rate start: It monitor that the frequency bias normal range or not. 6). Stator winding earth-fault start: Fundamental wave zero-sequence voltage over limit start; The terminal third harmonic voltage start; The third harmonic voltage (between the terminal and the neutral) start rate. 7). Low-frequency over-current start: Set against the short fault of the units start processing. 8). Over-excitation start: Monitor the over-excitation of the generator-transformer unit. 9). Generator excitation-loss, low-excitation start: Voltage among rotor poles under amount start; Reactive power reverse start. 10). Reverse-power start: Start reverse-power criterion through judging the direction of 125

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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active power from generator terminal. 11). Rotor winding earth-fault start: It includes rotor positive voltage to ground, negative voltage to ground and voltage between positive pole and negative pole. 12). Stator and rotor winding overload start: Take the current of generator terminal and DC excitation current of rotor winding as start mount to judge the fault. 13). Other starts: Any input analog can be used as start mount, the start mode includes abruption component start and over or under limit start. 3.5.2 Digital Start Any one or multiplex digital value can be set as start value. The mode includes switch-on start and switch-off start. 3.5.3 Manual Start 3.6 Warning Signal It includes power down warning signal, record start signal, error-warning signal. The signal output while providing relay connection, which can be connected to center signal circuit. 3.7 The set has perfect function of data analyzing, error distance-measurement adopts multiple algorithms to calculate synthetically and reach high precision of 2 percent error of metallic earth. 3.8 Realizing many timing modes including GPS module timing, impulse timing, serial port timing. Sampling synchronously all the net is realized through GPS satellite synchronous clocking, while record data with absolute time standard made the remote dynamic recorder realized data analyze synchronously. 3.9 Communication The set provides Ethernet port with standard TCP/IP protocol and adopt IEC 870-5-103 communicate protocol. The recorder can share data when connected to local MIS net and realize remote control through connecting Ethernet card to MIS net. It completes the function of data transfer, remote display, setting modification, manual start. 3.10 Work Environment Temperature: -5°C～+45°C Relative humidity: ≤90 % 3.11 Size Standard PK-10 cupboard: 2260/2360(Height) mm × 800(Width) mm × 600(Depth) mm. It can be made for special. 126

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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3.1 Hardware Illustration The set adopts 6U panel design and has perfect ability to protect the set from disturbance. It is convenience to install, maintain and debug. The board distribute from the left to the right as: X1 to X6: analog input board；X7: main board; X8: digital input board; X9: power board. 4.1 The Upper Layer Board It includes Indicator lights of power, run, start and error. Power indicator light：It is on when the power source works well. Run indicator light: It flashes when units work well. When there is something wrong, it will always be on or off. Start indicator light：It is on when units begin to record. Error indicator light：When something wrong occurs in the units, it is on. 4.2 Analog Input Board: It can accomplish data-collection and calculation of 12 analog channels and transient record start discrimination with 32-bit high-speed DSP and 16-bit A/D chip. To meet the demand of kinds of measure scale through regulating the secondary side of the isolated transformer, AC analog take high precision isolated transformer as transform device. 4.3 Main Board It is composed with ETX industrial computer as the core. It completes the task of monitoring management, saving the settings, storage and transfer of record data. It controls all boards and transfer data through the bus. 4.4 Digital Input Board The use of 32 bit high-speed DSP made it capable to accomplish data-collection of 128 digital channels and digital start discrimination of transient record. To eliminate Common Mode Interference caused by power and common ground wire, the internal bus thought optical isolator is isolated from input circuit absolutely. 4.5 Power Board There are 5V, ±12V, 24V for the inside and start signal relay, error alarming relay, signal reset relay on the board.

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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3.2 Recorder Monitor Software Illustrations The software mainly completes the task of running and adjusting management, setting value’s adjustment, recording data’s storage and printing. Supply power to the set, it will start system, and go into the main interface of the software automatically. 5.1 Main Interface The running state of the set displayed on the page header. The recent 1000 data recording information list in the page. The information include data file name, start type, starting channel number and size of the file. Double clicking the item in the list box will open the analysis software automatically where you can analyze the data file.

5.2 Integrated Settings There are communication parameters, password and exit submenu in this menu. 5.2.1 Communication Parameters The default local IP address is 10.0.4.1; the communication parameters include port and IP address. You can communicate one or two sets through setting the port and IP address. Default port is 2404; Default IP address of set is 10.0.4.11(the other is 10.0.4.12). 5.2.2 Password Set or change the operating password.

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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5.2.3 Exit After verifying the password, exit the program. 5. 3 1# settings (or 2# settings) There are manual start, run settings, system settings, channel attributes, RMS, digital state, proportion factor, digital output debug, analog zeroing, manual set time, printer select, print font select, analog settings print and digital settings print.

5.3.1 Manual Start Pressing the submenu, the sets will start record man-made and create data files. 5. 3.2 Run Settings The settings include over or under of analog, rate of change of analog, digital, sequence component and other, etc. If the value you set is 0, it will quit this start mode. Change the settings value through input by keyboard. Pressing the OK button or ENETER key, confirm the change and exit. Pressing CANCEL button, the value is invalid.

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5. 3.2.1 Over/Under and Abruption Settings Set the settings of the analog channels. For the over/under settings, upper limit settings must be more than the lower limit. The reference values: Upper limit settings: 110% of Un; Lower limit settings: 90% of Un; Upper limit settings of 3U0: 10% of Un or 8~10V; Upper limit settings of 3I0: 10% of In or 1A; Rate of change: 10% of rated value. 5.3.2.2 Digital Settings

To select channel enabled or disabled with mouse, if choose channel enabled, then select Digital

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start: “closed-open”, “open-closed”. Press the OK button or ENTER key to save the change and exit. Press CANCEL button to exit directly. 5.3.2.3 Sequence and Others Settings Set the DSP board type in the system parameter (reference 5.3.3.1) first. The settings of the generator terminal board include all of the settings. The settings of main transformer board include positive-sequence voltage upper limit settings, positive-sequence voltage lower limit settings, negative-sequence current over limit settings, negative-sequence over limit settings, over-excitation settings. The other board has no settings in the page.

The reference value: Positive-sequence voltage upper limit settings: 100%Un; Positive-sequence voltage lower limit settings: 90%Un; Negative-sequence current over limit settings: 10%Un; Negative-sequence voltage over limit settings: 10%Un; Over-excitation settings: 1.1 ~1.3; Reverse-power settings: 3% of rated power; The Third Harmonic of zero-sequence over limit settings: 0.5~10V; Ratio of third harmonic over limit settings: 1.1~1.3; Reactive power reverses settings: 3% of rated power; The current fluctuates for 10% in 1.5s: 10% of rated current. 131

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5.3.2.4 Debug Settings To facilitate debugging, set some commonly used parameters. When using, select by the mouse. For all settings, press OK button or ENTER key to pass the password authentication, the settings will be confirmed. The settings save in the hard disk that exchanges the Original settings. At the same time, the settings transmit to the record sets. If errors occur when saving the settings such as network communication error, the hint will be displayed on the screen. Since the settings are directly related to the operation of the device, we should ensure the value correct and preserve effectively. 5.3.3 System Settings 5.3.3.1 DSP Kind Double click the DSP item to select the type of the board: generator terminal board, main transformer board and the other board. 5.3.3.2 Other Settings Sampling frequency of period A and B: 20/10/5/2 kHz Optional, Default: 10 kHz； Sampling frequency of period C：1/0.5 kHz Optional，

Default: 1 kHz；

Sampling frequency of period D：50/10/1 Hz Optional， Default: 1 Hz； Sampling length of period A：

40ms-50ms Optional， Default: 40ms；

Sampling length of period B：

100ms-10000ms Optional，Default: 100ms；

Sampling length of period C：

1s-20s Optional，

Sampling length of period D：

10min-30min Optional， Default: 1 min；

Default: 1s；

Analog threshold voltage of start: 50V(DR is running)、0V(Sets is testing); Settings of Frequency deviation: 0.5Hz; Settings of Frequency rate of change: 0.1Hz/s。 When complete setting, click the OK button to effect the settings and close the integrated settings dialog. Click the CANCEL button to exit the integrated settings dialog directly. 5.3.4 Channel Attributes Set the analog channel attributes which include analog channels name, signal frequency, phase sequence, units of the first and units of the second. Set the digital channel attributes that include digital channels name. 132

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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5.3.5 RMS The RMS and phase angle of all of analog channels display real-time. 5.3.6 Proportion Factor

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To adjust the precision of the analog channel, input the actual value and the channel number that has the signal in corresponding location, then click compute button, the proportion factor will be computed automatically and hint you to save the right value. Note: the actual input signal must be integer. 5.3.7 Digital Output Debug

The function of this menu is to test the indicator lights on the upper layer board and the contact of digital output. It includes start indicator light, set error indicator light and Reset signal. 5.3.8 Analog Channels Zeroing

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In the analog channels zeroing dialog, you can adjust the zero of the sample board or single channel. Note: prudent use of this function for the DC channel. 5.3.9 Manual Set Time Transmit the time of the background computer to the sets. It is used for debugging the GPS. 5.3.10 Settings Print You can print the segment info, analog settings and digital settings.

3.3

Analysis Software

The analysis software is mainly applied to backstage unit, analysis substation or other manager. It can analyze the data file transmitted by the communication software, and help operators analyze the failure cause correctly. The function of the software includes file manager, view, system parameters, display control, analysis (phasor computation, sequence quantity computation, frequency computation, power computation, power angle analysis, synchronous, harmonic analysis, current fluctuates analysis, third harmonic computation, measured impedance computation, digital change table, fault report,

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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distance-measurement), print etc. In the analysis software, all of the analysis and server function are based on the waveform. 6.1 Hardware and Installation Windows98/2000/XP，Memory: 256M. It’s a green software and no installation. There are 4 files in the folder that are wlbfx.exe, fushi.dll, mgr.dll and wtfx.exe. Double click the “wlbfx.exe” in the explorer or my computer to open the analysis software. 6.2 How-to-use 6.2.1 Start The software main interface will occur when startup the software. It includes 4 parts: menu and hot key tool bar, channel indication bar, state indication bar and channel waveform display zone. The menu and hot key tool bar can complete all kinds of functions provided by the program and all function is included in menu function.

Menu and Hot key tool bar The function offered by the hot key tool bar is already included in the menu. Channel indication bar display the screen channel information. State indication bar indicates the time where is the time-mark line. Channel waveform display zone is used to display current channel waveform of screen channel.

6.2.2 Instruction of Menu Function 6.2.2.1 File In the file menu, there are submenus of open data file, open record database, open directory, import, export COMTRADE, print screen, option, exit etc. 136

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6.2.2.1.1 Open Data File Choose Open Data File of file. The Open Data File dialog will be view. Select the drive and the path that you want to get a file form, the list box will display the files corresponding to the format chosen. Use the mouse or the UP, DOWN key to select the data file, and in the right of the dialog, you can find the data file information such as user name, startup time, startup type, startup channel and fault time length etc. Select the data file that you want to analysis, press Open to get the Analysis window.

6.2.2.1.2 Open Record Database Recorder Monitor Software stores the data files in the default directory. Choose Open Record Database of file. The Records list of faults currently is available to your PC appears. Double click the selected record to open it, or select record first, press the open button to open it and close the dialog.

6.2.2.1.3 Open Directory Choose this submenu, open the explorer to view the default directory of data files. You can copy and find the useful data file conveniently. 6.2.2.1.4 Import Reserved to compatible other format of data file. 6.2.2.1.5 Export COMTRADE 137

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Microcoputer Dynamic Recorder for Generator-transformer Unit

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Change the opened data file to COMTRADE. 6.2.2.1.6 Communication Ethernet communication. Execute the “ping + Ip address” command in start menu to ensure that the net is communicated. It is used to transmit the data files and also can start record manually from remote. 6.2.2.1.7 Print Screen Copy the current screen to the clipboard. 6.2.2.1.8 Option This submenu is used for setting the operating parameters needed by the program. It includes analog channel display ratio and Directories setting. In the analog channel display ratio sheet, you can set each of the channel display ratio; In the directories setting sheet, you can set the directories used by Analysis center. 6.2.2.1.9 Exit To exit the analysis software, press “Exit” of “File”, or click the right-button of the mouse to popup the menu then select the “exit” submenu. 6.2.2.2 Display Control It includes many control functions for waveform displayed on channel, e.g. waveform compression and tension on time axis, coaxial display of all channels on the same time axis, waveform displayed on different time axis, mixed display of analog channel and digital channel waveform, all display of analog channel and digital channel waveform. You can click the shortcut on the hot key tool bar to control the waveform compression and tension. Program implies that all analog show in different time axis during the first running. Use Page Up、Page Down and CTRL+ “↑”、 CTRL+ “↓” to choose different channels and input analog or digital on channel indication bar to choose waveform. There are channel name and value where the time-mark line is in the channel indication bar. Pressing the right button of the mouse on the channel name to popup the menu, in this menu you can change the channel to display, adjust the display ratio of Y axis. The button upon the channel indication bar is used to choose the amplitude or RMS. To change the display time，you can drag the time-mark line to the place or double click the position where you want the time-mark line to be. To position precisely, press the LEFT, RIGTH key on the keyboard. In the state indication bar, the relative time and the absolute time of the current file is displayed. Right click the mouse to popup the menu, select the second time-mark line in the waveform display zone. The distance of the two time-mark line stands for time length. The distance 138

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of the two time-mark line can be fixed as half cycle, one cycle, two cycles frequently. Use the quick positioning function to set the main time-mark line to the start time of each period. 6.2.2.3 Analysis This menu includes all of the analysis function. 6.2.2.3.1 Power Angle Analysis Using unit value saturated reactance to compute the power angle and show the power angle curve. Moving the mouse or “←” and “→” to observe the value at different time. 6.2.2.3.2 Synchronous The function of the submenu is to analyze frequency different of the generator and transformer when the digital channels start. The window shows the frequency different curve of setting generator and transformer and amplitude, phase of setting analog channel. Moving the time cursor, it will display frequency different and amplitude, phase of analog channel at different times. 6.2.2.3.3 Harmonic analysis It is used to determine the content of harmonic component of any analog in any one time-interval. The highest harmonic frequency is up to 99 times. The compute result is list in the list box. It also lists the percentage of harmonic component to fundamental component. It can dispose four analog signals in the same time at most. The compute result can be printed. The result of one channel signal can be printed to 99 times, and multi channel signals can be printed to 49 times.

6.2.2.3.4 Current Fluctuates Analysis The user can compute four group of the current fluctuate value which is generator, transformer, and defined by the users. The channels which to be analyzed can be defined by the user. 139

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6.2.2.3.5 Phasor Computation It is used to compute the fundamental voltage or the amplitude and phase position of the three A, B and C phases and the amplitude at any time, it adopts Fourier algorithm. You can input number in the channel number column to analyze different channel. And you can change different time in the compute time combo box with click the up and down arrow of the combo box or fix the cursor in the combo box then press the UP, DOWN key in the keyboard to analyze the value at different time. Press “Print” button, to print the result at current time.

6.2.2.3.6 Sequence Quantity Computation It is used to compute the amplitude and phase position of the positive, negative and zero sequence components at any time. It adapts Fourier algorithm, the steps are similar to phasor computation.

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6.2.2.3.7 Power Computation In this menu, you can achieve the active power and reactive power, and the power curve display in the screen. The user can change the compute channel and time span.

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6.2.2.3.8 Measured Impedance Computation Compute the measured impedance value of the generator. 6.2.2.3.9 Third Harmonic Computation Compute the third harmonic value of the selected channel. The default is the fourth channel but the user can change it. 6.2.2.3.10 Digital Change Table The digital change table is used to analyze and print the digital change state in the current data file. If the digital is changed, the digital channel number, change time, change state will be list in the list box. 6.2.2.3.11 Distance-measurement You can analyze the distance-measurement in the data file of lines. Select the parameters saved in the file or input the parameters manually before compute. 6.2.2.3.12 Fault Report Before printing the user can select the channels and time span which to be printed freedom. 6.2.2.3.13 Steady Data This submenu is used for analyzing the steady record data file stored during running. 6.2.2.4 Users In this menu, you can view or hide the toolbar, status bar and display toolbar. 6.2.2.5 Help It includes About sub-menu which used to show the version number.

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Esp Control System

NAGARUNA THERMAL POWER PROJECT UNITS-#1&2

Chapter Ⅸ ESP Control System

The control system is applied with upper & low order computer. The low order part is placed in the HV &LV panel and the communication cable is for duplexer and the communication principle is TCP/IP,MODBUS with the communication distance no more than 1500 meters.The control mode has two ways: remote and local, but the main control way is remote control. And the remote control part is placed in the dust-discharging control room. The two sets of upper order computer can be the back-up for each other, which mean if one set of upper order does not work; the other can control both two ESPs. The remote mode control can be alternated to the local control; either the local control can be switched to remote control. Here is a diagram of the control system for you to reference.

The core of the control system is the controller EPIK, so here is a detail introduction of the controller as follows. Zhejiang Sunyard environmental protection Engineering Co.,ltd has a great developing power and with the continuous innovation for which makes we lead a advanced place in the field of electrical control products and technology. The second generation controller for ESP of Zhejiang sunyard environmental protection Engineering Co.,Ltd is on the base of ALSTOM technology. The new feature of the controller is that each contains the EPOQ (Electrostatic Precipitator Optimizing Q algorithm) optimized software, PCR (Power Control Rapping) software and OpOpt(Opacity optimizing) software. The controller applied with the most advanced technology in the field of computer control, intellectual control, net communication and industrial field bus. The controlling mode “Checking-Diagnosis-Control” has greatly increased the capacity of the controller for ESPs. 1.

The main features of EPIK series controller: The controller chip is DSP (digital signal processor) with high speed and accurate 143

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Esp Control System

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sampling process. It monitors the second current & voltage on real time. It applies with the Spark level follow function and by setting the parameters such as the spark step, spark rate limitation rising time & slop in advance, then supplying the average current & voltage to the field by a line rising voltage way to stabilized the dust discharging rate. Compared with the traditional controller for ESP, the EPIK controller has a higher efficiency of dust discharging, more obvious energy saving effect and lower frequency rapping way. Generally speaking, the power saved is more than 30%, the absolute dust emission decreased more than 10% and the rapping frequency reduced more than 30%. The unique feature for the EPIK controller is that the controlling of high voltage part controlled silicon was fixed together with the rapping part in order to carry out the PCR (power control rapping) function. Moreover, the system of EPIK controller can be connected with MIS system, DCS system, Remote terminal Unit easily. 1.1

The EPIK main functions: Control function： a. Spark following control b. Peak value following control c. Flash frequency following control d. Phase recovery following control e. Use the auto intermission power supply and pulse power supply control（EPOQ）。 f. Feed-back of dust concentration control g. Reduction power rapping control Communication web control function： a. With standard industry Ethernet interface。 b. Transmit the signal of primary voltage & current, second voltage ¤t; spark rate, on-off, malfunction of the equipment, transformer or ESP problem signals under running mode to the master computer and DCS. c.The on-off function, voltage rising or reducing and adjusting could be operated through the CTR plate by the operator. Protect function： a. Load cut off, short circuit protection b. Over current protection c. Oil temperature over limitation protection & excitation protection Function on the panel a. Primary voltage & current, second voltage & current displayed on the meter。 b. Main loop closed up, equipment problem, transformer problem, ESP problem warning There are also some special and unique measures that the EPIK controller can 144

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Esp Control System

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actualize. 1). The average spark level follows function.

2). PCR software by changing the field intension when rapping to attain the aim of reducing the dust grain conglutination and improve the dust discharging effect.

3). The advanced optimize software for ESP power supply running(EPOQ)

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2

Esp Control System

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The Computer controlled communication system The ESPs High voltage control, rapping control, dust discharging control, heater control can all be monitored and actualized by the computer. The manage system is windows 2000, and the programming software is Ifix or VB 6.0. The system absorbs the advanced technology of ALSTOM and Zhejiang sunyard improve the function to make it suitable for different conditions. 2.1 Displaying screen T/R running table. It includes the communication state of each high voltage silicon controlled rectifier; I2 setting value, running mode and start & stop state; V1、V2、I1、I2 spark rate and running state.

2.2T/R sketch map Simulate the running value of each meter (primary V & I, second V & I) on the panel. 146

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Esp Control System

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2.3 Comparing diagram of the Current Use the different color to show the difference between the setting value and real value of second current for each rectifier.

2.4 The record table of T/R state. Record the error occurred time and at this time the value of V1、I1、V2、I2

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2.5 Rapping running Display the start time, stop time and running period of the rapping motor.

Protract the curve and display the power, opacity for each casing

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600M.W.PLANT Electric Course

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