ShortcircuitIEC
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ShortCircuit Analysis IEC Standard
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
CORTO CIRCUITO Características principales:
Estándar de ANSI/IEEE & IEC. Análisis de fallas transitorias (IEC 61363). Efecto de Arco (NFPA 70E2000) Integrado con coordinación de dispositivos de protección. Evaluación dispositivos.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
automática
de
Slide 2
Purpose of ShortCircuit Studies • A ShortCircuit Study can be used to determine any or all of the following: – Verify protective device close and latch capability – Verify protective device interrupting capability – Protect equipment from large mechanical forces (maximum fault kA) – I2t protection for equipment (thermal stress) – Selecting ratings or settings for relay coordination ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 3
Types of ShortCircuit Faults
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 4
Types of ShortCircuit Faults Types of SC Faults •ThreePhase Ungrounded Fault •ThreePhase Grounded Fault •Phase to Phase Ungrounded Fault •Phase to Phase Grounded Fault •Phase to Ground Fault
Fault Current •ILG can range in utility systems from a few percent to possibly 115 % ( if Xo < X1 ) of I3phase
(85% of all faults).
•In industrial systems the situation ILG > I3phase is rare. Typically ILG ≅ .87 * I3phase •In an industrial system, the threephase fault condition is frequently the only one considered, since this type of fault generally results in Maximum current. ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 5
ShortCircuit Phenomenon
v(t)
i(t)
v(t)= Vm∗ Sin(ω t + θ ) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 6
v(t)
i(t)
di v(t)= Ri + L = Vm× Sin( ωt + θ ) (1) dt Solving equation 1 yields the following expression  t Vm Vm i(t)= × sin( ωt + θ  φ ) + × sin( θ  φ )×e L Z Z R
Steady State
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Transient (DCOffset)
Slide 7
AC Current (Symmetrical) with No AC Decay
DC Current
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 8
AC Fault Current Including the DC Offset (No AC Decay)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 9
Machine Reactance ( λ = L I )
AC Decay Current
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 10
Fault Current Including AC & DC Decay
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 11
IEC ShortCircuit Calculation (IEC 909) • Initial Symmetrical ShortCircuit Current (I"k) • Peak ShortCircuit Current (ip) • Symmetrical ShortCircuit Breaking Current (Ib) • SteadyState ShortCircuit Current (Ik) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 12
IEC ShortCircuit Calculation Method • Ik” = Equivalent V @ fault location divided by equivalent Z • Equivalent V is based bus nominal kV and c factor • XFMR and machine Z adjusted based on cmax, component Z & operating conditions ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 13
Transformer Z Adjustment • KT  Network XFMR • KS,KSO – Unit XFMR for faults on system side • KT,S,KT,SO – Unit XFMR for faults in auxiliary system, not between Gen & XFMR • K=1 – Unit XFMR for faults between Gen & XFMR ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 14
Syn Machine Z Adjustment • KG – Synchronous machine w/o unit XFMR • KS,KSO – With unit XFMR for faults on system side • KG,S,KG,SO – With unit XFMR for faults in auxiliary system, including points between Gen & XFMR
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 15
Types of ShortCircuits • NearToGenerator ShortCircuit – This is a shortcircuit condition to which at least one synchronous machine contributes a prospective initial shortcircuit current which is more than twice the generator’s rated current, or a shortcircuit condition to which synchronous and asynchronous motors contribute more than 5% of the initial symmetrical shortcircuit current ( I"k) without motors. ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 16
NearToGenerator ShortCircuit
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 17
Types of ShortCircuits • FarFromGenerator ShortCircuit – This is a shortcircuit condition during which the magnitude of the symmetrical ac component of available shortcircuit current remains essentially constant.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 18
FarFromGenerator ShortCircuit
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 19
Factors Used in If Calc • κ – calc ip based on Ik” • μ – calc ib for neartogen & not meshed network • q – calc induction machine ib for neartogen & not meshed network • Equation (75) of Std 609090, adjusting Ik for neartogen & meshed network • λmin & λmax – calc ik ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 20
IEC ShortCircuit Study Case
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 21
Types of ShortCircuits When these options are selected • Maximum voltage factor is used • Minimum impedance is used (all negative tolerances are applied and minimum resistance temperature is considered) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 22
Types of ShortCircuits When this option is selected • Minimum voltage factor is used • Maximum impedance is used (all positive tolerances are applied and maximum resistance temperature is considered) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 23
Voltage Factor (c) • Ratio between equivalent voltage & nominal voltage • Required to account for: • Variations due to time & place • Transformer taps • Static loads & capacitances • Generator & motor subtransient ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 24
Calculation Method
• Breaking kA is more conservative if the option No Motor Decay is selected
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 25
IEC SC 909 Calculation
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 26
Device Duty Comparison
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 27
Mesh & NonMesh If • ETAP automatically determines mesh & nonmeshed contributions according to individual contributions • IEC Short Circuit Mesh Determination Method – 0, 1, or 2 (default)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 28
LG Faults
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 29
LG Faults Symmetrical Components
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 30
Sequence Networks
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 31
LG Fault Sequence Network Connections If = 3 × Ia 0 3 × VPr efault If = Z1 + Z 2 + Z0 if Zg = 0
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 32
LL Fault Sequence Network Connections
I a 2 = − I a1 3 × VPr efault If = Z1 + Z 2
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 33
LLG Fault Sequence Network Connections I a 2 + I a1 + I a 0 = 0 = I a VPr efault If = Z0 Z 2 Z1 + Z0 + Z2 if Zg = 0
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 34
Transformer Zero Sequence Connections
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 35
Solid Grounded Devices and LG Faults Generally a 3  phase fault is the most severe case. L  G faults can be greater if : Z1 = Z 2 & Z 0 < Z 1 If this conditions are true then : I f3φ < I f 1φ This may be the case if Generators or Y/∆ Connected transformer are solidly grounded.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 36
Zero Sequence Model • Branch susceptances and static loads including capacitors will be considered when this option is checked • Recommended by IEC for systems with isolated neutral, resonant earthed neutrals & earthed neutrals with earth fault factor > 1.4
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 37
Unbalanced Faults Display & Reports Complete reports that include individual branch contributions for: •LG Faults •LLG Faults •LL Faults
Oneline diagram displayed results that include: •LG/LLG/LL fault current contributions •Sequence voltage and currents •Phase Voltages ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 38
Transient Fault Current Calculation (IEC 61363)
Total Fault Current Waveform
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 39
Transient Fault Current Calculation (IEC 61363)
Percent DC Current Waveform
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 40
Transient Fault Current Calculation (IEC 61363)
AC Component of Fault Current Waveform
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 41
Transient Fault Current Calculation (IEC 61363)
Top Envelope of Fault Current Waveform
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 42
Transient Fault Current Calculation (IEC 61363)
Top Envelope of Fault Current Waveform
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 43
IEC Transient Fault Current Calculation
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 44
Unbalanced Faults Display & Reports Complete reports that include individual branch contributions for: •LG Faults •LLG Faults •LL Faults
Oneline diagram displayed results that include: •LG/LLG/LL fault current contributions •Sequence voltage and currents •Phase Voltages ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 45
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 46
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 47
TEMA 2
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 48
Protective Device Coordination ETAP Star
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
ETAP START PROTECCION Y COORDINACION Características principales: Curvas para dispositivos.
más
de
Actualización automática Corriente de Corto Circuito.
75,000 de
Coordinación tiempocorriente de dispositivos. Autocoordinación de dispositivos. Integrados unifilares.
a
los
diagramas
Rastreo o cálculos en diferentes tiempos.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 50
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 51
Agenda • Concepts & Applications • Star Overview • Features & Capabilities • Protective Device Type • TCC Curves • STAR Shortcircuit • PD Sequence of Operation • Normalized TCC curves • Device Libraries
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 52
Definition • Overcurrent Coordination – A systematic study of current responsive devices in an electrical power system.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 53
Objective • To determine the ratings and settings of fuses, breakers, relay, etc. • To isolate the fault or overloads.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 54
Criteria • Economics • Available Measures of Fault • Operating Practices • Previous Experience
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 55
Design • Open only PD nearest (upstream) of the fault or overload • Provide satisfactory protection for overloads • Interrupt SC as rapidly (instantaneously) as possible • Comply with all applicable standards and codes • Plot the Time Current Characteristics of different PDs ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 56
Analysis When: • New electrical systems • Plant electrical system expansion/retrofits • Coordination failure in an existing plant
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 57
Spectrum Of Currents • Load Current – Up to 100% of fullload – 115125% (mild overload)
• Overcurrent – Abnormal loading condition (LockedRotor)
• Fault Current – Fault condition – Ten times the fullload current and higher ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 58
Protection • Prevent injury to personnel • Minimize damage to components – Quickly isolate the affected portion of the system – Minimize the magnitude of available shortcircuit
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 59
Coordination • Limit the extent and duration of service interruption • Selective fault isolation • Provide alternate circuits
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 60
Coordination C t
D B
A A C
D
B
I ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 61
Protection vs. Coordination • Coordination is not an exact science • Compromise between protection and coordination – Reliability – Speed – Performance – Economics – Simplicity ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 62
Required Data •
Oneline diagrams (Relay diagrams)
•
Power Grid Settings
•
Generator Data
•
Transformer Data – Transformer kVA, impedance, and connection Motor Data
•
Load Data
•
Fault Currents
•
Cable / Conductor Data
•
Bus / Switchgear Data
•
Instrument Transformer Data (CT, PT)
•
Protective Device (PD) Data – Manufacturer and type of protective devices (PDs) – Oneline diagrams (Relay diagrams)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 63
Study Procedure • Prepare an accurate oneline diagram (relay diagrams) • Obtain the available system current spectrum (operating load, overloads, fault kA) • Determine the equipment protection guidelines • Select the appropriate devices / settings • Plot the fixed points (damage curves, …) • Obtain / plot the device characteristics curves • Analyze the results
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 64
Time Current Characteristics • TCC Curve / Plot / Graphs • 4.5 x 5cycle loglog graph • Xaxis: Current (0.5 – 10,000 amperes) • Yaxis: Time (.01 – 1000 seconds) • Current Scaling (…x1, x10, x100, x100…) • Voltage Scaling (plot kV reference) • Use ETAP Star AutoScale
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 65
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 66
TCC Scaling Example • Situation: – A scaling factor of 10 @ 4.16 kV is selected for TCC curve plots.
• Question – What are the scaling factors to plot the 0.48 kV and 13.8 kV TCC curves?
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 67
TCC Scaling Example • Solution
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 68
Fixed Points Points or curves which do not change regardless of protective device settings: • Cable damage curves • Cable ampacities • Transformer damage curves & inrush points • Motor starting curves • Generator damage curve / Decrement curve • SC maximum fault points ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 69
Capability / Damage Curves It 2
t
I2 t
I2 t
I 2t 2
Motor Gen
Xfmr
Cable
I
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 70
Cable Protection • Standards & References – IEEE Std 8351994 IEEE Standard Power Cable Ampacity Tables – IEEE Std 8481996 IEEE Standard Procedure for the Determination of the Ampacity Derating of FireProtected Cables – IEEE Std 7381993 IEEE Standard for Calculating the Current Temperature Relationship of Bare Overhead Conductors – The Okonite Company Engineering Data for Copper and Aluminum Conductor Electrical Cables, Bulletin EHB98
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 71
Cable Protection The actual temperature rise of a cable when exposed to a short circuit current for a known time is calculated by:
Ι2 t A= T2 + 234 0.0297log T1 + 234
Where: A= Conductor area in circularmils I = Short circuit current in amps t = Time of short circuit in seconds T1= Initial operation temperature (750C) T2=Maximum short circuit temperature (1500C)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 72
Cable ShortCircuit Heating Limits Recommended temperature rise: B) CU 75200C
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 73
Shielded Cable The normal tape width is 1½ inches
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 74
NEC Section 110‑14 C •
(c) Temperature limitations. The temperature rating associated with the ampacity of a conductor shall be so selected and coordinated as to not exceed the lowest temperature rating of any connected termination, termination conductor, or device. Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both.
•
(1) Termination provisions of equipment for circuits rated 100 amperes or less, or marked for Nos. 14 through 1 conductors, shall be used only for conductors rated 600C (1400F).
•
Exception No. 1: Conductors with higher temperature ratings shall be permitted to be used, provided the ampacity of such conductors is determined based on the 6O0C (1400F) ampacity of the conductor size used.
•
Exception No. 2: Equipment termination provisions shall be permitted to be used with higher rated conductors at the ampacity of the higher rated conductors, provided the equipment is listed and identified for use with the higher rated conductors.
•
(2) Termination provisions of equipment for circuits rated over 100 amperes, or marked for conductors larger than No. 1, shall be used only with conductors rated 750C (1670F).
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 75
Transformer Protection Standards & References
• –
National Electric Code 2002 Edition
–
C37.912000; IEEE Guide for Protective Relay Applications to Power Transformers
–
C57.12.59; IEEE Guide for DryType Transformer ThroughFault Current Duration.
–
C57.1091985; IEEE Guide for LiquidImmersed Transformer ThroughFaultCurrent Duration
–
APPLIED PROCTIVE RELAYING; J.L. Blackburn; Westinghouse Electric Corp; 1976
–
PROTECTIVE RELAYING, PRINCIPLES AND APPLICATIONS; J.L. Blackburn; Marcel Dekker, Inc; 1987
–
IEEE Std 2421986; IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems
–
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 76
Transformer Category ANSI/IEEE C57.109
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 77
Transformer Categories I, II
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 78
Transformer Categories III
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 79
Transformer FLA
200
t (sec)
Thermal I2t = 1250
(DD LL) 0.87
Infrequent Fault (DR LG) 0.58
2
Frequent Fault
Mechanical K=(1/Z)2t Inrush
2.5
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Isc
25
I (pu)
Slide 80
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 81
Transformer Protection
M Any Location – NonSupervised
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 82
Transformer Protection •
Turn on or inrush current
•
Oil Level
•
Internal transformer faults
•
Fans
•
External or through faults of major magnitude
•
Oil Pumps
•
Pilot wire – Device 85
•
Repeated large motor starts on the transformer. The motor represents a major portion or the transformers KVA rating.
•
Fault withstand
•
Thermal protection – hot spot, top of oil temperature, winding temperature
•
Devices 26 & 49
•
Harmonics
•
Reverse over current – Device 67
•
Over current protection – Device 50/51
•
Gas accumulation – Buckholz relay
•
Ground current protection – Device 50/51G
•
Over voltage –Device 59
•
Voltage or current balance – Device 60
•
Differential – Device 87
•
Tertiary Winding Protection if supplied
•
Over or under excitation – volts/ Hz – Device 24
•
Relay Failure Scheme
•
Breaker Failure Scheme
•
Sudden tank pressure – Device 63
•
Dissolved gas detection
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 83
Recommended Minimum Transformer Protection Protective system
Winding and/or power system grounded neutral grounded Up to 10 MVA
Winding and/or power system neutral ungrounded Up to 10 MVA
Above 10 MVA
Above 10 MVA 
√

√
Time over current
√
√
√
√
Instantaneous restricted ground fault
√
√


Time delayed ground fault
√
√


√

√
√ √
√
√ √
Differential
Gas detection Over excitation Overheating ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC


Slide 84
Question What is ANSI Shift Curve?
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 85
Answer • For deltadelta connected transformers, with linetoline faults on the secondary side, the curve must be reduced to 87% (shift to the left by a factor of 0.87) • For deltawye connection, with single linetoground faults on the secondary side, the curve values must be reduced to 58% (shift to the left by a factor of 0.58) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 86
Question What is meant by Frequent and Infrequent for transformers?
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 87
Infrequent Fault Incidence Zones for Category II & III Transformers Source Transformer primary side protective device (fuses, relayed circuit breakers, etc.) may be selected by reference to the infrequent fault incidence protection curve Infrequent Fault Incidence Zone*
Category II or III Transformer Fault will be cleared by transformer primary side protective device Optional main secondary –side protective device. May be selected by reference to the infrequent faultincidence protection curve Fault will be cleared by transformer primary side protective device or by optional main secondary side protection device Feeder protective device
Frequent Fault Inciden ce Zone*
Fault will be cleared by feeder protective device Feeders
* Should be selected by reference to the frequent fault incidence protection curve or for transformers serving industrial, commercial and institutional power systems with secondary side conductors enclosed in conduit, bus duct, etc., the feeder protective device may be selected by reference to the infrequent fault incidence protection curve. Source: IEEE C57 ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 88
Motor Protection •
Standards & References –
IEEE Std 6201996 IEEE Guide for the Presentation of Thermal Limit Curves for Squirrel Cage Induction Machines.
–
IEEE Std 12552000 IEEE Guide for Evaluation of Torque Pulsations During Starting of Synchronous Motors
–
ANSI/ IEEE C37.962000 Guide for AC Motor Protection
–
The Art of Protective Relaying – General Electric
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 89
Motor Protection • Motor Starting Curve • Thermal Protection • Locked Rotor Protection • Fault Protection
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 90
Motor Overload Protection (NEC Art 43032 – ContinuousDuty Motors)
• Thermal O/L (Device 49) • Motors with SF not less than 1.15 – 125% of FLA
• Motors with temp. rise not over 40°C – 125% of FLA
• All other motors – 115% of FLA ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 91
Motor Protection – Inst. Pickup I
1 = XS + X d "
LOCKED ROTOR
Recommended Instantaneous Setting:
I
RELAY PICK UP =
I
PICK UP
∗ 1.6 TO 2
LOCKED ROTOR
If the recommended setting criteria cannot be met, or where more sensitive protection is desired, the instantaneous relay (or a second relay) can be set more sensitively if delayed by a timer. This permits the asymmetrical starting component to decay out. A typical setting for this is:
RELAY PICK UP =
I I
PICK UP
∗ 1.2 TO 1.2
LOCKED ROTOR
with a time delay of 0.10 s (six cycles at 60 Hz) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 92
Locked Rotor Protection • Thermal Locked Rotor (Device 51) • Starting Time (TS < TLR) • LRA – LRA sym – LRA asym (1.51.6 x LRA sym) + 10% margin
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 93
Fault Protection (NEC Art / Table 43052) • NonTime Delay Fuses – 300% of FLA
• Dual Element (TimeDelay Fuses) – 175% of FLA
• Instantaneous Trip Breaker – 800%  1300% of FLA*
• Inverse Time Breakers – 250% of FLA
*can be set up to 1700% for Design B (energy efficient) Motor ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 94
Low Voltage Motor Protection • Usually preengineered (selected from Catalogs) • Typically, motors larger than 2 Hp are protected by combination starters • Overload / Shortcircuit protection
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 95
Lowvoltage Motor Ratings Continuous amperes
Range of ratings 9250 —
Nominal voltage (V)
240600
—
Horsepower
1.51000
—
—
009
Quantity
NEMA designation
Overload: overload relay elements
3
OL
Short circuit: circuit breaker current trip elements
3
CB
Fuses
3
FU
Undervoltage: inherent with integral control supply and threewire control circuit
—
—
Ground fault (when specified): ground relay with toroidal CT
—
Starter size (NEMA)
Types of protection
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
—
Slide 96
Minimum Required Sizes of a NEMA
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
UM
TER E
C FLC
R HP
Combination Motor Starter System
Slide 97
Required Data  Protection of a Medium Voltage Motor •
Rated full load current
•
Service factor
•
Locked rotor current
•
Maximum locked rotor time (thermal limit curve) with the motor at ambient and/or operating temperature
•
Minimum no load current
•
Starting power factor
•
Running power factor
•
Motor and connected load accelerating time
•
System phase rotation and nominal frequency
•
Type and location of resistance temperature devices (RTDs), if used
•
Expected fault current magnitudes
•
First ½ cycle current
•
Maximum motor starts per hour
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 98
MediumVoltage Class E Motor Controller Ratings
Nominal system voltage Horsepower Symmetrical MVA interrupting capacity at nominal system voltage Types of Protective Devices
Class El (without fuses)
Class E2 (with fuses)
23006900 08000 2575
23006900 08000 160570
Quantity
NEMA Designation Phase Balance
Overload, or locked Rotor, or both: Thermal overload relay TOC relay IOC relay plus time delay
3 3 3
OL OC TR/O
Thermal overload relay
3
OL
TOC relay
3
OC
IOC relay plus time delay
3
TR/OC
3
FU
3
OC
1 1
GP GP
Short Circuit: Fuses, Class E2 IOC relay, Class E1 Ground Fault TOC residual relay Overcurrent relay with toroidal CT
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Current balance relay
1
BC
Negativesequence voltage 1 relay (per bus), or both
—
Undervoltage: — Inherent with integral control supply and threewire control circuit, when voltage falls sufficiently to permit the contractor to open and break the sealin circuit
UV
Temperature: — Temperature relay, operating from resistance sensor or thermocouple in stator winding
OL
NEMA Class E1 medium voltage starter
NEMA Class E2 medium voltage starter
Slide 99
Starting Current of a 4000Hp, 12 kV, 1800 rpm Motor First half cycle current showing current offset.
Beginning of run up current showing load torque pulsations.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 100
Starting Current of a 4000Hp, 12 kV, 1800 rpm Motor  Oscillographs
Motor pull in current showing motor reaching synchronous speed
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 101
Thermal Limit Curve
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 102
Thermal Limit Curve Typical Curve
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 103
(49) I2 T
O/L
tLR
MCP
(51)
ts
200 HP
Starting Curve
MCP (50)
LRAs
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
LRAasym
Slide 104
Protective Devices • Fuse • Overload Heater • Thermal Magnetic • Low Voltage Solid State Trip • ElectroMechanical • Motor Circuit Protector (MCP) • Relay (50/51 P, N, G, SG, 51V, 67, 49, 46, 79, 21, …) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 105
Fuse (Power Fuse) • Non Adjustable Device (unless electronic) • Continuous and Interrupting Rating • Voltage Levels (Max kV) • Interrupting Rating (sym, asym) • Characteristic Curves – Min. Melting – Total Clearing
• Application (rating type: R, E, X, …) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 106
Fuse Types • Expulsion Fuse (NonCLF) • Current Limiting Fuse (CLF) • Electronic Fuse (S&C Fault Fiter)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 107
Total Clearing Time Curve
Minimum Melting Time Curve
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 108
Current Limiting Fuse (CLF) • Limits the peak current of shortcircuit • Reduces magnetic stresses (mechanical damage) • Reduces thermal energy
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 109
Current (peak amps)
Current Limiting Action Ip
t a = tc – t m
Ip’
ta = Arcing Time tm = Melting Time ta
tm
Time (cycles)
tc ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
tc = Clearing Time Ip = Peak Current Ip’ = Peak Letthru Current
Slide 110
© 19962009 OperationInc. Technology, Inc. Notes: – Workshop Notes: Protective Device Coordination ©19962009 Operation Technology, – Workshop ShortCircuit IEC
Slide 111
LetThrough Chart Peak LetThrough Amperes
7% PF (X/R = 14.3) 230,000
300 A 100 A
12,500
60 A
5,200
100,000
Symmetrical RMS Amperes ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 112
Fuse Generally: • CLF is a better shortcircuit protection • NonCLF (expulsion fuse) is a better Overload protection • Electronic fuses are typically easier to coordinate due to the electronic control adjustments
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 113
Selectivity Criteria Typically: • NonCLF:
140% of full load
• CLF:
150% of full load
• Safety Margin: 10% applied to Min Melting (consult the fuse manufacturer)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 114
Molded Case CB • ThermalMagnetic • Magnetic Only
Types
• Motor Circuit Protector (MCP) • Integrally Fused (Limiters)
• Poles
• Current Limiting • High Interrupting Capacity
• Interrupting Capability
• Frame Size • Trip Rating • Voltage
• NonInterchangeable Parts • Insulated Case (Interchange Parts)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 115
MCCB
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 116
MCCB with SST Device
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 117
Thermal Maximum
Thermal Minimum
Magnetic (instantaneous)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 118
LVPCB • Voltage and Frequency Ratings • Continuous Current / Frame Size / Sensor • Interrupting Rating • ShortTime Rating (30 cycle) • Fairly Simple to Coordinate • Phase / Ground Settings • Inst. Override ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 119
LT PU
CB 2
CB 1 LT Band
CB 2
ST PU
480
kV
CB 1
IT
ST Band If =30 kA
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 120
Inst. Override
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 121
Overload Relay / Heater • Motor overload protection is provided by a device that models the temperature rise of the winding • When the temperature rise reaches a point that will damage the motor, the motor is deenergized • Overload relays are either bimetallic, melting alloy or electronic
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 122
Overload Heater (Mfr. Data)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 123
Question What is Class 10 and Class 20 Thermal OLR curves?
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 124
Answer • At 600% Current Rating: – Class 10 for fast trip, 10 seconds or less – Class 20 for, 20 seconds or less (commonly used)
20
– There is also Class 15, 30 for long trip time (typically provided with electronic overload relays) 6
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 125
Answer
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 126
Overload Relay / Heater • When the temperature at the combination motor starter is more than ±10 °C (±18 °F) different than the temperature at the motor, ambient temperature correction of the motor current is required. • An adjustment is required because the output that a motor can safely deliver varies with temperature. • The motor can deliver its full rated horsepower at an ambient temperature specified by the motor manufacturers, normally + 40 °C. At high temperatures (higher than + 40 °C) less than 100% of the normal rated current can be drawn from the motor without shortening the insulation life. • At lower temperatures (less than + 40 °C) more than 100% of the normal rated current could be drawn from the motor without shortening the insulation life.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 127
Overcurrent Relay • TimeDelay (51 – I>) • ShortTime Instantaneous ( I>>) • Instantaneous (50 – I>>>) • Electromagnetic (induction Disc) • Solid State (Multi Function / Multi Level) • Application
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 128
© 19962009 OperationInc. Technology, Inc. Notes: – Workshop Notes: Protective Device Coordination ©19962009 Operation Technology, – Workshop ShortCircuit IEC
Slide 129
TimeOvercurrent Unit • Ampere Tap Calculation – Ampere Pickup (P.U.) = CT Ratio x A.T. Setting – Relay Current (IR) = Actual Line Current (IL) / CT Ratio – Multiples of A.T. IL
CT
= IR/A.T. Setting
= IL/(CT Ratio x A.T.
I Setting) R
51
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 130
Instantaneous Unit • Instantaneous Calculation – Ampere Pickup (P.U.) = CT Ratio x IT Setting – Relay Current (IR) = Actual Line Current (IL) / CT Ratio – Multiples of IT CT
IL
= IR/IT Setting
= IL/(CT Ratio x IT Setting)
IR 50
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 131
Relay Coordination • Time margins should be maintained between T/C curves • Adjustment should be made for CB opening time • Shorter time intervals may be used for solid state relays • Upstream relay should have the same inverse T/C characteristic as the downstream relay (CO8 to CO8) or be less inverse (CO8 upstream to CO6 downstream) • Extremely inverse relays coordinates very well with CLFs ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 132
Situation 4.16 kV CT 800:5
50/51
Relay: IFC 53
CB
Cable CU  EPR
13/C 500 kcmil
Isc = 30,000 A DS
5 MVA 6%
Calculate Relay Setting (Tap, Inst. Tap & Time Dial) For This System
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 133
Solution Transformer:
5,000kVA = 694 A 3 × 4.16kV 5 IR = IL × = 4.338 A 800
IL =
I Inrsuh = 12 × 694 = 8,328 A Set Relay:
IL IR R
CT
125% × 4.338 = 5.4 A TAP = 6.0 A TD = 1
(6/4.338 = 1.38)
Inst (50) = 8,328 ×
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
5 = 52.1A = >55 A 800
Slide 134
Question What T/C Coordination interval should be maintained between relays?
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 135
Answer B t
A
CB Opening Time + Induction Disc Overtravel (0.1 sec) + Safety margin (0.2 sec w/o Inst. & 0.1 sec w/ Inst.)
I ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 136
Recloser • Recloser protects electrical transmission systems from temporary voltage surges and other unfavorable conditions. • Reclosers can automatically "reclose" the circuit and restore normal power transmission once the problem is cleared. • Reclosers are usually designed with failsafe mechanisms that prevent them from reclosing if the same fault occurs several times in succession over a short period. This insures that repetitive line faults don't cause power to switch on and off repeatedly, since this could cause damage or accelerated wear to electrical equipment. • It also insures that temporary faults such as lightning strikes or transmission switching don't cause lengthy interruptions in service.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 137
Recloser Types • Hydraulic • Electronic – Static Controller – Microprocessor Controller
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 138
Recloser Curves
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 139
TEMA 3
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 140
Transient Stability
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Topics • What is Transient Stability (TS) • What Causes System Unstable • Effects When System Is Instable • Transient Stability Definition • Modeling and Data Preparation • ETAP TS Study Outputs • Power System TS Studies • Solutions to Stability Problems ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 142
What is Transient Stability • TS is also called Rotor Angle Stability Something between mechanical system and electrical system – energy conversion
• It is a Electromechanical Phenomenon Time frame in milliseconds
• All Synchronous Machines Must Remain in Synchronism with One Another Synchronous generators and motors This is what system stable or unstable means ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 143
What is Transient Stability • Torque Equation (generator case)
T = mechanical torque P = number of poles
φ
air
= airgap flux
Fr = rotor field MMF
δ = rotor angle
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 144
What is Transient Stability • Swing Equation
M
= inertia constant
D
= damping constant
Pmech
= input mechanical power
Pelec
= output electrical power
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 145
What Causes System Unstable • From Torque Equation T (prime mover) Rotor MMF (field winding) AirGap Flux (electrical system)
• From Swing Equation Pmech Pelec Different time constants in mechanical and electrical systems ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 146
What Causes System Unstable • In real operation Shortcircuit Loss of excitation Prime mover failure Loss of utility connections Loss of a portion of inplant generation Starting of a large motor Switching operations Impact loading on motors Sudden large change in load and generation ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 147
Effects When System Is Instable • Swing in Rotor Angle (as well as in V, I, P, Q and f)
Case 1: Steadystate stable Case 2: Transient stable Case 3: Smallsignal unstable Case 4: First swing unstable ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 148
Effects When System Is Instable • A 2Machine Example
• At δ = 180º (OutofStep, Slip the Pole)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 149
Effects When System Is Instable • Synchronous machine slip poles – generator tripping • Power swing • Misoperation of protective devices • Interruption of critical loads • Lowvoltage conditions – motor dropoffs • Damage to equipment • Area wide blackout • … ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 150
Transient Stability Definition • Examine One Generator
• Power Output Capability Curve
∀ δ is limited to 180º ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 151
Transient Stability Definition • Transient and Dynamic Stability Limit After a severe disturbance, the synchronous generator reaches a steadystate operating condition without a prolonged loss of synchronism Limit: δ < 180° during swing
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 152
Modeling and Data Preparation • Synchronous Machine
Machine Exciter and AVR Prime Mover and Governor / Load Torque Power System Stabilizer (PSS) (Generator) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 153
Modeling and Data Preparation
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 154
Modeling and Data Preparation • Typical synchronous machine data
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 155
Modeling and Data Preparation • Induction Machine Machine Load Torque
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 156
Modeling and Data Preparation • Power Grid ShortCircuit Capability Fixed internal voltage and infinite inertia
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 157
Modeling and Data Preparation • Load Voltage dependency Frequency dependency
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 158
Modeling and Data Preparation • Load
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 159
Modeling and Data Preparation • Events and Actions
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 160
Modeling and Data Preparation Device Type
Action
Bus
3P Fault
LG Fault
Clear Fault
Branch
Fraction Fault Clear Fault
PD
Trip
Generator
Droop / Isoch Start
Loss Exc.
Grid
P Change
V Change
Delete
Motor
Accelerate
Load Change
Delete
Lumped Load
Load Change Delete
MOV
Start
Wind Turbine
Disturbance
Gust
MG Set
Emergency
Main
Close
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
P Change
V Change
Delete
Ramp
Slide 161
Power System TS Studies • Fault 3phase and single phase fault Clear fault Critical Fault Clearing Time (CFCT) Critical System Separation Time (CSST)
• Bus Transfer Fast load transferring
• Load Shedding Underfrequency Undervoltage
• Motor Dynamic Acceleration Induction motor Synchronous motor ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 162
Power System TS Studies • Critical Fault Clearing Time (CFCT) Fault
Clear fault Clear fault
1 cycle
1 cycle unstable
unstable
unstable
stable
CFCT
Clear fault Clear fault
Cycle
• Critical Separation Time (CSST) Fault
Separation Separation
1 cycle
1 cycle unstable
unstable
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
unstable
stable
CSST
Separation Separation
Cycle
Slide 163
Power System TS Studies • Fast Bus Transfer Motor residual voltage 1 0.8 Vmotor 0.6 0.4 0.2 0 1
0.8
0.6
0.4
0.2
0
s
0.2
0.4
0.6
0.8
1
0.2 0.4 0.6 0.8 1
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 164
Power System TS Studies • Fast Bus Transfer δ
Ttransfer
ES = System equivalent per unit volts per hertz EM = Motor residual per unit per hertz ER = Resultant vectorial voltage in per unit volts per hertz
≤ 10 cycles
δ ≤ 90 degrees ER ≤ 1.33 per unit (133%) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 165
Power System TS Studies • Load Shedding
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 166
Power System TS Studies • Motor Dynamic Acceleration Important for islanded system operation Motor starting impact Generator AVR action Reacceleration
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 167
Solution to Stability Problems • Improve System Design Increase synchronizing power
• Design and Selection of Rotating Equipment Use of induction machines Increase moment of inertia Reduce transient reactance Improve voltage regulator and exciter characteristics ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 168
Solution to Stability Problems • Application of Power System Stabilizer (PSS) • Add System Protections Fast fault clearance Load shedding System separation OutOfStep relay …
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 169
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
TEMA 4
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 171
Harmonic Analysis
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
ARMONICAS Características principales:
Exploración de frecuencia. Flujo Armónico de Carga. Dimensionamiento y Diseño de Filtros. Evaluación Automática del límite de distorsión. Factores de la influencia teléfono (TIF & I*T)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
del
Slide 173
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 174
Types of Power Quality Problems
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 175
Waveform Distortion • Primary Types of Waveform Distortion – DC Offset – Harmonics – Interharmonics – Notching – Noise
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 176
Harmonics • One special category of power quality problems • “Harmonics are voltages and/or currents present in an electrical system at some multiple of the fundamental frequency.” (IEEE Std 399, Brown Book)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 177
Nonlinear Loads • Sinusoidal voltage applied to a simple nonlinear resistor • Increasing the voltage by a few percent may cause current to double
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 178
Fourier Representation • Any periodic waveform can be expressed as a sum of sinusoids • The sum of the sinusoids is referred to as Fourier Series (6pulse)
I ac =
2 3 1 1 1 1 I d (cosωt − cos 3ωt + cos 7ωt − cos11ωt + cos13ωt π 5 7 11 13
∞
⇒ ∑ I h cos(hωt + Φ h ) h =1
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 179
Harmonic Sources • Utilities (Power Grid) – Known as “Background Harmonic” – Pollution from other irresponsible customers – SVC, HVDC, FACTS, … – Usually a voltage source
• Synchronous Generators – Due to Pitch (can be eliminated by fractionalpitch winding) and Saturation – Usually a voltage source ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 180
Harmonic Sources (cont’d) • Transformers – Due to magnetizing branch saturation – Only at lightly loaded condition – Usually a current source
• Power Electronic Devices – Charger, Converter, Inverter, UPS, VFD, SVC, HVDC, FACTS (Flexible alternating current transmission systems) … – Due to switching actions – Either a voltage source or a current source
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 181
Harmonic Sources (cont’d) • Other NonLinear Loads – Arc furnaces, discharge lighting, … – Due to unstable and nonlinear process – Either a voltage source or a current source
• In general, any load that is applied to a power system that requires other than a sinusoidal current
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 182
Harmonic I and V
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 183
Classification of Harmonics • Harmonics may be classified as: – Characteristic Harmonics Generally produced by power converters
– NonCharacteristic Harmonics Typically produced by arc furnaces and discharge lighting (from nonperiodical waveforms)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 184
Phase Angle Relationship • Fundamental Frequency
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 185
Phase Angle Relationship • Third Order
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 186
Phase Angle Relationship • Fifth Order
• Seventh Order
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 187
Order vs. Sequence
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 188
Characteristic Harmonics
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 189
Characteristic Harmonics (cont’d)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 190
Harmonic Spectrum %
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 191
HarmonicRelated Problems • Motors and Generators – Increased heating due to iron and copper losses – Reduced efficiency and torque – Higher audible noise – Cogging or crawling – Mechanical oscillations
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 192
HarmonicRelated Problems (cont’d) • Transformers – Parasitic heating – Increased copper, stray flux and iron losses
• Capacitors (var compensators) – Possibility of system resonance – Increased heating and voltage stress – Shortened capacitor life ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 193
HarmonicRelated Problems (cont’d) • Power Cables – Involved in system resonance – Voltage stress and corona leading to dielectric failure – Heating and derating
• Neutrals of fourwire systems (480/277V; 120/208V) – Overheating
• Fuses – Blowing ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 194
HarmonicRelated Problems (cont’d) • Switchgears – Increased heating and losses – Reduced steadystate current carrying capability – Shortened insulation components life • Relays – Possibility of misoperation • Metering – Affected readings ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 195
HarmonicRelated Problems (cont’d) • Communication Systems – Interference by higher frequency electromagnetic field
• Electronic Equipment (computers, PLC) – Misoperation
• System – Resonance (serial and parallel) – Poor power factor
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 196
Parallel Resonance • Total impedance at resonance frequency increases • High circulating current will flow in the capacitanceinductance loop
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 197
Parallel Resonance
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 198
Capacitor Banks
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 199
Capacitor Banks
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 200
Capacitor Banks
Say, Seventh Harmonic Current = 5% of 1100A = 55 A
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 201
Capacitor Banks
Resistance = 1% including cable and transformer CAF = X/R = 7*0.0069/0.0012 =40.25 Resonant Current = 55*40.25 = 2214 A ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 202
Parallel Resonance (cont’d) Cause:
Source inductance resonates with capacitor bank at a frequency excited by the facilities harmonic sources
Impacts: 1. Excessive capacitor fuse operation 2. Capacitor failures 3. Incorrect relay tripping 4. Telephone interference 5. Overheating of equipment ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 203
Harmonic Distortion Measurements • Total Harmonic Distortion (THD) – Also known as Harmonic Distortion Factor (HDF), is the most popular index to measure the level of harmonic distortion to voltage and current – Ratio of the RMS of all harmonics to the fundamental component – For an ideal system THD = 0% – Potential heating value of the harmonics relative to the fundamental
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 204
Harmonic Distortion Measurements (cont’d) – Good indicator of additional losses due to current flowing through a conductor – Not a good indicator of voltage stress in a capacitor (related to peak value of voltage waveform, not its heating value) ∞
THD =
2 F ∑ i 2
F1
Where Fi is the amplitude of the ith harmonic, and F1 is that for the fundamental component. ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 205
Harmonic Distortion Example Find THD for this waveform
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 206
Harmonic Example • Find THD for this Harmonic Spectrum
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 207
Adjustable Speed Drive – Current Distortion
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 208
Adjustable Speed Drive – Voltage Distortion
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 209
Harmonic Distortion Measurements (cont’d) • Individual Harmonic Distortion (IHD)  Ratio of a given harmonic to fundamental  To track magnitude of individual harmonic Fi IHD = F1
• Root Mean Square (RMS)  Total  Root Mean Square of fundamental plus all harmonics  Equal to fundamental RMS if Harmonics are zero ∞ 2 RMS =
∑F
i
1
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 210
Harmonic Distortion Measurements (cont’d) • Arithmetic Summation (ASUM) – Arithmetic summation of magnitudes of all components (fundamental and all harmonics) – Directly adds magnitudes of all components to estimate crest value of voltage and current – Evaluation of the maximum withstanding ratings of a device ∞
ASUM = ∑ Fi 1
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 211
Harmonic Distortion Measurements (cont’d) • Telephone Influence Factor (TIF) – Weighted THD – Weights based on interference to an audio signal in the same frequency range – Current TIF shows impact on adjacent communication systems ∞
∑ (W F ) i
TIF =
2
i
1
∞
∑F
2
i
1
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 212
Harmonic Distortion Measurements (cont’d) • I*T Product (I*T) – A product current components (fundamental
and harmonics) and weighting factors I •T =
H
2 ( I ⋅ T ) ∑ h h h =1
where Ih = current component Th= weighting factor h = harmonic order (h=1 for fundamental) H = maximum harmonic order to account ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 213
Triplen Harmonics • Odd multiples of the third harmonic (h = 3, 9, 15, 21, …) • Important issue for groundedwye systems with neutral current • Overloading and TIF problems • Misoperation of devices due to presence of harmonics on the neutral
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 214
Triplen Harmonics
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 215
Winding Connections
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
•
Delta winding provides ampere turn balance
•
Triplen Harmonics cannot flow
•
When currents are balanced Triplens behave as Zero Sequence currents
•
Used in Utility Distribution Substations
•
Delta winding connected to Transmission
•
Balanced Triplens can flow
•
Present in equal proportions on both sides
•
Many loads are served in this fashion
Slide 216
Implications • Neutral connections are susceptible to overheating when serving singlephase loads on the Y side that have high 3rd Harmonic • Measuring current on delta side will not show the triplens and therefore do not give a true idea of the heating the transformer is subjected to • The flow of triplens can be interrupted by appropriate isolation transformer connection • Removing the neutral connection in one or both Y windings blocks the flow of Triplen harmonic current • Three legged core transformers behave as if they have a “phantom” delta tertiary winding ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 217
Modeling in Harmonic Analysis • Motors and Machines – Represented by their equivalent negative sequence reactance
• Lines and Cables – Series impedance for low frequencies – Long line correction including transposition and distributed capacitance
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 218
Modeling in Harmonic Analysis (cont’d) • Transformers – Leakage impedance – Magnetizing impedance
• Loads – Static loads reduce peak resonant impedance – Motor loads shift resonant frequency due to motor inductance ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 219
Reducing System Harmonics • Add Passive Filters – Shunt or Single Tuned Filters – Broadband Filters or Band Pass Filters – Provide low impedance path for harmonic current – Least expensive
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 220
Reducing System Harmonics (cont’d) • Increase Pulse Numbers – Increasing pulse number of convert circuits – Limited by practical control problems
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 221
Reducing System Harmonics (cont’d) • Apply Transformer Phase Shifting – Using Phase Shifting Transformers – Achieve higher pulse operation of the total converter installation
• In ETAP – Phase shift is specified in the tab page of the transformer editor
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 222
Reducing System Harmonics (cont’d) • Either standard phase shift or special phase shift can be used
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 223
Reducing System Harmonics (cont’d) • Add Active Filters – Instantly adapts to changing source and load conditions – Costly – MVA Limitation
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 224
Voltage Distortion Limits Recommended Practices for Utilities (IEEE Bus Voltage Individual Total Voltage 519): Distortion Distortion At
(%)
THD (%)
69 kV and below
3.0
5.0
69.001 kV through 161kV
1.5
2.5
161.001 and above
1.0
1.5
PCC
In ETAP: Specify Harmonic Distortion Limits in Harmonic Page of Bus Editor:
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 225
Current Distortion Limits Recommended Practices for General Distribution Systems (IEEE 519):
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 226
TEMA 5
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 227
Motor Starting Dynamic Acceleration
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
ARRANQUE DE MOTORES Características principales:
Aceleración motores.
dinámica
de
Parpadeo (Flicker) de tensión. Modelos dinámicos de motores. Arranque estático de motores. Varios dispositivos de arranque. Transición de carga.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 229
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 230
Why to Do MS Studies? • Ensure that motor will start with voltage drop • If Tst 80% • Generation bus voltage > 93%
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 231
Why to Do MS Studies? • Ensure motor feeders sized adequately (Assuming 100% voltage at Switchboard or MCC) • LV cable voltage drop at starting < 20% •
LV cable voltage drop when running at fullload < 5%
•
HV cable voltage drop at starting < 15%
•
HV cable voltage drop when running at fullload < 3%
• Maximum motor size that can be started across the line •
Motor kW < 1/6 kW rating of generator (islanded)
•
For 6 MW of islanded generation, largest motor size < 1 MW
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 232
Motor Sizing • Positive Displacement Pumps / Rotary Pumps
•
p = Pressure in psi
•
Q = fluid flow in gpm
•
n = efficiency
• Centrifugal Pumps
•
H = fluid head in feet
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 233
Motor Types • Synchronous • Salient Pole • Round Rotor
• Induction • Wound Rotor (slipring) • Single Cage CKT Model
• Squirrel Cage (brushless) • Double Cage CKT Model
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 234
Induction Motor Advantages • Squirrel Cage • Slightly higher efficiency and power factor • Explosive proof
• Wound Rotor • Higher starting torque • Lower starting current • Speed varied by using external resistances
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 235
Typical Rotor Construction
• Rotor slots are not parallel to the shaft but skewed
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 236
Wound Rotor
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 237
Operation of Induction Motor • AC applied to stator winding • Creates a rotating stator magnetic field in air gap • Field induces currents (voltages) in rotor • Rotor currents create rotor magnetic field in air gap • Torque is produced by interaction of air gap fields
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 238
Slip Frequency • Slip represents the inability of the rotor to keep up with the stator magnetic field • Slip frequency S = (ωsωn)/ωs where ωs = 120f/P ωn = mech speed
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 239
Static Start  Example
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 240
Static Start  Example
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 241
Service Factor
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 242
Inrush Current
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 243
Resistance / Reactance • Torque Slip Curve is changed by altering resistance / reactance of rotor bars. • Resistance ↑ by ↓cross sectional area or using higher resistivity material like brass. • Reactance ↑ by placing conductor deeper in the rotor cylinder or by closing the slot at the air gap.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 244
Rotor Bar Resistance ↑ • Increase Starting Torque • Lower Starting Current • Lower Full Load Speed • Lower Efficiency • No Effect on Breakdown Torque
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 245
Rotor Bar Reactance ↑ • Lower Starting Torque • Lower Starting Current • Lower Breakdown Torque • No effect on Full Load Conditions
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 246
Motor Torque Curves
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 247
Rotor Bar Design • Cross section Large (low resistance) and positioned deep in the rotor (high reactance). (Starting Torque is normal and starting current is low). • Double Deck with small conductor of high resistance. During starting, most current flows through the upper deck due to high reactance of lower deck. (Starting Torque is high and starting current is low). ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 248
Rotor Bar Design • Bars are made of Brass or similar high resistance material. Bars are close to surface to reduce leakage reactance. (Starting torque is high and starting current is low).
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 249
Load Torque – ID Fan
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 250
Load Torque – FD Fan
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 251
Load Torque – C. Pump
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 252
Motor Torque – Speed Curve
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 253
Double Cage Motor
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 254
Motor Full Load Torque • For example, 30 HP 1765 RPM Motor
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 255
Motor Efficiency • kW Saved = HP * 0.746 (1/Old – 1/New) • $ Savings = kW Saved * Hrs /Year * $/kWh
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 256
Acceleration Torque • Greater Acceleration Torque means higher inertia that can be handled by the motor without approaching thermal limits
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 257
Acceleration Torque
P
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 258
Operating Range • Motor, Generator, or Brake
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 259
Rated Conditions
Terminal Current
Load(kva)
• Constant Power
kvar
0.8
Terminal Voltage
1.0
L1
Ir
0.8 Terminal Voltage
1.0
P = Tm Wm , As Vt ( terminal voltage ) changes from 0.8 to 1.1 pu, Wm changes by a very small amount. There fore, P is approx constant since Tm (α w²m) is approx. constant
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 260
Starting Conditions • Constant Impedance Starting Conditions
Constant Impedance
P
It
Kva LR
I LR
.8 kva
.9 I LR
LR
0.9
Terminal Voltage
1.0
Vt
(pu)
0.9 Terminal Voltage
1.0
Vt
(pu)
KVA LR = Loched  rotor KVA at rated voltage = 2HP 2 ≡ Code letter factor ≡ Locked – rotor KVA ∕ HP Z st =
______ KVA B KVA LR
KVR = rated voltage
____ KVR ² KVB
Pu, Rst = Zst cos θ st , Xst= Zst sin θ st
KVB = Base voltage KVAB = Base power
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 261
Voltage Variation • Torque is proportional to V^2 • Current is proportional to V I 100% voltage
v1
80% voltage p R
ws
0 I
wm
0
ws
wm
Load 100% V
Tst α ( operating voltage) ² _____________ Rated voltage
80% V
Ist α ( _____________ operating voltage) Rated voltage T st
T’ st
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
T
Slide 262
Frequency Variation • As frequency decreases, peak torque shifts toward lower speed as synchronous speed decreases. • As frequency decrease, current increases due reduced impedance. I
T em
F1
F1
F2 › F1
F 2 › F1
0
W3 = 120 ___f RPM P
0 WS1
WS2
Wm
WS1
WS2
Wm
Adjustable speed drive : Typical speed range for variable torque loads such as pumps and fans is 3/1,maximun is 8/1 ( 1.5 to 60 Hz)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 263
Number of Poles Variation •
As Pole number increases, peak torque shifts toward lower speed as synchronous speed decreases. Nro. of poles variation
T em
2 P  poles
W′S =
P  poles
WS ___ 2
P
Load
0
R
W′S
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
WS
Wm
Slide 264
Rotor Z Variation • Increasing rotor Z will shift peak torque towards lower speed. Rotor – Resistance Variation
r2
r3
r4
r1 P R
Q
S
r1 › r2 › r3 › r4
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 265
Modeling of Elements • Switching motors – Zlr, circuit model, or characteristic model • Synch generator  constant voltage behind X’d • Utility  constant voltage behind X”d • Branches – Same as in Load Flow • Nonswitching Load – Same as Load flow • All elements must be initially energized, including motors to start ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 266
Motor Modeling 1. Operating Motor – Constant KVA Load
1. Starting Motor – During Acceleration – Constant Impedance – LockedRotor Impedance – Circuit Models
Characteristic Curves After Acceleration – Constant KVA Load ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 267
LockedRotor Impedance • ZLR = RLR +j XLR
(10 – 25 %)
POWER FACTOR
• PFLR is much lower than operating PD. Approximate starting PF of typical squirrel cage induction motor:
HORSE POWER RATING ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 268
Circuit Model I • Single Cage Rotor – “Single1” – constant rotor resistance and reactance
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 269
Circuit Model II • Single Cage Rotor – “Single2”  deep bar effect, rotor resistance and reactance vary with speed [Xm is removed]
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 270
Circuit Model III • Double Cage Rotor – “DB1” – integrated rotor cages
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 271
Circuit Model IV • Double Cage Rotor – “DB2” – independent rotor cages
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 272
Characteristic Model • Motor Torque, I, and PF as function of Slip – Static Model
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 273
Calculation Methods I • Static Motor Starting – Time domain using static model – Switching motors modeled as Zlr during starting and constant kVA load after starting – Run load flow when any change in system
• Dynamic Motor Starting – Time domain using dynamic model and inertia model – Dynamic model used for the entire simulation – Requires motor and load dynamic (characteristic) model ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 274
Calculation Methods II
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 275
Static versus Dynamic • Use Static Model When – Concerned with effect of motor starting on other loads – Missing dynamic motor information
• Use Dynamic Model When – Concerned with actual acceleration time – Concerned if motor will actually start
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 276
MS Simulation Features • Start/Stop induction/synchronous motors • Switching on/off static load at specified loading category • Simulate MOV opening/closing operations • Change grid or generator operating category • Simulate transformer LTC operation • Simulate global load transition • Simulate various types of starting devices • Simulate load ramping after motor acceleration
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 277
Automatic Alert • • • • •
Starting motor terminal V Motor acceleration failure Motor thermal damage Generator rating Generator engine continuous & peak rating • Generator exciter peak rating • Bus voltage • Starting motor bus • Grid/generator bus • HV, MV, and LV bus • User definable minimum time span ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 278
Starting Devices Types • AutoTransformer
• Y/D Winding
• Stator Resistor
• Partial Wing
• Stator Reactor
• Soft Starter
• Capacitor at Bus
• Stator Current Limit
• Capacitor at Motor Terminal
– Stator Current Control
• Rotor External Resistor
– Torque Control
– Voltage Control
• Rotor External Reactor ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 279
Starting Device • Comparison of starting conditions
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 280
Starting Device – AutoXFMR
• C4 and C3 closed initially • C4 opened, C2 is closed with C3 still closed. Finally C3 is open ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 281
Starting Device – AutoXFMR • Autotransformer starting EX. 50% Tap Vmcc 3IST MCC
line
M
VMCC
50% tap
5VMCC
IST
VM
Autotransformer starter
PFST ( with autotransformer) = PFST ( without autotransformer)
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 282
Starting Device – YD Start
• During Y connection Vs = VL / √3 • Phase current Iy = Id / √3 and 3 to 1 reduction in torque ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 283
Starting Device – Rotor R
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 284
Starting Device – Stator R
• Resistor
RL
5VMCC
VMCC
PFST ( with resistor) =
50% tap
VM
RLR XLR
1[pu tap setting ]² * [ 1 (PFST
=
XL
without resistor)²]
1 (0.5)² * [1(PFST)²]
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 285
Starting Device Stator X • Reactor RL
5VMCC
VMCC 50% tap
PFST ( with reactor) = [pu tap setting ] * PFST
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
XL
VM
RLR XLR
(without reactor)
Slide 286
Transformer LTC Modeling • LTC operations can be simulated in motor starting studies • Use global or individual Tit and Tot
V limit
Tit
Tot T
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 287
MOV Modeling I • Represented as an impedance load during operation – Each stage has own impedance based on I, pf, Vr – User specifies duration and load current for each stage
• Operation type depends on MOV status – Open statusclosing operation – Close statusopening operation
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 288
MOV Modeling II • Five stages of operation Opening
Closing
Acceleration
Acceleration
No load
No load
Unseating
Travel
Travel
Seating
Stall
Stall
• Without hammer blow Skip “No Load” period • With a micro switch Skip “Stall” period • Operating stage time extended if Vmtr < Vlimit
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 289
MOV Closing • With Hammer Blow MOV Closing
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 290
MOV Opening • With Hammer Blow MOV Opening
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 291
MOV Voltage Limit • Effect of Voltage Limit Violation I
ACCL
STALL
VMTR < V LIMIT
UNSETTING
TRAVEL
Tacc
Tpos
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Travel
Tstl
Slide 292
TEMA 6 ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 293
ShortCircuit ANSI Standard
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
CORTO CIRCUITO Características principales:
Estándar de ANSI/IEEE & IEC. Análisis de fallas transitorias (IEC 61363). Efecto de Arco (NFPA 70E2000) Integrado con coordinación de dispositivos de protección. Evaluación dispositivos.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
automática
de
Slide 295
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 296
ShortCircuit Analysis Types of SC Faults •ThreePhase Ungrounded Fault •ThreePhase Grounded Fault •Phase to Phase Ungrounded Fault •Phase to Phase Grounded Fault •Phase to Ground Fault
Fault Current •ILG can range in utility systems from a few percent to possibly 115 % ( if Xo < X1 ) of I3phase
(85% of all faults).
•In industrial systems the situation ILG > I3phase is rare. Typically ILG ≅ .87 * I3phase •In an industrial system, the threephase fault condition is frequently the only one considered, since this type of fault generally results in Maximum current. ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 297
Purpose of ShortCircuit Studies • A ShortCircuit Study can be used to determine any or all of the following: – Verify protective device close and latch capability – Verify protective device Interrupting capability – Protect equipment from large mechanical forces (maximum fault kA) – I2t protection for equipment (thermal stress) – Selecting ratings or settings for relay coordination ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 298
System Components Involved in SC Calculations • Power Company Supply • InPlant Generators • Transformers (using negative tolerance) • Reactors (using negative tolerance) • Feeder Cables and Bus Duct Systems (at lower temperature limits) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 299
System Components Involved in SC Calculations • Overhead Lines (at lower temperature limit) • Synchronous Motors • Induction Motors • Protective Devices • Y0 from Static Load and Line Cable ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 300
Elements That Contribute Current to a ShortCircuit • Generator • Power Grid • Synchronous Motors • Induction Machines • Lumped Loads (with some % motor load) • Inverters • I0 from YgDelta Connected Transformer ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 301
Elements Do Not Contribute Current in PowerStation • Static Loads • Motor Operated Valves • All Shunt Y Connected Branches
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 302
ShortCircuit Phenomenon
v(t)
i(t)
v(t)= Vm∗ Sin(ω t + θ )
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 303
v(t)
i(t)
di v(t)= Ri + L = Vm× Sin( ωt + θ ) (1) dt Solving equation 1 yields the following expression  t Vm Vm i(t)= × sin( ωt + θ  φ ) + × sin( θ  φ )×e L Z Z R
Steady State
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Transient (DCOffset)
Slide 304
AC Current (Symmetrical) with No AC Decay
DC Current
© 19962009Operation OperationTechnology, Technology,Inc. Inc.––Workshop WorkshopNotes: Notes:ShortCircuit ShortCircuitIEC ANSI ©19962009
Slide 305
AC Fault Current Including the DC Offset (No AC Decay)
©19962009 © 19962009Operation OperationTechnology, Technology,Inc. Inc.––Workshop WorkshopNotes: Notes:ShortCircuit ShortCircuitIEC ANSI
Slide 306
Machine Reactance ( λ = L I )
AC Decay Current
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 307
Fault Current Including AC & DC Decay
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 308
ANSI Calculation Methods 1) The ANSI standards handle the AC Decay by varying machine impedance during a fault.
ANSI
2) The ANSI standards handle the the dc offset by applying multiplying factors. The ANSI Terms for this current are: •Momentary Current •Close and Latch Current •First Cycle Asymmetrical Current ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 309
Sources and Models of Fault Currents in ANSI Standards Sources •Synchronous Generators •Synchronous Motors & Condensers •Induction Machines •Electric Utility Systems (Power Grids)
Models All sources are modeled by an internal voltage behind its impedance. E = Prefault Voltage R = Machine Armature Resistance X = Machine Reactance (X”d, X’d, Xd) ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 310
Synchronous Generators Synchronous Generators are modeled in three stages.
Synchronous Motors & Condensers Act as a generator to supply fault current. This current diminishes as the magnetic field in the machine decays.
Induction Machines Transient Reactance
Treated the same as synchronous motors except they do not contribute to the fault after 2 sec.
Subtransient Reactance
Electric Utility Systems
Synchronous Reactance
The fault current contribution tends to remain constant. ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 311
½
Cycle Network
This is the network used to calculate momentary shortcircuit current and protective device duties at the ½ cycle after the fault.
1 ½ to 4 Cycle Network This network is used to calculate the interrupting shortcircuit current and protective device duties 1.54 cycles after the fault.
30Cycle Network This is the network used to calculate the steadystate shortcircuit current and settings for over current relays after 30 cycles.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 312
Reactance Representation for Utility and Synchronous Machine ½ Cycle
1 ½ to 4 Cycle
30 Cycle
X”d
X”d
X”d
X”d
X”d
X’d
HydroGen with Amortisseur winding
X”d
X”d
X’d
HydroGen without Amortisseur winding
0.75*X”d
0.75*X”d
X’d
X”d
X”d
X”d
1.5*X”d
Utility
Turbo Generator
Condenser
Synchronous Motor
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
α
α
Slide 313
Reactance Representation for Induction Machine ½ Cycle
1 ½ to 4 Cycle
>1000 hp , 250, at 3600 rpm
X”d
1.5*X”d
All others, >= 50 hp
1.2*X”d
3.0*X”d
< 50 hp
1.67*X”d
α
Note: X”d = 1 / LRCpu
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 314
Device Duty and Usage of Fault Currents from Different Networks ½ Cycle Currents (Subtransient Network)
1 ½ to 4 Cycle Currents (Transient Network)
HV Circuit Breaker
Closing and Latching Capability
Interrupting Capability
LV Circuit Breaker
Interrupting Capability

Fuse
Interrupting Capability
SWGR / MCC
Bus Bracing

Relay
Instantaneous Settings

30 Cycle currents are used for determining overcurrent settings.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 315
Momentary Multiplying Factor
MFm is calculated based on: • Fault X/R (Separate R & X Networks) • Location of fault (Remote / Local generation) Comparisons of Momentary capability (1/2 Cycle) SC Current Duty
Device Rating
HV CB
Asymmetrical RMS Crest
C&L RMS C&L RMS
HV Bus
Asymmetrical RMS Crest
Asymmetrical RMS
Symmetrical RMS Asymmetrical RMS
Symmetrical RMS Asymmetrical RMS
LV Bus
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Crest
Slide 316
Interrupting Multiplying Factor MFi is calculated based on: • Fault X/R (Separate R & X Networks) • Location of Fault (Remote / Local generation) • Type and Rating of CB
Comparisons of Interrupting Capability (1 ½ to 4 Cycle)
HV CB LV CB & Fuse
SC Current Duty
Device Rating
Adj. Symmetrical RMS*
Adj. Symmetrical RMS*
Adj. Symmetrical RMS***
Symmetrical RMS
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 317
HV CB Closing and Latching Duty Calculate ½ Cycle Current (Imom,rms,sym
) using ½ Cycle Network.
• Calculate X/R ratio and Multiplying factor MFm
• Imom,rms,Asym=
MFm * Imom,rms,sym
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 318
HV CB Interrupting Duty Calculate 1½ to 4 Cycle Current (Imom,rms,sym
) using ½ Cycle Network.
• Determine Local and Remote contributions (A “local” contribution is fed predominantly from generators through no more than one transformation or with external reactances in series that is less than 1.5 times generator subtransient reactance. Otherwise the contribution is defined as “remote”). • Calculate no AC Decay ratio (NACD) and multiplying factor MFi NACD = IRemote / ITotal ITotal = ILocal + IRemote (NACD = 0 if all local & NACD = 1 if all remote) • Calculate Iint,rms,adj
= MFi * Iint,rms,Symm
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 319
HV CB Interrupting Capability • CB Interrupting kA varies between Max kA and Rated kA as applied kV changes – MVAsc capability. • ETAP’s comparison between CB Duty of Adj. Symmetrical kA and CB capability of Adjusted Int. kA verifies both symmetrical and asymmetrical rating. • The Option of C37.0101999 standard allows user to specify CPT. • Generator CB has higher DC rating and is always compared against maximum through SC kA. ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 320
LV CB Interrupting Duty •
LV CB take instantaneous action.
•
Calculate ½ Cycle current Irms, Symm (I’f) from the ½ cycle network.
•
Calculate X/R ratio and MFi (based on CB type).
•
Calculate adjusted interrupting current Iadj, rms, symm = MFi * Irms, Symm
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 321
Fuse Interrupting Duty Calculate ½ Cycle current Iint,rms,symm
from ½ Cycle Network.
• Same procedure to calculate Iint,rms,asymm
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
as for CB.
Slide 322
LG Faults
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 323
LG Faults Symmetrical Components
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 324
Sequence Networks
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 325
LG Fault Sequence Network Connections If = 3 × Ia 0 3 × VPr efault If = Z1 + Z 2 + Z0 if Zg = 0
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 326
LL Fault Sequence Network Connections
I a 2 = − I a1 3 × VPr efault If = Z1 + Z 2
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 327
LLG Fault Sequence Network Connections I a 2 + I a1 + I a 0 = 0 = I a VPr efault If = Z0 Z 2 Z1 + Z0 + Z2 if Zg = 0
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 328
Transformer Zero Sequence Connections
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
Slide 329
Solid Grounded Devices and LG Faults Generally a 3  phase fault is the most severe case. L  G faults can be greater if : Z1 = Z 2 & Z 0 < Z 1 If this conditions are true then : I f3φ < I f 1φ This may be the case if Generators or Y/∆ Connected transformer are solidly grounded.
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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Unbalanced Faults Display & Reports Complete reports that include individual branch contributions for: •LG Faults •LLG Faults •LL Faults
Oneline diagram displayed results that include: •LG/LLG/LL fault current contributions •Sequence voltage and currents •Phase Voltages ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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©19962009 © 19962009Operation OperationTechnology, Technology,Inc. Inc.––Workshop WorkshopNotes: Notes:ShortCircuit ShortCircuitIEC ANSI
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©19962009 © 19962009Operation OperationTechnology, Technology,Inc. Inc.––Workshop WorkshopNotes: Notes:ShortCircuit ShortCircuitIEC ANSI
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SC Study Case Info Page
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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SC Study Case Standard Page
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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SC Study Case Adjustments Page
Tolerance Adjustments
•Transformer Impedance •Reactor Resistance •Overload Heater Resistance
Length Adjustments •Cable Length •Transmission Line Length
Temperature Corrections
Adjust Fault Impedance
•Transmission Line Resistance
•LG fault Impedance
•Cable Resistance
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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Tolerance Adjustments Z 'Transforme r = Z Transforme r * (1 ± Tolerance ) Length 'Cable = LengthCable * (1 ± Tolerance ) Length 'Transmissi onLine = LengthTransmissi onLine * (1 ± Tolerance ) Positive tolerance value is used for IEC Minimum If calculation. Negative tolerance value is used for all other calculations.
Adjustments can be applied Individually or Globally
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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Temperature Correction (234.5 + Tc ) R'Copper ' = RBASE * (234.5 + Tb ) ( 228.1 + Tc ) R' Alumi = RBASE * ( 228.1 + Tb ) RBASE = Resistance at base tempereatu re R' = Resistance at operating temperatur e Tb = Conductor base temperatur e in C Tc = Conductor temperatur e limit in C
Temperature Correction can be applied Individually or Globally ©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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System for SC Study Power Grid U1 X/R = 55
Transformers T1 X/R PS =12 PT =12 ST =12 T2 X/R = 12
Gen1 Voltage Control Design Setting: %Pf = 85 MW = 4 Max Q = 9 Min Q = 3
Lump1 Y open grounded
©19962009 © 19962009Operation OperationTechnology, Technology,Inc. Inc.––Workshop WorkshopNotes: Notes:ShortCircuit ShortCircuitIEC ANSI
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System for SC Study
Tmin = 40, Tmax = 90
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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System for SC Study
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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ShortCircuit Alerts • Bus Alert • Protective Device Alert • Marginal Device Limit
©19962009 Operation Technology, Inc. – Workshop Notes: ShortCircuit IEC
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Bus SC Rating Type of Device MV Bus (> 1000 Volts)
LV Bus (
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