Testing Distance Protection Practical Example of Use
Testing Distance Protection
Manual Version: Expl_DST.AE.1 - Year 2011 © OMICRON electronics. All rights reserved. This manual is a publication of OMICRON electronics GmbH. All rights including translation reserved. The product information, specifications, and technical data embodied in this manual represent the technical status at the time of writing and are subject to change without prior notice. We have done our best to ensure that the information given in this manual is useful, accurate, up-to-date and reliable. However, OMICRON electronics does not assume responsibility for any inaccuracies which may be present. The user is responsible for every application that makes use of an OMICRON product. OMICRON electronics translates this manual from the source language English into a number of other languages. Any translation of this manual is done for local requirements, and in the event of a dispute between the English and a non-English version, the English version of this manual shall govern.
2
Preface This paper describes how to test distance protection zones. It contains an application example which will be used throughout the paper. The theoretical background of the distance protection function will be explained. This paper also covers the definition of the necessary Test Object settings as well as the Hardware Configuration for distance protection tests. Finally the Distance or Advanced Distance test modules are used to perform the tests which are needed for the distance protection zones. Supplements: Requirements:
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Sample Control Center file Example_Distance_Distance_ENU.occ (referred to in this document). Test Universe 2.40 or later; Distance or Advanced Distance and Control Center licenses.
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1
Application Example Network Coupling Transformer 231 kV/115.5 kV/10.5 kV(±16%) 160 (42) MVA Z = 14.2% Yyn0d5
t/s 1.6 1.2 0.8 0.4 0.0
220 kV S²sc=15 GVA
Z t
Z t
32.5 km
110 kV BB A
110 kV BB B
10 km
20.1 km
110 kV BB C
Feeder of the application example
Figure 1: Network and zone diagram of the application example
110 kV Protection functions (21) Characteristic of distance zones: Quadrilateral or Mho 600/1
Distance Relay
Figure 2: Feeder connection diagram of the application example
Note: Testing of associated functions (e.g., Automatic Reclosure, Switch on to Fault), are not part of this document.
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Parameter Name
Parameter Value
Frequency
50 Hz
VT (primary/secondary)
110000 V / 110 V
CT (primary/secondary)
600 A /1 A
Power System Data
Distance protection general settings Distance protection pickup settings (secondary values)
Solidly grounded
Transformer starpoint
64°
Line angle (short-circuit angle sc)
0.218 /km
Secondary line reactance per length unit (/km)
32.5 km (20.19 miles)
Line length in km (miles)
0.6
Zero sequence compensation factor K0 1)
0°
Angle for the Zero sequence compensation factor
1.2 s
Trip time for forward-pick-up
1.6 s
Trip time for non-directional pick-up
Overcurrent
Pick-up program Pick-up value for phase faults = 1.5 x In CT 3I0 / pick-up value for neutral current =0.2 x In CT
1.5 A 0.2 A Forward
Operating mode Z1
6
X(Z1) Reactance of zone 1
2.9
Rphph (Z1) Resistance for phase to phase faults of zone 1 Rphe (Z1) Resistance for phase to ground faults of zone 1 Trip time zone 1 (valid for phase to phase and phase to ground faults)
2.9 0s
Distance protection zone settings for quadrilateral shapes (secondary values)
Notes
Forward
Operating mode Z2
9.2
X(Z2) Reactance of zone 2
4.4
Rphph (Z2) Resistance for phase to phase faults of zone 2 Rphe (Z2) Resistance for phase to ground faults of zone 2 Trip time zone 2 (valid for phase to phase and phase to ground faults)
4.4 0.4 s Reverse
Operating mode Z3
5.6
X(Z3) Reactance of zone 3
2.7
Rphph (Z3) Resistance for phase to phase faults of zone 3 RphE (Z3) Resistance for phase to ground faults of zone 3 Trip time zone 3 (valid for phase to phase and phase to ground faults)
2.7 0.8 s
Notes: 1) = The structure of this parameter is depends on the manufacturers (see chapter 2.3 ). In this example this factor is valid for all zones. Table 1: Relay parameters for this example (quadrilateral impedance diagram)
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Parameter Name
Parameter Value
Notes
Forward
Operating mode Z1
6.66
Reach for phase to phase faults of zone 1
6.66
Reach for phase to ground faults of zone 1 Trip time zone 1 (valid for phase to phase and phase to ground faults)
0s
Distance protection zone settings for mho shapes (secondary values)
Forward
Operating mode Z2
10.2
Reach for phase to phase faults of zone 2
10.2
Reach for phase to ground faults of zone 2 Trip time zone 2 (valid for phase to phase and phase to ground faults)
0.4 s Reverse
Operating mode Z3
6.22
Reach for phase to phase faults of zone 3
6.22
Reach for phase to ground faults of zone 3 Trip time zone 3 (valid for phase to phase and phase to ground faults)
0.8 s
Table 2: Relay parameters for this example (mho shape / see table 1 for all other paramters)
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2
Theoretical Introduction to Distance Characteristics Distance relays are applied as short-circuit protection in almost all systems where overcurrent relays cannot be used for reasons of selectivity, a requirement for fault detection or where this is a need for short disconnection times. They are mainly applied in ring networks with multiple feeds and meshed HV networks. 1.0
1.0
Isc1
Isc3
0.5
Isc2
0.5
Figure 3: Limits of application for overcurrent protection relays
2.1
Impedance Diagrams Based on the primary line data and the projected object data, the reach and the behavior during arc faults are defined in the impedance diagram. 110 kV
600 A 1A
Z´line 0.404 Ω64, 32.5 km
110kV 3
BB A
110 V 3
R
Figure 4: 110 kV line configuration
220 kV S²sc=15 GVA Zone 2 Zone 1
t/s 1.6 1.2 0.8 0.4 0.0
Z t
Zone 3 110 kV BB A
110 kV BB B
Figure 5: Time grading diagram for this example
There are different types of impedance characteristics. For this example only the Quadrilateral and Mho types will be used.
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1
2 1
3 1
4 1 5 1 1. 2. 3.
4 1
2 1
4.
5. 6.
1
Settings of zone 1 Settings of zone 2 Settings of zone 3 Setting of the line angle (it depends on the type of relay, whether this setting exists or not) Setting of the distance characteristic angle Directional characteristic (the directional characteristic depends on the type of relay)
5 1
6 1 3 1
Figure 6: Settings of an impedance diagram (quadrilateral) for a 7SA6 (Siemens AG)
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1
4 1
2 1
5 1
1 3
1 6
7 1
7 1 5 1
4 1
1. 2.
1 2
3. 4.
1
5. 6. 7.
Setting of zone 1 for phase faults Setting of zone 2 for phase faults Setting of zone 3 for phase faults Setting of zone 1 for ground faults Setting of zone 2 for ground faults Setting of zone 3 for ground faults Setting of the line angle
3 1 6 1
Figure 7: Settings of an impedance diagram (mho) for a SEL 421
Note: For the logic of the Ground Distance Elements see chapter 2.3 .
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2.2
Line Impedance Angle (Short-Circuit Angle) A factor which is characteristic of a particular fault is the short-circuit angle between the fault voltage and current. This angle depends on the voltage level and the protected equipment (e.g., overhead line, cable and transformer). This can be examined more closely.
Short circuit angle sc
380 kV
220 kV
110 kV
10 ... 30 kV
Electric arc
Approx. 85°
Approx. 80°
Approx. 72°
30 ... 50°
Approx. 0°
Table 3: Short-circuit angle and voltage levels
a) b)
7SA6 (Siemens AG) SEL 421
1105
1211
Figure 8: Line impedance angle for different distance protection devices
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2.3
Zero-Sequence Compensation Phase to Phase Fault
Phase to Ground Fault
Protected Line Relay
1- Zline
Zline
Protected Line Relay
Zline
1- Zline Zline = Line impedance
1- Zline
Zline
1- Zline
Zline
Zline Zline
1- Zline Zg
= Ground impedance
= Fault position (0...1)
1- Zline
= Fault loop
1- Zg
Zg
Zloop 2 Zline
Zloop 2Zline
Zg
1- Zg
Zloop Zline Zg
Zloop Zline Zg
For phase to phase faults the distance between the relay and the fault can be calculated from the loop impedance by just using the line impedance. However, for phase to ground faults the ground impedance is also needed. To take the ground impedance into account, a zero sequence compensation factor (grounding factor) is used. The definition of this factor depends on the manufacturer of the relay: Factor
Definition
kL
RE X and E RL XL Z0 ZL
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Zg Zline Z0 ZL 3ZL
Rg RE 1 R 0 1 RL Rline 3 R1 X XE 1 X g 0 1 XL Xline 3 X1
Manufacturer
Zg Z0 3 1 Zline Zline
Examples include AEG, Alstom, Areva, SEL, Siemens
Examples include Siemens
Examples include ABB
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Some examples for the settings of these parameters are shown below
Figure 9: Zero sequence compensation factor for SEL 421
Figure 10: Zero sequence compensation factor for distance protection devices from SIEMENS
Setting this factor will influence the resulting zone for phase to ground faults as shown below.
X/
1 kL Z1
Zone setting
Resulting zone
Z1
R/
Figure 11: Influence of the zero sequence compensation factor on the zone
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3
Practical Introduction The Advanced Distance test module and the Distance test module are designed for testing distance protection functions (e.g., impedance diagram, trip times, etc.). Note:
The functionality of the Advanced Distance test module and the Distance test module is different!
Figure 12: Test View of the Advanced Distance test module and Distance test module
For all following discussions, the Advanced Distance test module is used. This test module incorporates the functionality of the Distance test module. The test module can be found on the Start Page of the OMICRON Test Universe. It can also be inserted into an OCC File (Control Center document).
3.1
Defining the Test Object Before testing can begin the settings of the relay to be tested must be defined. In order to do that, the Test Object has to be opened by double clicking the Test Object in the OCC file or by clicking the Test Object button in the test module.
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3.1.1 Device Settings General relay settings (e.g., relay type, relay ID, substation details, CT and VT parameters) are entered in the RIO function Device.
Note:
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The parameters V max and I max limit the output of the currents and voltages to prevent damage to the device under test. These values must be adapted to the respective Hardware Configuration when connecting the outputs in parallel or when using an amplifier. The user should consult the manual of the device under test to make sure that its input rating will not be exceeded.
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3.1.2 Defining the Distance Protection Parameters More specific data concerning the distance protection relay can be entered in the RIO function Distance. The definition of the distance impedance diagram has to be made here as well.
Note:
Once an Advanced Distance / Distance test module is inserted, this RIO function is available.
System Settings The first tab contains the definition of the system data, the relay behavior as well as the relay tolerances.
6 4 1
7 4
3 2 3 4
2 1
4
5 4
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1.
The line length and line angle are the magnitude and angle of the impedance Z of the protected line. They are needed to calculate faults correctly with respect to the power system. Z R
jX
jX
Protected Line
2.
R
If the line reactance X is set in the relay, then the impedance Z has to be calculated out of the reactance Ω X X l 0.218 km 32.5 km 7.88 Ω (see Table 1). X and the line angle . Line length = Z sin sin sin 64 Regarding the feeder connection diagram (Figure 2) the PT is placed at line. If at busbar is chosen, the voltage will have the nominal value after tripping. At line
At busbar
Protected object; e.g. line Busbar
3.
Protected object; e.g. line Busbar
The CT starpoint has to be set according to the connection of the secondary windings of the CT. For this example the feeder connection diagram (Figure 2) shows that the CT grounding is towards the line. Dir. line
Busbar
Busbar
4. 5.
6. 7.
Dir. busbar
Relay
Protected object; e.g. line
Relay
Protected object; e.g. line
Busbar
Busbar
Relay
Protected object; e.g. line
Relay
Protected object; e.g. line
The impedance and time tolerances are found in the relay manual. The grounding factor compensates the effect of the ground impedance on the distance zones (see chapter 2.3 ). For further information on the settings of the grounding factor the Help function should be used. Select this checkbox to enter all impedances in primary values. This checkbox must be activated, if a 5 A relay is tested which uses 1 A as reference for the impedance calculation..
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Zone Settings In the second tab, the distance zones are entered.
As shown above, no zone is set by default. Click New to insert a zone. Afterwards the characteristic editor can be opened by clicking edit. Here the distance zone can be entered.
Click Add to add a new element to the Element list. The element can be either a line or an arc. > A line has to be set with an angle and a point on the line. This point can be set either in cartesian or in polar coordinates. Therefore, the options Line cartesian and Line polar exist. > A circle has to be set with a center point, a radius, a start angle, an end angle as well as a direction. As the center can be set in cartesian as well as in polar coordinates, the options Arc cartesian and Arc polar can be used.
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It is also possible to use Predefined shapes.
1 1 1. 2. 3.
2
3
Mho shape Lens/Tomato shape Quadrilateral
2
3
Now the zones can be defined by combining several elements. Note:
The shape of a distance zone depends on the type of relay as well as on the settings in the relay. The shape can be found in the relay manual. The elements for one quadrilateral as well as for one mho shape are shown below.
Quadrilateral shape (Siemens 7SA6)
Mho shape (SEL 421)
X/
X/
Z1 X1
R/
R/
R1 Relay Parameters
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Relay Parameters
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After the first zone has been defined, the Zone settings tab will look like this:
1 2
If additional zones are required the first zone can be copied (1) and appended to the list (2). Afterwards the settings of the other zones can be adapted. After all the zones have been entered the list could look like this: 3
3. 4. 5.
6. 7.
4
5
6
7
3
5
6
The number of each zone can be defined here. The label of the zones is set automatically but a name can also be entered manually. Four different types of zones can be defined: > Tripping: These zones resemble the tripping zones of the relay. > Starting: This is a zone which normally causes starting only. It is also possible to define a range on the impedance plane in which starting will be followed by tripping after the maximum operating time. > Extended: This is a tripping zone which is only activated occasionally, e.g., by means of "manual close" detection, autoreclosure, etc. > Non tripping: There can be no tripping in this zone, even if it is overlapped by a tripping zone. One example of its use is to model load blinding. With this option the fault loop for each zone can be defined. Therefore, it is possible to set different zones for phase to phase or phase to ground faults. Each zone can also be deactivated.
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After all of the zones are defined, the tripping time for each zone can be set. It is also possible to define separate tolerances for each of the zones.
Note:
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In this example different starting zones have been defined. The zones ZS1 are only in the forward direction. Therefore, the forward directional end time is set as the tripping time for these zones. The zones ZS2 cover the complete impedance plane and, therefore, have the nondirectional end time as the tripping time (see Table 1).
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3.2
Global Hardware Configuration of the CMC Test Set The global Hardware Configuration specifies the general input/output configuration of the CMC test set. It is valid for all subsequent test modules and, therefore, it has to be defined according to the relay’s connections. It can be opened by double clicking the Hardware Configuration entry in the OCC file.
3.2.1 Example Output Configuration for Protection Relays with a Secondary Nominal Current of 1 A
VA
VC VB
VN
IA IB IC IN
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3.2.2 Example Output Configuration for Protection Relays with a Secondary Nominal Current of 5 A
VA
VC VN
VB
IA
IC IB
Note:
IN
Make sure that the rating of the wires is sufficient when connecting them in parallel. The following explanations only apply to protection relays with a secondary nominal current of 1 A.
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3.2.3 Analog Outputs
The analog outputs, binary inputs and outputs can all be activated individually in the local Hardware Configuration of the specific test module (see chapter 3.3 ). 3.2.4 Binary Inputs 4
3
1 2
1. 2. 3.
Trip
Start
4.
The start command is optional (it is needed if Starting is selected as a time reference in the test). The trip command has to be connected to a binary input. BI1 … BI10 can be used. For wet contacts adapt the nominal voltages of the binary inputs to the voltage of the circuit breaker trip command or select Potential Free for dry contacts. The binary outputs and the analog inputs etc. will not be used for the following tests.
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3.2.5 Wiring of the Test Set for Relays with a Secondary Nominal Current of 1A Note:
The following wiring diagrams are examples only. The wiring of the analog current inputs may be different if additional protective functions such as sensitive ground fault protection are provided. In this case IN may be wired separately.
Protection Relay VA VB VC (-) (-) IA IB IC IN
Trip optional
(+) Start (+)
Protection Relay VA VB VC (-) (-) IA IB IC IN
Trip optional
(+) Start (+)
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3.3
Local Hardware Configuration for Distance Protection Testing The local Hardware Configuration activates the outputs/inputs of the CMC test set for the selected test module. Therefore, it has to be defined for each test module separately. It can be opened by clicking the Hardware Configuration button in the test module.
3.3.1 Analog Outputs
3.3.2 Binary Inputs
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3.4
Defining the Test Configuration
3.4.1 General Approach When testing the distance protection function, the following steps are recommended: > Pick-up Test: The respective pick-up function (e.g., Overcurrent starting) is tested. This test is not explained in this document. > Trip time test: The trip times of the distance protection function are verified. > Zone reach test: The zone reaches of the distance protection are verified. The trip time test, as well as the zone reach test, is performed with the Advanced Distance test module.
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3.4.2 Trip Time Test Trigger and Settings tabs:
2
6
1 7
3
4 5
1. 2. 3. 4. 5. 6. 7.
The trigger for this test will be the trip contact. The test model will be Constant test current. This test current is automatically set to 2 x Inom. This current has to be above the pick-up current and so it may have to be increased. Here the angle at which the fault occurs can be set. In this example the mode of the fault inception is set to random. A Load current during the pre-fault state will not be used in this example. Ignore nominal characteristic ignores the zone settings of the test object for the search test. In this example it is not selected. These times define the pre-fault, fault and post-fault states. |t should be ensured, that the Max. fault: time is longer than the non-directional end time setting. The time reference defines whether the fault inception or the start contact is used as a reference for the trip time measurement. In this example it is set to Fault inception.
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Shot Test tab:
1 2
The trip times are tested with the shot test. With this test method test shots can be placed in the impedance plane. These test shots can either be set manually by entering R and X or |Z| and Phi values or an angle can be entered (1) and the values can be set relative to the respective zone (2). To do so, the option |Z| relative has to be selected. If this option is used, the test shots will be adapted whenever the zone settings change. The Follow line angle change option can also be selected in which the angle of the test shots will be adapted whenever the line angle changes. For this test, test shots are placed both inside and outside of the tripping zones. Hence, it is possible to test the trip times of all the tripping zones, as well as the directional and non-directional end time.
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3.4.3 Zone Reach Test In the Trigger and the Settings tab the same adjustments as for the trip time test apply. For the zone reach test the Search Test is used. With this tab the user can define search lines. The test module applies test shots along these lines to search for the reach of each zone. It is also possible to use the Check Test. With this test lines are again defined. However, this time test shots will be placed along these lines outside the tolerance bands. This confirms if the zone reach is within the defined tolerances.
3 1
6
1 2
5 4
4
5
6 3
1. 2. 3. 4. 5. 6.
Search lines can be defined either by dragging a line in the impedance plane or by setting a start point, an angle and the length. After a line has been defined, Add is clicked to add them to the list of test lines. By activating Follow line angle change and Relative test lines can be defined in a way that they adapt to changes of the zone settings or the line angle. In the forward and reverse direction, one search line is defined to test the reactance settings X of the zones. The resistance settings R of the zones are tested in the same way. Using search lines in parallel to the resistance search lines, the characteristic angle is confirmed. Test lines along the line angle can also be set. This confirms that the relay works correctly in the area where faults normally occur.
Feedback regarding this application is welcome by email at
[email protected].
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