Testing Directional Ground Fault Determination Practical Example of Use
Testing Directional Ground Fault Determination
Version: Expl_GndFlt_SteadyState.ENU.1 - Year: 2014 © OMICRON OMICRON electr electroni onics. cs. All rights rights reserv reserved. ed. This application note is a publication of OMICRON electronics GmbH. All rights including translation reserved. Reproduction of any kind, for example, photocopying, microfilming, optical character recognition and/or storage in electronic data processing systems, requires the explicit consent of OMICRON electronics. Reprinting, wholly or in part, is not permitted. 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. 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 e vent of a dispute between the English and a non-English version, the English version of this manual shall govern. We have done our best to ensure that the information given in this manual is useful, accurate, u p-to-date and reliable. However, OMICRON electronics does not assume responsibility for any inaccuracies which may be present. Please use this note only in combination with the related product manual that contains several important safety instructions. The user is responsible for every application that makes use of an OMICRON product.
2
Content Preface ......................................................................................................................................................... 4 1
Application Example ............................................................................................................................ 5
2
Theoretical Introduction to Directional Ground Fault Determination ............................................. 7 2.1 Characteristic of the Ground Fault Current.................................................................................... 7 2.2 Determination of the Fault Direction .............................................................................................. 8 2.2.1 2.2.2
2.3 3
Directional Characteristic for Isolated Networks ............................................................................... 8 Directional Characteristic for Compensated Networks ......................................................... ........... 10
Voltage Measurement for Directional Ground Fault Determination ............................................ 12
Practical Introduction to Steady-State Directional Ground Fault Testing .................................... 14 3.1 Defining the Test Object .............................................................................................................. 14 3.1.1
3.2
Device Settings ............................................................ ................................................................... 15
Global Hardware Configuration of the CMC Test Set ................................................................. 16 3.2.1 Example Output Configuration for the Directional Ground Fault Function ........................... ........... 16 3.2.2 Analog Outputs ............................................................ ................................................................... 17 3.2.3 Binary Inputs ................................................................ .................................................................. . 17
3.3
Local Hardware Configuration for Directional Ground Fault Testing........................................... 18 3.3.1 Analog Outputs ............................................................ ................................................................... 18 3.3.2 Binary Inputs ................................................................ .................................................................. . 18
3.4
Defining the Test Configuration ................................................................................................... 19 3.4.1 3.4.2 3.4.3
General Approach ........................................................ ................................................................... 19 Ground Fault Test Module ........................................................................................ ...................... 21 Directional Test ............................................................ ................................................................... 26
Support....................................................................................................................................................... 27
© OMICRON 2014
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Preface This paper describes how to test the directional ground fault determination function (based on steady-state values) for permanent ground faults in isolated and compensated networks . It contains an application example that will be used throughout the paper. The theoretical background of the steady-state directional ground fault determination function will be explained. This paper also covers the definition of the necessary Test Object settings as well as the Hardware Configuration for testing this function. Finally, the Ground Fault test module will be used to test the directional decision of the related relay function. Supplements: Sample Control Center file Example_GroundFault_SteadyState.occ (referred to in this document). Requirements: Test Universe 3.00 or later; Ground Fault; Ramping and Control Center licenses.
Note:
© OMICRON 2014
Testing the transient ground fault determination is not described in this document. For further information regarding this subject, see Example_GroundFault_Transient.pdf.
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1
Application Example 20 kV
20 kV Protection Functions (21) Distance Protection Function (not a part of this document)
200/1
(67N) Directional Ground Fault Function Distance Relay
A
N
a
n
A
N
a
n
A
N
a
n
20000 V IN
3
100 V 3
VResidual
da
dn
da
dn
da
dn
100 V 3
60/1
Figure 1: Feeder connection diagram of the application example
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Parameter Name
Parameter Value
Frequency
50 Hz
VT (primary / secondary phases / secondary open delta)
20000 V
CT (primary/secondary)
100 V
3
3
60 A /1 A
0.04 IN,nom
Ground Fault Settings
0.4
1)
Vnom 3
Notes 100 V 3
VResidual (open delta winding) is connected CT ratio of the cable type (split core) current transformer Note: For overhead lines the phase CTs are connected to a Holmgreen circuit. In this case use the CT ratio of the phase CTs. Pick-up value of the ground fault determination in forward and reverse direction; depending on the manufacturer, the relay may have different settings for both directions. (IN,nom is a reference current that can be obtained from the relay manual. In this case it is the rated current of the protective relay) 1) Pick-up value of residual voltage
cos phi
Directional characteristic. Depends on the transformer star point connection (see chapter 2.2 )
1s
Delay time of the directional decision
= The Pick-up value depends on the transformer star point connection.
Table 1: Relay parameters for this example
Note:
© OMICRON 2014
In this example, the directional ground fault function indicates the direction of the fault (forward or reverse), but it does not trip.
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2
Theoretical Introduction to Directional Ground Fault Determination
2.1
Characteristic of the Ground Fault Current A fault inception is a sudden change of state in the power system. Therefore, the power system will transition from one steady-state into another. In isolated networks, the fault current during and after this transition is mainly caused by the phase-to-ground capacities of the network. In compensated networks, the Petersen coil (arc extinction coil) that is connected between the star point and ground also contributes to the fault current. Therefore, the time signal of the ground fault current consists of two basic components:
1
2
Figure 2: Characteristic of the ground fault current (with Petersen coil )
1.
2.
The transient ground fault current, which is caused by discharging and charging of the power system components. The peaks of this current can be several times higher than the nominal current of the power system. It has a frequency range between 500 Hz and 8 kHz for the discharge and 70 Hz to 4 kHz for the charge of the phase-to-ground capacities of the power system. After fault inception, it lasts only for a few periods of the nominal frequency of the power system. Transient ground fault relays can use this current to determine the direction of a ground fault. The steady-state ground fault current, which is caused by the phase-to-ground capacity of the non-faulty phases and – for compensated networks only – by the Petersen coil. The magnitude of the ground fault current depends on the phase-to-ground capacities and on the network configuration (isolated or compensated) and therefore can be much smaller than the magnitude of the nominal current. As it is a steady-state current, it has the nominal frequency of the network (50 Hz or 60 Hz). This ground fault current can be used by the directional ground fault determination function (sensitive, permanent or wattmetrical ground fault detection) to determine the direction of the ground fault.
Note:
© OMICRON 2014
The following document will only focus on the directional ground fault determination based on steady-state values.
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2.2
Determination of the Fault Direction
2.2.1 Directional Characteristic for Isolated Networks
VC
180°
1 +90°
N
G
0°
VResidual VB
-90°
+90°
2
VC 180°
VB
0°
IC
-90°
+90°
IB IN IA IB IC
ICap IN
3
VC 180°
0°
VB -90°
Figure 3: Primary voltages and currents during a ground fault in an isolated medium voltage radial network
Figure 3 shows the primary values of an isolated radial network during a ground fault. The voltages and currents can be explained as follows: 1.
As the star point of the network is not solidly grounded, a ground fault will not cause a short circuit. Therefore, the voltage between the faulty phase and the star point N will not break down. Instead, the phase voltage will be dragged to ground potential. This will cause the residual voltage between the star point N and ground. Additionally, the magnitude of the phase-to-ground voltages of the non-faulty phases will rise to the magnitude of the phase-to-phase voltages, and the angle between the phase-to-ground voltages will change from 120° to 60°. During the ground fault, the phase-to-phase voltages will remain as they were before.
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2.
3.
The phase-to-ground capacities of the non-faulty phases and the ground fault form fault loops . The currents in these loops are driven by the phase-to-ground voltages. Because of the capacities, the fault current in each phase will lead the respective voltages by 90°. The sum of the currents in all phases IN is measured by a cable type CT or, for overhead lines, by the sum of three phase CTs connected in parallel by a Holmgreen circuit. In non-faulty feeders, the sum current will have an angle of -90° with reference to the vector diagram of the voltages (1). All the fault loops mentioned in (2) will go through the faulty feeder. Therefore, the sum of all capacitive currents of all non-faulty feeders will flow through the cable type CT in the faulty feeder. This current is the capacitive ground fault current of the network ICap . The fault loops of the faulty feeder , however, will go through the cable type CT two times and in different directions. Therefore, the cable type CT cannot measure the capacitive currents of the faulty feeder! The resulting current IN through the cable type CT is the capacitive ground fault current of the network ICap . As ICap is the sum of the capacitive currents in all non-faulty feeders. It is usually significantly higher than the capacitive current in a single non-faulty feeder. Also the capacitive current in the faulty feeder is shifted by 180° in comparison to the non-faulty feeders. Therefore, it will have an angle of 90° with reference to the vector diagram of the voltages (1).
Based on the direction of the current sums IN in the faulty and the non-faulty feeder, the relay can decide on the direction of the fault. +90°
IN Faulty Feeder
VC
Forward IPick-up
180°
VResidual
0°
IPick-up
VB
IN Non-Faulty Feeder -90°
Reverse
Figure 4: Directional characteristic of the directional ground fault protection function for isolated networks (sin- circuit) with primary voltages and currents
Figure 4 shows the directional characteristic for isolated networks. As the ground fault currents are capacitive currents, the direction can be determined by analyzing the imaginary part of the current. This is also called sin- circuit. The relay at the faulty feeder will indicate "Forward", whereas the relays at nonfaulty feeders will indicate "Reverse". Therefore, the faulty feeder can be detected by observing the directional indicators of all relays at the busbar. Note:
© OMICRON 2014
Depending on the phase-to-ground capacities of the respective non-faulty feeder, the current sum in this feeder may be below the pick-up value. Therefore, some non-faulty feeders may not show "Reverse".
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2.2.2 Directional Characteristic for Compensated Networks
VC
180°
1 +90°
N
G
0°
VResidual VB
-90°
+90°
2
VC 180°
VB
0°
IC
-90°
IB IN IA IB IC
+90°
ICap
3
VC 180°
0°
IN VB ICap -90°
IInd
Figure 5: Primary voltages and currents during a ground fault in a compensated medium voltage radial network
Figure 5 shows the primary values of a compensated radial network during a ground fault. The voltages and currents can be explained as follows: 1.
As the star point of the network is not solidly grounded a ground fault will not cause a short circuit. Therefore the voltage of the faulty phase will not break down. Instead it will be dragged to ground potential. This will cause the residual voltage between the star point N and ground. Also the magnitude of the phase-to-ground voltages of the non-faulty phases will rise to the magnitude of the phase-to-phase voltages, and the angle between the phase-to-ground voltages will change from 120° to 60°. During the ground fault, the phase-to-phase voltages will remain as they were before.
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2.
3.
The phase-to-ground capacities of the non-faulty phases and the ground fault form fault loops . The currents in these loops are driven by the phase-to-ground voltages. Because of the capacities, the fault current in each phase will lead the respective voltages by 90°. The sum of the currents in all phases IN is measured by a cable type CT. In non-faulty feeders, the sum current will have an angle of -90° with reference to the vector diagram of the voltages (1). All the fault loops mentioned in (2) will go through the faulty feeder. Therefore, the sum of all capacitive currents of all non-faulty feeders will flow through the cable type CT in the faulty feeder. This current is the capacitive ground fault current of the network ICap . The fault loops of the faulty feeder , however, will go through the cable type CT two times and in different directions. Therefore, the cable type CT cannot measure the capacitive currents of the faulty feeder! The Petersen coil that is placed between the star point and ground will also form a fault loop through the ground fault . The current in this fault loop is driven by the residual voltage VResidual . This inductive current IInd will be added to the capacitive ground fault current ICap and therefore, will compensate it. The detuning v quantifies this compensation, and it is defined as follows: ICap IInd v IInd
In most applications the inductive current will be higher than t he capacitive current to avoid resonances at the nominal frequency of the network. Also the Petersen coil is not an ideal inductivity, and it therefore has a resistive component that shifts the current through the inductivity along the real axis (0°). Therefore, in most applications, the sum of the currents IN through the cable type CT of the faulty feeder will be in the fourth quadrant (depending on the application, it may also be in the first quadrant). Based on the direction of the current sums IN in the faulty and the non-faulty feeder, the relay can detect if the fault is in forward direction. Reverse VC
+90°
IPick-up
Forward IPick-up
180°
0°
VResidual
IN Faulty Feeder
VB IN Non-Faulty Feeder -90°
Figure 6: Directional characteristic of the directional ground fault protection function for compensated networks (cos- circuit) with primary voltages and currents
Figure 6 shows the directional characteristic for compensated networks. As the current sum in the faulty feeder is partly resistive, the relay can detect the faulty feeder by analyzing the real part of the current. This is also called cos- circuit. The relay at the faulty feeder will indicate "Forward". Therefore, the faulty feeder can be detected by observing the directional indicators of all relays at the busbar. Note:
© OMICRON 2014
As the current sum in non-faulty feeders is capacitive, its real part is almost zero. Therefore, the relay is not able to detect the fault direction in non-faulty feeders, and it will not show "Reverse".
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2.3
Voltage Measurement for Directional Ground Fault Determination For correct ground fault direction determination and for the pick-up of the residual voltage, the direction and the magnitude of the measured voltages must be correct. Figure 7 shows the connection and the phasors of the different voltages. A
B
20,000 V
C
100 V
3
100 V 3
3
A
N
A
N
A
N
V A VB
a
n
a
n
a
n
V Residual
da
dn
da
dn
da
dn
VC
Measured residual voltage at open delta winding Primary VC
VC
+90°
N
180°
Secondary
G
0°
VResidual VB
+90°
180°
0°
VResidual VB
-90°
-90°
Calculated zero sequence voltage from phase voltages Primary VC
Secondary
N
180°
VC
+90°
G
0°
+90°
180°
V0
0°
V0
VB
-90°
VB
-90°
Figure 7: Voltage measurement for directional ground fault protection
It is possible to either measure the residual voltage at an open delta winding or to calculate the zero sequence voltage out of the phase voltages. The measured residual voltage will be: V Residual
V
A
VB V C
3
The calculated zero sequence voltage will be: V0
V
A
© OMICRON 2014
VB V C
3
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Table 2 shows an example of how to calculate the respective voltages. Primary Voltages
Secondary Voltages
V A 0 kV 0° V B 20 kV -150° 20 kV +150° V C
V A 0 V 0° V B 100 V -150° 100 V +150° V C
Residual Voltage
V Residual
V
A
VB V C 3
100 V 180°
Zero Sequence Voltage 1 a a2 V1 V A 1 2 a VB V 2 1 a 3 VC 1 1 1 V 0 V0
V
A
VB V C
3
57.74 V 180° Table 2: Example of the voltages during a ground fault
© OMICRON 2014
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3
Practical Introduction to Steady-State Directional Ground Fault Testing There are different approaches on testing protection systems: > Conventional testing: The test values are defined manually to test specific parameters or specific protection functions. Simulation-based testing: The test values are obtained from a transient simulation of the > power system to test the function of the protection system as a whole. The Ground Fault test module is designed for simulation-based testing of transient ground fault relays and directional ground fault relays based on steady-state values. It is able to simulate the power system and to directly output the simulation results with a CMC test device. This test module can be found on the start screen 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:
The CT data of the cable type CT is entered. Add a new Test Object if you are testing with an OCC-file where this setting interferes with other tests (e.g. overcurrent or distance protection). 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.
© OMICRON 2014
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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 the Directional Ground Fault Function
V A
I A
VC
VResidual
VB
N
IB IC
N
N
Figure 8: Wiring of the analog outputs of the CMC test set.
© OMICRON 2014
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3.2.2 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 ). 3.2.3 Binary Inputs 4
3
2 1 1. 2. 3. 4.
The binary contacts of the directional indicators have to be connected to binary inputs. Any free binary input can be used. Depending on other protection functions (e.g. overcurrent or distance protection), some binary contacts may already be used. For wet contacts, adapt the nominal voltages of the binary inputs to the voltage of the respective signal, or select Potential Free for dry contacts. The binary outputs and analog inputs etc. will not be used for the following tests.
F o r w a r d D i r e c t i o n
R e v e r s e D i r e c t i o n
Figure 9: Wiring of the binary inputs of the CMC test set.
© OMICRON 2014
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3.3
Local Hardware Configuration for Directional Ground Fault 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
© OMICRON 2014
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3.4
Defining the Test Configuration
3.4.1 General Approach When testing the directional ground fault protection function, the following steps are recommended:
>
Pick-up Test: Testing the current and voltage pick-up value of the ground fault directional determination.
The pick-up test should be a secondary test with the current injection at the inputs of the protection device. This test can be performed with the Ramping test module and will not be explained in this document. For more information about testing pick-up values with the Ramping test module, please see the example file Example_Ramping_Overcurrent.pdf.
© OMICRON 2014
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>
Directional Test: Verifying the directional decision by simulating the fault currents at a faulty and a nonfaulty feeder.
When using a cable type CT for the directional ground fault protection, it is recommended to perform the directional test with primary current injection. With this method, it is possible to test if the relay detects the correct fault direction including the wiring of the cable type CT. In this case, the current outputs of the CMC test set are injected through a test lead that goes through the cable type CT at least once. The more often the test lead goes through the cable type CT, the lesser the current output of the CMC test set can be in order to simulate the primary ground fault current. Figure 10 shows the wiring of the CMC test set for testing with primary current injection.
Protection Relay
A
N
a
n
da
dn
A
N
a
n
da
dn
A
N
a
n
da
dn
Figure 10: Wiring of the CMC test set for testing the directional ground fault function with primary injection
Note:
Depending on the relay type, it may be necessary to also simulate the phase-to-ground voltages.
The directional test is performed with the Ground Fault test module.
© OMICRON 2014
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3.4.2
Ground Fault Test Module
1
2
3
The Ground Fault test module simulates ground faults in a power system that consists of:
2.
Infeed: Transformer:
3.
Network:
1.
This is the source for the power system. It transforms the power from the infeed to the test network. It also provides the star point for possible Petersen coil or resistor connections. This is a radial network that consists of one busbar and multiple feeders that are connected to the busbar. Figure 11 shows the elements of the network. The ground fault will always be simulated in feeder A. Feeder B will always be a nonfaulty feeder. (See below for how to simulate forward or reverse faults.) All remaining feeders are combined to one element, the "Remaining System".
Feeder E Feeder D Feeder C Feeder B Feeder A
Figure 11: Definition of the network elements of the test module Ground Fault
To test a ground fault relay, the parameters of these elements have to be set.
© OMICRON 2014
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Test tab 1.
2.
1
2 3
3. 4.
4 5 6
5.
7
6.
7.
The nominal frequency of the network can be entered here. It is also possible to use the frequency from the test object. With this option, the network type can be set. Choose Cable if the network to be simulated is a pure cable network or a mix between cables and overhead lines. Select Open line if a pure overhead line network should be simulated. The phase in which the fault should be simulated can be selected here. Select Permanent to test the directional ground fault function based on steady-state values. Select Transient to test transient ground fault relays. Note: See Example_GroundFault_Transient.pdf for more information on testing transient ground fault relays. The ground fault will always be simulated in feeder A. To define whether a faulty or a non-faulty feeder should be simulated, the relay location can be changed. Select Feeder A to simulate a faulty feeder or Feeder B to simulate a non-faulty feeder. This option defines the direction of the CT star point. When injecting the current directly to the cable type CT as shown in Figure 10, this setting has to be set to Dir. line. To simulate a ground fault correctly, the t est module needs a ground fault resistance. This is the resistance between the faulty phase and ground. The default value can be used, if this value is unknown.
Transformer tab Enter the nominal voltages of the transformer here. 9. Define the grounding of the transformer star point with these options. Select Isolated if the simulated network should have no connection between star point and ground (see also chapter 2.2.1 ). Choose Compensated for compensated networks (see also chapter 2.2.2 ). The detuning must be set if Compensated is selected. For compensated networks, it is also possible to add a grounding resistance in parallel to the Petersen coil. This increases the resistive part of the ground fault current. This setting is entered as primary value. 10. Here, the rated power of the transformer is defined. 11. Also the transformer impedance has to be set for the simulation. This parameter is equivalent to the relative short circuit voltage and can be found on the name plate of the transformer. 12. This value is the short circuit power of the infeed at the HV side of the transformer. 8.
8
9
10 11 12
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Network tab 1.
1 2.
2
3.
3
For the simulation, it is also necessary to enter the line parameters of the faulty feeder. These values resemble the line or cable between the busbar and the fault. The resistance and the reactance have to be defined for the positive and the zero sequence as primary values. These parameters define the primary capacitive ground fault current. Network: The combined ground fault current of the remaining system. Feeder A: The ground fault current that is caused by the phase-to-ground capacities of the faulty feeder. Feeder B: The ground fault current of the non-faulty feeder. When testing with primary injection as shown in Figure 10, the number of windings through the cable type CT must be entered at Prim.:, whereas Sec.: is set to one. Figure 12 shows how to define the CT nominal currents for testing with primary current injection. Note: If the test current exceeds the maximum output currents of the CMC test set, the number of windings through the cable type CT can be increased. If the test is performed with secondary current injection, the CT ratio of the respective CT must be entered here. In this case, it is also possible to use the CT r atio from the test object by selecting the checkbox.
4
3
2
1
Figure 12: Setting the CT nominal currents for testing with primary injection
© OMICRON 2014
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General tab 1.
1
2
2.
3 3.
Here, the start condition of the test can be set. This defines the behavior of the test module after clicking the Start/continue test button on the toolbar. When selecting Immediately, the test will begin as soon as Start/continue test is clicked. If On binary input: is activated, the test will only start when the selected binary input is triggered. When On time trigger is selected, the test will only start after a signal from a connected time source as specified in the Hardware Configuration. The prefault time defines the time before the ground fault is simulated. This time only applies if Transient is selected at the Test tab. With this option, the duration of the fault can be defined. Make sure the time is long enough to get the correct reaction from the relay.
Time Assessments 4
5
6
7
8
It is also possible to do time measurements of the connected binary triggers. 4. 5.
6. 7. 8.
The name of the measurement can be entered here. With this option, it is possible to ignore all changes of the binary inputs before the selected event. This ensures that the time measurement is not influenced by binary signals that occurred before the measurement. For the time measurement, a start and a stop condition have to be defined. These conditions can be either events like the start of the voltage output or the fault inception or binary inputs. To assess the time measurement, the expected time as well as the respective tolerances must be entered here. Consult the relay manual to define the tolerances. The measured time as well as the deviation to the expected time are displayed after the test. If the measured deviation is within the tolerances, the measurement will be assessed as passed. Otherwise, it will be assessed as failed.
Right-click the measurement, and select Add to add more measurements if necessary.
© OMICRON 2014
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Time Signal View
1
The time signal view shows analog and binary signals of the test. It can be used to check whether the binary contacts of the relay reacted as expected. Also the cursors (1) can be used via dragging to measure times manually.
© OMICRON 2014
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3.4.3
Directional Test
The directional test is performed by simulating the same ground faults but changing the relay location. As shown in Figure 13, the first test is performed with the relay located in the faulty feeder (Feeder A). The second one is then performed with the relay in a non-faulty feeder (Feeder B). The r emaining settings of the Test view are equal.
Figure 13: Definition of a faulty and a non-faulty feeder
The assessment of the test depends on the test step: > Faulty Feeder : During this test, the relay must detect the forward direction of the fault correctly. The time assessments can be used to measure the time between the start of the ground fault output and t he appearance of the forward direction indicator. With this measurement, it is possible to check whether the forward direction was detected correctly and to confirm the delay time of the directional decision. The time signal view can also be used to check whether the relay operated as expected. Non-Faulty Feeder: During this test, the relay detects either a fault in reverse direction, or it is not able > to detect any direction. If the relay can detect the reverse direction, the time measurement can be used for assessment. Otherwise, the time signal view can be used to check whether the relay operated as expected. Note:
The test can always be assessed manually by selecting Manual Assessment on the Home ribbon.
Feedback regarding this application is welcome via email to
[email protected].
© OMICRON 2014
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