11 PROTECTION TIMING CHECKS
There is no need to check every protection function. Only one protection function needs to be checked as the
purpose is to v
erify the timing on the processor is functioning correctly.
11.1 DEPENDENCY CONDITIONS
Some protection elements can be set to have dependencies on the availability of the protection communication
channel(s) and on the status of the v
oltage transformer supervision function (VTS).
If you are testing a distance model, the distance protection can be permanently enabled, or it can be set so that it
is only enabled in the event of a failure of the protection communications channel(s).
The overcurrent and earth faults elements can be permanently enabled, or can be set so that they are only
enabled:
● in the event of a failure of the protection communications channel(s)
● in the event of a VTS alarm
● according to a logical combination of both conditions.
If these elements are enabled with a dependency upon the above conditions, it is necessary to simulate the
condition to test the correct operation of the protection function.
A communications failure can be simulated by setting the Test Loopback cell to Disabled and checking that the IED
raises a Comms Fail alarm.
At the end of the test, clear the communications alarms and reset the statistics.
A VTS alarm can be raised by applying a 3-phase voltage to the VT inputs and then removing one phase voltage
for a duration exceeding the VTS Time Delay setting.
At the end of the tests, clear the VTS alarm.
11.2 OVERCURRENT CHECK
If the overcurrent protection function is being used, test the overcurrent protection for stage 1.
1.
Check for any possible dependency conditions and simulate as appropriate.
2. In the CONFIGURATION column, disable all protection elements other than the one being tested.
3. Make a note of which elements need to be re-enabled after testing.
4. Connect the test circuit.
5. Perform the test.
6. Check the operating time.
11.3 CONNECTING THE TEST CIRCUIT
1. Use the PSL to determine which output relay will operate when an overcurrent trip occurs.
2.
Use the output relay assigned to Trip Output A.
3. Use the PSL to map the protection stage under test directly to an output relay.
Note:
If using the default PSL, use output relay 3 as this is already mapped to the DDB signal Trip Command Out.
Chapter 20 - Commissioning Instructions P54A/B/C/E
478 P54xMED-TM-EN-1
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