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Voltage protection Chapter 11
Verifying settings by secondary
injection
7 Voltage protection
7.1 Two step undervoltage protection (PUVM, 27)
Prepare the IED for verification of settings as outlined in section 1 "Overview" and section 2
"Preparing for test" in this chapter.
7.1.1 Verifying the settings
Verification of Start-value and time delay to operate for Step1
Procedure
1. Make sure that the IED settings are appropriate, especially the
Start-value, the definite time delay and the 1 out of 3 operation
mode.
2. Supply the terminal with three-phase voltages at their rated values.
3. Slowly decrease the voltage in one of the phases, until the START
signal appears.
4. Note the operate value and compare it with the set value.
5. Increase the measured voltage to rated load conditions.
6. Make sure that the START signal resets.
7. Instantaneously decrease the voltage in one-phase to a value about
20% lower than the measured operate value.
8. Measure the time delay for the TRIP signal, and compare it with the
set value.
Extended testing
Procedure
1. The test above can now be repeated for Step2.
2. The tests above can be repeated for 2 out of 3 and for 3 out of 3 op-
eration mode.
3. The tests above can be repeated to check security, i.e. the start and
operate signals, that are not supposed to appear, - do not.
4. The tests above can be repeated to check the time to reset.
5. The tests above can be repeated to test the inverse time characteris-
tic.
7.1.2 Completing the test
Continue to test another function or end the test by changing the test mode setting to off. Restore
connections and settings to their original values, if they were changed for test purposes.
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