11.7 Frequency protection
11.7.1 Underfrequency protection SAPTUF (81)
Prepare the IED for verification of settings outlined in Section "Preparing the IED to
verify settings".
11.7.1.1 Verifying the settings
Verification of PICKUP value and time delay to trip
1. Check that the IED settings are appropriate, for example the pickup value and the
time delay.
2. Supply the IED with three-phase voltages at their rated values and initial frequency.
The initial frequency is calculated using Equation 103.
0.02 /0.04 0.04
r
StartFrequency floor f StartFrequency
IECEQUATION16059 V1 EN (Equation 103)
3. Slowly decrease the voltage frequency bysteps of 40 mHz until the TRIP signal
appears; during each step apply the voltage signal for a time that is either at least 10%
longer than (tDelay+100ms) or a suitable time to monitor the function.
4. Note the frequency value at which the START signal appears and compare it with
the set value StartFrequency.
5. Note the frequency value at which the TRIP signal appears and compare it with the
set value StartFrequency.
6. Increase the frequency until its rated value is reached.
7. Check that the PICKUP signal resets.
8. Supply the IED with three-phase voltages at their rated values and frequency 20
mHz over the set value StartFrequency.
9. Decrease the frequency with a 40 mHz step, applying it for a time that is at least 10%
longer than (tDelay+100ms).
10. Measure the time delay of the TRIP signal, and compare it with the set value tDelay.
Note that the measured time consists of the set value of the time delay plus the
minimum trip time of the pickup start function (80 - 90 ms).
Extended testing
1. The test above can be repeated to check the time to reset.
2. The tests above can be repeated to test the frequency dependent inverse time
characteristic.
Verification of the low voltage magnitude blocking
1MRK 504 165-UUS - Section 11
Testing functionality by secondary injection
Transformer protection RET670 2.2 ANSI 223
Commissioning manual
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