P92x/EN CM/E11 Techncal Guide
Commissioning Guide
Page 22/28 MiCOM P921-P922-P923
abcd
Settings
[81R] Rate of change of
frequency
Default values
Group 1/2
1
st
stage activated No No/Yes
1
st
stage 1.0 Hz/s Hz/s
2
nd
stage activated No No/Yes
2
nd
stage 1.0 Hz/s Hz/s
3
rd
stage activated No No/Yes
3
rd
stage 1.0 Hz/s Hz/s
4
th
stage activated No No/Yes
4
th
stage 1.0 Hz/s Hz/s
5
th
stage activated No No/Yes
5
th
stage 1.0 Hz/s Hz/s
6
th
stage activated No No/Yes
6
th
stage 1.0 Hz/s Hz/s
5.5.3 Test example : stage df/dt1 & df/dt2
First program the first stage of df/dt at +0.5 Hz/s and the second stage at –0.5 Hz/s.
NOTE : the setting of the Dt should be low as mush as it is possible than
the period in order to detect the small variation within the time.
Select for example a range of frequency from 50 Hz to 51 Hz with a variation of
1 mHz every 1 ms. The result is shown in the table (1
st
line). If you assign the 1
st
threshold to the tripping relay (RL1), so tripping will occur.
Repeat the test with a range of (50 – 49 Hz), now the 2
nd
threshold will operate.
Also you can assign these threshold to output relays and LEDs and verify the
functioning of these elements.
Nominal frequency
selected
Frequency df dt df/dt
50 51 Hz 1 mHz 1 ms 1 Hz/s
50 49 Hz –1 mHz 1 ms –1 Hz/s
Action check : (if output relays and LEDs are associated)
1. Appearance of an Alarm message on the display
2. Flashing of the "Alarm" LED
3. Illumination of the "TRIP" LED if tripping is programmed
4. Illumination of the LEDs associated with the stages df/dt1 & df/dt2
5. Trip relay operation RL1 if programmed
6. Operation of output relay associated with the stages df/dt1 & df/dt2
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