GE MiCOM P40 Agile Technical Manual page 270

Chapter 11 - Frequency Protection Functions
Stage
1 -
2 -
3 -3.0
4 -3.0
5 -3.0
In this scheme, tripping of the last two stages is accelerated by using the independent rate of change of frequency
element. If the frequency starts falling at a high rate (> 3 Hz/s in this example), then stages 3 & 4 are shed at
around 48.5 Hz, with the objective of improving system stability. Stage 5 serves as an alarm and gives operators
advance warning that the situation is critical.
244
Rate of Change of Frequency
Rate of Change of Frequency Setting (Hz/Sec.)
"df/dt+t [81R]" Elements
Time Setting (Sec.)
-
-
0.5
0.5
0.1
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