Stage
Rate of Change of Frequency
"df/dt+t [81R]" Elements
Rate of Change of Frequency Setting (Hz/Sec.) Time Setting (Sec.)
1 - -
2 - -
3 -3.0 0.5
4 -3.0 0.5
5 -3.0 0.1
In this scheme, tripping of the last two stages is accelerated by using the independent rate of change of frequency
element. If the fr
equency 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.
Chapter 11 - Frequency Protection Functions P14x
244 P14xEd1-TM-EN-1
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