ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-200
E. Setting instructions
Several rate-of-change of frequency stages are often needed
and the additional stages are achieved by configuring the func-
tion as many times as is necessary.
Settings:
Rate-of-change of frequency df/dt
Absolute frequency Frequency
Undervoltage BlockVoltage
Delay Delay
The rate-of-change of frequency function only trips when the
rate-of-change is higher than setting, the absolute frequency
criterion picks up and the voltage is not lower than the under-
voltage setting.
The additional absolute frequency criterion prevents unwanted
operation of the rate-of-change function during power system
transients. Where it is desired that the rate-of-change function
should operate without regard to the absolute frequency, this is
achieved by setting the absolute frequency criterion to ‘0’.
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