Function
20
VME420_D00026_03_M_XXDE/04.2019
3.16 Frequency alarm in case of measuring voltage failure
(Menu -> AL -> <U Hz)
If the voltage of the monitored system falls to the point where the frequency
can no longer be determined, this parameter is used to set how the frequency
alarm should behave.
On: The device sets the underfrequency/overfrequency alarm (factory set-
ting).
Off: The device does not set a frequency alarm.
Note for <U Hz = Off:
If there are transients (depending on circuit breakers and
system parameters) when the voltage of the monitored
system fails or returns, the device may still briefly output a
frequency alarm.
To avoid this behaviour, the relay to which frequency alarms
are assigned must be delayed by means of t
on1
or t
on2
and
t
off
.
If the frequency of the monitored system slowly returns (e.g.
due to a starting generator), the frequency monitoring only
becomes active when the frequency is within specified limits
(≥10 Hz).
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