Installation and Operating Manual System Protection Relay Energy ...

Fail Safe
The default relay operation is failsafe,
meaning the relay contact is energised in
the ‘normal’ condition and de-energised
in the ‘tripped’ condition. Setting Failsafe
to ‘N’ will change the default relay state
to de-energised, so the relay will energize
on trip. Press ‘Enter’ to select the Failsafe
function, then use the Up/Down keys to
change between Y and N.
Select TripPoint and press ENTER. The
value displayed is in real units – in this
case, AC Volts. Use the up/ down keys to
adjust the trip voltage to 100. When
finished, press ENTER.
DIFF means differential or hysteresis.
This is used to give stability to the relay,
and to stop it from nuisance tripping.
When the measured signal level is very
close to the trip point, electrical noise
and spikes can lead to spurious
energize/de-energize relay operations
when the level momentarily exceeds the
trip point, then returns to its normal
level. The DIFF setting increases the
threshold between trip and reset points
to add stability to noisy systems. The
parameter is a real unit – in this case, AC
volts. Set the value to 3 volts.
Note: Too little hysteresis may lead to nuisance tripping, whilst too much hysteresis
may mean the relay will not drop back in after a trip. Hysteresis settings can cause
problems if set unnecessarily high. The default setting is 1% of the nominal range, but
this can be increased as required for ‘noisy’ signals.
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