three conditions is not valid. The start duration value START_DUR, available in the
Monitored data view, indicates the percentage ratio of the start situation and the
set operating time.
In case detection of temporary earth faults is not desired, the activation
of
START
output can be delayed with setting
Start delay time. The same
setting can be also used to avoid restarting of the function during long
lasting post-fault oscillations, if time constant of post-fault oscillations
is very long (network losses and damping is low).
To keep the operate timer activated between current spikes during
intermittent or restriking earth fault, the
Reset delay time should be set
to a value exceeding the maximum expected time interval between fault
spikes (obtained at full resonance condition). Recommended value is at
least 300 ms.
Figure 252: Operation in “General EF” mode
Operation mode “Alarming EF” is applicable in all kinds of earth faults in unearthed
and compensated networks, where fault detection is only alarming. It is intended
Protection functions
1MRS757644 H
492
620 series
Technical Manual
