ABB 615 series Technical Manual page 460

Section 4
Protection functions
454
• Transient is detected by the Transient detector (indicated with PEAK_IND output)
• Ground fault is detected by the GFC at time of transient
• Fault direction equals Directional mode setting
• Estimated stabilized fundamental frequency residual current exceeds the set Min trip
current level
When a required number of intermittent ground-fault transients set with the Peak counter
limit setting are detected without the function being reset (depends on the drop-off time set
with the Reset delay time setting), the PICKUP output is activated. The INTR_EF output
is activated to indicate the fault type is intermittent or restriking ground fault. The operate
timer is kept activated as long as transients occur during the drop-off time defined by
setting Reset delay time.
The TRIP output is activated when Trip delay time has elapsed, required number of
transients has been detected, ground fault is detected by the GFC, fault direction matches
the Directional mode setting and estimated stabilized fundamental frequency residual
current exceeds set Minimum trip current setting.
The Reset delay time starts to elapse from each detected transient. Function is reset if time
between current peaks is more that Reset delay time or if the General Fault Criterion
release is reset. After TRIP output activation, PICKUP and TRIP outputs are reset
immediately at the falling edge of General Fault Criterion release, that is, when zero-
sequence voltage falls below Voltage pickup value. This should be considered if
"Intermittent EF" mode is applied in case ground faults are only alarmed to avoid
repetitive pickup and trip events.
To keep the operate timer activated between current spikes during
intermittent or restriking ground fault, Reset delay time should be set to a
value exceeding the maximum expected time interval between (obtained
at full resonance condition). The recommended value is at least 300 ms.
1MAC059074-MB A
615 series ANSI
Technical Manual