GFC
release
INTR_EF
PEAK_IND
Reset timer
Reset delay time
IG
VG
Reset delay time
Figure 251: Example of operation of Transient detector: indication of detected
transient by PEAK_IND output and detection of restriking or intermittent earth fault
by INTR_EF output (setting Peak counter limit = 3)
Operation logic
MFADPSDE supports three operation modes selected with setting Operation mode:
“General EF”, “Alarming EF” and “Intermittent EF”.
Operation mode “General EF” is applicable in all kinds of earth faults in unearthed
and compensated networks. It is intended to detect all kinds of earth faults
regardless of their type (transient, intermittent or restriking, permanent, high or
low ohmic). The setting
Voltage start value defines the basic sensitivity of the
MFADPSDE function.
In “General EF” mode, the operate timer is started in the following conditions.
• Earth fault is detected by the General Fault Criterion (GFC)
• Fault direction equals
Directional mode setting
• Estimated stabilized fundamental frequency residual current exceeds the set
Min
operate current level
The
START
output is activated once
Start delay time has elapsed.
OPERATE
output
is activated once
Operate delay time has elapsed and the above three conditions
are valid. Reset timer is started if any of the above three conditions is not valid.
In case fault is transient and self-extinguishes,
START
output stays activated
until the elapse of reset timer (setting Reset delay time). After
OPERATE
output
activation,
START
and
OPERATE
outputs are reset immediately, if any of the above
1MRS757644 H
Protection functions
620 series
Technical Manual
491
