GFC
release
INTR_EF
PEAK_IND
Reset timer
Reset delay time
IG
VG
Reset delay time
Figure 327: 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 four operation modes selected with setting Operation mode:
"General EF", "Alarming EF", "Intermittent EF" and "Transient EF".
General EF
Operation mode “General EF” is applicable to various earth faults in high-impedance
earthed networks, that is, in compensated, unearthed and high-resistance earthed
networks. It detects earth faults regardless of their type (transient, intermittent or
restriking, permanent, high or low ohmic) and provides definite operate time for
protection regardless of the fault type.
In “General EF” mode, the operate timer is started in the following conditions.
• Earth fault is detected by the GFC
• Fault direction equals
Directional mode setting
•
Estimated stabilized fundamental frequency residual current
I
o stab
1
exceeds the
set
Min operate current level which is applied in current magnitude threshold
supervision, and which is further defined with setting
Operating quantity
(available options are "Adaptive", "Amplitude" and "Resistive").
1MRS759142 F
Protection functions
REX640
Technical Manual
569