ABB RELION 620 Series Technical Manual page 486

Section 4
Protection functions
480
hundreds of ohms of fault resistance. Therefore the application of
transient detection is limited to low ohmic earth faults.
VG
IG
PEAK_IND
GFC
release
Reset timer
INTR_EF
Reset delay time
GUID-A5B0DD30-710A-4E95-82F8-1D2692452239 V2 EN
Figure 241: 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
1MRS757644 F
Reset delay time
620 series
Technical Manual