ABB RELION REX640 Technical Manual page 574

Protection functions
Figure 330: Operation in "Intermittent EF" mode, Peak counter limit = 3
Transient EF
Operation mode "Transient EF" is dedicated for detecting fast transient faults
where the fault current stays on only for a very short time. It is recommended
method in networks, where network damping has very small value or when parallel
resistor of the coil is not used, for example in sub-transmission networks.
In the "Transient EF" mode, the fault direction is determined from the beginning of
the fault and is held until earth-fault is detected by GFC.
In the "Transient EF" mode, the operate timer is started when the following
conditions are met.
• Earth fault is detected by the GFC
• Fault direction equals Directional mode setting and fault direction detection is
done only at the beginning of the fault
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1MRS759142 F
REX640
Technical Manual