ABB RELION 620 Series Technical Manual page 488

Section 4
Protection functions
482
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Figure 242: Operation in "General EF" mode
Operation mode "Alarming EF" is applicable in all kinds of earth faults in unearthed
and compensated networks, where fault detection is only alarming. It is intended to
detect 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 "Alarming EF" mode, the operate timer is
started during the following conditions.
• Earth fault is detected by the 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
not valid in the "Alarming EF" mode. Reset timer is started if any of the above three
1MRS757644 F
620 series
Technical Manual