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
conditions are not valid. In case the fault is transient and self-extinguishes, START
output stays activated until the elapse of reset timer (setting
Reset delay time
).
In case detection of temporary earth faults is not desired, the activation
of START output can be delayed with setting
Start delay time
.
To keep the operate timer activated between current spikes during
intermittent or restriking earth fault, the
Reset delay time
should be set
to a value exceeding the maximum expected time interval between fault
spikes (obtained at full resonance condition). The recommended value is
at least 300 ms.
1MRS758755 C Protection functions
REC615 & RER615
Technical Manual
401
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