RFL 9300 RFL Electronics Inc.
August 9, 2001 4 - 7 (973) 334-3100
4.2.6 FD PHASE - PHASE FAULT DETECTOR
Parameter #25 (FD PHASE) controls the local phase overcurrent fault detector. It can be set to
either 6 amperes or 8 amperes. It should be set above the maximum expected load, with a 10
to 15-percent safety margin. 6 amperes will be suitable for most applications. The phase over-
current fault detector is triggered when the peak true CT current value exceeds the peak value
of the setting i.e. 8.5A pk for a 6Arms setting and 11.25A for a 8Arms setting.
A high fault detector current setting does not compromise sensitivity, because the steady-state
fault detector is supplemented by several current-change fault detectors that are very sensitive.
The fault detectors are always monitoring the true CT current regardless of whether the relay is
configured for 2-terminal or 3-terminal operation. These detectors require no settings, and in-
clude the following:
o Peak Change
o Pulse-Width Change
o Slope Change
o Polarity Change
4.2.7 FD GND - GROUND FAULT DETECTOR
Parameter #26 (FD GND) controls the local ground overcurrent fault detector current. It can be
set to either 0.5 amperes or 1.0 amperes. It should be set above the maximum expected 3I
0
due to unbalanced load. 0.5 amperes will be suitable for most applications. The ground overcur-
rent fault detector monitors the integral value of the true CT current in order to de-sensitize its
response to transients.
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