Saturday, July 16, 2016
Testing of RESTRICTED EARTH FAULT RELAY (87N)
Restricted Earth Fault Relay is tested with secondary injection test set with
electronic meter.
. Isolate the Relay current Measuring Element & Trip Alarm contact by
inserting the Test Block MMB01.
. Set the seal in coil rating to 0.2 A dc.
. Set the trip level value to 0.2 A.
. Connect the Relay trip output contacts (terminal # 1 & 2) to both trip the
test set, and stop a timer.
. Inject single phase current into current element (terminal # 5 & 6) & slowly increase the current until the 0.2A is reached.
. Checked that the output contacts closed and right side flag (on the relay
front operated).
. Inject 5 times the current setting i.e. 1A, in the relay and note that the
timing is < 50ms.
. Connect the Relay Trip output contacts (terminals # 1 & 2) to REF- Lockout Relay circuit (86-coil with series cut-off contact) and the output of Lockout contact to both trip the test set, and stop a timer, (refer schematic diagram)
. Apply 125VDC to lockout relay circuit.
. Inject single phase current into current element (terminal # 5 & 6) & slowly increase the current until the 02.A is reached.
. Checked that the ouput contacts (terminal # 1 & 2) closed and both Flags
(left “Trip” flag and right” Seal in flag”) operated plus the operation of
lockout relay.
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