Testing of Relay MF - Restricted Earth Fault Protection (64)

Before testing, relay technical data and set voltage value to be                                       checked.

            .   Relay connection to be checked according to approved technical                              design. Particular attention should be paid to the correct wiring and                               value of any external resistors indicated on the wiring diagram/relay                            rating information.     

            .     With the relay removed its case, check electrically that the CT                                 shorting switch is closed.

            .     Relay operating voltage to be tested by injection voltage by test plug.                    Increase  the voltage until the relay just operates. Noted operating                     voltage which should correspond to the setting VR  of the relay with a                         tolerance of ± 10%. Note the current in the relay, it should be                                        approximately 38mA at setting. Note Drop off/Pick-up ratio, should be            greater than 50%.

            .    Stability test of the relay to be performed by secondary current                                injection.

            .     Stability test to be performed for two cases: in protected zone and out                               of protected zone.

            .     Operation of the relay trip contacts and indicators to be checked