JRV 402 Neutral earthing resistor monitoring relay

Features

• Solid state reliability
• Built in Trip test facility
• High sensitivity
• Low burden

Principle of Operation:

A very low DC current is passed through the NER and this is monitored in the relay. If there is an open circuit in resistor or considerable change in the resistor value the same is detected in the monitoring circuit. After detecting the change, timer is shorted and output relay is deenergized at the end of internally set time delay ( 5 Sec ) The relay contact may be connected externally to Alarm/Trip circuit as required. Normally the output relay is kept energized. If there is a failure in Aux. Supply the output relay releases and extends the Alarm/Trip signal.

Application:

The relay is used to monitor the neutral earthing resistor.Transformer neutral is earthed through a resistance. This resistor is called as Neutral Earthing Resistor (NER). Neutral Earthing resistors are used to restrict the fault current through the transformer during earth fault conditions. The healthiness of NER is important as an open resistor would render earth leakage protection in operative and hazardous.