FDB’S EMGUARD EARTH LINE CONTINUITY MONITOR

A major advantage of the EMGUARD is its high immunity against AC induced voltage in the earth conductor (even where relatively tight limits are required on earth continuity impedance increase) so making it possible to accurately monitor long cable runs (in excess of 1km) without nuisance tripping.

The EMGUARD system features an extra conductor (pilot is utilised and this is connected via an end of line terminator to the framework of the machine at a different point to that of the earth conductor). A circulating current is passed round the pilot/earth loop which, when interrupted due to impedance increase, short circuit or open circuit (loss of earth) causes the opening of the supply to the machine.

Specifications include 110V, 240V or 440V 30-120Hz with an adjustable impedance range of 1 to 20 ohms. Response times on impedance increase are ±3 seconds and short circuit or open circuit ±1 second.

As well as precise impedance increase detection, the EMGUARD will also detect a short circuit between pilot and earth or open circuit of the earth conductor. The EMGUARD is fail-safe in operation, i.e. will trip on loss of energising supply and features auto reset (when system correct), remote test facility and LED status indication.

The EMGUARD can be connected to any existing “active” end of line terminator (diode or zener diode) and can be supplied complete with this type of terminator. Also available is a unique passive resistor type end of line device which will give much higher levels of stability, especially where temperature variation can take place at the remote apparatus.