Pilot Cable Monitor Function

The PCM177 pilot cable monitor is an earth continuity relay. It provides earth continuity protection in accordance with AS/NZS 2081 ensuring the earth connection through a trailing/reeling cable is maintained. A pilot cable is connected to earth via a diode, the PCM177 detects open and short circuits between the pilot and earth conductors of the trailing cables.

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Earth Continuity Relay

An Earth Continuity Relay is designed to provide earth continuity protection. The method used is called pilot earth loop or earth continuity monitoring, where an additional core pilot cable is included with the power and earth cores in the trailing or reeling cables, which supply power to the machines.

The Relay monitors the return path resistance between pilot and earth of the cable. The maximum allowable loop resistance is 45 ohms with underground mining operations. Higher resistance values may be used for long cable runs used in surface mining operations.