Cable fault detection system employing remote terminals without DC power supply using digital communication over optical fibres

This paper describes a cable fault detection system (CFD) employing a current differential relay using fibre optic digital communication and remote-end terminals that do not require a DC power supply. For many years, analog pilot wire relays have been used for CFD because DC power supplies are generally not available at cable headends. The authors have developed a remote device, for installation at cable head-ends, which can be powered from either fault currents or the normal flow of power through the cable, and is able to transmit digital fault current data using optical fibre. The paper describes the architecture developed to realize extremely low-power consumption together with other features of the device, and also presents the field trial results.