SYSTEM FOR MONITORING EARTH AND SHORT-CIRCUIT OF ONE-POINT EARTHING SYSTEM

摘要

PURPOSE:To detect whether earth or short-circuit is generated or not in the non-working status of a system and to discriminate whether a detecting function is normal or not by calculating impedance between branch points of an earthing cable. CONSTITUTION:Respective pairs of exciting transformers CT10-CT1n and current detecting transformers CT20-CT2n are connected between respective branch points of earthing cables 70-7n in an earthing network consisting of an one-point earthing system. The transformers CT10-CT1n in respective paths are successively excited, loop currents of respective paths are detected by the transformers CT20-CT2n forming pairs with the transformers CT10-CT 1n synchronously with the excitation and the loop impedance is calculated on the basis of the loop currents to detect whether earth or short is generated or not. Prior to said detection, the transformers CT10-CT1n are excited with a constant voltage and output signals from the transformers CT10-CT1n are detected to discriminate whether short-circuit or disconnection is generated or not in the transformers, wirings or the like.