A METHOD FOR DETERMINING AN EARTH-SHORTED BRANCH CIRCUIT IN¹AN ELECTRICAL SUPPLY OR DISTRIBUTOR NETWORK

摘要

In a process for detecting a branch circuit (14A, 14B, ...) subject to earth leaks in an electric power supply or distribution system, in which an earth leak quenching choke (2) is inserted between the mains neutral point and earth, with mains operation switched off, the difference for each individual circuit (14A, 14B, 14C) of the admittances resulting as the quotient of the branch zero current and the neutral point earth voltage is determined before and after each change in the neutral point impedance and the circuit in which this difference is at its maximum is taken as the one subject to earth leaks. The quench coil is plunger choke coil (2) in which the plunger setting is altered between the measurements. The admittances of the individual circuits (14A, 14B, 14C) are calculated from measurements of the branch zero currents as the sum of the three branch phase currents (e.g. with a Holmgreen circuit) and the biasing voltage between the neutral point and earth, taking account of the phase relationship between the zero currents and biasing voltage and complexly subtracted for each individual branch.