Isolation monitors and measuring device for an electrical power system with isolated neutral

摘要

An isolation monitor is electrically connected between the earth and an isolated neutral of a transformer which supplies AC electrical power to the main distribution network. In order to measure and to locate an isolation fault occurring somewhere on the feeders, each feeder is equipped with a toroid current measuring transformer, and comprises further a secondary winding connected to a processing locator performing synchronous demodulation. Two first and second transmission lines are provided between the isolation monitor and the locator. The first synchronous line transmits synchronization pluses from the monitor to the locator, and the second line transmits to the locator the demodulated values of the input voltage furnished by the monitor.