Fault monitoring equipment e.g. three=phase parallel connected public lighting system - changing state of mechanical bistable relay when abnormal operation is detected, using low voltage to identify installation through time delay and interrogating voltage to detect operation of earth contactor

摘要

Each electrical installation on an electrical network has a component board (7) which is supplied from a central distribution box at different times by a normal system voltage, a very low voltage and an interrogating voltage. At normal operating voltage, a monitor (12) changes the state of an electromagnetic memory (19) if any fault on the protected installation (8) is detected. A very low voltage identifies the installation through a time delay and comparison relays (16,17,18) and an interrogating voltage detect operation of an earth contactor (20) controlled by memory state (19). ADVANTAGE - Faulty lighting units on lighting system may be identified from remote point so that time of repair staff may be used to optimum effect.