Line fault detector for electrified fencing - uses operational amplifiers and threshold comparators from line voltages

摘要

An electrified protective fence comprising a wire or grid isolated from the ground is subjected to a pulsed current supply. Faults such as open or short circuits are detected to sound an alarm. Two live wires (L1,L1') are powered from a pulse generator (G) which is powered from a low voltage dc source. The pulses are applied to the lines via a transformer with two secondary windings (S1,S2). The remote ends are looped and applied to bridge circuits (R1,R2,R1',R2'). the transformer ends of the lines are connected to earth via resistors (R3) and low voltage pulses are obtd. with voltages which represent current flow in the lines. These outputs are applied to operational amplifier circuits which include time constant elements. Threshold amplifiers drive relay circuits to provide warning signals if the lines are open or short circuited.