AC or DC differential leakage current detector - includes transformer linkage between two mains wires and oscillator detector controlling cut=out relay

摘要

The high sensitivity differential electrical protection device includes a homopolar transformer having a single toroidal magnetic core with the two mains conductors passing through it. A secondary winding is formed on the core in order to receive any fault signal. A generator consisting of a high frequency oscillator producing a signal of frequency, which is higher than the mains frequency, applies its output to the secondary winding. A variation in the oscillator signal is produced if any leakage current occurs. An electronic processing circuit responds to the oscillator signal, operating a relay cut-out switch, if the detected variation exceeds a threshold. The circuit may also detect and indicate the nature of the fault.