MEASURING INSTRUMENT FOR A RESISTIVE ELECTRIC LEAKAGE CURRENT

摘要

An Earth resistance sneak current measurement apparatus is provided to measure a changing earth resistance sneak current of a test line in each half period of power source exactly and rapidly, thereby rapidly managing in the abnormal occurrence of the test line. A sneak current detection circuit(41) detects a synthesis sneak current from a test line(20). A current-voltage transforming circuit(42) converts a synthesis sneak current from the sneak current detection circuit into a voltage corresponding to the synthesis sneak current and outputs the voltage. An amplifier(43) amplifies an output signal from the current-voltage transforming circuit. A phase inverter(44) inverts the output signal phase of the amplifier into 180°. A synchronizing signal generator(45) detects voltage from the measurement line and generates the synchronizing signal. A first half-wave integrator(46) receives a synchronizing signal from the synchronizing signal generator and integrates the output signal from the amplifier in a half period unit. A second half-wave integrator(47) receives the synchronizing signal from the synchronizing signal generator and integrates the output signal from the phase inverter in the half period unit. A sample hold circuit(48) receives the synchronizing signal from the synchronizing signal generator, samples the output of the first and second half-wave integrators by turns in each half period, and maintains the corresponding output for the half period.