Zero-phase current detecting apparatus

A zero-phase current detecting apparatus comprising:

• a zero-phase-sequence current transformer that includes a magnetic core and a detection coil wound around the core, and that detects a zero-phase current flowing in an electric power line;
• and
• a feedback loop is made up of
• a pulse generating unit that applies an excitation pulse signal to one end of the detection coil;
• a current detecting unit that converts a current flowing through the detection coil into a voltage and outputs the voltage;
• a peak detecting unit that detects a peak value of the voltage output from the current detecting unit;
• an adding unit that outputs a difference between a target value and the peak value detected by the peak detecting unit;
• and
• a current regulating unit that regulates the current flowing in the detection coil based on the difference output from the adding unit, wherein
• the zero-phase current is detected based on the difference output from the adding unit as a result of regulation of the peak value so as to be the target value in the adding unit.