Resonance measurement of capacitance current in ineffectively earthed power systems

Capacitance current is an important parameter for single phase ground fault protection and control in ineffectively earthed power systems. A novel method for the capacitance current measurement is presented in the paper. An adjustable reactor is in series connection with the open-delta side of a zero sequence voltage transformer. System resonance frequency is sought by injecting a current signal with variable frequency. By changing the reactor inductance value, another resonance frequency can also be sought. The ground capacitance and ground capacitance current can thus be calculated using the two resonance frequencies for the power systems. Experimental work shows that the proposed method has produced results of high precision in real-time, without the need to interrupt power supply.