Measuring Methods of Ground Capacitance for Distribution Systems

Most mining power systems utilize ineffectively grounded sources to restrict the residual current for single-phase grounding fault, so as to reduce outage and shock hazard. In practice, with the system expansion and topology changing, the residual current and zero sequence voltage caused by grounding faults vary dynamically, and some arcing ground faults easily cause over-voltage and induce multiple faults. In order to improve it, on-site safety evaluation for ground fault is developed by the authors. Ground capacitance is an important parameter for the on-site safety evaluation. With voltage transformer leakage impedance accounted, three novel methods for the capacitance measurement (resonance measurement, injecting one signal measurement, and injecting two signals measurement) are proposed in the paper. Dynamic power system experimentations are carried out. Experimentation results show that the proposed methods are with high precision, and can measure in real-time without power supply interrupting.