抄録
This paper describes the test results about ground fault phenomena caused by dielectric breakdown between primary and secondary winding of transformer, which ground fault current flows through B-type earthing resistance. The test results are as follows. The distribution line system keeps three-phase AC voltage waveforms after islanding condition, when the system connects with the single-phase photovoltaic power generation systems and the no-load running three-phase motor-generator load. In this case, the value of the ground faults current decreases after islanding condition. On the other hand, the distribution line system does not keep three-phase AC voltage waveforms after islanding condition, when the systems does not connect with the no-load running three-phase motor-generator load. Depending on the circumstances, the value of the system line to line voltage enlarges 1.7 times, and the value of the ground faults current does not decrease after islanding. These phenomena affect electrical appliances. It is necessary to keep three-phase AC voltage waveforms after islanding condition by certain measures.
