Examination of Rectifier AC Side Electric Circuit Ground Fault Detection Method in DC Electric Railway Substation

Abstract

There are no ground fault protection devices in the AC circuit between the rectifier transformer and rectifier of DC electric railway substations. Therefore, the ground faults in the AC electric circuit are expected to be protected by overcurrent relays or DC ground fault overvoltage relays (64P) installed in the upper system. However, these protections are inadequate, so we examined methods to detect ground faults in the AC circuit between the rectifier transformer and rectifier. Thus, it was found that the ground fault current included a third harmonic current that was absent when there were no ground faults. Therefore, we created a prototype device to extract the third harmonic current, and confirmed that ground faults in the AC electric circuit between the rectifier transformer and rectifier could be detected by artificial ground fault tests.