The Study Of Single-phase-to-earth Fault Line Selection Device Based On Shortly Turning On And Off Low Resistor Method Without Impulsion In Ungrounded Neutral System

Low sensitivity and low reliability in the relays of single-phase-to-earth fault line selection's device are always the problems in ungrounded neutral system. Through reviewing of the existing theories on fault line selection systematically, this paper points out the defects and drawbacks of those. It points out the single-phase-to-earth fault line selection project that turning on and off a low resistor for a while when the single-phase grounding fault occurs. We utilizes the idea about Thyristor Switched Capacitor (TSC) .The resistor can be rapidly switched on at zero-voltage moment and switched off at zero-current moment without surge .It reduce the effect to power system. We designs a suit of equipment of fault line selection according to this project .The device's hardware and software is explained in detail.