The Study On Shortly Turning On And Off Low Resistor Method Of Single-phase-to-earth Fault Line Selection In Ungrounded Neutral System

Low sensitivity and low reliability in the relays of single-phase-to-earth fault line selection 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 introduces the idea that a low resistor can be turned on and off for a while when the single-phase grounding fault occur. Through a further analysis of characteristic of the zero-sequence transient grounding current in-depth, the paper prove the feasibility of the single-phase-to-earth fault line selection project and bring forward the selective principle of the neutral interposing resistance.