Analysis of Single-phase Grounding Fault with Line-Broken on Overhead Transmission Lines

Single-phase grounding faults with line-broken occur frequently in overhead distribution systems of 6~66 kV, which may endanger personal safety and interrupt power supply. Considering the grounding points on load side and the types of loads, the currents and voltages at grounding and broken points and protection installation positions and on the load sides were analyzed respectively, and the formulas and phasor diagrams of voltages and currents at each point were deduced. The study results show that voltages of grounding points and protection installation positions have a relationship with load characteristics and fault resistance. However, the broken point voltage has a relationship with load characteristics only. PSCAD simulation proves correctness of the conclusions. Thus a theoretical foundation is established to identify the single-phase grounding faults, line-broken faults and grounding faults with line-broken.