Cable Fault Differential Current Protection Method Based on Dual Current Transformer

摘要

As the urban construction process accelerates, the proportion of cable distribution in distribution networks is increasing, and the incidence of cable failures is also increasing. Due to the various forms of single-phase grounding faults, fault protection is greatly affected by factors such as transition resistance, neutral grounding mode and current transformer imbalance. Fault troubleshooting is difficult, and cable trench explosions and other accidents occur frequently, which seriously affects the reliability of power supply. Therefore, it is necessary to study and improve the grounding fault protection method for distribution network. In this paper, the zero-sequence current distribution characteristics of single-phase grounding faults are analyzed in distribution network with neutral point ungrounded, arc-suppression coil grounded and small-resistance grounded. On this basis, considering the influence of transition resistance and the current transformer error, a cable fault differential current protection method based on dual current transformer is proposed. By installing two sets of current transformers with different ranges at the two ends of the cable, the current transformer error is reduced to some extent, and the sensitivity of the differential protection is improved. The simulation results show that compared with the traditional single transformer, the cable fault differential current protection based on dual current transformer has higher resistance to transition resistance and sensitivity.