Combined line selection of single-phase grounding faults considering harmonic injection of distributed powers

Abstract

With the improvement of the requirements for the safe operation of distribution network lines, the harmonics injected by distributed power generation make the existing line selection methods ineffective, and the fault line selection method with a single criterion becomes more and more difficult to meet the line selection work after the single-phase ground fault occurs in the complex distribution network system. Therefore, a single-phase grounding fault joint line selection for resonant grounding system considering the injection harmonics of distributed power sources is proposed. In view of the characteristics of different phases and periodic changes of transient zero-sequence current of fault lines and sound lines after a single-phase grounding fault occurs in the resonant grounding system, the transient zero-sequence current is calculated by multi-scale cross-sample entropy according to the difference in low-frequency period. Then, according to the high-frequency phase difference, the weighted transient energy method and the synchronous squeeze wavelet transform are used to calculate the reconstruction error of the high-frequency transient zero-sequence current. In addition, the weighted transient energy method is used to control the calculation amount and determine the fault line through three criteria: multi-scale cross-sample entropy, weighted transient energy and reconstruction error. The experimental results show that the joint line selection method is less affected by different fault conditions and this method has high accuracy and strong anti-interference.

Keywords

• distributed power supply
• resonant grounding system
• joint line selection
• multi-scale cross-sample entropy
• weighted transient energy
• synchronously squeeze wavelet transform