Fault Judgment Method for Feeder in Smart Distribution Network Based on Voltage Phase Comparison

A large number of distributed generations (DGs) are penetrating into smart distribution network (SDN). Due to complicated fault characteristics and control strategies of DG, it is difficult for pilot protection dependent on correct identification of fault direction to reliably locate fault. A fault detection method derived from the judgement on the integrity of the protected line model is proposed in this paper. Instead of the analysis on the explicit fault characteristics of DG, the proposed method emphasizes the mathematical model of the protected line. Firstly, an elaborately-selected physical quantity is defined based on the mathematical constraints of the model. Then, the integrity of the model can be judged by analyzing the variation trend of the defined physical quantity in case of the faults either internal or external to the line in question. The results of fault detection based on the integrity of the protected line model can be used as the basic information for pilot protection to constitute the fault judgment method. In this paper, the reference voltage is defined as the physical quantity to judge whether the line model is intact. The setting principles of the impedance in reference voltage are analyzed in detail, so that the proposed method can adapt to the operating characteristics of smart distribution network. Simulation confirms that the proposed method is basically unaffected by the fault characteristics of DG. With help of the identification on the integrity, the pilot protection is improved to accurately locate the fault section.