Study on Cause Analysis and Evaluation Method of a Class of Overvoltage in Low-voltage Distribution Network

There are many kinds of overvoltage problems in low-voltage distribution network, and the influence is serious. The causes of overvoltage are various and difficult to identify. In the paper, a kind of overvoltage phenomenon of low-voltage distribution network caused by three-phase imbalance and excessive transformer grounding resistance is analyzed by theory and measured data, and the severity of overvoltage problem in the substation area is calculated by analytic hierarchy process. The phenomenon widely exists in low-voltage distribution network. In order to quickly identify such high-voltage phenomenon from massive distribution transformer monitoring terminal data, the paper proposes a discriminant method based on three-phase imbalance state index and transformer grounding resistance state index, and introduces the risk preference type utility function to evaluate the influence degree. The method can determine which factors lead to the overvoltage problem of 380V three-phase four-wire low-voltage distribution network in a certain period of time, and evaluate the influence degree of these factors on the overvoltage problem. Finally, the effectiveness of the method is verified by analyzing the measured data.