Detection and location method of distribution network grounding line based on loop impedance method

Abstract

The accuracy of the existing grounding detection system is usually relatively high in identifying the grounding point at the level of transmission network, but it is poor in identifying the grounding point at the level of distribution network. In this paper, a detecting method for locating the ground wire of the distribution network based on the loop impedance method is proposed. It is less affected by environmental factors, has a low cost, and is suitable for low-voltage distribution network detection under different operating conditions of the system. The main contents of this paper are presented as follows: First, the unit-length line impedance equation is derived. The relationship between frequency and line length is proposed, considering the influence of frequency on current detection. Second, the optimal frequency point for detecting the line current of the grounding wire is demonstrated. Then, the current threshold method considering environmental factors to determine the existence of the grounding wire is analyzed. Third, a general equation for judging the existence of the grounding wire is proposed. To locate the specific grounding, a loop impedance ranging method based on the optimal frequency point is proposed. Finally the correctness of the theoretical analysis, as well as the predictive method, is verified through the PSCAD/EMTDC.