An asymmetrical fault location method based on communication system in distribution network with DGs

The introduction of DG in distribution system will deteriorate selectivity and sensitivity of the existing relay. This paper presents a novel method based on negative sequence current (I₂) scalar product (I₂SP) to identify the direction of an asymmetrical fault. And by combining fault direction distinguishing methods with communication system, a new asymmetrical fault line searching and locating scheme is proposed. The paper divides the buses into different types and proposes different methods accordingly to estimate the fault directions. The I₂SP method is presented for buses connecting with 3 or more branches, while I₁CP method and WWC method are for buses connecting with 2 branches. IED at each bus uses a corresponding method to determine the direction of an asymmetrical fault without voltage information, and then sends the identified fault direction signals to the centralized controller to search and locate the fault. In this scheme, current data do not need to be transferred in the communication system, and that will relieve the pressure of communication system and lower the demand for real-time operation. The case study shows that the proposed scheme is of great adaptability to the operation mode change and the simulation verifies the feasibility of the scheme.