Integrated scheme for high impedance fault detection in MV distribution system

High impedance fault (HIF) in MV distribution with restricted fault current cannot be detected and cleared by conventional overcurrent relays. HIF exposes great hazard for personal safety and property security. In this paper, an integrated scheme utilizing different features of HIF is presented. Various documented field data has been investigated and summarized to get the most distinctive features of HIF. Based on these features, a simulation model using arc thermal equation and random factor has been developed. The integrated scheme investigates into different scopes of the fault features ranging from transient high frequency, harmonic distortion to fundamental intermittent. EMTP (Electromagnetic Transients Program) simulation results show that the integrated scheme can detect most HIFs, and discriminate HIF from other interference scenarios such as CT saturation, load nonlinearity and capacity transients. Therefore, this scheme achieves a better result with reliability and security.