Methodology for Obtaining Key Transient Information of Unsymmetrical Earth Fault in Overhead Transmission Line

Obtaining key transient information at fault points accurately is of practical significance in failure-cause identification and rebuilding plan formulation for overhead transmission line (OTL). The paper proposed a method for excavating key transient information during unsymmetrical earth fault. Based on the inversion theory, the required transient current traveling wave at fault points could be obtained. Combining with fault type, a mathematical model of current amplitude, fault angle and fault resistance was constructed. Furthermore, improved firefly algorithm (IFFA) was adopted to solve model parameter. Simulation results demonstrated that the proposed method contributed to accurately reproduce traveling wave at the fault points and excavate the key transient fault information.