Estimation of Fault Resistance Using Fault Record Data

Information about typical fault resistances of transmission lines will help improve the settings of distance relays. This paper proposes an offline method for estimating the fault resistance of transmission lines using the COMTRADE fault files available from digital distance relays. The proposed method uses the fault records at both ends of a line, but synchronization of the data sets is not required. Simulation and lab experimental results show that the estimated fault resistance has good accuracy with 2% average error. Finally, the method was applied to estimate the fault resistances of more than 50 phase-to-ground faults of a utility company. The ranges of fault resistance values are determined for faults on the company's 240 kV and 138 kV lines.