A novel high impedance fault detection technique in distribution systems with distributed generators

Conventional overcurrent relaying based protection scheme has limitation to detect high impedance faults in distribution systems due to random, nonlinear and low magnitude fault currents. The problem becomes further complicated in presence of distributed generators in distribution systems due to bidirectional flow of power and reduction of fault current contribution from the main grid. This paper presents a one-cycle sum of superimposed component of residual voltage based method to detect high impedance faults in distribution systems integrated with distributed generators. The performance of the scheme is evaluated for high impedance faults at different locations of a 7-node radial distribution system integrated with distributed generators. The scheme is also tested for different non-fault events like capacitor switching and load switching, which often produce similar characteristics as that of high impedance faults. PSCAD/EMTDC software is used for generating data for different test cases and the method is implemented using Matlab software. Results clearly show that the proposed scheme can assist conventional overcurrent relay in detecting high impedance faults in distribution systems integrated with distributed generators in a more reliable and faster way.