The effect of high resistance faults on a distance relay

The design and operating behavior of a distance relay suitable for the protection of a transmission feeder is described in the paper. The relay uses a Fourier filter to derive the voltage and current phasors and a digital measuring technique that combines symmetrical components and the complex different equation of the fault loop circuit. The relay was simulated using the model language in PSCAD/EMTDC. The operating behavior of the relay was assessed using two different simulated networks with both solid and resistive faults. The data generated by PSCAD/EMTDC describes the voltage and current signals at the relay location both immediately before and during the fault. The signals include the DC offset and the effects of high frequency traveling waves. The data is applied to the relay simulator, which than evaluates whether the impedance trajectory of the fault enters one or more of the operating zones. The results are presented in graphical form using an R-X diagram.