Fault detection in direct current transmission lines using discrete fourier transform from single terminal current signals

Line commutated converter based high voltage transmission line fault current rises instantly due to the absence of inductance as which is present in ac. In dc currents there is no natural current zero so interruption of current is difficult and therefore the focus of the paper is to identify the fault in less time so that trip command can be initiated to the dc breaker. The dc lines are economical for long length so at far end distance fault identification is essential. The converter control in dc transmission lines control the power and provides synchronous interconnection between two ac systems. The discrete Fourier transform is used to extract the dc current at rectifier end of the dc transmission line and the processed current is compared with the threshold value to identify the fault. The factors considering the effect of fault location and fault resistance are considered for the accuracy, reliability and selectivity.