High-resistance faults on two terminal parallel transmission line: Analysis, simulation studies, and an adaptive distance relaying scheme

Performance of conventional nonpilot distance relay is affected by ground fault resistance, prefault system conditions, mutual effects of parallel lines and shunt capacitance influences. The work presented in this paper addresses the problems encountered by conventional non pilot distance relay when protecting two terminal parallel transmission lines. One of the key points of this paper is the detailed analysis of the apparent impedance as seen from the relaying point taking into account the effects of transmission line parameter uncertainties, mutual effects of parallel lines for simple and more complex configuration, shunt capacitance influences and variations in the system external to the protected line. Based on extensive computer simulations of the infeed/outfeed, fault resistance, mutual coupling and shunt capacitance effects on the relay characteristics, an adaptive digital distance relaying scheme is proposed using radial basis function neural network which provides more efficient approach for training, computation, adaptation and tripping than the conventional feed forward network using back propagation algorithm. In addition, the proposed adaptive scheme improves the performance of distance, relay for double-circuit lines using modified compensation factor. Moreover, the scheme does not require separate communication channel for data transmission. The results of computer simulation show the improvement of sensitivity and selectivity of the relay.