Adaptive distance protection of double-circuit lines based on differential equation fault loop model

The paper presents an adaptive procedure for digital distance protection device that allows to compensate for the negative influence of the reactance effect, caused by fault resistance and pre-fault power flow. The procedure utilizes locally measured phase currents and voltages and has been designed to operate with double-circuit power lines. The algorithm calculates on-line shift vector components that allow to change the position of relay operating characteristics. As a result, it is possible to avoid mis- or maloperation of the distance relay. Evaluation of the algorithm has been performed with use of voltage and current signals obtained from versatile simulations in ATP-EMTP.