Research on the selection method of phase sequence arrangement of double-circuit transmission lines on the same tower

The phase sequence arrangement of double-circuit transmission line on the same tower influences both three-phase unbalance degree of the line and direction judgment of zero sequence power directional component. Based on the length of the line, considering the effects of phase sequence arrangement on transmission line unbalance degree and normal operation of the relay protection device, put forward a selection method of phase sequence arrangement of double-circuit transmission line on the same tower. The method could make the unbalanced degree of current under the rules and minimize the probability of relay protection malfunction when external inter-phase short circuit faults happen by selecting an optimal phase sequence arrangement. Take advantage of ATP/EMTP to build fault and normal model of double-circuit transmission lines on the same tower and to calculate the zero-sequence unbalance degree and zero sequence circulating current unbalance degree. According to the results of simulation, this method selects BCA / BCA as the optimal phase sequence arrangement when the length of lines is 20 km.