A new decoupling method for asymmetry‐parameter quadruple‐circuit lines on same tower

Abstract

Quadruple‐circuit lines with different self‐impedances have been applied in power system with the development of power industry. However, the different self‐impedances in quadruple‐circuit lines will cause problems in fault analysis and related relay protection in the lines. The impedance matrix of these lines is different from that of symmetrical lines, and existing methods cannot completely eliminate all mutual impedance. A new method is proposed to decouple these asymmetrical quadruple‐circuits lines in this paper. The phase‐to‐phase mutual impedance is eliminated first, and then the line‐to‐line mutual impedance is eliminated according to the circulating current method. The mathematical deduction is formulated to ensure the complete decoupling of the impedance matrix. The fault conditions can be used to obtain the relationship between the independent sequence networks, which can be used to calculate the fault current. Power Systems Computer Aided Design (PSCAD) simulations indicate that the decoupling method is suitable for fault analysis of the quadruple‐circuit lines with different self‐impedances. The related fault analysis method is quite accurate and easy to be applied. The fault analysis accuracy is not affected by the fault resistance, fault type, fault location, or length of lines. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.