A cross-differential protection scheme for quadruple-circuit lines with asymmetric parameters

Quadruple-circuit lines with asymmetric parameters have been widely built to increase power transmission capacity. The asymmetric parameters of the lines lead to different current characteristics compared with traditional lines. A cross-differential protection scheme based on negative sequence fault current is proposed to overcome the deficiency of traditional protection scheme. The fault superimposed networks of quadruple-circuit lines are discussed to analyze the fault sequence currents of each line. Differential currents are deduced to form the relay criterion. The threshold values of protection are calculated according to characteristics of superimposed fault sequence currents. Corresponding operational logic is also introduced to ensure the stability and reliability of protection. Finally, the reliability of the proposed protection scheme is verified. Copyright (C) 2015 John Wiley & Sons, Ltd.