Analysis and treatment of current unbalance abnormal situation of 750 kV double-circuit parallel transmission line

Abstract

At present, the biggest problem faced by short-distance double-circuit parallel lines is the three-phase parameter asymmetry problem caused by non-transposition. This leads to three-phase current asymmetry, especially during heavy load performance is more prominent. Take a 750 kV double circuit parallel erection line in actual operation as an example, use EMTPE electromagnetic transient simulation software to simulate and analyze the current imbalance phenomenon. This paper studies the influence of phase sequence arrangement, distance between loops, distance between wires, line length, equivalent impedance, ground wire conditions and line power flow on current imbalance, and puts forward reasonable restraining measures. The simulation results show that when the line power flow is heavy, the double circuit lines are arranged in the same phase sequence and the distance between circuits is relatively short, there will be a large amplitude of zero sequence current on the line, mainly circulation current. If it is not suitable to adjust the protection measures, it can be considered to adjust the double-circuit lines to reverse phase sequence operation mode. The research results can provide reference for the engineering design of double-circuit parallel transmission lines.