Unsymmetrical opening of mutually coupled transmission lines

• We model unsymmetrical opening of mutually coupled transmission lines.
• The model is applied to a five bus test system.
• Several cases of symmetrical and unsymmetrical opening of transmission lines have been simulated.

The aim of this paper is to present a systematic approach of solving unsymmetrical faults due to unsymmetrical opening of mutually coupled transmission lines. Opening a transmission line is equivalent to adding, in parallel with it, another transmission line but having the negative impedance of the same line. This is straightforward if the line is not mutually coupled with other lines in the system. Mutual coupling between parallel and adjacent lines exist due to proximity. Such mutual coupling must be taken into consideration when modifying the bus impedance matrix for the purpose of fault studies due to the opening of mutually coupled transmission lines. In this paper, a systematic approach to applying the bus impedance matrix method for faults involving the switching of mutually coupled lines is presented. The approach is applied to several cases of simulation of symmetrical and unsymmetrical switching of mutually coupled transmission lines.