Transient stability comparision of 3F and 6F systems for single & three pole switching

This paper mainly deals with the transient stability analysis of a 3Phi double circuit line in comparison with that of equivalent 6Phi transmission line. The method of conversion of 3Phi double circuit line into 6Phi line using 3Phi/6Phi transformers and the method of obtaining corresponding equivalent p.u. reactance values are explained. A computer program in MATLAB is developed using Gauss-seidelpsilas iterative method for power flow and Modified Eulerpsilas method for transient stability analysis. These methods are used to analyze the unsymmetrical faults viz. SLG fault with single pole and three pole switching. Swing curves for different clearing times are obtained and finally the critical clearing time, critical clearing angle and maximum permissible angular swing are found for different cases. From the results it is concluded that the 6Phi transmission line exhibits enhanced transient stability when compared with equivalent 3Phi double circuit line.