Performance of uncompensated and series capacitor-compensated 500 kV long transmission line under subnormal frequency conditions

The paper suggests an analytical method to ascertain the performance of uncompensated and series capacitor-compensated 500 kV line working below the minimum allowable frequency of 48.5 Hz. The method is based on the assumption that the ABCD generalised circuit constants of a long line change both in magnitude and phase angle. This is accounted for in the analysis. Results of such an analytical work tally with the experimental test results. This method also highlights the effects of change of location of a series capacitor on the receiving end voltage, active and reactive powers transferred by the line and on power factor of system load during the under-frequency operation. This study shows that the under-frequency operation of the power system is associated with the reduction in overall power factor of system load and rise in receiving-end voltage of the line. It also concludes that a judiciously located series capacitor results in minimum loss of revenue to the supply utility and minimum rise in receiving-end voltage in a series capacitor-compensated long line