Effects of compensated AC transmission links under normal/subnominal frequency operation

The purpose of this paper is to evaluate the effectiveness of uncompensated & series capacitor compensated 400 kV line working below the minimum allowable frequency of 48.5 Hz , 49 Hz and 50 Hz. The method is based on the assumption that the ABCD generalised circuit constants of a long line change both in magnitude & phase angle.This method also highlights the effects of change of location of a series & shunt capacitor on the receiving end & sending end voltage ,active & reactive powers transferred by the line & on power factor of system load during the power frequency operation.This paper shows that the under frequency operation of the power system is associated with the reduction in overall power factor of the system load & rise in receiving end voltage of the line. A comparative study is made between symmetrical and unsymmetrical schemes. An analytical approach is presented for comparative performance assessment of long distance AC transmission line.