Improving the security of subtransmission systems by use of temporary insertion of series and shunt reactances

At present high quality of electric power service is required especially as far as the security of power supply is concerned. With reference to a subtransmission system interconnected with a main transmission one the paper presents the results of a study aimed to analyse the possibility to use temporary inserted series reactors and shunt capacitances in order to control the power flows in a way as to avoid transformer or line overloads during severe contingencies in the transmission system. Two different criteria for the choice of the rating of the series and shunt reactances are presented and discussed in the paper.