Impact of Series Compensation on the voltage profile of transmission lines

This paper investigates effect of series compensation on transmission voltages and provides recommendations for the operation. The paper also shows that not knowing the effects of series compensation on voltages can lead to operational problems. This paper has demonstrated that series compensation can lead to either low or high voltages depending on the line loading condition as well as on how the voltage control is set. If the voltage is inadequately controlled on the one end of the capacitor, then the other side of the capacitor might lead to voltage problems. The sensitivity study is based on a full approved WECC base case and it is performed using GE PSLF program. A 500kV transmission line from Midpoint substation (Idaho Power Company) to Summer Lake substation (BPA) is taken as an example and monitored in this study. In June 2007 a field test is performed on the same line by Idaho Power EMS team who tested the remedial action schemes (RAS) functionality with bypassing of the series. The information given here would be valuable for grid operators that deal with compensated lines and switch in and out series capacitors.