Series-Capacitor Line Protection - Fundamentals and New Challenges

Demand for electricity increases every year. New generation resources, particularly wind and solar inverter-based resources (IBRs), are connecting to the existing transmission grid. Thus, there are significant increases in the need to transfer power across the transmission grid. Building new transmission lines takes years and the demand is now. To meet this demand, utilities need to use the existing transmission lines. A series-capacitor placed on the line changes the line reactance and increases transmission-line capacity and efficiency. The result is enhanced power transfer without overburdening the lines. This paper reviews the fundamentals of series-capacitor-bank protection. Discussed are challenges like voltage and current inversion, MOV conduction, bypass switching, and the effects on nearby lines. In addition is information on the use and protection impacts of modern static synchronous series compensator (SSSC) devices instead of traditional series capacitors.