Series Capacitor

A capacitor bank inserted in series with a transmission line to partially cancel the line's inductive reactance, effectively reducing the line's electrical length, increasing voltage stability margins, and boosting power transfer capability — often by 40–70% on long EHV lines where stability limits, not thermal limits, are the binding constraint. Series capacitors require elaborate protective systems (Metal Oxide Varistors and bypass switches) to limit overvoltages across the capacitor during fault conditions. They also require sub-synchronous resonance (SSR) studies to ensure nearby generators will not experience harmful torsional oscillations.

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