A 24,000-Kilovar Series Capacitor in a 230-Kv Transmission Line

The necessity for long distance transmission of electric power has grown rapidly during recent years. Line reactance becomes a problem of increasing importance when transmission distances continue to increase. Long lines cannot be loaded sufficiently for maximum over-all economy because of limitations imposed by transient stability an kilovar requirements. The most important alternative to reduction in equivalent line impedance by further increase in transmission voltage, is the use of line reactance compensation. Such compensation can best be obtained through the use of capacitors operating in series with the line conductors. To permit the use of series capacitors rated on the basis of normal load conditions, it is necessary to protect them effectively during line fault conditions. To make maximum use of line reactance compensation with capacitors it is necessary to by-pass and protect them only during line fault condition and reinsert them with minimum delay after the line fault is cleared. Lack of means for accomplishing the latter has prevented the use of capacitors for line reactance compensation where the primary objective is increasing power transmission. While protective devices have been developed which are adequate for use with series capacitors when used to improve voltage regulation, they are by far too slow in operation to meet the requirements when series capacitors are used to increase power transmission.