Thyristor protected series capacitors project at Southern California Edison Co

Southern California Edison Co. (USA) has embarked on replacing several 500 kV series capacitors on its 500 kV transmission system. With the modern technological developments and advancements in the field of capacitor cans and thyristors, SCE was faced with a challenge to choose one of the several alternative technologies for the new replacement series capacitor protection. SCE could replace the existing series capacitors with the old spark gap technology, use the metal oxide bypass protective technology which was developed around the early eighties or could push the technological bar and go in for "thyristor protected series capacitors". Considering all facts and economics, SCE decided in 1998 to proceed with the new "thyristor protected series capacitors" technology. Since then two such series capacitor banks have been already installed and are operating satisfactorily at SCE\´s Vincent substation. Additional five banks are programmed for replacement in next four to five years.