Application of series air-core inductors to distribution capacitor banks improves reliability

Many utilities have experienced blown fuses on three phase distribution capacitor banks caused by failed capacitor cells, lightning, back-to-back capacitor switching transients, etc. Traditional capacitor protection on distribution circuits includes lightning arrestors, expulsion fuse current limiting fuse links, and pre-insertion inductors. This paper will summarize the experiences of utilizing air core inductors in series with shunt-connected three phase distribution capacitor banks. Enhanced circuit protection is achieved using this low-cost capacitor protection method available to the distribution engineer.