Fault Location in Capacitor Banks – How to Identify Faulty Units Quickly and Restore the Bank to Service

摘要

Capacitor banks are critical substation assets that play a vital role in providing reactive power support,thereby increasing the power system capacity. Capacitor banks are constructed as single-wye, doublewye,or H-bridge configurations and can be grounded or ungrounded. Capacitor banks consist of anumber of single-phase capacitor units connected in series and parallel to achieve the desired voltageand VAR rating. Similarly, each capacitor unit consists of a number of individual capacitor elementsconnected in series and parallel. The capacitor units can be externally or internally fused, fuseless, orunfused. Although modern capacitor units are more reliable than earlier units, faults within the unitsand elements still occur. When the element overvoltages resulting from these unit or element failuresbecome too high, the capacitor bank needs to be taken out of service and the faulty units must bereplaced.It is important that capacitor bank outage time be as short as possible. Normally, the majority of theoutage time is spent locating the faulty unit. Identifying the faulty unit in a capacitor bank helps returnthe bank to service in a minimum amount of time. If the bank is externally fused, then the unit with theblown fuse is usually the faulty unit, making identification obvious. If the bank is internally fused,fuseless, or unfused, then fault location is very difficult because there is no visual indication of thefaulted unit. This results in an extended outage of the capacitor bank. Although it is not possible toidentify the faulty unit in an internally fused, fuseless, or unfused bank, identifying the faulted phaseand section helps minimize the outage time.This paper analyzes various capacitor bank configurations and proposes a method to help locate thefaulty units for each configuration. The paper also provides results that verify the proposed methodsusing a power system simulator.