Which type of fusing is used may depend on can manufacturer or utility preference andprevious experience.Because the SCBs are built from the individual capacitor units the overall connectionsmay vary. Typically used SCB configurations are:1. Delta-connected banks (generally used only at distribution voltages)2. Single wye-connected banks3. Double wye-connected banks4. H-configuration, where each phase is connected in a bridgeAdditionally, the SCB star point, when available, can be either grounded , grounded viaimpedance or isolated from ground. Which type of SCB grounding is used depends onvoltage level, used circuit breaker, utility preference and previous experience. Manyutilities have standard system grounding principle to ground neutrals of SCB above100 kV.Switching of SCB will produce transients in power system. The transient inrush currentduring SCB energizing typically has high frequency components and can reach peakcurrent values, which are multiples of SCB rating. Opening of capacitor bank circuitbreaker may produce step recovery voltages across open CB contact, which canconsequently cause restrikes upon the first interruption of capacitive current. In modernpower system the synchronized CB closing/opening may be utilized in such a mannerthat transients caused by SCB switching are avoided.7.10.2.1 SCB protection GUID-9E537AFB-BB23-4431-AC98-D4827A608F81 v2IED protection of shunt capacitor banks requires an understanding of the capabilitiesand limitations of the individual capacitor units and associated electrical equipment.Different types of shunt capacitor bank fusing, configuration or grounding may affectthe IED selection for the protection scheme. Availability and placement of CTs andVTs can be additional limiting factor during protection scheme design.SCB protection schemes are provided in order to detect and clear faults within thecapacitor bank itself or in the connected leads to the substation busbar. Bank protectionmay include items such as a means to disconnect a faulted capacitor unit or capacitorelement(s), a means to initiate a shutdown of the bank in case of faults that may lead toa catastrophic failure and alarms to indicate unbalance within the bank.Capacitor bank outages and failures are often caused by accidental contact by animals.Vermin, monkeys, birds, may use the SCB as a resting place or a landing site. Whenthe animal touches the HV live parts this can result in a flash-over, can rapture or acascading failures that might cause extensive damages, fire or even total destruction ofthe whole SCB, unless the bank is sufficiently fitted with protection IEDs.1MRK 505 370-UUS A Section 7Current protectionBusbar protection REB670 2.2 ANSI 237Application manual
