Capacitor overcurrent protection for industrial distribution systems

Many industrial facilities apply power factor correction capacitors to enhance their electrical system efficiency. Power factor improvement, power loss reduction, release of system capacity, and voltage improvement can all be achieved by applying capacitors in industrial plants. Protection of these capacitor banks against excessive overcurrents is a critical part of the safe and reliable operation of the bank. We review different considerations in the selection of capacitor fuse applications and the philosophies behind them. Individual and group fusing are discussed. Continuous current, transient current, fault current, tank rupture curve coordination, voltage on good capacitors during a fault, energy discharged into a failed unit, outrush current, and coordination with unbalance detection schemes are topics covered. Examples of actual applications of capacitors in industrial distribution systems are presented throughout.