A morphological filter to distinguish a fault from capacitor switching

Modern numerical relays have substantially reduced false operation of overcurrent relays used for capacitor protection. However, faster and more reliable operation can be useful. This paper proposes a morphological filter for fast and clear distinction between fault currents and switching currents that can benefit all types of overcurrent relays used for protection of capacitor banks. The filter performance is tested using waveforms generated from PSCAD/EMTDC^® simulation of a standardized test-system.