Effect of harmonic pollution on low voltage overcurrent protection

Current harmonics can produce undesired effect on protection devices, the most common being nuisance tripping on instantaneous overcurrent protections. This paper focuses on the effects of harmonics on overcurrent protection devices, describing the structure and behaviour of circuit breakers fitted with thermal-magnetic trip units and with electronic trip units. Situations in which undesired effects are more likely to occur, as well as some mitigation strategies, are then discussed.