Influence of harmonic injections on the performance of certain analog and digital protection and regulation equipment

An investigation into harmonic performance of representative controllers for reclosers, voltage regulators, and capacitor banks. An appropriately rated current amplifier applies four categories of terminal voltage and currents to the devices under test: a control sequence without harmonics, a sequence of waveforms having voltage harmonics only, a sequence having current harmonics only, and a sequence having a combination of voltage and current harmonics. Electromechanical recloser control exhibits significant difficulty in detecting faults in the presence of harmonics. Digital reclosers identify the faults but show significant delay; newer model microprocessor-based relays show no significant difficulties in the presence of harmonics. Voltage regulator controls show no abnormal operation; capacitor bank control has significant difficulty. Experimental results are presented and discussed.