Experimental investigation of corona onset in contaminated polymer surfaces

Concerns about corona and its harmful effects, particularly in polymer insulators, have increased in recent years. Research involving corona identification, quantification, and formation mechanism is important to understand the aging process and to avoid premature failures. This paper investigates the corona inception and its relation with polymer surface conditions. Experiments of visual corona identification and Radio Interference Voltage (RIV) measurements were performed. Corona onset voltage was investigated in arrangements simulating different service conditions. Wet and contaminated insulating surfaces were reproduced. An RTV coated insulating sample and a polymer insulator were used. The electric field (E-field) at corona onset was numerically evaluated through computational simulations using the Finite Element Method. Corona onset voltage, E-field and RIV were analyzed according to the contamination level. The results clearly show how certain service conditions, particularly the association water droplets and pollution, enhance the E-field and can lead to corona onset.