Surface charge accumulation of post insulator: Dominant charge transition under different conditions

Abstract

Abstract An insulator surface charge may be responsible for flashover along the insulator surface. In this study, experimental investigations of post insulator surface charge are performed using a variety of voltage, gas type, and gas pressure conditions. Combining the model of surface charge transport, the dominant charge transition is revealed considering gas partial discharge. The results show that hetero‐polar charge accumulates near the high voltage electrodes on the insulator at one atmospheric pressure with an applied DC voltage ranging from −10 to −60 kV. The area ratio of the hetero‐polar charge increases from 23% to 53%. It also generates a reversed polarity of surface charges. Under −20 kV, the surface charge near the grounded electrode gradually becomes homo‐polar charges with the decrease of SF6 in 0.5 MPa SF6/N2 gas mixtures. In this case, the most dominant pathway for charge accumulation is through the insulation gas rather than the insulator. For the 20%SF6/80%N2 gas mixtures, homo‐polar charge speckles appear near the grounded plate electrode when the pressure of SF6/N2 gas mixtures decreases to 0.1 MPa. This means that the partial discharge occurs in gas side under a lower gas pressure. Refer to the presenting findings, the dominant charge transition on post insulators is provided as an important reference.