Influence of voltage reversal on space charge behavior in oil-paper insulation

Abstract

The presence of space charge is a serious threat to the reliability of insulation material under voltage polarity reversal. The results of space charge evolution in oil-paper insulation during external voltage polarity inverse at room temperature were presented in this paper. A mirror image effect charge was observed in the steady state, but the formation of it was affected by the first polarizing, which could cause a change of electrical property. The results showed that the mirror image effect was independent of the involved nature, type and dynamics of charge. Experiments of different reversal polarities and periods indicated that the slow decay of heterocharge retained from previous homocharge injection was the cause of electric field enhancement. And the reversal period therefore had an effect on voltage polarity reversal, namely the shorter the reverse period, the higher the stress enhancement. The reliability of oil-paper insulation could be influenced by the polarity reversal because charge injection and distribution were unpredictable, and space charge modified and in return was affected by the field as well.Index Terms -Space charge, pulse electroacoustic method, oil-paper insulation, voltage reversal, mirror image effect, stress enhancement.

Description of space charge transport in oil‐paper insulation using adaptive time‐stepping transient upstream finite element method

“…The local truncation error R n can be acquired according to (25) and (26). Assume that each time step has a maximum permissible error R max , and the step size of next time is ∆t n+1 .…”

“…In addition, it has been observed from Figures 7 and 8 that a great deal of homocharges are accumulated in the oil-paper under the electrical stresses. This is mainly due to that the number of trapped charges in oil-paper are increased with stressing duration [25][26][27][28][29][30].…”

Review of accumulative failure of winding insulation subjected to repetitive impulse voltages

“…On the one hand, the existence, migration, and dissipation of space charges affect the electric field distribution in the dielectric directly. This can either weaken or strengthen the local electric field in the dielectric and thus affects the breakdown voltage of the dielectric [129–131]. On the other hand, the trapping, detrapping, and recombination of space charges may cause emission of photons or release local mechanical energy, which can break the chemical bonds in the dielectric and thus affect the insulation characteristics of the dielectric [74, 132].…”

Investigation on space charge properties of Nomex insulation paper in the mining dry type transformer during hygrothermal ageing

“…Considerable research works [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] have been done on the mechanism of dielectric degradation and space charge characteristics of transformer insulation paper especially in cellulose paper and oil-immersed Nomex insulation paper. Liuet al [18] measured the space charge distribution of oil-impregnated synthetic fibreboard with different moisture contents at room temperature and indicated that the space charge characteristics of insulation paper would change within the difference of moisture contents.…”