Effect of Moistures on Space Charge and Trap Level Characteristics of Oil-Impregnated Pressboards

Abstract

Oil-paper insulation as an irreplaceable insulation system in the electrical power transformer is inevitably suffering the water intrusion on working condition, which will make dielectric performance degraded and insulation aging accelerated. In high interest of explaining the deterioration effect of absorbing moisture on the dielectric properties of oil-paper insulation system and corresponding mechanism, the space charge and trap level characteristics are investigated for the specially prepared oil-impregnated pressboards with different moisture contents. The Pulsed Electro Acoustic and Isothermal Surface Potential Decay experiments are performed to test the space charge distributions and evaluate the trap level depths, respectively. It is indicated that the polarity of injected space charges is alternated with the decaying rate being raised when the absorbing moisture is aggravated in oil-impregnated pressboards. The charge carriers are more prone to be captured by the shallow-level traps that have been introduced by water permeation near pressboard surface than the intrinsic deep-level traps inside pressboard. The captured charge carries accounts for the significantly exacerbated space charge accumulation as manifested by the surface charges of oil-impregnated pressboards.

Effect of multi‐factors on heterocharges for oil‐impregnated paper in converter transformer using modified charge transport model

“…Therefore, the study of heterocharge has become a hot spot [4]. The existing literature [5][6][7] suggests that moisture, temperature, and oil-paper thickness are important factors that affect the production of heterocharges. Zhang…”

“…Guan et al analyze the effect of moisture absorbing on the space charge distribution. The results indicate that homocharge and heterocharge increase with the increase in moisture content [6]. Hao et al studied the effect of moisture on the charge distribution in a multilayer oil-impregnated paper insulation system.…”

“…The existing literature [5][6][7] suggests that moisture, temperature, and oil-paper thickness are important factors that affect the production of heterocharges. Zhang et al focus on the space charge distribution affected by the different oil-paper thickness and different temperatures.…”

“…The existing literature [5–7] suggests that moisture, temperature, and oil‐paper thickness are important factors that affect the production of heterocharges. Zhang et al.…”

“…analyze the effect of moisture absorbing on the space charge distribution. The results indicate that homocharge and heterocharge increase with the increase in moisture content [6]. Hao et al.…”