New Method for Shallow and Deep Trap Distribution Analysis in Oil Impregnated Insulation Paper Based on the Space Charge Detrapping

Abstract

Abstract:Space charge has close relation with the trap distribution in the insulation material. The phenomenon of charges trapping and detrapping has attracted significant attention in recent years. Space charge and trap parameters are effective parameters for assessing the ageing condition of the insulation material qualitatively. In this paper, a new method for calculating trap distribution based on the double exponential fitting analysis of charge decay process and its application on characterizing the trap distribution of oil impregnated insulation paper was investigated. When compared with the common first order exponential fitting analysis method, the improved dual-level trap method could obtain the energy level range and density of both shallow traps and deep traps, simultaneously. Space charge decay process analysis of the insulation paper immersed with new oil and aged oil shows that the improved trap distribution calculation method can distinguish the physical defects and chemical defects. The trap density shows an increasing trend with the oil ageing, especially for the deep traps mainly related to chemical defects. The greater the energy could be filled by the traps, the larger amount of charges could be trapped, especially under higher electric field strength. The deep trap energy level and trap density could be used to characterize ageing. When one evaluates the ageing condition of oil-paper insulation using trap distribution parameters, the influence of oil performance should not be ignored.

Effect of Temperature on Space Charge Distribution of Oil–Paper Insulation under DC and Polarity Reversal Voltage

“…E = 0 kV/mm indicates a short-circuit. Equations (6) and 7show that the homocharge within the sample will reduce σ d and E d , while the heterocharge will increase σ d and E d . Before the voltage polarity is reversed, the space charge accumulated within the sample is homocharge, making σ d and E d decrease.…”

“…Moreover, the test results show that space charge remains basically unchanged during voltage polarity reversal. Therefore, the effect of the internal space charge on the interface charge density and electric field during voltage polarity reversal is equivalent according to Equations (6) and (7). The electric field, and charge density, at the interface vary linearly with the applied field stress during voltage polarity reversal.…”

“…Accumulation and decay of space charge in oil-paper insulation is affected by temperature, moisture, aging, electric field, and so on [5][6][7][8]. Tang et al studied the space charge characteristics of multi-layer oil-impregnated paper at high temperatures, and concluded that space charge distribution and charge mobility were affected by the temperature [9].…”

Space/Interface Charge Analysis of the Multi-Layer Oil Gap and Oil Impregnated Pressboard Under the Electrical-Thermal Combined Stress

“…= s e f + s h f + s et + s ht (5) There are a large number of traps existing within the insulation materials [16]. Those traps are caused by the physical and chemical defects [17][18][19][20][21]. When charge carriers move in the medium, it is possible to be entrapped.…”

Space Charge Accumulation and Decay in Dielectric Materials with Dual Discrete Traps

“…The charge trapping/de-trapping properties determine the formation and accumulation of space charges in dielectric materials [1][2][3][4]. When a dielectric material is subjected to a high electric field, free charges can be injected into the bulk of the material from electrodes [5] or can be generated by ionization [6], and they can be captured by trapping centers, which form space charges.…”