Space Charge Behavior of Oil-Impregnated Paper Insulation Aging at AC-DC Combined Voltages

Abstract

-The space charge behaviors of oil-paper insulation affect the stability and security of oilfilled converter transformers of traditional and new energies. This paper presents the results of the electrical aging of oil-impregnated paper under AC-DC combined voltages by the pulsed electroacoustic technique. Data mining and feature extractions were performed on the influence of electrical aging on charge dynamics based on the experiment results in the first stage. Characteristic parameters such as total charge injection and apparent charge mobility were calculated. The influences of electrical aging on the trap energy distribution of an oil-paper insulation system were analyzed and discussed. Longer electrical aging time would increase the depth and energy density of charge trap, which decelerates the apparent charge mobility and increases the probability of hot electron formation. This mechanism would accelerate damage to the cellulose and the formation of discharge channels, enhance the acceleration of the electric field distortion, and shorten insulation lifetime under AC-DC combined voltages.

Space Charge Behavior of Oil-paper Insulation Thermally Aged under Different Temperatures and Moistures

“…It meant that the higher the ageing temperature was, the faster oil paper was aged and the deeper trap energy level was. Hence space charge injection and migration were affected, and recombination weakened, so there was more charge [20]. As a result, charge injection and space charge cloud movement were more obvious.…”

“…Space charge injection and movement slowed down. Recombination became weak and more charge was trapped [20]. Therefore the homogeneous charge accumulation became more and more obvious.…”

“…It is worth mentioning that the acquisition of them is bases on isothermal charge equation and there have been some assumptions. Details can be found in [20].…”

“…If the carriers are not trapped again, trap energy level E t and trap energy density N t can be calculated according to Eqs. (1) and (2) [19,20]. It is worth mentioning that the acquisition of them is bases on isothermal charge equation and there have been some assumptions.…”

Influence of Endurance tests on Space Charge Distribution of 160kV HVDC XLPE Cable

“…However, a long-term thermal ageing or high temperature thermal stress will greatly deteriorate the XLPE material. Average charge density, total space charge, apparent charge mobility and trap energy distribution were the characteristic parameters of space charge which could be used for the evaluation of aging state [13][14][15][16].…”