热老化过程中老化温度对油纸绝缘空间电荷特性的影响

Effect of Aging Temperature on Space Charge Characteristics in Process of Thermal Aging

通过研究不同老化过程中老化温度对油纸绝缘的空间电荷特性,可为换流变压器在长期高温运行下油纸绝缘的空间电荷特性提供试验依据。利用电声脉冲法研究了油纸绝缘在4种不同老化温度下、不同老化阶段的空间电荷特性,结果表明在热老化的不同阶段,油纸绝缘在极化过程中的空间电荷特性具有明显差异,而这种差异与老化程度之间并非简单的一一对应关系。一方面随着老化程度的增加,油纸绝缘的陷阱能级深度增加,空间电荷积聚量增加,并且升高老化温度会加剧这一过程;另一方面,在不同温度下进行热老化都会导致油纸的介电常数发生变化,进而也会影响油纸绝缘中空间电荷的积聚。分析表明油纸绝缘在老化过程中的空间电荷特性和介电常数虽然对老化温度敏感,但是温度的影响不完全符合Arrhenius方程,这可能与老化后纤维素化学键的断裂以及单体化学基团的生成速率有关。

Studying the effect of aging temperature on space charge characteristics of oil-paper insulation in the different aging processes can provide experimental bases for space charge characteristics of oil-paper insulation of converter transformers while running for a long time under high temperature. Consequently, we studied the variations of space charge characteristics of oil-paper insulation with thermal aging under different ambient temperatures by using the pulsed electroacoustic method. The results show that space charge characteristics are different at different aging status, and there is no simple correspondence between the difference of space charge characteristics and the degree of aging. But the more seriously the oil-paper insulation is thermally aged, the deeper the trap energy level will be, hence more space charge is trapped, which can be speeded up by the increase of the ambient temperature. Thermal aging under different ambient temperatures will all lead to the change of real permittivity of oil-paper, which will affect space charge accumulation in return. Variations of space charge behavior and real permittivity of oil-paper insulation during thermal aging are sensitive to the ambient temperature of thermal aging, but the effect of ambient temperature does not fit the Arrhenius law very well, it may be caused by the rupture of chemical bonds and the formation of monomer chemical groups.