型式试验对挤塑绝缘高压直流电缆老化状态的影响研究

Influence of Type Test on Ageing Status of Extruded Cross-linked Polyethylene(XLPE) High Voltage Direct Current(HVDC) Cables

通过对国内自行研制的200 k V挤塑绝缘交联聚乙烯电缆的空间电荷、松弛电流和热性能进行测试,分析了型式试验对电缆绝缘的影响。型式试验前后,主绝缘中部切片试样在表面区域均存在明显的异极性空间电荷分布,且电荷积累量变化不大,状态因子、熔融热焓、结晶热焓和交联度变化亦不明显,表明型式试验对电缆中部绝缘的老化程度影响较小。切片脱气处理后,试样表面区域的异极性空间电荷积累和短路时空间电荷平均单位体积密度显著降低,表明空间电荷行为受制造过程中残留的交联副产物影响很大。空间电荷、等温松弛电流和差示扫描量热的测试结果的关联性较好,均能有效反映老化状态的变化,可用于挤塑绝缘直流电缆的绝缘状态评估。

The influence of type test on cable insulation was analyzed by testing the space charge,iso-thermal relaxation current（IRC）, and thermal properties of 200 k V home-made extruded XLPE HVDC cables. The degassed samples from the central section of main insulation had distinct heteropolar space charge distribution on the surface before and after type test, while the accumulation of space charge changed little, and the status factor, enthalpy, and crosslinking degree had little change also, which indicated that the influence of type test on the ageing degree of central insulation of cables was small.After degassing treatment, the accumulation of heteropolar space charge and the average charge density reduced significantly, this indicated that the space charge behavior was influenced by crosslinking byproducts. The test results of IRC and DSC show good relevance and can effectively reflect the change of ageing status, which means that they are suitable to evaluate the insulation status of extruded XLPE HVDC cables.