交联副产物对交联聚乙烯中空间电荷行为的影响

The Influence of Cross-linked By-products on Space Charge Behaviour in XLPE

为了研究交联聚乙烯(cross-linked polyethylene,XLPE)在直流高压下的空间电荷特性与材料内部交联副产物的关系,测试了3种经过不同脱气处理(0、24、72 h)的交联聚乙烯试样在直流预压后的空间电荷分布,并通过气相色谱–质谱联用仪测试了3种试样内部交联副产物的残余量。研究表明:随着脱气时间的延长,试样内部的交联副产物种类没有改变,但每种副产物的残余量均明显减少。未脱气试样在直流高压下,靠近两侧电极处均积累了大量的异极性电荷,并且电荷量随着电场升高明显增多。试样经过脱气处理后,内部积累的空间电荷量明显减少。低电场下电极附近仅观察到少量的同极性电荷,当电场升高后,异极性电荷逐渐代替同极性电荷成为主导。这说明,交联聚乙烯材料内部的异极性电荷主要来源于直流电场下交联副产物的解离,并且电场越高,副产物解离形成的离子电荷越多。脱气处理能有效减少交联聚乙烯内部交联副产物的残余量,进而改善其空间电荷特性。

To study the relationship between cross-linked by-products of cross-linked polyethylene （XLPE） and space charge characteristics under high voltage direct current （HVDC）, three kinds of XLPE samples were degassed for various hours （Oh, 24h, 72h）. Space charge distribution in these samples was detected after DC was applied. The measurement was based on pulsed electro-acoustic measurement （PEA） principle. The remaining cross-linked by-products in the samples were detected by gas chromatograph-mass spectrometer （GC-MS）. It shows that with the increase of degassing time, the kinds of cross-linked by-products unchanged, but the amount was significantly reduced. Under HVDC, samples not degassed accumulated large amounts of heterocharges near two electrodes. Besides, charge amount increased significantly as the electric field was strengthened. The internal space charge accumulation in samples degassed was significantly reduced. In low electric field, there were only few homocharges near two electrodes. As the electric field increased, heterocharges gradually became dominant. It indicates that, under DC electric field, heterocharges mainly come from the dissociation of cross-linked by-products in XLPE. And the higher the electric field is, the more ionic charges accumulate. Degassing treatment can effectively reduce the amount of cross-linked by-products in XLPE, so it can improve the space charge characteristics.