采用表面电位衰减法表征高压交联聚乙烯电缆绝缘中空间电荷的输运特性

Characterizing Space Charge Transportation in HV XLPE Cable Insulation Based on Surface Potential Decay Measurement

空间电荷积聚是影响高压直流交联聚乙烯(crosslinked polyethylene,XLPE)电缆运行安全的重要原因,定量表征XLPE中空间电荷的输运特性,对抑制空间电荷积聚、提高电缆绝缘可靠性具有重要意义。采用厚200μm的XLPE薄膜为试样,通过表面电位衰减(surface potential decay,SPD)法测量其陷阱能级分布、载流子迁移率和体电导率。结果表明,电子陷阱能级深度分布在0.8～1.07eV,在1.01eV处存在陷阱密度中心;空穴陷阱能级深度分布在0.71～1.06eV,分别在0.89eV和1.01eV处存在陷阱密度中心。正、负电荷的迁移率分别为1.5×10-14 m2/(V.s)、1.7×10-15 m2/(V.s)。体电导率随场强降低而减小,逐渐达到稳定值约5×10-17 S/m。研究表明:交联剂过氧化二异丙苯受热分解形成的副产物苯乙酮和α-甲基苯乙烯,是导致浅能级空穴陷阱密度显著大于电子陷阱密度、从而使正电荷具有较高迁移率的主要原因。

Space charge accumulation is an important reason that affects the safety of crosslinked polyethylene（XLPE）insulated DC power cable.A quantitative description of space charge dynamics within XLPE insulation under DC field can provide helpful information for inhibiting the charge built-up and improve the reliability of the cable.Space charge transportation features in 200μm-thick XLPE films were investigated by means of surface potential decay measurement.Trap energy depth distribution,effective mobility and field dependent conductivity were calculated.Results show that trap energy depth covers the range from 0.8eV to 1.07eV for electron and from 0.71eV to 1.06eV for hole,the effective mobility for negative and positive charges are 1.7×10-15 m2/（V.s）and 1.5×10-14 m2/（V.s）,respectively.The conductivity decreases with the fall of surface potential,approaching a steady value of about 5×10-17 S/m.It is proposed that the presence of acetophenone andα-methylstyrene which are byproducts from thermal decomposition of dicumyl peroxide are responsible for the shallower trap depth as well as the higher mobility of positive charge.