不同直流场强下乙丙橡胶的空间电荷特性

Space Charge Characteristics of Ethylene Propylene Rubber Under Different DC Electric Field

乙丙橡胶在电缆绝缘中的应用日益广泛,空间电荷积聚成为影响其绝缘性能的关键因素之一。为了明确乙丙橡胶中空间电荷的行为特性及形成机制,文中基于PEA法对乙丙橡胶在直流场强下的空间电荷分布进行了研究,分析并讨论了不同场强下乙丙橡胶内空间电荷的分布规律以及其消散特性。实验结果表明:乙丙橡胶的电荷注入的阈值场强为2.5～5 kV/mm。根据不同场强下乙丙橡胶内空间电荷的行为特性,可将其分为4个阶段,分别为无电极注入阶段、双电极注入阶段、注入电荷迁移复合阶段、阳极注入主导阶段。此外,不同场强下陷阱密度及深度的差异会影响乙丙橡胶内部空间电荷的消散特性。在较高场强下,正极性空间电荷包的形成引起乙丙橡胶内部电场畸变,这可能会影响其介电强度,并使绝缘老化。

It has been known that the ethylene propylene rubber (EPR) is widely used in MV/HV power cables which are strongly affected by the formation and movement of space charge in their insulation layer. In this paper, the space charge distribution of EPR under different DC electric field is measured by using pulsed electro-acoustic (PEA) method for revealing the formation mechanism and characteristics of space charge in EPR. The results show that the homo - charge injection occurs under the electrical field strength more than 2.5 kV/mm. The total charge quantity is increased with the rise of electric field. The formation process of the space charge in EPR during polarization can be divided into four stages:(I) no charge injection,(II) bipolar injection,(III) charge transformation and recombination ,and(IV)anode injection. When the DC voltage is removed, the dissipation of the space charge is affected by the depth and density of traps in EPR. The electric field inside EPR samples is distorted by the positive space charge packet under high electric field strength, which may affect the insulation aging and the breakdown voltage.