高温高场强下XLPE及其纳米复合材料电导机制转变的实验研究

Experimental Study on the Transference of Conduction Mechanisms of XLPE and its Nano-composite Under High Temperature and High Electrical Stress

为研究交联聚乙烯（cross-linked polyethylene,XLPE）在高场强下电导机制的转变过程,测量了XLPE及XLPE/Si O2纳米复合材料在20、50和80℃下和2~70 kV/mm场强下的电流特性。此外,利用多种电导机制的数学公式,对这两种XLPE的电场–电流密度曲线进行拟合,从而分析不同温度与高场强下上述两种XLPE在非欧姆区的电导转变机制。结果表明：温度、场强、纳米掺杂与预压效应都会对XLPE的电导产生影响。通过分析发现,随着场强升高,这两种XLPE的电导机制从低场强区的欧姆电导发展为高场强区的体效应（Poole-Frenkel）,而后至高场强的电极效应（Schottky）。且这种转变的阈值场强随温度升高而降低。另外,纳米掺杂与预压过程能有效降低相同温度与场强下XLPE的电流密度。此外,预压过程能减小相同温度与电场下的电流密度并提升上述两种转变的阈值场强。

To research the current properties of pure crosslinked polyethylene（XLPE） and XLPE/Si O2 nano-composite material, their current densities were measured under different temperatures（e.g. 20, 50 and 80℃） and under different stresses from 2 to 70 kV/mm respectively. Besides, some mathematical formations of conduction mechanism were used to fit the experimental results and analyze the transference of the above two kinds of XLPE＇s conduction mechanisms in non-ohmic region. It shows that the conduction of the two kinds of XLPE can be influenced by temperature, electrical stress, nano-composite and electrical pre-stressing. The analysis results show that conduction mechanisms of the above two kinds of XLPE transfer from ohmic conductivity to bulk-limited effect（Poole-Frenkel） firstly and then to electrode-limited effect（Schottky） if the electrical stress improves gradually. Moreover, the higher the temperature, the lower the transferring threshold field. The doped nanocomposite and electrical pre-stressing process can improve the threshold field and the doped nano-composite can also reduce the current density effectively. In addition, pre-stress process facilitates to improve the injection threshold and reduce the current density.