考虑电导损耗对高压XLPE海缆低频介电特性的影响

Influence of conductance loss on low-frequency dielectric properties of high-voltage XLPE submarine cable

随着海上风电的快速发展,高压XLPE海缆在海洋输电系统中承担着传输电能的重任。为了研究热氧老化对高压XLPE海缆频域介电特性的影响,本文在135℃下对XLPE试样进行加速老化试验,分别对不同老化程度的高压海缆XLPE试样进行频域介电特性测试。在分析实测试样介电特性时,发现有大量电导损耗和极化损耗相互叠加于中低频域内,影响了应用频域介电特性评估高压XLPE海缆绝缘老化状态的准确性。针对这一问题,本文推导出分离介电响应数据中电导损耗和极化损耗的方法。最后探究电导损耗对模型参数辨识精度的影响,并提出表征老化程度的特征参数。结果表明:高压XLPE海缆的频域介电曲线随着老化程度加深而向高频方向移动,且低频段内弥散现象越发明显;将复介电常数虚部中的电导损耗去除后能够提高Havriliak-Negami(H-N)模型参数辨识的精度;提取的特征参数弛豫强度?ε和高频介电常数ε∞能够表征高压海缆XLPE绝缘的老化状态,可实现高压XLPE海缆绝缘老化的评估。

With the rapid development of offshore wind power,high-voltage XLPE submarine cables are palying critical role in transmitting electricity in the marine transmission system.In order to investigate the effect of thermal oxygen ageing on the frequency domain dielectric properties of high-voltage XLPE submarine cables,XLPE samples were conducted accelerated ageing experiments at 135℃,and the frequency domain dielectric properties of XLPE samples with different ageing degree were tested.When analyzing the dielectric properties of measured samples,we found that a large amount of conductance loss and polarization loss were superimposed in the low and medium frequency domains,which seriously affected the accuracy of applying frequency domain dielectric properties to assess the ageing state of high-voltage XLPE submarine cable insulation.To slove this problem,a method for separating conductance loss and polarization loss in dielectric response data was deduced.Finally,the effect of conductance loss on the accuracy of model parameter identification was explored,and a characteristic parameter to characterize the ageing degree was proposed.The results show that the frequency domain dielectric curves of high-voltage XLPE submarine cables shift towards high frequency as the ageing progresses,and the low-frequency dispersion phenomenon becomes more apparent.The accuracy of H-N(HavriliakNegami) model parameter identification can be improved by removing the conductance loss in the imaginary part of complex dielectric constant.The relaxation strength ? ε and high-frequency dielectric constant ε∞ could characterize the insulation ageing state of high-voltage XLPE submarine cables,which can realize the assessment of insulation ageing for high-voltage XLPE submarine cables.