XLPE表面缺陷对电场及击穿电压的影响

电缆中间接头施工过程中易造成XLPE表面划伤、附着污染颗粒和表面受潮三种缺陷,为评估缺陷对接头运行性能的影响,建立了电缆中间接头XLPE绝缘片状模型,分析了不同缺陷下电场的变化,探究了不同缺陷对电场及击穿电压的影响程度。结果表明,XLPE在划伤时划痕处的电场产生严重畸变,为非划痕处的1.6倍;受潮时XLPE表面附着污染水中导电杂质越多,污染水的电导率越高,从而使其导电性能增强,电场强度变大,是同界面处非受潮部分的1.22~1.40倍;XLPE表面附着污染颗粒时,颗粒与其交界面处电场发生较严重畸变,是同界面无缺陷时的1.50倍左右,划痕对XLPE绝缘的电场影响最严重。通过试验结果显示正常无缺陷时的击穿电压为129.6kV,划伤缺陷的击穿电压为59.1kV,受潮缺陷的击穿电压为69.7kV,杂质缺陷的击穿电压为59.2kV,划痕对XLPE绝缘的击穿电压影响最严重。研究成果为探究不同缺陷对电缆中间接头XLPE绝缘性能的影响提供了重要依据。

Influence of Typical Cable Defects on Electric Field and Breakdown Voltage of XLPE

In the construction process of cable intermediate joint,it is easy to cause three defects of XLPE:surface scratch,adhesion of pollution particles and surface moisture.In order to evaluate the impact of defects on joint operation performance,this paper establishes XLPE insulation sheet model of cable intermediate joint,analyzes the change of electric field under different defects,and explores the impact degree of different defects on electric field and breakdown voltage.The results show that the electric field at the scratch site is seriously distorted when XLPE is scratched,which is 1.6 times of the non-scratch site;When XLPE is wet,the more conductive impurities are attached to the surface of polluted water,the higher the conductivity of polluted water,thus enhancing its conductivity and increasing its electric field strength,which is 1.22-1.40times of the non-wet part at the same interface;When pollution particles are attached to XLPE surface,the electric field at the interface between particles and XLPE is seriously distorted,which is about 1.50 times of the interface without defects,scratches have the most serious impact on the electric field of XLPE insulation.The experimental results show that the breakdown voltage of normal defects is 129.6kV,that of scratch defects is 59.1kV,that of damp defects is 69.7kV,and that of impurity defects is 59.2kV;Scratches have the most serious impact on the breakdown voltage of XLPE insulation.The results provide an important basis for exploring the impact of different defects on XLPE insulation performance of cable intermediate joint.