基于多元非线性回归模型的XLPE电缆终端环形损伤故障特征

Fault Characteristics of XLPE Cable Terminal Ring Damage Based on Multiple Nonlinear Regression Model

配电网10 k VXLPE电缆终端在制作过程中切除外半导电层用力不均匀,或因终端内水分、腐蚀液等渗入引起局部导体损耗和绝缘层介损突变,使沿XLPE绝缘层环形截面方向出现异常温升带,均会破坏绝缘层并留下易被忽视的环形伤痕。当环形伤痕位于原本电场分布不均的电缆终端上时,将使场强畸变更加明显,甚至会导致环形伤痕内空气电离而发生局部放电并引发故障。该文通过仿真分析了环形伤痕的宽度、位置和跨度与伤痕处最大场强的关系,结果表明宽度、位置和跨度交互影响环形伤痕处畸变电场分布;为此提出了利用最小二乘法构建以宽度、位置和跨度为自变量,最大场强为因变量的多元非线性回归模型,经验证该模型用于评估XLPE电缆终端环形损伤故障的程度具有较好的效果,为掌握10k VXLPE电缆终端的环形伤痕故障特征并进行故障诊断提供了新的思路和方法,显著提高了配电网运行可靠性。

The 10 k V XLPE cable terminal of the distribution network is not uniformly cut during the manufacturing process of the outer semi-conductive layer, and the local conductor loss or the sudden change of the dielectric loss of the insulating layer due to the penetration of moisture and corrosive liquid in the terminal may lead to abnormal temperature rise bands along the direction of the circular cross section of the XLPE insulating layer, which will damage the insulation layer and leave circular scars that are easily overlooked. When the ring-shaped flaw is located at the cable terminal where the electric field is unevenly distributed, the field strength distortion will be more obvious, and even the air ionized in the ring-shaped flaw will cause partial discharge and failure. In this paper, the relationship between the width, position and span of the ring scar and the maximum field strength at the scar is analyzed through simulation. The results show that the width, position and span will affect the distortion electric field distribution at the ring scar. The position and span are independent variables, and the maximum field strength is the dependent variable multivariate nonlinear regression model. It has been verified that this model is used to evaluate the degree of ring damage failure of XLPE cable terminals. Therefore,new ideas and methods for grasping the characteristics of ring-shaped flaws and fault diagnosis of 10 k V XLPE cable terminals can be provided, which significantly improve the reliability of the distribution network operation.