杂质对交联聚乙烯电缆内部电场和空间电荷分布影响

The Influence of Impurities on Electric Field and Space Charge Distribution in XLPE Cable

杂质会影响交联聚乙烯(XLPE)电缆内部电场及空间电荷分布,在电缆绝缘老化与击穿中起着重要作用,因此研究杂质对电缆中电场及空间电荷分布的影响具有重要的意义。本文采用二阶四面体单元剖分的有限元方法计算各节点的电位分布,然后求各节点电位的负梯度得到各节点上的电场强度,对电位移矢量求散度可得各节点的电荷密度。以一个带有杂质颗粒的交联聚乙烯电缆模型为例进行计算,结果表明:在电场作用下,杂质颗粒会离解造成其周围电荷密度集中;杂质颗粒表面积聚的电荷量随颗粒半径的增大而增大,电荷密度随半径的增大而减小;杂质颗粒越靠近高压侧其表面积聚的电荷量越大;杂质颗粒周围的电荷密度值与相对介电常数关系不大,但与电阻率关系密切。

Impurities affect the electric field and space charge distribution in cross-linked polyethylene(XLPE)cables,and play an important role in aging and breakdown of cable insulation.Therefore,it is very important to study the influence of impurities on electric field and space charge distribution in cable.In this paper,the potential distribution of each node is calculated by the finite element method of the second-order tetrahedral element meshing.Then the electric field strength of each node is calculated by deriving the negative gradient of the potential of each node,and the charge density of each node is obtained by calculating the divergence of the electric displacement vector.Taking a XLPE cable model with impurity particles as an example,the calculation results show that,under the effect of the electric field,the impurity particles will dissociate and cause the charge concentration around them.The charge amount accumulated on the surface of the impurity particles increases with the increase of the radius of the particles,and the charge density decreases with the increase of the radius.The closer the impurity particle is to the side of the high voltage,the greater the charges accumulated on the surface of the impurity particles.The charge density value around the impurity particles is not related to the relative permittivity,but it is closely related to the resistivity.