直流电压下交流XLPE电缆的空间电荷积累特性研究

发布时间：2018-04-10 01:17

  本文选题：增容改造　切入点：空间电荷　出处：《东北电力大学》2017年硕士论文

【摘要】：将交流电缆线路改为直流运行可以充分利用原有输电走廊,最大限度地发挥原有输电线路的输送能力。而实际运行的交流XLPE电缆绝缘材料在设计时并没有考虑空间电荷积累问题。直流电压下,交流XLPE电缆中空间电荷积累严重,会造成局部的电场强度成倍增加,影响电缆的绝缘强度以及加速电缆绝缘的老化。为研究交流XLPE电缆在直流电压下的空间电荷积累和电场分布特性,本文应用COMSOL多物理场仿真软件,模拟了温度梯度下电缆绝缘中的温度场,并基于绝缘样品电导率模型,研究了温度梯度、场强、加压时间及极性反转等因素对66kV交流电缆的电场以及空间电荷行为的影响。直流稳态电压下,电缆绝缘中电场分布和空间电荷积累明显受温度梯度的影响。电场分布由绝缘材料的电导率所决定,在较高温度梯度时可能出现电场分布翻转现象;温度梯度使得高温侧的空间电荷容易发生脱陷,加速了载流子向低温侧的迁移,导致了低温侧正负极性空间电荷的严重积累。当温差为45℃、加压8小时时,低温侧空间电荷密度达-0.15C/m~3,绝缘外侧场强最大值为6.71 kV/mm,该数值低于66kV交流电缆绝缘的场强设计值。极性反转电压下,暂态电场分布取决于介电常数和电导率的共同作用,且以介电常数为主,暂态最大场强出现在缆芯附近,均大于其稳态时的最大场强。暂态最大场强值与温度梯度、电压的幅值以及电压极性反转时间密切相关,温度梯度和电压幅值越大,暂态最大场强越大;反转时间越短,最大暂态场强越高,且暂态最大场强的位置越靠近缆芯导体。绝缘中载流子的定向迁移以及空间电荷的入陷、脱陷、中和、消散等行为使得极性反转过程中该处正负极性空间电荷积累的总数量达到了动态最大值是导致最大暂态场强出现的根本原因。研究结果为66kV电缆线路改为直流运行时直流工作电压的确定及未来直流配电网的构建奠定了基础。
[Abstract]:Changing AC cable line to DC operation can make full use of the original transmission corridor and maximize the transmission capacity of the original transmission line.However, space charge accumulation is not considered in the design of practical AC XLPE cable insulation materials.Under DC voltage, the accumulation of space charge in AC XLPE cable is serious, which will result in the increase of local electric field strength, which will affect the insulation strength of cable and accelerate the aging of cable insulation.In order to study the space charge accumulation and electric field distribution characteristics of AC XLPE cable under DC voltage, the temperature field in cable insulation under temperature gradient is simulated by using COMSOL multi-physical field simulation software, and based on the conductivity model of insulation sample.The effects of temperature gradient, field strength, pressure time and polarity reversal on the electric field and space charge behavior of 66kV AC cable were studied.The electric field distribution and space charge accumulation in cable insulation are obviously affected by temperature gradient under DC steady voltage.The electric field distribution is determined by the conductivity of the insulating material, and the electric field distribution may be reversed at a higher temperature gradient, which makes the space charge of the high temperature side prone to detrapping, and accelerates the migration of the carrier to the low temperature side.It leads to the serious accumulation of space charge in the low temperature side of positive and negative electrode.When the temperature difference is 45 鈩，

本文编号：1729015