高压直流电缆附件XLPE/SIR材料特性及界面电荷积聚对电场分布的影响

Effect of Material Properties of XLPE/SIR and Interface Charge Accumulation on Electric Field Distribution of HVDC Cable Accessory

双层绝缘介质界面电荷积聚是导致高压直流电缆附件界面放电的重要原因。该文测量分析交联聚乙烯(XLPE)和硅橡胶(SIR)两种介质的介电性能、电导特性和导热特性;通过建立高压直流附件电-热仿真模型,研究不同温度下XLPE/SIR界面电荷积聚特性及局部电场畸变引起的附件内部电场变化规律。实验结果表明,室温下SIR的电导率略高于XLPE材料,随着温度的升高,XLPE的电导率增加较为明显,而SIR的电导率增加则相对缓慢,高温下两种介质电导率不匹配是导致界面电荷积聚的重要原因。室温下XLPE/SIR界面积聚负电荷面密度约为3.42×10^(−4)C/m^(2),这部分电荷会增强电缆主绝缘电场,削弱应力锥根部电场畸变,主绝缘电场增加约36%,应力锥根部电场畸变下降约62%。当温度超过约36℃时,XLPE/SIR界面开始积聚正电荷,随着温度的升高,开始出现极性反转现象,造成应力锥根部局部电场畸变加重,70℃时最大畸变电场达到12kV/mm。

Interface charge accumulation between double-layer dielectric is the key factor causing interface discharge of the high voltage direct current(HVDC)cable accessory.In this paper,the dielectric properties,conductivity and thermal conductivity of XLPE and SIR were measured.The charge accumulation properties of the XLPE/SIR interface and the variation of internal electric field caused by local electric field distortion were studied.The experimental results show that as the temperature increases,the conductivity of XLPE increases significantly,while the conductivity of SIR increases relatively slowly.The mismatch of the conductivity of the two materials at high temperature is an important reason for the interface charge accumulation.At room temperature,the negative charge at the XLPE/SIR interface is about 3.42×10^(−4)C/m^(2),which will enhance the electric field of the cable main insulation and weaken the electric field distortion at the root of the stress cone.Electric field of the main insulation increases about 36%and the electric field distortion at the stress cone root decreases about 62%.When the temperature exceeds about 36℃,positive charges begin to accumulate at the interface of XLPE/SIR.As the temperature increases,polarity reversal phenomenon occurs,which leads to aggravation of the local electric field distortion at the root of stress cone,and the maximum distortion electric field reaches 12kV/mm at 70℃.