冷热循环单周期内电缆附件XLPE-SiR界面局部放电演变特性研究

Study on the Evolution Characteristics of Partial Discharge at the XLPE-SiR Interface of Cable Accessories Under a Single Thermal Cycling

电力系统的日负荷特性导致配电电缆处于持续的冷热负荷循环状态。现场经验表明,在电力系统负荷突变或环境温度变化剧烈过程中,电缆附件绝缘故障频繁发生,而对于这种运行条件下的电缆附件界面绝缘特性的研究却鲜有报道。为此,该文对电缆附件界面预制传感器,探究冷热循环单周期内的界面压力变化情况。首先,对预置半导电突起缺陷的电缆附件进行50个周期的冷热循环预老化实验。随后,将一个冷热循环周期内附件面压及温度变化情况与一个周期内的局部放电情况进行对比分析。实验结果表明,在一个冷热循环周期内电缆附件的局部放电将经历4个阶段,在温度上升与下降阶段都将出现短暂的局部放电活跃现象,而在温度恒定、界面状态稳定时,局部放电反而相对受到抑制。经分析,认为该现象是由于冷热负荷循环过程中界面温度与界面压力两方面因素相互作用而导致的。最后,从硅橡胶主绝缘的材料特性与界面空腔放电的角度出发,解释了一个冷热循环周期内附件界面局部放电行为特性。

The load characteristics of the power system lead to the result that power distribution cables operate under continuous thermal cyclings.Field experiences show that accessories’failure caused by interface discharge always occurs when cable operating temperature change due to the load changes or ambient temperature differences,while the study on the discharge characteristics under such circumstances is still not in depth.Therefore,this paper uses prefabricated sensors for interface pressure measurement,and firstly conducts preaging experiments of 50 thermal cyclings on the cable accessories with semiconductive protrusion defects.Then,by setting up a comparison sample,the changes of the surface pressure and temperature of the accessories are compared with the partial discharge(PD)features under the single thermal cycling.The experimental results show that the partial discharge at the interface of the cable accessories would go through four stages during thermal cycling,in which the PD excitation would appear while temperature rises and declines,and PD would get suppressed while the interface state is stable.This phenomenon happens due to the interaction of two factors,the interface temperature and the interface pressure during the process.Finally,from the perspective of the material properties of silicone rubber and the interfacial cavity discharge,the partial discharge behavior characteristics of the accessory interface during a single thermal cycling are dynamically explained.