温度对电缆附件界面缺陷处局放引发影响机制研究

温度对局部放电(partial discharge，PD)的发展过程有着重要的影响，但温度对PD的引发机制目前尚不明确。针对温度变化对电缆附件界面缺陷处PD引发机制进行研究。首先，对电缆附件界面单元与缺陷位置进行设计与仿真，并对界面单元不同温度下气隙缺陷PD特征进行测量。然后，搭建含有半导电层突起缺陷的电缆电热老化平台，通过电流通断模拟冷热负荷对电缆运行温度的影响。对界面单元和缺陷附件的局部放电起始电压（partial discharge inception voltage，PDIV）和PD相位谱图（phase resolved partial discharge，PRPD）进行对比分析，结果表明：随着测试温度的升高，界面单元的PDIV从8.3 kV降至6.9 kV，局部放电量有大幅提升，PRPD图显示出明显的内部放电特征。真实电缆附件缺陷处PD则会在温度快速上升时出现短暂的活跃，此时局部放电量与局部放电数都会出现明显增加，温度稳定后PD逐渐被抑制。上述现象主要与温度变化导致的界面处空间电荷分布和界面材料热胀冷缩所带来的“呼吸效应”有关，研究结果表明：真实电缆附件在大温度梯度下进行局放测试可提高局放检出率，为解决传统测试对局放检出可靠性不足提供了理论依据。

Influence of Temperature on Initiation Mechanism of Partial Discharge at the Interface Defects of Cable Accessories

Temperature has an important influence on the partial discharge (PD) development, but the effect of temperature on the PD initiation mechanism is still not fully understood. Thus, this paper investigated the influence of temperature on the PD initiation mechanism at the interface defects of cable accessories. First, the interface unit and defects of cable accessories were designed and simulated, and the PD features of air-gap defects under different temperature were measured. Then, an electrothermal aging platform for cables with semi-conductive-layer protrusion defects was constructed, simulating the influence of cooling and heating loads on the operating temperature of cables through the on-off current. Afterward, the partial discharge inception voltage (PDIV) and the phase resolved partial discharge (PRPD) spectrum of samples were analyzed comparatively. Obtained results showed that, as the test temperature applied on the unit increased, PDIV would decrease from 8.3 kV to 6.9 kV accordingly, and the PRPD spectrum presented obvious internal discharge characteristics. Meanwhile, tests on the actual defects of the cable accessory showed that when the temperature rose quickly, the temporary PD excitation occurred and the number and amplitude of PD increased significantly. When the temperature was stabilized, however, the increment slowed down. The phenomenon can be interpreted through the space charge distribution of the interface due to temperature changes and the “breathing effect” caused by the thermal expansion and contraction of the interface material. The research reveals that PD signals in the interface defect are easier to be detected when cable accessories are operating under high temperature gradient, which may provide theoretical references for the unreliability of traditional PD detection.