电树枝对10 kV电缆接线套管电场分布特性的影响及修复策略研究

Influence of Electric Branch on Electric Field Distribution Characteristics of 10 kV Cable Bushing and Repair Strategy

10 kV环网柜具有电压等级高、容量大、体积小、重量轻等优点而在配电系统中起到电压等级转换、电能质量提升等关键作用。但由于运行环境多存在潮湿污秽情况、长时间满负荷甚至过负荷运行等恶劣工况,环网柜内的绝缘附件(如10 kV电缆接线套管)容易出现沿面闪络现象,在绝缘材料上产生电树枝从而导致绝缘损伤甚至失效。笔者基于有限元模型和工频耐压试验分别对0.8 mm烧蚀深度电树枝存在时的10 kV电缆接线套管电场分布特性和绝缘性能进行分析,同时利用打磨修复方法对出现电树枝的接线套管进行处理并提出相关修复策略。研究结果表明:电树枝出现后,接线套管周围的电场分布明显畸变,击穿电压稍有下降,但会出现局部放电。在打磨深度分别为0、0.5、1、1.5、2 mm时,击穿电压分别为38.6、46.3、43.0、39.1、38.5 kV。在考虑一定的安全裕度的基础上,认为打磨深度1.0 mm是能够保证打磨修复电树枝后接线套管绝缘强度的阈值,并基于此提出现场修复10 kV电缆接线套管的修复策略。通过对电树枝出现时接线套管周围电场分布特性以及打磨修复深度对接线套管绝缘性能影响的研究,能够为接线套管的绝缘设计及检测修复提供理论依据。

10 kV ring network cabinet has the advantages of high voltage level,large capacity,small volume,light weight and so on,and plays a key role in voltage level conversion and power quality improvement in the distribution system.However,because the operating environment is often wet and dirty,long time at full load or even over load operation and other bad conditions,the insulation accessories in the ring network cabinet(such as 10 kV cable bushing)are prone to flashover along the surface,generating electrical branches on the insulation material,resulting in insulation damage or even failure.Based on the finite element model and power frequency voltage test,the electric field distribution characteristics and insulation performance of 10 kV cable bushing in the presence of electrical branches at 0.8 mm ablation depth were analyzed respectively.At the same time,the bushing with electrical branches was treated by grinding and repair method and relevant repair strategies were proposed.The results show that the electric field distribution around the bushing is significantly distorted,and the breakdown voltage drops slightly,but partial discharge occurs.when the grinding depth is 0,0.5,1,1.5 and 2 mm,the breakdown voltage is 38.6,46.3,43.0,39.1 and 38.5 kV,respectively.On the basis of considering a certain safety margin,it is considered that the grinding depth of 1.O mm is the threshold value which can ensure the insulation strength of the wiring sleeve after grinding and repairing the electrical branch.Based on this,the repair strategy of repairing 10 kV cable wiring sleeve on site is proposed.By studying the electric field distribution characteristics around the bushing and the influence of grinding and repairing depth on the insulation performance of the bushing,it can provide a theoretical basis for the insulation design,detection and repair of the bushing.