不同粗糙度界面和脱气处理对500kV XLPE直流电缆工厂接头的影响

Effect of Different Roughness Interface and Degassing Treatment on 500kV XLPE DC Cable Factory Joint

为了研究不同粗糙度界面和脱气处理对500kV高压直流交联聚乙烯(cross-linked polyethylene,XLPE)电缆工厂接头材料和绝缘特性的影响,将商用的500kV高压直流电缆颗粒,分别在80目、400目、1000目、2000目砂纸打磨和未打磨的#0000试样表面二次注入硫化,制备了不同粗糙度界面的XLPE试样;在常压和70℃的条件下对1000目打磨且二次硫化的XLPE试样进行脱气处理,获得了脱气0、12、36和90h的XLPE试样(#1000)。对所得试样进行了差示扫描、机械拉伸、空间电荷、电流密度和直流击穿实验,结果表明随着砂纸目数的增加,试样界面处的平均片晶厚度不断减小,结晶度不断增加,同时断裂拉伸率和电流密度呈现出先增大后减小的趋势,而空间电荷积聚量、阈值场强和直流击穿场强先减小后增大,其中#1000试样是各参数变化趋势改变的拐点。脱气处理降低了#1000试样的平均片晶厚度和断裂伸长率,增加了试样内部的结晶度,同时也减少了试样内部空间电荷积聚和电流密度,提高了直流击穿场强。增加工厂接头界面的光滑度和脱气时间都有助于改善本体与恢复绝缘之间的连接关系,提高工厂接头的绝缘特性,但相同条件下依然低于本体绝缘。

To study the effects of different roughness interfaces and degassing treatment on factory joint materials and insulation characteristics of 500kV high voltage direct current(HVDC) cross-linked polyethylene(XLPE) cables, the commercial 500 kV XLPE cable pellets were injected into the surface of the sample polished by sandpaper(#80, #400,#1000, #2000, and unpolished #0000). The XLPE samples were obtained after vulcanization. The #1000 samples were degassed at 70℃ for 0, 12, 36 and 90h, respectively.Physico-chemical and electrical experiments were performed on the obtained samples. The results show that as the number of sandpaper grit meshes increases, the average lamellae thickness at the interface decreases and the crystallinity increases. Meanwhile, the elongation at break and the current density show a trend of first increasing and then decreasing,while the space charge accumulation, threshold strength and DC breakdown first decrease and then increase. Among them,the #1000 sample is the inflection point. The degassing treatment reduces the average lamella thickness and elongation at break of #1000 samples, increases the crystallinity, reduces the space charge accumulation and current density inside the sample, and increases the DC breakdown field strength.Increasing the smoothness and degassing durations of the factory joint interface can help to improve the connection between the main body and the return insulation and improve the insulation characteristics of the factory joint. But it is still lower than the main body insulation under the same conditions.