550kV GIS盆式绝缘子小型化设计(三)——缩比结构验证

Compact Design of 550 kV Basin-Type Spacer in Gas Insulated Switchgear(PartⅢ)--Downsized Structure Verification

为制造经小型化设计的550 kV盆式绝缘子并验证其电气性能,采用3D打印结合环氧树脂浇注工艺制备了1:10缩比绝缘子。首先,将氧化铝填料与光敏树脂复合作为低相对介电常数(3.98~4.20)3D打印浆料,根据光固化与流变特性确定填料含量及打印参数后,利用立体光固化3D打印机制备低介电常数的绝缘子主体。随后,将二氧化钛填料与环氧树脂复合作为高相对介电常数(11.32~14.58)真空浇注浆料,浇注至3D打印绝缘子预留的高介电常数区域内,加热固化完成缩比绝缘子的制造。0.2 MPa下SF6氛围中的工频耐压实验结果表明,优化后的绝缘结构具有更优的绝缘强度。相同绝缘距离下,几何形状优化绝缘子闪络电压较常规绝缘子提高13.6%,几何形状/介电分布联合优化的绝缘子提高13.8%;绝缘距离减少15%后,联合优化绝缘子耐电强度与常规绝缘子相当;当法兰侧“楔形”气隙内存在金属丝时,相同绝缘距离下,仅进行形状优化的绝缘子耐电强度提升幅度降低至6.7%,而联合优化绝缘子由于在法兰侧形成低电场区域,闪络电压仍可提高13.1%。结果表明,几何形状/介电分布联合优化绝缘子具有显著的绝缘优势。

Solid insulators are key components in gas insulated equipment including gas insulated switchgear(GIS)and gas insulated transmission line(GIL).Surface flashover across the spacer/gas interface threats the running of GIS/GIL.Hence,it is urgent to enhance the surface insulation strength of spacer especially in the situations where compact design and/or the usage of eco-friendly gases are required.Numerous studies revealed that locally intensified electric(E)field caused by dielectric mismatch or metal particles mainly accounts for the insulation failure of spacer.To design and fabricate a downsized 550 kV spacer in GIS that takes both the structure optimization and dielectric distribution optimization into account,a fabrication method that considering E field mitigation effectiveness and the fabrication efficiency was proposed.Firstly,1:10 downsized dielectrically graded 550 kV spacers were fabricated by combining stereolithography 3D printing technology with epoxy resin casting technique.Specifically,alumina/UV-cured resin composite was prepared as a low relative permittivity(3.98<εr<4.20)3D printed slurry to fabricate the main parts of insulators.The characterizations of composites’photocuring and rheological behaviors indicated that the doping of alumina fillers decreases the photo-curing depth and increase the viscosity particularly in high fillers’loading content.The processing performance of composite deteriorated when loading content exceeds 30%,since the viscosity pronouncedly increases.After determining fillers’loading content and printing parameters,the main part of spacers with low permittivity was fabricated by stereolithography 3D printing.Characterization of its dielectric properties confirmed the correctness of permittivity range.Subsequently,titania/epoxy resin composite was prepared as high relative permittivity(11.32<εr<14.58)vacuum casted slurry.To guarantee good match at interface,composite with 30%titania loading content was selected.The characterizations of composites’rheological behaviors indicated that the viscosity of composite dramatically decreases with the increase of temperature,benefiting the flowing of slurry in the reserved high permittivity region in the 3D printed spacer.After determining the curing conditions,the slurry was heated and then cured to finish the downsized spacer manufacturing.Secondly,flashover tests of spacers before and after optimization ware carried out in compressed SF6 gas.Characterizations of power frequency withstand voltage indicated that insulation structures after optimization exhibit improved electrical performance.Comparing with an original insulation structure,geometrically optimized spacer shows a 13.6%flashover voltage improvement,and this improvement increase to 13.8%for geometrically/dielectrically optimized spacer.After reducing a 15%of insulation distance,geometrically/dielectrically optimized spacer shares the same insulation level with the original structure.When a metal wire existing in the wedgy airgap at the flange side,improved electrical strength of the geometrically optimized spacer at the same insulation distance reduces to 6.7%.In contrast,owing to the low electric field area forming by the spacer with further optimized dielectric distribution,a 13.1%flashover voltage improvement still could be maintained,indicating the insulation excellence of the geometrically/dielectrically optimized spacer.The proposed spacer construction strategy takes both optimization effectiveness and fabrication efficiency into account,and the fabricated dielectrically graded 550 kV spacers exhibit excellent surface electrical insulation properties,offering the possibility of reducing size of GIS tank,and is considered as an essential step towards the industrial application of 3D printed spacer in GIS/GIL.