STUDIES ON INSULATION DESIGN OF HIGH VOLTAGE DIELECTRIC SPACERS USED IN VACUUM

真空用高压介质间隔件绝缘设计研究

• 批准号: 11650284
• 负责人: YAMAMOTO Osamu
• 金额: $ 2.37万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650284/
• 关键词: Vacuum; surface discharge; charging; Surface roughness; insulation design; compact spacer; Spacer shape; cathode electric field; 固体材料; スペーサ

The charging of a dielectric insulator is considered to be a critical phenomenon leading bridged vacuum gaps to flashover. The goal of this study is to obtain an engineering aspect for designing the shape of spacer taking the charging phenomena into account. To investigate the charging process, we have employed an electrostatic method, which uses a small isolated part of the cathode as a probe. This probe technique enables us a real-time observation of surface charging under a ramped or stepwise DC voltage excitatin. We have also employed a simulation technique that analyzes the charge distribution on the insulator based on the secondary emission electron avalanche (SEEA) model.First, the influence of surface roughness on the charging of an insulator in vacuum has been investigated. A cylindrical insulating spacer made of acryl resin (PMMA), Teflon (PTFE) or alumina ceramics (92% Al_2O_3) is exarnined under rarnped, or stepped DC voltage application. Each sample has a roughness ranging … More from 0.15 to 50 μm. The results exhibit that the surface roughness decisively affects the charging, which is more pronounced for more highly polished insulators. For instance, the smooth surface of a cylindrical specimen made of PMMA or alumina acquires charge several times higher than that with rough surface. The specimen made of PIFE is hard to acquire the surface charge irrespective of its surface roughness. When an insulator is subjected to a stepwise DC voltage, the probe signal shows that the charging occurs with considerable delay, ranging from 10^<-5>s up to 10 s depending on the material, the voltage height and also the surface roughness of the insulator. Two-dimensional Monte Carlo simulation based on the secondary emission electron avalanche model has been performed to analyze the progress of the charging. During the delay period, positive charge accumulates on the surface of the insulator near the cathode, which further accelerates the charging.Second, the specimen in the shape of a conical frustum has been investigated. The spacer with a slight positive or a negative cone angle (-25゜≦α≦+2゜ ) acquires a positive charge of which density increases almost linearly with the applied voltage. The more positively angled spacer acquires no charge. These results agree with the theoretical prediction based on the SEEA mechanism. On the contrary, the spacer with a cone angle α<-25゜ acquires a localized negative charge. This result differs from the theoretical prediction in which a considerably high-density negative charge accumulates over the surface. We have shown that the progress of negative charging ceases due to the relaxation of the electric field near the cathode TJ.These results clearly show the importance of surface treatments and the spacer shape in the insulation design. Overall results show that insulators that are hard to acquire the surface charge have very good insulation performance. Less

介质绝缘子的带电被认为是导致桥接真空间隙闪络的关键现象。本研究的目的是获得一个工程方面的设计考虑到充电现象的间隔的形状。为了研究充电过程，我们采用了静电的方法，它使用一个小的隔离部分的阴极作为探针。这种探针技术使我们能够在斜坡或步进直流电压激励下实时观察表面充电。我们还采用了基于二次发射电子雪崩（SEEA）模型的模拟技术来分析绝缘体上的电荷分布。首先，研究了表面粗糙度对真空中绝缘体带电的影响。本文研究了由丙烯酸树脂（PMMA）、聚四氟乙烯（PTFE）和氧化铝陶瓷（92%Al_2O_3）制成的圆柱形绝缘垫片在分级或阶梯形直流电压作用下的性能。每个样品的粗糙度范围 ...更多信息 0.15 ~ 50 μm。结果表明，表面粗糙度决定性地影响充电，这是更明显的更高度抛光的绝缘体。例如，由PMMA或氧化铝制成的圆柱形样品的光滑表面获得比具有粗糙表面的样品高几倍的电荷。用PIFE材料制成的试件，无论其表面粗糙度如何，都很难获得表面电荷。当绝缘体经受步进式DC电压时，探测信号显示充电以相当大的延迟发生，范围从10 μ <-5>s到10 s，这取决于绝缘体的材料、电压高度以及表面粗糙度。基于二次发射电子雪崩模型的二维Monte Carlo模拟分析了充电过程。在延迟期间，正电荷在阴极附近的绝缘体表面上积累，这进一步加速了充电。第二，研究了截头圆锥体形状的试样。具有轻微的正或负锥角（-25 α）的间隔物获得正电荷，其密度随所施加的电压几乎线性地增加。角度更正的间隔物不带电荷。这些结果与基于SEEA机制的理论预测相一致。相反，具有锥角α&lt;-25 ° C的间隔物获得局部负电荷。这一结果不同于理论预测，其中相当高密度的负电荷积累在表面上。我们已经表明，由于阴极TJ附近的电场的松弛，负充电的进展停止。这些结果清楚地显示了在绝缘设计中的表面处理和间隔物形状的重要性。结果表明，表面电荷不易获得的绝缘子具有很好的绝缘性能。少

项目成果

山本修: "真空中円錐台形スペーサの帯電特性-角度依存性に関する理論と実験結果の比較-"電気学会論文誌A. 120巻. 1070-1075 (2000)

Osamu Yamamoto：“真空中截头圆锥形垫片的充电特性 - 关于角度相关性的理论与实验结果的比较”，日本电气工程师学会会刊，第 120 卷，1070-1075 (2000)

O.Yamamoto, T.Takuma, S.Hamada et al.: "Influence of Surface Roughness on Charging of an Insulating Spacer in Vacuum"Trans.IEE of Japan. Vol.119, No.10. 1221-1228 (1999)

O.Yamamoto、T.Takuma、S.Hamada 等：“表面粗糙度对真空中绝缘垫片充电的影响”Trans.IEE of Japan。

山本修: "真空中の固体誘電体帯電現象における表面粗さの影響響"電気学会論文誌A. 119巻. 1221-1228 (1999)

Osamu Yamamoto：“表面粗糙度对真空中固体介电材料充电现象的影响”日本电气工程师学会会刊 A.卷 119. 1221-1228 (1999)

Osamu Yamamoto: "Delay characteristics of surface charging on a cylindrical Insulator in Vacuum"IEEE Trans. on Dielectrics and Electrical Insulation. Vol.7. 812-817 (2000)

Osamu Yamamoto：“真空中圆柱形绝缘体表面充电的延迟特性”IEEE Trans。

O.Yamamoto, T.Takuma, S.Hamada, Y.Tanabe, Y.Kakehashi, S.Ikoma, K.Nishimura: "Delay characteristics of surface charging on a cylindrical insulator in vacuum"Proc.of the 11th Int.Symp.on High Voltage Engineering (ISH), London. No.3.341. 4 (1999)

O.Yamamoto、T.Takuma、S.Hamada、Y.Tanabe、Y.Kakehashi、S.Ikoma、K.Nishimura：“真空中圆柱形绝缘体表面充电的延迟特性”Proc. of the 11th Int.Symp。