Reliability and Performance of Composite Electrical Insulation at Cryogenic Temperature for Superconducting Power Apparatus

超导电力设备低温复合电绝缘的可靠性和性能

• 批准号: 15560240
• 负责人: NAGAO Masayuki
• 金额: $ 2.3万
• 依托单位: Toyohashi University of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15560240/
• 关键词: Cryogenic Temperature; Spacer; Foreign Particles; Creeping Discharge; Electric Breakdown; Small Gap; 極低温絶縁; 微小ギャップ; 帯電; 紙-氷複合絶縁; 導電性異物; 微小傷; 氷・絶縁紙複合絶縁系; 氷結時圧力; Cryogenic Temperature; Spacer; Foreign Particles; Creeping Discharge; Electric Breakdown; Small Gap; 極低温絶縁; 微小ギャップ; 帯電; 紙-氷複合絶縁; 導電性異物; 微小傷; 氷・絶縁紙複合絶縁系; 氷結時圧力

The world's largest class superconducting coil is used for the "Large-scale Helical Device". Its electrical insulation system might be exposed to considerably severe multiple stresses including cryogenic temperature, large mechanical stresses and strong magnetic fields. It is therefore very important to study its electrical insulation performance in order to establish the reliability of the coil. If a superconductor quenches from superconducting state to normal state, the liquid coolant vaporizes very easily and turns into high-density gas at cryogenic temperature, which may reduce its withstanding voltage. Furthermore, it is very difficult to completely remove foreign particles from the insulated space. So it is required to clarify the influence of foreign particles and electrification on the insulation performances.This research was conducted using electrode system that simulated the insulation system to investigate the behavior of small gaps and foreign particles with the breakdown characteristics of insulation. The breakdown voltage of insulation system that has a small gap in liquid helium is shown in Fig.1. The breakdown voltage increased with decrease of voltage rising rate when the polarity of voltage was positive, but the breakdown voltage was almost constant with decrease of voltage rising rate when the polarity of voltage was negative. Assuming that positive charge can move along the spacer surface that is in contact which the metallic electrode, lower rising rate of applied voltage would bring more significant charge accumulation on the spacer, leading to the field enhancement which reduces the breakdown voltage. It became also clear that conductive foreign particles affect the breakdown voltage while dielectric foreign particles do not.

世界上最大的类超导线圈用于“大型螺旋设备”。其电绝缘系统可能会暴露于相当严重的多重应力，包括低温温度，较大的机械应力和强磁场。因此，研究其电绝缘性能以建立线圈的可靠性非常重要。如果超导体从超导状态到正常状态淬灭，则液体冷却液会非常容易蒸发，并在低温温度下转变为高密度的气体，这可能会降低其耐静电电压。此外，很难完全从绝缘空间中清除异物。因此，需要阐明异物颗粒和电气对绝缘性能的影响。这项研究是使用电极系统进行的，该系统模拟了绝缘系统，以研究具有绝缘特征的小间隙和异物的行为。液态氦气间隙较小的绝缘系统的故障电压如图1所示。当电压的极性为正时，击穿电压随电压上升速率的降低而增加，但是当电压的极性为负时，击穿电压几乎恒定，电压上升速率的降低。假设正电荷可以沿着金属电极接触的间隔表面移动，则较低的施加电压速率将带来更大的电荷积累，从而导致磁场增强，从而降低了故障电压。同样很明显，导电外颗粒会影响击穿电压，而介电外颗粒则不会。