Estimation of inter-conductor stray capacitance for HVDC transmission line of negative neutral beam injector

M. Vishnudev, D. Parmar, H. Shishangiya, A. Gahlaut, V. Mahesh, M. Bandyopadhyay, A. Chakraborty
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引用次数: 1

Abstract

Neutral beam injectors inject multi megawatt neutral beams, several tens of amperes and energies from few 100 kV to MV, into the tokamak for heating and diagnostic purposes. The neutral beams are produced through the route of neutralization of ion beams. The ion beams of machines like ITER shall use large area RF based negative ion sources, for plasma production, coupled to multi-grid (3-7), extractor and accelerator systems. Depending on the energy requirements and the beam optics the gaps between the extractor and accelerator stages can range between a few mm to few tens of mm. The multi-aperture multi-grid extractor accelerator systems also provide the route for the gas being fed in the ion source for the plasma production to escape to the surroundings. As a result, the gas density in the gaps is high and can lead to breakdowns often referred to as Paschen breakdowns. A major source of stored energy could be the inter conductor stray capacitance of the high voltage transmission line. These breakdowns could lead to damage of the grid segments and thereby considerable down time of the injector. One of the possible routes to reduce the stored energy could be to reduce the inter conductor stray capacitance by increasing the distance between the conductor and the outer ground cover. This will result in a transmission line with a complex geometry and direct estimation of inter conductor stray capacitance of such complex geometry is difficult. Hence a technique is proposed to estimate the inter conductor stray capacitance of a complex geometry transmission line. A study has been carried out to estimate the inter conductor stray capacitance for various configurations of the transmission line using the method of stored energy in the COMSOL platform. The estimates for one such configuration have been validated experimentally from measured values of capacitance for a 1 m long prototype element. The results of these studies and the experimental observations shall be presented and discussed.
负中性束注入器高压直流输电线路导体间杂散电容估算
中性束注入器向托卡马克注入数兆瓦的中性束,几十安培和从几个100千伏到MV的能量,用于加热和诊断目的。中性束是通过离子束中和的途径产生的。像ITER这样的机器的离子束应该使用基于射频的大面积负离子源,用于等离子体生产,并与多网格(3-7)、萃取器和加速器系统耦合。根据能量需求和光束光学,萃取器和加速器级之间的间隙可以在几毫米到几十毫米之间。多孔径多栅格萃取器加速器系统还为离子源中的气体提供了一条通道,供等离子体生产逃逸到周围环境中。因此,间隙中的气体密度很高,可能导致故障,通常称为Paschen故障。高压输电线路的导体间杂散电容可能是存储能量的一个主要来源。这些故障可能会导致网格段的损坏,从而导致注入器的大量停机时间。减少存储能量的可能途径之一是通过增加导体与外部地盖之间的距离来减少导体间的杂散电容。这将导致传输线具有复杂的几何形状,并且难以直接估计这种复杂几何形状的导体间杂散电容。为此,提出了一种估算复杂几何传输线导体间杂散电容的方法。利用COMSOL平台中存储能量的方法,对不同配置的传输线导体间杂散电容进行了估计。对一种这样的配置的估计已经通过1米长的原型元件的电容测量值进行了实验验证。这些研究的结果和实验观察结果将被提出和讨论。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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