Development of a New Method and a Discharge Indicator for the Evaluation of Isolating Gases

As part of the design and dimensioning of systems for high-voltage applications such as high-voltage laboratories, transformer stations or converter halls, it is necessary to minimize the distances for reasons of cost optimization between voltage-carrying components and the ground electrodes. In this case, the insulating medium is atmospheric air. To avoid electrical break-downs or so-called flashovers, the air clearances have to be designed adequately. Conventional air clearance calculation is based on empirically determined equations with correction factors for climatic conditions and used geometries. Here, the breakdown voltage, which leads to an electrical arc, is considered particulary. However, before electrical breakdowns occur, phenomena such as Townsend, Streamer and Leader discharge occur. Therefore, this publication attempts to investigate the forerunners of an electrical breakdown from high-voltage-carrying components with the help of electrical discharge mechanisms. Using the high-voltage direct current test center at the chair of High Voltage Engineering (TU Dortmund University) as motivation, the ignition criteria of a direct current source to a grounded wall is examined, in order to optimize the spacing respectively verify the new method as presented.