The role of microparticles in initiating the electric breakdown in high–voltage vacuum insulation systems

The paper presents the hypotheses of initiating mechanisms of the electric breakdown in vacuum insulation systems caused by small material granules, i.e. the microparticles. The microparticles detached from the parent electrode have an electric charge and move in the inter–electrode area due to the electric field. The role of a microparticle in initiating the breakdown in a vacuum insulation system depends to a considerable extent on the microparticle energy at the moment of its impact against the opposite electrode, i.e. on its velocity at the impact time. The paper presents calculation of the microparticle velocity values at the moment of the impact against the opposite electrode under the conditions existing in practice in the vacuum insulation systems. It was assumed for purposes of the calculation that the microparticles are spherical and made of copper, aluminum or iron, and are subjected to constant electric field. Minimum values of the microparticle velocity necessary to cause plastic deformation of the electrode surface in result of the impact are determined. (The calculations have been carried out with the computer program developed in C# language on the Visual Studio 2013 environment.)