Insulation & Dielectric Breakdown Design Considerations in Sub-Atmospheric Environments

Summary form only given. A detailed knowledge of electrical insulation and high voltage design techniques is essential if reliable high voltage systems are to be designed and manufactured for use in sub-atmospheric environments. The trend is towards more advanced systems operating at higher voltages in compact, economical packages that have been submitted to a battery of diagnostic techniques to ensure a high quality assembly. If materials are to be operated under much more demanding specifications, better information is required on the limits of these materials and on their design and manufacturing techniques. The purpose of this paper is to present an overview of high voltage electrical/electronic design considerations required to specify and apply electrical insulation to high-voltage parts, components and systems used in sub-atmospheric environments. It became evident early in the advent of developing high voltage equipment for the electrical power utilities that corona and partial discharges shortened the life of the electrical insulation and equipment. However, difficulties arose with utilizing commercial partial discharge test equipment to evaluate electronic systems used in sub-atmospheric environments. Problem areas are high frequency applications, non-sinusoidal wave forms such as pulses, low pressure or high altitude, and environmental extremes in temperature and plasma. Operating voltage, frequency, temperature, ambient gas composition, pressure, radiation, and structural requirements must be known when designing insulation for high voltage equipment. When selecting an insulating material for a high voltage application, the right data seems to be difficult to find. Mechanical and chemical data are usually abundant. However, the electrical data are a simple tabulation of constants, with no hint of how these constants will vary with respect to operating condition.