Gaseous Insulation for High-Voltage Apparatus

A group of halogenated gaseous compounds have been investigated to determine their impulse (1¿x40-microsecond wave) and 60-cycle strength in uniform and nonuniform fields at pressures of 1,2, and 3 atmospheres. The scope of this investigation was confined to bare electrodes, and additional testing will be required to determine the behavior of these gases with various types of solid insulation. It has been found that sulphur hexafluoride (SF6) possesses superior insulating properties for high-voltage apparatus, even at these relatively low pressures. Data obtained in an approximately uniform field indicate that at 30 pounds gauge. pressure this gas approaches the impulse strength of oil. Therefore, certain classes of high-voltage apparatus advantageously may use this gas for their insulation, if other properties are adequate.