Gaseous insulation for high-voltage transformers

SULFUR HEXAFLUORIDE in high-voltage apparatus fulfills these requirements of a gaseous dielectric: 1. dielectric strength should be high at a low-gauge pressure; 2. temperature of condensation should be equal to or lower than that at which the apparatus is operated; 3. the gas itself and its products of decomposition should not be toxic or of readily controllable toxicity. Similarly, the gas should not corrode materials of construction; 4. the gas should be chemically inert and thermally stable; 5. it should have a high heat transfer coefficient.