Improved glass-ceramic envelope for vacuum interrupters

This study describes an improved hermetic glass-ceramic-to-metal seal which provides a high strength mechanical joint. The new sealing joint reduces electrical stress at the metal interface and is especially suitable for vacuum interrupters designed for high voltage applications requiring high reliability. An improved design of the glass-ceramic-to-metal seal is presented which uses a `U' section metal end flange. A novel high voltage vacuum interrupter design is presented for a load break switch and fault interrupting applications using fewer components than at present. It has been shown how different features can be incorporated into the glass-ceramic envelopes to avoid the requirement for metallic vapour shields or for external sheds or corrugations to enhance dielectric behaviour. The design could be used directly for an outdoor application eliminating the need for external insulation. Finite element modelling has been used to analyse the seal and interrupter design mechanically and electrically.