7. Cutting through the void

The dielectric properties of vacuum have long been known, and have been used, for example, in vacuum bulbs for X-ray tubes. The use of vacuum in switchgear was envisaged as early as 1920, but, due to technological contingencies, has only been effective at industrial level since 1960. Since the 1970s, vacuum technology has gained in popularity because of the advantages it offers over oil or air:

• space-saving ;

• better safety ;

• greater endurance.