The oil circuit breaker used oil as the insulating and interrupting medium. The breakers usually used a dashpot to direct the flow of oil towards the breaking contacts. As they moved apart the arc was drawn in oil. The combination of speed of opening, oil insulation qualities and the gas...
Not sure if you have solved your problem with regard to RMU fuses but for information the most popular makes are Brush Fusegear and Cooper Busmann, who are now the same company.
In the distance past GEC also supplied fuses
They are always oil immersed fuses to IEC282-1, BS2692-1 and ESI12-8
Yes, it is Hawker Siddeley. The circuit breaker is the dead tank type with magnetic actuator designed by Whipp & Bourne following their success with the pole mounted Recloser
As you mentioned Canada, I thought I would refer you to BC Hydro who have extensive experience of SF6 switchgear for outdoor use. This includes both those that leak and those that do not.
They currently purchase a SF6 / vacuum circuit breaker from FKI Switchgear in the UK
