Electrical arcing that previously took place in oil is now taking place in a vacuum interrupter, which prevents arcing from contaminating the insulating oil. Typical inspection intervals for vacuum interrupter technology are between 300,000 to 500,000 operations, compared with 100,000 operations for conventional, non-vacuum arc quenching technology. Additionally, there is no time limit set for maintenance with vacuum interrupter technology.
The vacuum diverter switch tap changer types VUCG and VUCL have the advantage of being built in the same housing as ABB's conventional tap changer types UCG and UCL. Upgrading conventional units already in service, with corresponding ABB vacuum types, does not require any specific construction adaptations and makes the installation of new vacuum units straightforward. Similarly, since the vacuum selector switch tap changer type VUBB does not position the change-over selector outside the cylinder, its rotational symmetry makes installation extremely simple and easy. It is also fully insulated between the different phases, and therefore applicable to delta connection.
The new vacuum reactance on-tank tap changer type VRLTC is fully insulated and mainly used for LV regulation - in this specific case, a reactor is used to bridge adjacent taps instead of a resistor. The unique electronic motor drive that controls the tap changer is fully integrated and can achieve one operation per second (compared to five seconds typically).
To secure reliable and safe service conditions, all new ABB vacuum tap changer types undergo a very demanding and extensive test program. All new ABB vacuum tap changer types have been successfully service type-tested for 600,000 operations. In addition, several test objects of each type have been mechanically endurance-tested for over 1,200,000 operations under both warm and cold conditions, versus the standard test requirement condition of 500,000 operations.
