Development of new optimized range of medium voltage vacuum interrupters

During several past years Schneider Electric developed new range of medium voltage vacuum interrupters (VI) for circuit-breaker and recloser applications. Objective of new range development was replacement of existing wide legacy offer with limited number of VI’s. New range offers compactness, higher dielectric withstand, higher short-circuit making and breaking capabilities and longer mechanical and electrical life comparing to previous range. The paper gives review of development process which consisted in multiple simulations and comprehensive validations plans at each stage of prototyping. To achieve robust dielectric design, electrostatic simulations considering aspects of internal and external insulation were done. Critical areas affecting dielectric properties of VI’s were defined, impact of mechanical and current breaking operations was studied. Mechanical simulations were carried out to define optimal shapes of parts from technical and manufacturing points of view. Electromagnetic studies were performed to improve arc control properties of radial magnetic field (RMF) contacts. Definition of contacts design took into account not only levels of short-circuit breaking currents and number of breaking operations but also more severe requirements for short-circuit making. As a result, 10 VI’s which cover applications for rated voltages up to 40.5kV and short-circuit currents up to 50kA were developed.