Development of a new vacuum interrupter for disconnecting and breaking in a shielded and solid insulated switchgear

Compactness of switchgear can be reached using a shielded solid insulation technology. Thus the size and costs can be reduced and the substation installation becomes easier and more attractive for customers. Constraints are then reported on the design of Vacuum Circuit Breaker in order to fulfill the whole standard requirements. A new embedded Vacuum Interrupter was developed that complies with requirements related to partial discharges, thermal cycles, mechanical endurance, breaking performance and disconnecting dielectric withstand. Multi-physics simulations were widely used to match industrial and technical requirements of such a complex system. For instance, overmolding simulation is mandatory to ensure the material homogeneity, the suitability of stresses with thermal constraints and that there are no holes. Radial Magnetic Field contacts were used to get compactness, cost effectiveness and breaking capacity. Contact material was also selected in order to obtain the best compromise between breaking performance, anti-welding property and low erosion. Thus the E2 electrical endurance class and 50 full interruptions at 25kA/15kV were achieved with less than 0.8mm erosion. No degradation of power frequency dielectric performance across isolating distance was found after breaking tests. Finally, this vacuum interrupter complies with the circuit-breaker and the disconnector standards.