High speed transfer switch with 50 kA and 50 kV ratings

The mechanical design and electrical parameters of a pneumatically operated transfer switch are given. This design is used to switch 3-s and 50-kA current pulses, and is easily capable of 75-kA operation (2×10¹⁰ I²t), with water-cooled versions capable of 20 kA continuously. Although the switch is not specifically designed to make or break 50 kA, it is provided with auxiliary Elkonite arcing contacts (which make first and break last). The arcing contacts have proven their value in protecting the main electrodes even under repetitive (50 kA) fault conditions. The results of extensive life testing and associated criteria are included