Scaling Criteria for Interruption Performance in Gas-Blast Circuit-Breakers

The high cost and complexity of short-circuit interruption testing of gas-blast power circuit-breakers make it essential to use most efficiently results of reduced power development tests in interrupter design. Due to the limited capacity of direct testing stations many EHV-breakers must be evaluated by indirect methods such as synthetic-testing of single interrupter units. The interpretation of synthetic-test data and the effective utilization of reduced power test data in circuit-breaker design can be enhanced by the development of accurate scaling criteria. The present paper demonstrates to what extend scaling of enthalpy-flow, current density, pressure, interruption capability, nozzle area ratio, contact spacing, and shape factors can extend the results of reduced power experimental tests to predict performance at full short-circuit ratings.