Breaking capacity of SF/sub 6/ circuit-breakers at low temperatures

The breaking performances of circuit breakers in the range of low temperatures (-25 degrees C) encountered in France are examined. A series of short line fault clearing tests was carried out on a chamber of a 245 kV 31.5 kA puffer-type circuit breaker. The test conditions selected permit separate variation of the gas density and pressure. A prior methodology analysis shows that to eliminate or minimize the influence of the other variables, i.e., the test circuit and wear, the best criterion is the minimum arcing time. No significant influence of temperature or the presence of droplets of SF/sub 6/ is observed on the performances at a given density of the gaseous phase; the minimum arcing time does not vary during the tests. These results justify, a posteriori, the practices of the test laboratories, which carry out breaking operations under ambient conditions.<>