Optical-fibre-based investigations of contact travel, gas pressure and particle concentration in SF6 puffer circuit breakers

Experimental results have been obtained about conditions within SF ₆ puffer circuit breakers during and after the interruption of fault currents up to 45 kA peak using optical-fibre sensors based on chromatic modulation. The particular parameters measured with the optical-fibre sensors were the contact travel, the gas pressure in both the puffer piston chamber and the circuit-breaker tank, the radiative emission from the electric arc and the concentration of micron-sized particles produced by the arcing. The experimental results are compared where possible with theoretical calculations from a computational-fluid-dynamics computer package. The possible role of the particulate material in the longer-timescale conditions within the circuit-breaker tank is considered and the need for a better understanding of the particulate-material properties and formation is highlighted