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 SF6 puffer circuit breakers during and after the interruption of fault currents up to 45kA peak using optical-fibre sensors based on chromatic modulation. The pa rticular parameters measured with the optical-fibre sensors were the contac t travel, the gas pressure in both the puffer piston chamber and the circui t-breaker tank, the radiative emission from the electric are and the concen tration of micron-sized particles produced by the arcing. The experimental results are compared where possible with theoretical calculations from a co mputational-fluid-dynamics computer package. The possible role of the parti culate material in the longer-timescale conditions within the circuit-break er tank is considered and the need for a better understanding of the partic ulate-material properties and formation is highlighted.