Arc radiation monitoring in a commercial EHV circuit breaker using optical fibre transmission

Measurements of total radiation losses from arcs in a commercial SF 6 puffer circuit breaker are analysed to give values of radiated power per unit arc length. Such an analysis is complicated by the need to take account of the optical fibre used for the transmission of the optical signal from within the high pressure tank and highly accelerated nozzle assembly of the circuit breaker. The analysis requires calibration of the system components and its validity is demonstrated through a comparison with the direct measurement of total radiation under laboratory conditions. The investigation makes possible in principle the quantification of radiation power transport during the operation of in-service circuit breakers and is therefore of some significance for condition monitoring of switchgear.