Intelligent optical fibre monitoring of oil-filled circuit breakers

Intelligent monitoring encompasses the extraction of information from data sets, which are only partially complete because of practical constraints on the deployment of measurement techniques. An experimental technique is des cribed for monitoring a number of conditions within oil-filled circuit brea kers from a single measurement method and using an optimised number of opti cal fibre sensing channels. The technique is based upon detecting changes i n the optical intensity of light transmitted through the circuit breaker me dium, using optical fibre delivery and capture at a number of different axi al and radial locations within the circuit breaker chamber. It has been use d during development testing at a short circuit test station for two oils w ith very similar physical characteristics but different kinematic viscosity as the are extinguishing media. Results are presented which examine the de pendence of the contact travel time upon are duration and oil type. Quantit ative information is given concerning the optical recovery time of the oil as a function of are duration and axial location within the circuit breaker . The technique also detects the occurrence of fresh oil injection into the contact gap and enables the duration of its occurrence to be determined.