Theoretical modelling of the interruption process of a puffer type interrupter

The physics occurring during the operation of a circuit breaker is very complex. Numerical modelling must take in to account the changing geometry during the operation, the fluid dynamics within the nozzle and the arc and the radiation transport within the arc. Because the flow characteristics of a puffer circuit breaker were not well known, it was necessary to develop numerical and experimental techniques which could be used to predict and measure the flow within a circuit breaker. Hence, a puffer circuit breaker was used to carry out a flow investigation and the results of this investigation were compared with the results of the numerical analysis. The numerical analysis was based on the use of a commercially available CFD package. The programme of work was divided in to two parts, the 'cold flow' and the 'hot flow' investigation. The first part involved the flow in the absence of an arc, the second part with the arc present. In the 'hot flow' analysis the arc was first represented by a simple heat source and subsequently by a full arc model.