The use of electric, magnetic and aerodynamic field computations for modelling the behaviour of electric arcs in high voltage interrupters and materials processors

Field modelling is contributing much to the understanding and design of equipment and devices in which electric arcs occur. The earliest preoccupation was mainly with electrostatic field calculations for ensuring that the circuit breaker geometry was not susceptible to unnecessary insulation failure. However the operation and behaviour of such arc devices depend not only upon E-field conditions but also upon aerodynamic fields used for controlling and extinguishing the electric arcs, thermal fields produced by the electric arc plasma itself, and magnetic fields for providing extra arc column control via electromagnetic drives. This paper attempts to illustrate how research is progressing to incorporate descriptions of these additional fields-aerodynamic, magnetic and thermal-to produce more integrated modelling of equipment involving high current arcs. The need is driven by the closer coupling between the various fields consequent upon the evolution of more efficient and cost effective device designs, one example of which is the SF₆ puffer circuit breaker wherein the aerodynamic, thermal and electric fields are tightly interactive. The evolution of self pressurising SF₆ interrupters is leading to a need to also couple external magnetic fields into the multidimensional fields systems in order to enhance the aerodynamic and thermal conditions within such a device