Supersonic nozzles are commonly used in
modern high voltage circuit breakers. The
thermodynamic and electrical behaviour of arcs
burning in such nozzles is closely related to the
nozzle geometry, the quenching and insulating
medium, and the parameters of the medium at
the nozzle inlet and exit.
Computational investigation has been carried out
on the thermal interruption capability of a
supersonic nozzle with different quenching and
insulating mediums. The critical rate of rise of
recovery voltage (RRRV), which is the most
important parameter determining the thermal
interruption capability of a circuit breaker, was
predicted for three gases of SF6, CO2 and N2
under typical practical operation conditions.