Abstract
The paper is devoted to the solution of short-circuit switching problem in distribution networks by application of synchronous HV gas-blast circuit breakers (SCB). The reduction of the arcing energy by reducing the arcing time can extend the SCB expected service life by increasing its electrical life, minimizing the thermal requirements of the interrupting chamber. The paper studies the gas flow arrangement in the switching gap of the double-flow model SCB. Well-balanced and stable gas flow removes surplus energy from the switching arc. Three types of nozzle geometry are investigated. A numerical simulation with a grid reconstruction is used. A gas flow energy accumulation into the nozzle throats is observed at t=0.8-0.9 ms after the contacts opening. We evaluate the bottom time limit of the active interactions between the gas flow and the arc column before current zero under the synchronous commutation. A zone of stagnation depends on the nozzle shape and size and determines the level of the thermal-dielectric interruption ability.
Highlights
The modern trends of increasing the rated voltage and short circuit breaking current per a break [1,2] with applying of alternative for SF6 medium [3,4] become an urgent problem for developers [5] and require new approaches for its solving.An idea of synchronous commutation as the effective method to enhance the interruption ability of synchronous HV gas-blast circuit breakers (SCB) is well known in scientific community [6,7]
An idea of synchronous commutation as the effective method to enhance the interruption ability of SCB is well known in scientific community [6,7]
The effective interactions between a switching arc and a gas flow removes the surplus energy from a gap between electrical contacts of the SCB
Summary
The modern trends of increasing the rated voltage and short circuit breaking current per a break [1,2] with applying of alternative for SF6 medium [3,4] become an urgent problem for developers [5] and require new approaches for its solving.An idea of synchronous commutation as the effective method to enhance the interruption ability of SCB is well known in scientific community [6,7]. After the tripping signal, the driving circuit for the breaking contact is excited by the synchronous pulse. The effective interactions between a switching arc and a gas flow removes the surplus energy from a gap between electrical contacts of the SCB. To provide it the gas flow should be wellbalanced and stable around current zero. In this case, the arcing time is significantly reduced, because the energy release during the arcing greatly decreases. The contacts opening and gas introduction times under the synchronous commutation are controversial issues (see below)
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