The development of PC based CAD tools for auto-expansion circuit breaker design

It is shown that, with the current understanding of basic arc physics, CAD tools based on a mathematical model encompassing all important physical processes can be developed to aid the design of auto-expansion circuit breakers. The model takes account of radiation transport, arc radiation induced inner wall ablation, turbulence enhanced momentum and energy transport and the moving parts of the breaker. With the aid of the PC based PHOENICS, a commercial general purpose computational fluid dynamics (CFD) package, the conservation equations for the gas and arc together with the relevant Maxwell's equations can be solved. The temperature, velocity and electric fields within the breaker can easily be visualised and the thermal interruption capability predicted. The effects of changing design parameters can be simulated in detail, thus reducing the number of short-circuit tests. Results are verified by available tests.