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To gain an increased understanding of circuit-breaker performance, and the corresponding specification and test issues, the interaction between circuit breaker and the connected network is being studied. In the course of this investigation, the modeling of high-frequency voltage transients is being addressed. The essence of the problem lies in the need to combine the electromagnetic modeling of the distributed nature of the interrupter, with the modeling of connected networks by lumped circuits and with the modeling of the electric are plasma within the interrupter. An equivalent circuits approach is proposed for combining different levels of approximation within each modeling domain and to provide computationally economic solutions. A hierarchy of model approximations is presented and examples of their applicability are given. As a result, an insight into a number of factors (e.g., network transients, current chopping, interrupter geometry, etc.) which produce and affect high-frequency overvoltages have been produced. Index Terms--Electromagnetic fields, equivalent circuits, extra high voltage circuit breakers, gas-insulated switchgear, power system simulation, resonance, skin effect, switching transients, transient analysis.

An experimental study, which reviews the various techniques that can be used for determination of anisotropy fields in recording media, is described. General agreement is seen for the other techniques mentioned and results for samples with differing degrees of texture show that the apparent anisotropy field of the grains as measured by these techniques is influenced greatly by orientation effects.