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Gas coordination

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Calculation parameters

Filling pressure
bar abs

SF6 percentage

Compartement volume

Calculation results

SF6 weight [kg]

N2 weight [kg]

SF6 equivalent density [g/l]

Gas mixture density [g/l]

Density ration to pure SF6

Estimated liquifaction point [C]

SF6 steam pressure curve and lines of constant density


X/R ratio and DC%
X/R Ratio and DC%

X/R ratio is simply the ratio of the system reactance to the system resistance, looking back to the power source from any point in a power circuit, assuming that a short circuit is applied to the system at that point. It is another way of stating the power factor of the source system.

For a given level of symmetrical fault current and a given circuit breaker contact part time, this X/R ratio establishes the value of asymmetrical fault current the breaker is required to interrupt. A higher X/R ratio, with its slower decay rate, will result in a higher asymmetrical fault current at contact part time. If the X/R ratio is too high, the asymmetrical fault current may exceed the breaker's interrupting capability.

In both the ANSI/IEEE and the IEC standards, the time constant of dc decay for distribution applications is standardized at 45 ms, which corresponds to a X/R ratio of 17 for a 60 Hz system.


Your Hz power grid network with X/R = has a time constant τ = ms. If you are using high voltage circuit breaker with min. opening time of ms and rated short circuit current kA, rated DC% of this circuit breaker for the normal high voltage network conditions, τ = 45 ms is %

Useful tables