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Capacity calculation

Principle of capacity calculation

Calculation of the transport capacity of a gas pipeline is governed by the laws of fluid mechanics, and particularly the Colebrook formula:

            P22 - P12 = A.d.L.λ.Q2/D5

where:

  • its diameter (D),
  • its length (L),
  • its roughness (λ),
  • the nature of the gas, characterised by its density (d),
  • the grid operating parameters (pressure at the system entry (P2) and exit (P1) points).

Calculating the capacity of a natural gas transport network like Teréga’s is
much more complicated. Simple application of a mathematical formula to one basicsection is not enough, because Teréga’s network consists of:

  • multiple sections with different characteristics, connected in series, in parallel, or branching;
  • many special systems such as compression stations, pre-expansion stations, metering stations etc..

Finally, this complex network is connected at several points to the infrastructures operated by adjacent operators, transporters and storage providers. Each has their own operating constraints which need to be considered when evaluating grid capacities.
To perform those calculations, Teréga models the characteristics of all the elementary systems making up its transport network. From that model, it is then possible to simulate all the supply and consumption situations envisaged by Teréga.

Calculating the maximum tradable fixed capacity

The maximum tradable fixed capacity of a system is the maximum flow that the system is likely to transport under a given reference situation known as the “design case”. The design case is determined by the transporter on the basis of the most demanding operating conditions that they are able to cover.

For its grid, Teréga generally uses two seasonal design cases:

  • in winter, the situation corresponds to the subscription forecasts at delivery points. These make it possible to deal with a peak in consumption which is likely to occur once every 50 years;
  • in summer, that situation corresponds to the maximum injection into storage and minimal draw-off over the Regional Grid, equivalent to the average consumption over previous Augusts.

Tradable capacities

Teréga publishes its subscribed and available tradable capacities

EN Standard TEREGA : 0 559 133 400EN Urgence Gaz : 0 800 028 800

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