ABSTRACT
  • Mastering the knowledge of gas characteristics is of increasing importance and complexity for the Transmission Division of Gaz de France: Increasing importance, in view of greater constraints brought in by the new legislation for market deregulation: more precise knowledge of energy balances required, and over shorter time steps,

  • Increasing complexity as opening the gas market involves a diversification of supply sources and greater variability of supply configurations. Improving energy metering at the delivery point, which includes allocating a more precise Calorific Value (CV) to quantities delivered, is therefore a key priority for work and improvement. Several methods, alone or in combination, make it possible to maintain and improve the accuracy of the energy delivered at each output point: increasing the total number of Chromatographs; operating the network under several restrictions to keep a constant CV; or, using a dynamic simulation of gas movements. The dynamic simulation method is currently undergoing testing at the Transmission Division of Gaz de France to determine gas quality at delivery points. This is done by an a posteriori reconstruction of the evolution of the various physical quantities over a period, at all points in the network. Used with network simulation software (SIMONE), this method has been in the testing phase for over eighteen months. We will be presenting results obtained on several parts of the network of Gaz de France. Relating to this testing, the Research Division of Gaz de France is also interested, in a more theoretical way, in the impact of the different parameters having an influence on the precise determination of gas quality.

GAZ DE FRANCE TRANSMISSIONNETWORK

The 30500 km HP network connects the 5 main supply points to 4300 delivery points (1000 industrial customers and 3300 distribution networks). Its main characteristics are in the 33 compressor stations which represent 633 MW of installed power and the 13 underground storage units (10 aquifers and 3 salt layers). It is strongly interconnected and the flows are often changing (Figure 1 - Summer/Winter flows comparison), following the consumption level and the supply optimisation of one of the most diversified European supply portfolios (the Northern Sea, Russia, Algeria, Nigeria, Qatar and Egypt). Therefore, the transmission network could be considered similar to a high pressure distribution network.

WHY CHANGES ARE NEEDED
Overview of current method

Until now, Gaz de France customers have been invoiced on a monthly basis, using Calorific Values provided by the Gas Quality Area (GQA) method. This method involves assigning a single daily CV to all delivery points in a given area, known as a Gas Quality Area ('Zone Qualité Gaz' en français). This value is obtained using the daily average of the Calorific Values supplying the area, weighted by incoming volumes (when there are several supply points) as shown on the Figure

This content is only available via PDF.
You can access this article if you purchase or spend a download.