Four Austrian Gas networks will be presented and used to discuss various aspects of network control and the role of hydraulic analysis. The main elements of network modelling will be briefly reviewed. Aspects of steady state vs. transient modelling as well as simulation vs. optimization will also be discussed. A variety of solution methods for different network structures will be pointed out. A practical solution for the Transient Optimization Problem which has been presented before (see [2] and [3]) will be outlined briefly. More emphasis will be laid on the discussion of the aspects of how various types of applications can be modelled (what are the questions to be answered, what are the criteria of optimization?).

1. Introduction

An Optimization expert once stated: real life problems are non linear, mixed integer, time dependant, and stochastic. It will be shown how this applies to the gas transmission problem, especially under the work requirements of rapidly varying conditions dispatching centers are facing today (similar to stock exchanges).

Gas transmission in and through Austria

Figures 1 and 2 show that Austria physically receives most of Figure 1 Austrian Gas Network as part of the European Transmission System it's imported gas from Russia via the Slovakian network at the border station of Baumgarten. However there is some additional supply by domestic gas fields and several storage fields. A large portion of the imported gas is being shipped through Austria via two transit lines, the West Austria Gaspipeline (WAG) to Germany and the Trans Austria Gaspipeline (TAG) to Italy and Slovenia. The TAG contains three parallel pipes and presently three compressor stations, while WAG is a single line with two compressor stations. Delivery into Austria occurs at main supply points in Baumgarten and several off take points along the transit lines. Figure 3 shows the local high pressure network spanned between the transit lines which transports the gas to the domestic customers. The network consists of three subsystems belonging to local distribution companies, but it is supervised by AGGM. It is a looped system with varying flow directions, presently operated without compressors, pressure being supplied at transit off takes, storage fields, and by OMV's primary distribution system. OMV's Primary Distribution System, PVS is a geographically small, but highly looped network connecting various distribution locations and storage plants. It serves the demands in the Vienna area and also feeds into the AGGM network. This network contains several pressure levels (medium to high).

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