SUMMARY

The gas transmission system simulator consists of a computer based model, used in an operational environment. The effect of any control action the gas dispatcher might execute can be examined using the simulator. With the simulator the behaviour of the gas network over a maximum period of 48 hours can be predicted. The SCADA (Supervisory Control and Data Acquisition) system provides measured pressures and flows and, with a parallel model, all pressures and flows over the whole grid are calculated in order to provide a starting situation for the predictive model. A hundred off take flows are predicted by a load forecast model which receives direct information from the meteorological office. All compressor and reducer set points can be provided via graphic screens. The same applies to pipeline connection changes in the network. As a result of a predictive simulation, predictive messages are generated. Via plots and predictive mimic diagrams the results can be evaluated. In addition, the system provides for leak detection, as well as the estimation of leak size and leak location. The gas transport system which is simulated consists of 4500 km of pipeline, segmented into 600 sections, 20 supply points, 100 off take points, up to 7 pipelines in parallel, 7 compressor stations, 2 interlinked transport systems each carrying a different type of gas and 5 mixing stations. The computer hardware used consists of a VAX 11/750 with 500 Megabytes of background storage and an attached processor: FPS 164. The simulator was put into operation in the course of 1985 at Gasunie in the Netherlands.

1. INTRODUCTION

Gasunie has put into operation a gas transport system simulator in the course of 1985. With a simulator alternative strategies can be evaluated. A strategy consists of a set of set point and valve position changes to be performed over a period of up to 48 hours. The best strategy will be adopted as the operating strategy. The result of a simulation is largely dependent on predicted off take flows. As time goes by these predictions will become more accurate. By repeatedly performing a simulation with the plan strategy and refreshed predictions, the operating strategy is monitored. If such a simulation results in a predictive alarm, this will be an incentive for the user to improve his operating strategy. Leak detection can be performed by the simulator. As all measurements are coming from one gas transport system, they ought to be consistent within measurement accuracy. This consistency can be checked by a model that runs in parallel with the gas transport system. Inconsistencies may be identified as being caused by a leak. The simulator can be used for training purposes. The gas transport situation of a day with great operational difficulty can be retrieved from tape. This situation may serve as an exercise to the trainee who has to find an adequate strategy. The motivation for installing a simulator is as follows. Gasunie wants to continue being a prudent operator.

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