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New Method for the Price Calculation of Natural Gases

In Germany, price calculations of natural gases in commercial transactions between public utilities and consumers are performed on the basis of the quantity of energy supplied. In order to avoid that all the gas quality data determining energy have to be measured at each place of consumption, so-called grid reconstruction systems may be used even in complex grids. Calorific values and other gas quality data are measured only at representative points in the grid. The data at the place of consumption are then determined with a program system subject to type approval.

Main pipelines of the gas supply grid in Germany (fig: BGW)

To control the dispatching of gases in pipelines grid reconstruction systems are used. Such systems contain measuring points where the volume flow, standard density, pressure, temperature and calorific value are measured. A program system combines the measured values with data describing the topology of the supply grid (geometry of the pipelines , feed-in and feed-out points, slides, valves, storage facilities, compressors etc.) to determine the dispatched volume flows. In this way the calorific values and other gas quality data may be calculated for any time and place of consumption.

In the past, the correctness of the data relevant to the consumer was ensured by type-approved measuring instruments and peripherals which were not subject to verification. The latter included the program system which was supervised by the verification authorities. The limited means to check the complex systems has now been improved considerably improved by fixing harmonised requirements for design and operation of these systems. The systems are treated as complex measuring facilities including hard- and software and may thus be subject to type approval meeting the requirements of the Verification Act with regard to measurement correctness, durability and testability. Essential requirements concern the software, data transmission and storage as well as testing by sampling at varying points so that measured and calculated values may be compared. These harmonised requirements and regulations provide the gas utilities with means for the projecting, installation and operation of the grid reconstruction systems. They also provide the verification authorities with a basis for uniform enforcement with the purpose to protect the consumer.

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