SGN is the second largest gas distribution company in the UK owning and operating two gas distribution networks made up of three Local Distribution Zones (LDZs) delivering natural and green gas through over 46,000 miles (74,000 km) of pipeline to 5.9 million homes and businesses across Scotland and the south of England. The distribution networks receive gas from the UK's National Transmission System (NTS), multiple biomethane producers and an LNG terminal.

The SGN Gas Control Centre has a key role to ensure there is a safe and reliable network to enable them to meet the daily demand whilst operating the networks within designed limits. National Grid Gas UK Transmission (NGG UKT), which operate the National Transmission System (NTS), require the provision of an hourly schedule of gas volumes (hourly profiles) taken through each of the NTS Offtakes into the LDZ in the form of Offtake Profile Notifications (OPNs). Although these profiles can be altered throughout the day to reflect changes in the demand, there are strict rules as to how much the profiles may change. Each OPN is scrutinized against the Uniform Network Code (UNC)(2) rules on submission to UKT.

To gain further insight and enable more efficient operation of its networks, SGN has deployed a real-time Gas Network Modelling System (GNMS) on the high pressure (100-1000 psig (7-69 barg)) parts of its networks. As well as providing a valuable stock monitoring tool, the GNMS utilizes data from the OPNs to predict the performance of the networks over the period of the current and next gas days.

This paper will discuss the OPN generation tool developed by SGN and Emerson and the implementation of the GNMS. Despite limitations in instrumentation in certain parts of the networks early indications are the GNMS is providing accurate results: this too will be discussed.

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