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Gas | Transmission vs Distribution

The gas supply network in the UK is divided into four sections: production; transmission; and distribution. The latter two, transmission and distribution, are often mistakenly overlooked as being the same process; however, not only are these transportation networks owned by completely different companies, but the process and networks are operated extremely different. Below is an illustration briefly explaining the general concept of each major step in the gas supply process.

Explanation...

  1. Oil Well: Using a boring machine, a large drill bit drills into the earth to try bring petroleum oil hydrocarbon to the surface from within the earth.
  2. Gas processing plant: Natural gas enters the gas processing plant in its pure, raw form and in this plant it is cleaned, separating any impurities and non-methane hydrocarbons and fluids to produce a ‘pipeline quality’ dry natural gas.
  3. Compressor stations: Once natural gas has started its national transmission journey, these compressor stations help to keep its transportation smooth and efficient by increasing the compression of the gas. This allows it to travel quickly and more efficiently. This needs to be performed at intervals of every 40-100 miles.
  4. Odorant: Because natural gas is naturally odorless and potentially deadly, for health and safety purposes an odor is added to the natural gas to enable leakages to be quickly identified.
  5. Distribution Company: After the gas has been nationally transmitted to where it is needed, at 49 points across the UK, gas enters the 8 distribution networks. Each distribution company is now in charge of ensuring the safe arrival of the natural gas to its household and business customers.
  6. Supply: Your gas has now been delivered. Each customer opts for one of the many energy utilities in order to pay for their gas supply. Part of this money is used by the utility to pay their gas distributor, and following that, the transmission network.

Transmission

Transmission is the nationwide transportation of natural gas in order for it to be passed on to one of the 8 area distribution networks. The sole owner of the transmission network in the UK is National Grid. All gas in the UK will pass through the National Grid’s National Transmission System (NTS) before reaching its area distribution network, and subsequently its final destination.

The UK’s NTS covers a distance of around 171,000 miles/ 275,000km (enough distances to go around the world almost 7 times). Within this network there are 25 compressors and 25 pressure regulators. These ensure that the gas travelling at long distance is efficiently compressed and non-harmful to the piping system. At transmission level, natural gas travels at high pressure; to be exact, anything between 200psi (pounds per square inch) to 1,500psi. This needs to be made the case at intervals of 40-100 miles; however, once this has been performed, the temperature rises quite considerably from around 5ºC to 48ºC. To counteract this, the gas then usually travels through a cooling system that prevents damage to the piping system. It will usually then travel through the transmission system at speeds of up to 25mph.

As shown in the map below, the National Transmission System in England, Scotland and Wales is entirely owned and operated by National Grid:

  • Click here to visit our page for the sole UK Gas Transmission company:
  • National Grid

Distribution

Gas distribution is done throughout smaller networks of area pipelines. This is conducted by the 8 distribution networks nationwide.

The 8 Gas Distribution Networks (GDN) each serve a different area of Britain. They are all owned by one of the four gas transportation companies. These are: National Grid; Northern Gas Networks; Wales & West Utilities; and SGN. Because these are regional monopolies, they are regulated to limit profit margins. Unlike through the transmission network, when gas travels through the distribution network it has to pass through a number of pressure reduction tiers in order to slow and disband the gas, making it more suitable for domestic delivery.

Below is a map of the area gas distribution network, displaying the borders of control for each of the four companies: