The National Grid electricity power supply network




The National Grid is the high-voltage electric power transmission network in Great Britain, connecting power stations and major substations and ensuring that electricity generated anywhere in England, Scotland and Wales can be used to satisfy demand anywhere else in the country.

The UK grid is connected as a wide area synchronous grid nominally running at 50 hertz. There are also undersea interconnections to northern France (HVDC Cross-Channel), Northern Ireland (HVDC Moyle), the Isle of Man (Isle of Man to England Interconnector), the Netherlands (BritNed) and the Republic of Ireland (EirGrid).

On the breakup of the Central Electricity Generating Board in 1990, the ownership and operation of the National Grid in England and Wales passed to the National Grid Company plc, later to become National Grid Transco, and now National Grid plc.


In Scotland the grid split into two separate entities, one for southern and central Scotland and the other for northern Scotland, connected by interconnectors to each other. The first is owned and maintained by SP Energy Networks, a subsidiary of Scottish Power, and the other by SSE. However, National Grid plc remains the System Operator for the whole UK Grid.


Mains electricity comes in to our homes at a voltage of 230 Volts (V). However it is not generated at 230 volts because the current in amps (A) needed to push the energy through extremely large cables would be huge. Big currents need thick cables that get hot. In our power stations electricity is generated at 25,000 volts (at a current of 100,000 amps).


Outside power stations there are huge step-up transformers that take the voltage from 25,000 volts to 275,000 volts (Kv). The voltage can be as high as 415,000 volts in the super grid.


It was  Nikola Tesla who established the principles of three-phase high-voltage electric power distribution while he was working for Westinghouse in the United States in the early 19th Century.





The transformer is a vital part of the National Grid in terms of limiting energy losses.

Electrical energy that is generated in power stations at a potential of 25 kV, is first stepped up to 400 kV by a transformer and then transmitted across the country in aluminium cables roughly 2 cm in diameter.

High voltages are used because the power loss per kilometre (I2R) for a given power output will be much less at high voltage and low current than at low voltage and high current. Despite this, even after the current has been reduced many transmission lines carry up to 2500 amps.

In Britain the grid system can meet a simultaneous demand of 56 000 MW supplied through some 8000 km of high-voltage transmission line. Alternating Current (AC) is used in the National Grid because it may be transformed to high voltage. In the early days of E generation Direct Current (DC) was used because generating plants were normally more local. The exception is the underground Cross-Channel link between Britain and France that uses DC because of the large losses in the dielectric with AC.







Maximum demand (2005/6): 63 GW (approx.) (81.39% of capacity)
Annual electrical energy used in the UK is around 360 TWh (1.3 EJ)
Capacity (2005/6): 79.9 GW (or 80 GW per the 2008 Seven Year Statement)
Number of large power stations connected to it: 181
Length of 400 kV grid: 11,500 km (circuit)
Length of 275 kV grid: 9,800 km (circuit)
Length of 132 kV (or lower) grid; 5,250 km (circuit)

Total generating capacity is supplied roughly equally by renewable, nuclear, coal fired and gas fired power stations. Annual energy used in the UK is around 360 TWh (1.3 EJ), with an average load factor of 72% (i.e. 3.61011/(8,760 57106).





Joule heating in cables: 857.8 MW
Fixed losses: 266 MW (consists of corona and iron loss; can be 100 MW higher in adverse weather)
Substation transformer heating losses: 142.4 MW
Generator transformer heating losses: 157.3 MW
Total losses: 1,423.5 MW (2.29% of peak demand)

Although overall losses in the national grid are low, there are significant further losses in onward electricity distribution to the consumer, causing a total distribution loss of about 7.7%. However losses differ significantly for customers connected at different voltages; connected at high voltage the total losses are about 2.6%, at medium voltage 6.4% and at low voltage 12.2%.

There is an average power flow of about 11 GW from the north of the UK, particularly from Scotland and northern England, to the south of the UK across the grid. This flow was anticipated to grow to about 12 GW by 2014.

Because of the power loss associated with this north to south flow, the effectiveness and efficiency of new generation capacity is significantly affected by its location. For example, new generating capacity on the south coast has about 12% greater effectiveness due to reduced transmission system power losses compared to new generating capacity in north England, and about 20% greater effectiveness than northern Scotland.





Power = current (A) Voltage (V)   In Physics Code: P = IV




Local distribution: 33,000 V
Railways: 25,000 V
Heavy industry: 11,000 V
Light Industry: 415 V
Homes: 230 V











SMART SERVICE STATIONS - This concept EV forecourt offers between 7.68 - 15.36MWh of solar assisted energy storage with a capacity of between 48-96 battery cartridges on a continuous charge cycle. Five of these stations (76.8MW) could recharge (refuel) up to 10 trucks or cars a minute at peak times.


During rush hour, up to 300 vehicles might be serviced in one hour if drivers don't dawdle, as in get out of their vehicles for any reason - there is no need using automated billing - but this would require registered users. The truck shown in these AutoCAD drawings is 3.55 wide x 3.5 high x 7.7M long (8 x 11.5 x 25 feet). This station could accommodate trucks 4.46M (14.77 feet) high as shown, or with a raised roof, almost any truck currently on the market - though longer thinner trucks are more fuel efficient.


During an eight hour day 2,400 trucks might be serviced using five forecourts on the assumption that we start every morning with 96 x 5 = 480 slow charged cartridges from off-peak supplies. The same forecourt might be used to service fuel-cell cars powered by stabilized hydrogen. One size fits all. The secret is to KISS the design (Keep It Simple Silly). There are only 28* moving parts in this station, not including the gearbox for the solar powered drive motor. This is possible because with this system the vehicles load the cartridges themselves.






The Guardian on soaring oil prices