National Grid (Great Britain)

In the electricity sector in the United Kingdom the National Grid is the high-voltage electric power transmission network serving Great Britain, connecting power stations and major substations and ensuring that electricity generated anywhere on it can be used to satisfy demand elsewhere. The network covers the great majority of Great Britain and several of the surrounding islands. It does not cover Ireland; Northern Ireland is part of a single electricity market with the Republic of Ireland.

The GB grid is connected as a wide area synchronous grid nominally running at 50 hertz. There are also undersea interconnections to other grids in northern France (HVDC Cross-Channel), Northern Ireland (HVDC Moyle), the Isle of Man (the AC Isle of Man to England Interconnector), the Netherlands (DC BritNed) and the Republic of Ireland (the DC 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 National Grid Company plc, later to become National Grid Transco, and now National Grid plc. In Scotland the grid was already split into two separate entities, one for southern and central Scotland and the other for northern Scotland, connected by interconnectors. The first is owned and maintained by SP Energy Networks, a subsidiary of Scottish Power, and the other by SSE. However, National Grid plc continues to be the transmission system operator for the whole GB grid.[1]

Benkid77 Puddington-Shotwick footpath 27 110809
400 kV power line in Cheshire


Electricity Pylon - Chatsworth Crescent - - 488767
Electricity pylons in an urban area in Pudsey, West Yorkshire.

At the end of the 19th century, Nikola Tesla established the principles of three-phase high-voltage electric power distribution while he was working for Westinghouse in the United States. The first to use this system in the United Kingdom was Charles Merz, of the Merz & McLellan consulting partnership, at his Neptune Bank Power Station near Newcastle upon Tyne. This opened in 1901,[2] and by 1912 had developed into the largest integrated power system in Europe.[3] The rest of the country, however, continued to use a patchwork of small supply networks.

In 1925, the British government asked Lord Weir, a Glaswegian industrialist, to solve the problem of Britain's inefficient and fragmented electricity supply industry. Weir consulted Merz, and the result was the Electricity (Supply) Act 1926, which recommended that a "national gridiron" supply system be created.[4] The 1926 Act created the Central Electricity Board, which set up the UK's first synchronised, nationwide AC grid, running at 132 kV, 50 Hz.

The grid was created with 4,000 miles of cables – mostly overhead cables – linking the 122 most efficient power stations. The first "grid tower" was erected near Edinburgh on 14 July 1928,[5] and work was completed in September 1933, ahead of schedule and on budget.[6][7] It began operating in 1933 as a series of regional grids with auxiliary interconnections for emergency use. Following the unauthorised but successful short term parallelling of all regional grids by the night-time engineers on 29 October 1937,[8] by 1938 the grid was operating as a national system. The growth by then in the number of electricity users was the fastest in the world, rising from three quarters of a million in 1920 to nine million in 1938.[9] It proved its worth during the Blitz when South Wales provided power to replace lost output from Battersea and Fulham power stations.[9] The grid was nationalised by the Electricity Act 1947, which also created the British Electricity Authority. In 1949, the British Electricity Authority decided to upgrade the grid by adding 275 kV links.

At its inception in 1950, the 275 kV Transmission System was designed to form part of a national supply system with an anticipated total demand of 30,000 MW by 1970. The predicted demand was already exceeded by 1960. The rapid load growth led the Central Electricity Generating Board to carry out a study in 1960 of future transmission needs. The report was completed in September 1960, and its study is described in a paper presented to the Institution of Electrical Engineers by Messrs E.S. Booth, D. Clark, J.L. Egginton and J.S. Forrest in 1962.

Considered in the study, together with the increased demand, was the effect on the transmission system of the rapid advances in generator design resulting in projected power stations of 2,000–3,000 MW installed capacity. These new stations were mostly to be sited where advantage could be taken of a surplus of cheap low-grade fuel and adequate supplies of cooling water, but these situations did not coincide with the load centres. West Burton with 4 x 500 MW machines, sited at the Nottinghamshire coalfield near the River Trent, is a typical example. These developments shifted the emphasis on the transmission system, from interconnection to the primary function of bulk power transfers from the generation areas to the load centres, such as the anticipated transfer in 1970 of some 6,000 MW from The Midlands to the home counties.

Continued reinforcement and extension of the existing 275 kV systems was examined as a possible solution. However, in addition to the technical problem of very high fault levels, many more lines would have been required to obtain the estimated transfers at 275 kV. As this was not consistent with the Central Electricity Generating Board's policy of preservation of amenities a further solution was sought. Consideration was given to both a 400 kV and 500 kV scheme as the alternatives, either of which gave a sufficient margin for future expansion. The decision in favour of a 400 kV system was made for two main reasons. Firstly the majority of the 275 kV lines could be uprated to 400 kV, and secondly it was envisaged that the operation at 400 kV could commence in 1965 compared with 1968 for a 500 kV scheme. Design work was started and in order to meet the programme for 1965 it was necessary for the contract engineering for the first projects to run concurrently with the design. One of these projects was the West Burton 400 kV Indoor Substation, the first section of which was commissioned in June 1965. From 1965, the grid was partly upgraded to 400 kV, beginning with a 150-mile (241 km) line from Sundon to West Burton, to become the super grid.

In the most recent issue of the code that governs the British Grid, the Grid Code,[10] the Supergrid is defined as referring to those parts of the British electricity transmission system that are connected at voltages in excess of 200 kV. British power system planners and operational staff therefore invariably speak of the Supergrid in this context although in practice the definition used captures all of the infrastructure owned by the National Grid company in England and Wales, and (in England and Wales) no other equipment.

In 2013 the construction of the 2.2 GW undersea Western HVDC Link from Scotland to North Wales started, which was completed in 2018.[11] This is the first major non-alternating current grid link within GB, though interconnectors to foreign grids already use HVDC.

Grid description

UK electricity production by source
UK electricity production by source 1980–2018[12][13][14][15]
UK Historical Net Electricity supplied
Electricity supplied (net) 1948 to 2008[16]
External image
Current grid status

The contiguous synchronous grid covers England (including the Isle of Wight), Scotland (including some of the Scottish islands such as Orkney, Skye[17] and the Western Isles which have limited connectivity[18]), Wales, and the Isle of Man.

Network size

The following figures are taken from the 2005 Seven Year Statement (SYS)[19]

  • 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)[20]
  • 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. 3.6×1011/(8,760 × 57×106).


Figures are again from the 2005 SYS.

  • 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%.[21] 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%.[22]

Generated power entering the grid is metered at the high-voltage side of the generator transformer.[23][24] Any power losses in the generator transformer are therefore accounted to the generating company, not to the grid system. The power loss in the generator transformer does not contribute to the grid losses.

Power flow

In 2009–10 there was 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.[25] Completion of the Western HVDC Link in 2018 added capacity for a flow of 2.2 GW between Western Scotland and North Wales.[26]

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.[27]


The UK grid is connected to adjacent European electrical grids by submarine power cables at an electricity interconnection level (transmission capacity relative to production capacity) which was 6% as of 2014.[28] The connections include direct-current cables to northern France (2 GW HVDC Cross-Channel), the Netherlands (1 GW BritNed), Northern Ireland (500 MW HVDC Moyle), Republic of Ireland (500 MW East–West Interconnector) and Belgium (1 GW Nemo link). There is also the 40 MW AC cable to the Isle of Man (Isle of Man to England Interconnector). There are plans to lay cables to link the UK with Norway (1.4 GW NSN Link), Denmark via the 1.4 GW Viking Link, a second link with France,[29] and Iceland in the future.[30]

Reserve services and frequency response

National Grid is responsible for contracting short term generating provision to cover demand prediction errors and sudden failures at power stations. This covers a few hours of operation giving time for market contracts to be established to cover longer term balancing.

Frequency-response reserves act to keep the system's AC frequency within ±1% of 50 Hz, except in exceptional circumstances. These are used on a second by second basis to either lower the demand or to provide extra generation.[31]

Reserve services are a group of services each acting within different response times:[31]

  • Fast Reserve: rapid delivery (within two minutes) of increased generation or reduced demand, sustainable for a minimum of 15 minutes.
  • Fast Start: generation units that start from a standstill and deliver power within five minutes automatically, or within seven minutes of a manual instruction, with generation maintained for a minimum of four hours.
  • Demand Management: reduction in demand of at least 25 MW from large power users, for at least an hour.
  • Short Term Operating Reserve (STOR): generation of at least 3 MW, from a single or aggregation of sites, within four hours of instruction and maintained for at least two hours.
  • BM Start-Up: mainstream major generation units maintained in either an energy readiness or hot standby state.

These reserves are sized according to three factors:[32]

  • The largest credible single generation failure event, which is currently either Sizewell B nuclear power station (1,260 MW) or one cable of the HVDC Cross-Channel interconnector (1,000 MW)
  • The general anticipated availability of all generation plants
  • Anticipated demand prediction errors

Control of the grid

The English and Welsh parts of the National Grid are controlled from the National Grid Control Centre which is located in St Catherine's Lodge, Sindlesham, Wokingham in Berkshire.[33][34][35][36] It is sometimes described as being a 'secret' location.[37] As of 2015 the system is under consistent hacker attack.[38]

Transmission costs

The costs of operating the National Grid System are recouped by National Grid Electricity System Operator (NGESO) through levying of Transmission Network Use of System (TNUoS) charges on the users of the system.[39] The costs are split between the generators and the users of electricity.[40]

Tariffs are set annually by NGET, and are zonal in nature—that is, the country is divided into zones, each with a different tariff for generation and consumption. In general, tariffs are higher for generators in the north and consumers in the south. This is representative of the fact that there is currently a north-south flow of electricity, and the additional stresses on the system increasing demand in areas of currently high demand causes.

Triad demand

Triad demand is measured as the average demand on the system over three half-hours between November and February (inclusive) in a financial year. These three half-hours comprise the half-hour of system demand peak and the two other half-hours of highest system demand which are separated from system demand peak and each other by at least ten days. These half-hours of peak demand are referred to as Triads.

Triad dates in recent years were:

Year Triad 1 Triad 2 Triad 3
2015/16 [41] Wednesday 25 November 2015, 17:00 – 17:30 Tuesday 19 January 2016, 17:00–17:30 Monday 15 February 2016, 18:00–18:30
2016/17 [42] Monday 5 December 2016, 17:00 – 17:30 Thursday 5 January 2017, 17:00 – 17:30 Monday 23 January 2017, 17:00 – 17:30
2017/18 [43] Monday 11 December 2017, 17:30 – 18:00 Monday 26 February 2018, 18:30–19:00 Monday 5 February 2018, 18:00–18:30

In April of each year, each licensed electricity supplier (such as Centrica, BGB, etc.) is charged a yearly fee for the load it imposed on the grid during those three half-hours of the previous winter. Exact charges vary depending on the distance from the centre of the network, but in the South West it is £21,000/MW. The average for the whole country is about £15,000/MW. This is a means for National Grid to recover its charges, and to impose an incentive on users to minimise consumption at peak, thereby easing the need for investment in the system. It is estimated that these charges reduced peak load by about 1 GW out of say 57 GW.

This is the main source of income which National Grid uses to cover its costs. (This is for high-voltage long-distance transmission: lower voltage distribution is charged separately.) The grid also charges an annual fee to cover the cost of generators, distribution networks and large industrial users connecting.

Triad charges encourage users to cut load at peak periods; this is often achieved by using diesel generators. Such generators are also routinely used by National Grid.[44]

Estimating costs per kW⋅h of transmission

If the total TNUoS or Triad receipts (say £15,000/MW·year × 50,000 MW = £750 million/year) is divided by the total number of units delivered by the UK generating system in a year (the total number of units sold – say 360 terawatt-hours (1.3 EJ).[40]), then a crude estimate can be made of transmission costs, and one gets the figure of around 0.2p/kW⋅h. Other estimates also give a figure of 0.2p/kW⋅h.[40]

However, Bernard Quigg notes: "According to the 06/07 annual accounts for NGC UK transmission, NGC carried 350TW⋅h for an income of £2012m in 2007, i. e. NGC receives 0.66p per kW hour. With two years inflation to 2008/9, say 0.71p per kW⋅h.",[45] but this also includes generators' connection fees.

Generation charges

In order to be allowed to supply electricity to the transmission system, generators must be licensed (by BEIS) and enter into a connection agreement with NGET which also grants Transmission Entry Capacity (TEC). Generators contribute to the costs of running the system by paying for TEC, at the generation TNUoS tariffs set by NGET. This is charged on a maximum-capacity basis. In other words, a generator with 100 MW of TEC who only generated at a maximum rate of 75 MW during the year would still be charged for the full 100 MW of TEC.

In some cases, there are negative TNUoS tariffs. These generators are paid a sum based on their peak net supply over three proving runs over the course of the year. This represents the reduction in costs caused by having a generator so close to the centre of demand of the country.

Demand charges

Consumers of electricity are split into two categories: half-hourly metered (HH) and non-half-hourly metered (NHH). Customers whose peak demand is sufficiently high are obliged to have a HH meter, which, in effect, takes a meter reading every 30 minutes. The rates at which charges are levied on these customers' electricity suppliers therefore varies 17,520 times a (non-leap) year.

The TNUoS charges for a HH metered customer are based on their demand during three half-hour periods of greatest demand between November and February, known as the Triad. Due to the nature of electricity demand in the UK, the three Triad periods always fall in the early evening, and must be separated by at least ten clear working days. The TNUoS charges for a HH customer are simply their average demand during the triad periods multiplied by the tariff for their zone. Therefore, (as of 2007) a customer in London with a 1 MW average demand during the three triad periods would pay £19,430 in TNUoS charges.

TNUoS charges levied on NHH metered customers are much simpler. A supplier is charged for the sum of their total consumption between 16:00 and 19:00 every day over a year, multiplied by the relevant tariff.

Major incidents

Power cuts due to either problems on the infrastructure of the supergrid (defined in the Grid Code as the transmission system operated by National Grid, which in England and Wales comprises lines energized at 275,000 volts and 400,000 volts), or due to lack of generation to supply it with sufficient energy at each point in time, are exceedingly rare. The nominal standard of security of supply is for power cuts due to lack of generation to occur in nine winters in a hundred.

The overall performance measure for electricity transmission is published on NGET's website[46] and includes a simple high-level figure on transmission availability and reliability of supply. For 2008–9 this was 99.99979%. Issues affecting the low voltage distribution systems – for which National Grid is not responsible – cause almost all the 60 minutes or so per year, on average, of domestic power cuts. Most of these low voltage distribution interruptions are in turn the fault of third parties such as workmen drilling through the street mains (or subterranean higher voltage) cables; this does not happen to major transmission lines, which are for the most part overhead on pylons. For comparison with supergrid availability, Ofgem, the electricity regulator, has published figures on the performance of 14 electricity distributors.[47][48]

Since 1990, there have been three power cuts of high national prominence that were linked to National Grid, two due to generation issues.

August 2003 incident

The first case was in 2003, and related to the condition of National Grid's assets. National Grid was implicated in a power cut affecting 10 per cent of London in August – see 2003 London blackout. Some news reports accused Grid of under-investment in new assets at the time; it transpired that a transformer oil leak had been left untreated, except for top-ups, for many months, pending a proper fix. It also transpired that there was a significant error in a protection relay setting which became evident, resulting in a power cut, only when the first fault, the oil leak, had a real effect. National Grid took some time to admit to these aspects of the incident.

May 2008 incident

The second case was in May 2008, and related to generation issues for which National Grid was not responsible. A power cut took place in which a protective shutdown of parts of the network was undertaken by the distribution network operators, under pre-arranged rules, due to a sudden loss of generating capacity causing a severe drop in system frequency. First, two of Britain's largest power stations, Longannet in Fife and Sizewell B in Suffolk, shut down unexpectedly ('tripped') within five minutes of one another. There was no relationship between the two trips: the first did not cause the second. Such a loss is most unusual; at that time, Grid secured only against the loss of 1320 MW – the "infrequent infeed loss limit" (which rose to 1800 MW from 2014). The two shutdowns caused a sudden 1,510 MW adverse change in the balance of generation and demand on the supergrid, and the frequency dropped to 49.2 Hz. Whilst the frequency was dropping to 49.2 Hz, or just after it reached that point, 40 MW of wind farms and more than 92 MW of other embedded generation (meaning, connected to the distribution system, rather than directly connected to the supergrid), such as landfill plant, tripped on the basis of the rate of change of frequency ('ROCOF') being high, just as it is supposed to do under the G 59/2 connection rules.

The frequency stabilised at 49.2 Hz for a short while. This would have been an acceptable frequency excursion, even though it was below the usual lower limit of 49.5 Hz, and recovery would not have been problematic. The fact that frequency stabilised at this level in spite of a beyond-design-basis event, could be viewed as reassuring. Ireland, which being a smaller system has a more temperamental (and therefore less stable) grid, sees about 10 frequency excursions below 49.5 Hz per year – Its target frequency being 50 Hz, just as in Britain. Consumers would not have noticed the small drop in system frequency; other aspects of their supply, such as voltage, remained perfect. There would, therefore, have been no consumer detriment; all would have been well at this point, had nothing further untoward occurred.

However, further issues affecting smaller generators arose because the frequency remained below 49.5 Hz for more than a few seconds, and because some generators' control settings were wrong. The connection standard G 59/2 for embedded generation states that they must not trip (cease generating) as a result of sustained low frequency, until frequency has fallen below 47 Hz. However, a number of embedded generators used out-of-date control software that is not compliant with G59/2, as it erroneously trips them (as per the previous standard, G/59, in force when they were designed and specified) if frequency falls below 49.5 Hz for a few seconds. For this reason, another 279 MW of embedded generation tripped as a result of the low frequency whilst it was at 49.2 Hz. This was a problem as the Grid had no remaining available fast-acting generation, or demand-response, reserve margins. The frequency fell as a result to 48.792 Hz.

Grid rules state that as frequency falls below 48.8 Hz, distribution network operators must apply compulsory demand control. This should start, if time permits, with voltage reduction, rapidly followed by the compulsory disconnection of, in stages, up to a final total of 60 per cent of all distribution-connected customers (a very small number of very large customers are connected directly to the supergrid; for them, other measures apply). There was no time to use voltage reduction (which keeps customers on supply, but subtly reduces their demand through reducing the voltage slightly); as a result, 546 MW of demand was automatically disconnected by distribution network operators. None of the directly supergrid-connected customers were cut off. National Grid had by now taken other measures to increase output at other generation sites (and demand had been reduced at those customer sites where the customer has volunteered for this to happen, in return for reimbursement, under demand-side response contracts with National Grid, or with their supplier). National Grid was then able to restore system frequency. The average duration of loss of supply to the 546 MW of mostly low-voltage-connected (e.g. domestic) demand affected was 20 minutes.

National Grid had time to issue a warning to all users of the supergrid – "demand control imminent" – which is one step away from its most serious warning "demand disconnection warning". During these incidents, the system was at risk to further generation loss which could have resulted in parts of the network being automatically disconnected by the operation of low frequency protection to ensure frequency is maintained within mandatory limits.[49][50][51]

August 2019

The third event occurred on 9 August 2019, when around a million customers across Great Britain found themselves without power.[52] Lightning struck a transmission line at 4:52 pm, causing the loss of 500 MW embedded generation. Almost immediately, Little Barford Power Station and Hornsea Wind Farm tripped within seconds of each other, removing 1.378 GW of generation which was in excess of the 1 GW of backup power the operator maintains.[53] The grid frequency fell to 48.914 Hz before load shedding kicked in to disconnect 5% of the local distribution networks (1.1 million customers for 15-20 minutes); this automatic action stabilised the remaining 95% of the system and prevented a larger blackout.[54] The outage caused stoppages of trains which led to substantial travel disruption for several hours, triggered the blackout of Ipswich hospital, and Newcastle Airport.[53]

Minor incidents

November 2015

On 4 November 2015 National Grid issued an emergency notice asking for voluntary power cuts because of "multiple plant breakdowns". No power cuts occurred but wholesale electricity prices rose dramatically, with the grid paying up to £2,500 per megawatt-hour.[55]

See also


  1. ^ "The GB electricity transmission network". Ofgem. Retrieved 25 June 2018.
  2. ^ Alan Shaw (29 September 2005). "Kelvin to Weir, and on to GB SYS 2005" (PDF). Royal Society of Edinburgh.
  3. ^ "Survey of Belford 1995". North Northumberland Online.
  4. ^ "Lighting by electricity". The National Trust. Archived from the original on 29 June 2011.
  5. ^ Electricity supply in the United Kingdom : a chronology – from the beginnings of the industry to 31 December 1985. Electricity Council. The Council. 1987. ISBN 085188105X. OCLC 17343802.CS1 maint: others (link)
  6. ^ The Secret Life of the National Grid: Wiring the Nation
  7. ^ "Power struggle: The National Grid was created to provide energy for all – but that's when the problems really began | Features | Culture". The Independent. Retrieved 21 August 2016.
  8. ^ Cochrane, Rob (1985). Power to the People. ISBN 0600358755.
  9. ^ a b Gerard Gilbert (22 October 2010). "Power struggle: The National Grid was created to provide energy for all – but that's when the problems really began". The Independent. Retrieved 17 October 2012.
  10. ^ "the British Grid Code" (PDF). Archived from the original (PDF) on 22 March 2011. Retrieved 3 February 2011.
  11. ^ "News | Western Link | National Grid & Scottish Power". Retrieved 18 June 2019.
  12. ^ "International Energy Statistics – EIA". Retrieved 21 August 2016.
  13. ^ "Archived copy" (PDF). Archived from the original (PDF) on 3 July 2016. Retrieved 2016-08-14.CS1 maint: Archived copy as title (link)
  14. ^ "Archived copy" (PDF). Archived from the original (PDF) on 8 October 2016. Retrieved 2016-08-14.CS1 maint: Archived copy as title (link)
  15. ^
  16. ^ "Digest of UK energy statistics: 60th Anniversary Report". Retrieved 16 December 2013.
  17. ^
  18. ^
  19. ^ [1]
  20. ^ [2]
  21. ^ "Archived copy". Archived from the original on 5 August 2016. Retrieved 2006-09-19.CS1 maint: Archived copy as title (link)
  22. ^ Time to Take a Fresh Look at CHP..., Simon Minett, director, DELTA Energy and Environment, October 2005
  23. ^ Metering Code of Practice 1 (Elexon Ltd)
  24. ^ Metering Code of Practice 2
  25. ^ Effect on Power Transfers Archived 28 July 2012 at the Wayback Machine, 2009 Seven Year Statement, National Grid
  26. ^ "Western Link project". Retrieved 10 February 2019.
  27. ^ PLC, National Grid Company. "2002 Seven Year Statement". National Grid – UK – Library. National Grid. Archived from the original on 19 December 2005. Retrieved 8 November 2013.
  28. ^ COM/2015/082 final: "Achieving the 10% electricity interconnection target" Text PDF page 2-5. European Commission, 25 February 2015. Archive Mirror
  29. ^ "France". National Grid. Archived from the original on 20 August 2016. Retrieved 21 August 2016.
  30. ^ "Interconnectors: Iceland". National Grid. 12 July 2016. Archived from the original on 21 July 2016. Retrieved 21 August 2016.
  31. ^ a b "Appendix D Description of Balancing Services", Operating the Electricity Transmission Networks in 2020 – Initial Consultation (PDF), National Grid, June 2009, archived from the original (PDF) on 23 December 2011, retrieved 8 January 2011
  32. ^ Gross, R; Heptonstall, P; Anderson, D; Green, T; Leach, M & Skea, J (March 2006). "The Costs and Impacts of Intermittency". UK Energy Research Centre. ISBN 1-903144-04-3. Archived from the original on 21 June 2008. Retrieved 15 July 2008.
  33. ^ "Agenda 22 May 2007". Archived from the original (PDF) on 14 July 2011. Retrieved 3 November 2010.
  34. ^ "NETA Despatch Instruction Guide". Archived from the original (PDF) on 14 July 2011. Retrieved 3 November 2010.
  35. ^ "Wind Turbine Price List Uk". Archived from the original on 3 November 2010. Retrieved 3 November 2010.
  36. ^ "National Grid Control Centre Visit | Royal Meteorological Society". 24 September 2012. Retrieved 21 August 2016.
  37. ^ "Power struggle: The National Grid was created to provide energy for all – but that's when the problems really began | Features | Culture". The Independent. Retrieved 21 August 2016.
  38. ^ Ward, Jillian. "U.K. Power Grid is Under Attack From Hackers Every Minute, Says Parliament" Bloomberg, 9 January 2015. Retrieved: 20 January 2015.
  39. ^ "Transmission Network Use of System (TNUoS) charges". National Grid ESO. Retrieved 20 September 2018.
  40. ^ a b c Andrews, Dave. "What is the cost per kWh of bulk transmission / National Grid in the UK (note this excludes distribution costs) | Claverton Group". Retrieved 21 August 2016.
  41. ^ Inenco, 2015/16 Triads, published 31 March 2016
  42. ^ Trident Utilities, 2016/17 Triad Periods Confirmed, published 29 March 2017, accessed 3 April 2018
  43. ^ Stark, History repeats itself: trends are hard to change, published 26 March 2018, accessed 3 April 2018
  44. ^ Andrews, Dave. "Commercial Opportunities for Back-Up Generation and Load Reduction via National Grid, the National Electricity Transmission System Operator (NETSO) for England, Scotland, Wales and Offshore. | Claverton Group". Retrieved 21 August 2016.
  45. ^ "Grid Operations | Claverton Group". Retrieved 21 August 2016.
  46. ^ "Transmission Performance Report". National Grid. Archived from the original on 11 January 2011. Retrieved 21 August 2016.
  47. ^
  48. ^ "Information for Consumers". Archived from the original on 19 July 2012. Retrieved 21 August 2016.
  49. ^ Murad Ahmed, Steve Hawkes (28 May 2008). "Blackouts hit thousands as generators fail". The Times.CS1 maint: Uses authors parameter (link)
  50. ^ Mark Milner, Graeme Wearden (28 May 2008). "Q&A: Blackout Britain". The Guardian.CS1 maint: Uses authors parameter (link)
  51. ^ George South (28 May 2008). "iPM: Blackout Britain?". BBC. Retrieved 21 August 2016.
  52. ^ "Major power failure affects homes and transport". BBC. 9 August 2019. Retrieved 9 August 2019.
  53. ^ a b Interim Report into the Low Frequency Demand Disconnection (LFDD) following Generator Trips and Frequency Excursion on 9 Aug 2019 - 16th August 2019
  54. ^
  55. ^ Stacey, Kiran; Adams, Christopher (5 November 2015). "National Grid in emergency plea for heavy users to power down". Financial Times. pp. front page.

Further reading

  • Hannah, Leslie (1979). Electricity Before Nationalisation, A Study in the Development of the Electricity Supply Industry in Britain to 1948. London & Basingstoke: Macmillan Publishers for the Electricity Council. ISBN 0-8018-2145-2.

External links

2003 London blackout

The 2003 London blackout was a serious power outage that occurred in parts of southern London and north-west Kent on 28 August 2003. It was the largest blackout in South East England since the Great Storm of 1987, affecting an estimated 500,000 people.

Power went off at about 18:26 British Summer Time. Power returned after 34 minutes at 19:00 BST, but is reported to have taken about two hours to be restored fully in some areas.

Aust Severn Powerline Crossing

Aust Severn Powerline Crossing is the longest powerline span in the United Kingdom with a span width of 1,618 m (5,308 ft).

Blackhillock Substation

Blackhillock Substation is an electrical substation located in the north east of Scotland, near the town of Keith in Moray.

It is owned and operated by Scottish Southern Electricity Network (SSEN). Covering an area the size of 24 football pitches, it is as of January 2019, the UK's largest substation and Europe's second biggest.Construction began in early 2015 to upgrade the existing substation so it could accommodate the new Caithness - Moray Subsea link. The £1bn construction project had four main elements: 400kV and 232kV gas-insulated substations, one 275kV air-insulated substation, a High Voltage Direct Current (HVDC) converter for the Caithness - Moray subsea link and a HVDC underground cable from the substation to Portgordon. In January 2019 construction and commissioning were completed making it the UK's largest operating substation. It is seen as integral to the UK electricity grid as the north of Scotland generates much renewable energy via windfarms. The upgrade was primarily done to accommodate the Beatrice Windfarm.


BritNed is a 1,000 MW high-voltage direct-current (HVDC) submarine power cable between the Isle of Grain in Kent, the United Kingdom; and Maasvlakte in Rotterdam, the Netherlands.

The BritNed interconnector would serve as a link for the foreseeable European super grid project.

Central Electricity Generating Board

The Central Electricity Generating Board (CEGB) was responsible for electricity generation in England and Wales for almost forty years, from 1957 to privatisation in the 1990s.Because of its origins in the immediate post-war period, when electricity demand grew rapidly but plant and fuel availability was often unreliable, most of the industry saw its mission as to provide an adequate and secure electricity supply, or "to keep the lights on" as they put it, rather than pursuing the cheapest generation route.

It was created in 1957 from the Central Electricity Authority, which had replaced the British Electricity Authority. The Electricity Council was also created at that time, as a policy-making body for the electricity supply industry.

Electricity Council

The Electricity Council was a governmental body set up in 1957 to oversee the electricity supply industry in England and Wales. The Council's responsibilities included:

advising the Secretary of State for Energy on matters relating to the electricity supply industry in England and Wales

helping the Electricity Boards in England and Wales to improve efficiency

advising on the financing of the industry in England and Wales

organising certain research

maintaining the industry-wide industrial relations machineryThe Council was formally wound up by The Electricity Council (Dissolution) Order 2001, made under the Electricity Act 1989, to be replaced by the Electricity Association.

Fawley Tunnel

Fawley Tunnel is a 3-metre (9.8 ft) diameter, 2-mile (3.2 km) long tunnel under Southampton Water between Fawley Power Station and Chilling near Warsash. It was constructed between 1962 and 1965 to carry two 400 kV circuits as part of the National Grid.The tunnel was built with a 3 feet 1.125 inch gage railway to help with maintenance access. The railway was operated with a single battery powered locomotive that was scrapped in the late 70s.

Grid code

A grid code is a technical specification which defines the parameters a facility connected to a public electric grid has to meet to ensure safe, secure and economic proper functioning of the electric system. The facility can be an electricity generating plant, a consumer, or another network.

The grid code is specified by an authority responsible for the system integrity and network operation.

Its elaboration usually implicates network operators (distribution or transmission system operators), representatives of users and, to an extent varying between countries, the regulating body.Contents of a grid code vary depending on the transmission company's requirements. Typically, a grid code will specify the required behavior of a connected generator during system disturbances. These include voltage regulation, power factor limits and reactive power supply, response to a system fault (e.g. short-circuit), response to frequency changes on the grid, and requirement to "ride through" short interruptions of the connection.

There is not a common grid code in all countries and each electric grid has its own grid code. Even in North America, There is no grid code that applies to all territories.

HVDC Cross-Channel

The HVDC Cross-Channel (French: Interconnexion France Angleterre) is the name given to two different high voltage direct current (HVDC) interconnectors that operate or have operated under the English Channel between the continental European and British electricity grids.

The first Cross-Channel link was a 160 MW link completed in 1961 and decommissioned in 1984, while the second was a 2000 MW link completed in 1986.

The current 2000 MW link, like the original link, is bi-directional and France and Britain can import/export depending upon market demands.

Huddersfield Narrow Canal Pylon

The Huddersfield Narrow Canal Pylon, (National Grid tower designation 4ZO251B), is an electricity pylon which stands with its feet over the Huddersfield Narrow Canal near Heyrod, Stalybridge, Greater Manchester, United Kingdom.

The Stalybridge substation was built while the canal was closed to navigation, encroaching on the former canal line, and the canal was culverted at this point from the head of Lock 8W to a point immediately downstream of the substation. The extent of the former culvert can still be seen, as it was reused to form the lock bywash.

When the canal reopened, the channel was diverted slightly to the east to avoid the substation compound. However, its way was obstructed by a pylon, and it had to pass between the pylon's legs.One side of the pylon carries the 400 kV Stalybridge–Thorpe Marsh circuit and the other a 275 kV Stalybridge transformer feeder circuit.

J. L. Eve Construction

J. L. Eve Construction was a civil engineering company from south London.

Load management

Load management, also known as demand side management (DSM), is the process of balancing the supply of electricity on the network with the electrical load by adjusting or controlling the load rather than the power station output. This can be achieved by direct intervention of the utility in real time, by the use of frequency sensitive relays triggering the circuit breakers (ripple control), by time clocks, or by using special tariffs to influence consumer behavior. Load management allows utilities to reduce demand for electricity during peak usage times (peak shaving), which can, in turn, reduce costs by eliminating the need for peaking power plants. In addition, some peaking power plants can take more than an hour to bring on-line which makes load management even more critical should a plant go off-line unexpectedly for example. Load management can also help reduce harmful emissions, since peaking plants or backup generators are often dirtier and less efficient than base load power plants. New load-management technologies are constantly under development — both by private industry and public entities.

National Grid Reserve Service

In order to balance the supply and demand of electricity on short timescales, the UK National Grid has contracts in place with generators and large energy users to provide temporary extra power, or reduction in demand. These reserve services are needed if a power station fails for example, or if forecast demand differs from actual demand. National Grid has several classes of reserve services, which in descending order of response time are: Balancing Mechanism (BM) Start-Up, Short-Term Operating Reserve, Demand Management and Fast Reserve.

National Grid plc

National Grid plc is a British multinational electricity and gas utility company headquartered in Warwick, United Kingdom. Its principal activities are in the United Kingdom and Northeastern United States. It has a primary listing on the London Stock Exchange, and is a constituent of the FTSE 100 Index. It has a secondary listing on the New York Stock Exchange.


RISSP stands for Record of Inter System Safety Precautions

. It is a written record of inter-system safety precautions to be compiled

in accordance with the provisions of Operating Code no. 8 (OC8). Where a High Voltage electrical boundary occurs, for instance between a power station and electrical utility, the safety controllers each side of the boundary must co-ordinate their activities. For the electrical transmission system in England, Wales and Scotland, the Ofgem-defined industry standard document OC8 of the Grid code defines how safety precautions can be managed with the Record of Inter System Safety Precautions (RISSP) independently from the safety rules of the connected parties. The purpose of the RISSP is to guarantee that safety precautions provided by a third-party can be quoted in a safety document so that work can take place.

Registered power zone

A registered power zone (RPZ) is an area of the National Grid (UK) network, geographical or electrical, specifically designated for the research, development and demonstration (R,D&D) of new technologies concerning the power network. Specifically to develop solutions to the problems associated with connecting generating capacity at the distribution network level.

TV pickup

TV pickup is a term used in the United Kingdom to refer to a phenomenon that affects electricity generation and transmission networks. It often occurs when a large number of people watch the same TV programmes while taking advantage of breaks in programming to use toilets and operate electrical appliances, thus causing large synchronised surges in national electricity consumption. Electricity networks devote considerable resources to predicting and providing electricity supply for these events, which in the UK, for example, typically impose an extra demand of around 200–400 megawatts (MW) on the Grid. Short-term supply is often obtained from pumped storage reservoirs, which can be quickly brought online, backed up by the slower fossil fuel and nuclear power stations. The largest ever pickup was on 4 July 1990, when a 2800 MW demand was imposed by the ending of the penalty shootout in the England v West Germany FIFA World Cup semi-final. In addition to pickups, the Grid also prepares for synchronised switch-offs during remembrance and energy-awareness events.

Telangana Power Generation Corporation

Telangana State Power Generation Corporation Limited is a power generating organization of Telangana. It has ceased to do power trading and has retained with powers of controlling system operations of power generation after formation of Telangana state.Telangana State Power Generation Corporation Limited has been incorporated under companies Act, 2013, on 19 May 2014 and commenced its operations from 2 June 2014.

Failure modes
and policies
Statistics and Production


This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.