Principal operations
Transmission UK
Our transmission operations in the UK encompass both electricity and gas transmission, comprising the following principal activities:
Electricity transmission owner
We own the electricity transmission system in England and Wales. Our electricity assets comprise approximately 7,200 kilometres of overhead line, about 690 kilometres of underground cable and 337 substations at 241 sites.
Gas transmission owner
We own the gas national transmission system in Great Britain. This comprises approximately 7,600 kilometres of high pressure pipe and 26 compressor stations, connecting to 8 distribution networks and to third party independent systems for onward transportation of gas to end consumers.
Electricity system operator
We are the Great Britain System Operator, responsible for managing the operations of both the England and Wales transmission system that we own and also the two high voltage electricity transmission networks in Scotland.
Day-to-day operation of the Great Britain electricity transmission system involves the continuous real-time matching of demand and generation output, ensuring the stability and security of the power system and the maintenance of satisfactory voltage and frequency. We are also designated as system operator for the new offshore electricity transmission regime.
Gas system operator
We operate the gas national transmission system. Day-to-day operation includes balancing supply and demand, maintaining satisfactory system pressures and ensuring gas quality standards are met.
French interconnector
We own and operate the UK assets, and a portion of the subsea cables, that comprise the electricity interconnector between England and France as part of a joint arrangement with the French transmission operator.
LNG storage
We own and operate four liquefied natural gas (LNG) storage facilities in Great Britain. With the scheduled closure of Dynevor Arms during 2009 the number of facilities will decrease to three.
As electricity transmission owner and gas transmission owner, we own and maintain the physical assets, develop the networks to accommodate new connections and disconnections, and manage a programme of asset replacement and investment to ensure the long-term reliability of the respective networks.
As electricity transmission system operator and gas transmission system operator, we undertake a range of activities necessary for the successful, efficient delivery, in real-time, of secure and reliable energy. In the case of electricity, this involves the continuous real-time balancing of supply and demand, and management of balancing services that include commercial arrangements with market participants that enable electricity demand or generation output to be varied. In the case of gas, we ensure the system supply and demand is balanced at the end of each day. We are also required to maintain levels of short-term gas reserves to ensure domestic and other non-interruptible gas supplies can be maintained during prolonged cold conditions.
Transmission UK - electricity system
Commissioned 434 circuit kilometres of overhead line, 18 super grid transformers and 41 circuit breakers.
Diverted two existing overhead line circuits into a newly constructed cable tunnel on the site of the 2012 Olympic Park.
Developed a strategic plan for infrastructure investment to support the UK Government to meet its climate change targets.
Implemented a mobile flood defence system to protect substations from flooding.
Transmission UK - gas system
Completed Trans-Pennine high pressure gas pipeline connecting the two main north-south pipelines to provide greater operational flexibility.
Commissioned two new pipelines in southern England to connect new gas fired power stations.
New electric drive compressor station completed at Wormington, allowing greater flexibility of flows.
We are exploring carbon capture and storage – a technology that transports CO2 emissions from power stations to depleted gas fields under the North Sea.
Transmission US - electricity networks
Significant expenditure on asset replacement to increase system reliability.
Capital investment delivered in New York in line with KeySpan merger commitment.
New England East-West Solution (NEEWS) project is under way to enhance the transmission system in three states.
Five year contract signed with the New Energy Alliance to support investment programme in New England.
Transmission US
In the US, we are involved in electricity transmission and our principal activities are as follows:
Electricity transmission owner
We own and operate an electricity transmission network of approximately 13,800 kilometres spanning upstate New York, Massachusetts, Rhode Island, New Hampshire and Vermont. Our US electricity transmission facilities operate at voltages ranging from 69 kV to 345 kV, utilising nearly 13,700 kilometres of overhead line, nearly 140 kilometres of underground cable and 524 substations.
We are the largest electricity transmission service provider in New England and New York by reference to the length of these high voltage transmission lines.
Canadian interconnector
We own and operate a 224 kilometre direct current transmission line rated at 450 kV that is a key section of an interconnector between New England and Canada.
As one of several transmission owners, we work with two distinct independent system operators in New England and New York. These non profit system operator entities for New England and New York are responsible for operating organised wholesale markets for energy, for operating reserves and capacity, for maintaining the operating reliability of the New England and New York networks, for coordinating the activities of the transmission owners, and for managing transparent transmission expansion planning processes.
The transmission owners are responsible for certain aspects of the operation of the facilities they each own, such as maintenance, equipment restoration and switching operations.
National Grid also works closely with the independent system operators in New England and New York to support efficient market and network operations and transmission investment.