Transmission & Distribution

Both inventors devised systems for transmitting power without conductors in the late 1800s and early 1900s. Neither achieved commercial success, leaving wired transmission dominant.

Consolidation created corporations able to develop AC systems at scale in Europe and the United States. Bridging DC and AC legacy equipment required rotary converters and motor-generators until a universal system emerged.

The pair constructed an open-magnetic-circuit transformer they called the secondary generator. It made transmission of alternating current practical by allowing voltage to be changed, which direct-current systems could not easily do.

A 2 kV, 130 Hz Siemens and Halske alternator fed several Gaulard transformers with series-connected primaries supplying incandescent lamps over 34 kilometres. The demonstration proved the feasibility of transmitting alternating current power over long distances.

Two Siemens and Halske alternators at 2 kV, 120 Hz supplied 19 km of cable and 200 parallel-connected step-down transformers with closed magnetic circuits, one per lamp. It marked the transition of alternating current from exhibition demonstration to commercial distribution service.

Following the Rome installation by a few months, the London scheme used Siemens alternators and 2.4 kV to 100 V step-down transformers with shunt-connected primaries, one per user. It spread the AC distribution model beyond Italy.

Working to improve the Gaulard-Gibbs design he considered impractical, Stanley produced a transformer suited to real distribution service. It became the technical basis for the Westinghouse approach to alternating current supply.

A steam-driven 500 V Siemens generator was stepped down to 100 volts to light lamps at 23 businesses over 4,000 feet. The success led Westinghouse to begin installing AC systems later that year.

The first designs for an AC motor appeared, running on polyphase current, with Westinghouse licensing Tesla's design. Practical three-phase machines followed from Dolivo-Dobrovolsky and Brown, though uptake was delayed by the scarcity of polyphase supply systems.

Power was delivered 14 miles down river from the plant to the city of Portland, Oregon. It was the first use of high voltage for single-phase alternating current transmission.

Built for the international electricity exhibition in Frankfurt, the 15 kV line connected Lauffen on the Neckar to Frankfurt, a distance of 175 kilometres. It showed for the first time that three-phase alternating current could carry power over long distances with acceptable losses, settling a technical argument and establishing three-phase high-voltage transmission as the model for bulk power movement in every grid built afterwards.

Osaka imported German generating equipment running at 50 hertz while Tokyo bought American equipment running at 60 hertz, an early procurement choice that split Japan into two frequency zones and left the country needing costly converter stations to move power between them ever since.

Voltages rose steadily through the early 20th century as interconnection of multiple generating plants over wide areas cut costs. Shared standby capacity improved reliability and allowed exploitation of remote hydroelectric and mine-mouth coal resources.

World War I saw large electrical generating plants built by governments to power munitions factories. This drove the linking of local generation and small distribution networks into wider grids, making transmission critical infrastructure.

The Electricity (Supply) Act established a Central Electricity Board to build a national network of high-voltage lines linking the country's many separate local power stations, replacing a fragmented patchwork with an integrated system for moving power to where it was needed.

The law created low-cost federal loans for rural electric cooperatives to build distribution lines into farming areas that private utilities had judged unprofitable to serve, extending mains electricity to most of rural America within about two decades.

The Union for the Coordination of Production and Transmission of Electricity linked the transmission systems of several countries into one synchronised network operating at the same frequency, the forerunner of today's continent-wide European grid coordination.

The Swedish company built the world's first commercial high-voltage direct current transmission line, running under the sea to the island of Gotland, proving a technology that decades later became the standard for very long-distance and undersea power links.

A single misconfigured protective relay near Niagara Falls cascaded into a failure that darkened most of the north-eastern United States and Ontario within minutes, exposing how tightly interconnected grids could turn a local fault into a continental emergency.

The US Northeast faced blackouts in 1965, 1977 and 2003, with further large failures in other regions in 1996 and 2011. These events exposed the reliability risks inherent in wide-area synchronous interconnection.

One of the longest high-voltage direct current transmission lines built up to that time linked the Inga hydropower complex on the Congo River to copper mines in Shaba province, an early demonstration that HVDC could move bulk power across a whole continent's width.

Historically transmission and distribution lines were often owned by the same company. Regulatory liberalisation from the 1990s led to separate companies handling each function, restructuring the industry around network access.

State Grid Corporation continued a decades-long programme of building direct current lines operating at 800 kilovolts and above, moving hydropower, wind and solar generated in the west and north of the country to industrial demand centres on the coast.

A sudden, unexplained loss of generation and voltage oscillations brought down most of the interconnected Spanish and Portuguese grid within seconds, cutting power to tens of millions of people for most of a day and prompting investigations into the resilience of a grid running on very high shares of solar and wind.

The interconnected transmission grid went down entirely on several occasions, plunging much of the country into blackout at once, a recurring failure blamed on an ageing, thinly meshed network that leaves the system with little redundancy when a single line or plant trips.

Lines intended to connect new renewable energy zones to the grid, including links between New South Wales and Victoria, ran behind schedule and over budget amid landowner opposition and construction cost inflation, slowing the pace at which new wind and solar capacity could be connected.

The direct current link, designed to allow large volumes of electricity to flow between the two countries at times of surplus or shortage, moved further through construction, part of a broader push toward a more connected Middle Eastern and North African grid.

The Green Energy Corridor programme added new high-capacity lines linking wind and solar-rich states such as Rajasthan and Gujarat to the national grid, addressing a persistent bottleneck in which renewable capacity had been built faster than the lines needed to evacuate its power.

The assessment concerned techniques for increasing capacity of existing lines to accommodate electrification and renewable energy. It highlighted a lag in deployment relative to European leaders.

The regulator awarded contracts to build and operate additional lines extending the country's already extensive direct current network, which carries hydropower more than two thousand kilometres from Amazon basin dams to the industrial south-east.

The power integration scheme linking the four countries increased the volume of hydropower traded across borders, a step towards the long-discussed ambition of a single ASEAN power grid that would let members trade surplus generation instead of building it all themselves.

The proposed link, which would run several thousand kilometres of high-voltage direct current cable under the Atlantic and the Bay of Biscay, remained one of the most ambitious cross-border transmission schemes under development anywhere, though it had yet to reach a final investment decision.

The Federal Energy Regulatory Commission moved to a first-ready, first-served process for reviewing new generation and storage projects seeking to connect to the grid, responding to queues in which thousands of projects, many of them renewable, had waited years for an interconnection study.

The land-and-subsea link between the United Kingdom and Denmark surpassed the 720 km North Sea Link. It marked a new distance record for cross-border high-voltage direct current transmission.

In April 2022 the administration streamlined environmental reviews for transmission projects, and in May 2022 announced competitive grants funded by the 2021 Bipartisan Infrastructure Law and the 2022 Inflation Reduction Act. The measures targeted the interconnection backlog holding back new generation.

A cascading failure across three regional grids left more than half the country's population without electricity for up to two days, the largest blackout in history by number of people affected and a stark demonstration of the risks of a thinly interconnected transmission system.

The agency engaged private companies to develop laser power beaming to supply low earth orbit satellites and to launch rockets. It extended power transmission concepts beyond terrestrial conductors.

The order attempted to reduce barriers to third-party investment and to the creation of merchant transmission lines where a public policy need is found. It extended the market-opening approach begun by Order 888.

The company powered a cable climber one kilometre vertically using a ground-based laser transmitter. The result revived interest in beamed power as a specialised transmission method.

The companies moved specialised high-capacity transmission technology from demonstration into commercial supply. It offered an option for dense urban corridors where conventional conductors are constrained.

A software fault that let operators lose track of a sagging line in Ohio triggered a chain reaction that cut power to around 50 million people across eight US states and one Canadian province, prompting a decade of work on mandatory reliability standards for the grid.

The study measured electric field strength at the edge of an existing right-of-way on a 765 kV line and found no increased risk of cancer or illness from living nearby. Such findings shaped siting and exposure policy for high-voltage corridors.

The order promoted wholesale competition through open access non-discriminatory transmission services by public utilities and addressed recovery of stranded costs. It spurred the establishment of regional transmission organisations in the United States.

Following a study of magnetic field strengths, the commission set a standard of 200 mG at the edge of the right-of-way using the winter-normal conductor rating. Related rulings also limited new New York transmission lines to 345 kV.