History of electric power transmission
Encyclopedia
The history of the technology of moving electricity far from where it was generated dates from the late 19th century. This includes movement of electricity in bulk (formally referred to as "transmission
), and the delivery of electricity ("distribution
") to individual customers. The distinction between the two terms did not exist in early years and were used interchangeably.
using high pressure water mains to deliver power to factory motors. London's system
delivered 7000 hp (5Megawatts) over a 180 miles (289.7 km) network of pipes carrying water at 800psi. These systems were replaced by cheaper and more versatile electrical systems, but by the end of the 19th century, city planners and financiers well aware of the benefits, economics, and process of establishing power transmission systems.
In the early days electric power usage, widespread transmission of electric power
had two obstacles. Firstly, devices requiring different voltages required specialized generators with their own separate lines. Street lights, electric motors in factories, power for streetcars and lights in homes are examples of the diversity of devices with voltages requiring separate systems. Secondly, generators had to be relatively nearby their loads (a mile or less for low voltage devices). It was known that long distance transmission was possible the higher the voltage was raised, so both problems could be solved if transforming voltages could be cheaply performed from a single universal power line.
Much of early electricity was direct current
, which could not easily be increased or decreased in voltage either for long-distance transmission or for sharing a common line to be used with multiple types of electric devices. Companies simply ran different lines for the different classes of loads their inventions required, for example, Charles Brush
's New York voltaic arc lights required up to 10,000 volts, Edison's incandescent lights used 110 volts, streetcars built by Siemens
or Sprague
required large motors in the 500 volt range, whereas industrial motors in factories used still other voltages. Due to this specialization of lines and because transmission was so inefficient that generators needed to be close by their loads, it seemed at the time that the industry would develop into what is now known as a distributed generation
system with large numbers of small generators located nearby their loads.
, they also knew that the capacity of a wire is proportionate to the square of the current traveling on it, regardless the voltage, and so by doubling the voltage, the same cable would be capable of transmitting the same amount of power four times the distance.
At the Paris Exposition of 1878
, electric arc lighting
had been installed along the Avenue de l'Opera and the Place de l'Opera, using electric Yablochkov arc lamps
, powered by Zénobe Gramme
alternating current dynamos. Yablochkov candles required high voltage, and it was not long before experimenters reported that the arc lights could be powered on a 7 miles (11.3 km) circuit. Within a decade scores of cities would have lighting systems using a central power plant that provided electricity to multiple customers via electrical transmission lines. These systems were in direct competition with the dominant gaslight
utilities of the period.
The idea of investing in a central plant and a network to deliver energy produced to customers who pay a recurring fee for service was familiar business model for investors: it was identical to the lucrative gaslight business, or the hydraulic and pneumatic power transmission systems. The only difference was the stuff being delivered was electricity not gas, and the "pipes" doing the delivering were flexible.
The California Electric Company
(now PG&E) in San Francisco in 1879 used two direct current generators from Charles Brush's company to supply multiple customers with power for their arc lights. This San Francisco system was the first case of a utility
selling electricity from a central plant to multiple customers via transmission
lines. CEC soon opened a second plant with 4 additional generators. Service charges for light from sundown to midnight was $10 per lamp per week.
In December 1880, Brush Electric Company set up a central station to supply a 2 miles (3.2 km) length of Broadway with arc lighting. By the end of 1881, New York, Boston, Philadelphia, Baltimore, Montreal, Buffalo, San Francisco, Cleveland and other cities had Brush arc light systems, producing public light well into the 20th century. By 1893 there were 1500 arc lights illuminating New York streets.
The first electricity system supplying incandescent lights was built by Edison Electric Illuminating Company in lower Manhattan eventually serving one square mile with 6 "jumbo dynamos" housed at Pearl Street Station
. When service began in September 1882, there were 85 customers with 400 light bulbs. Each dynamo produced 100 kW- enough for 1200 incandescent lights, and transmission was at 110 volts via underground conduits. The system cost $300,000 to build with installation of the 100000 feet (30,480 m) of underground conduits one of the most expensive parts of the project. Operating expenses exceeded income in the first two years and fire destroyed the plant in 1890. Edison's lights were cheaper, provided light that was warmer and operated at much lower voltages than the arc lights. Further, Edison had a three wire system so that either 110 volts or 220 volts could be supplied to power some motors.
' production of turbogenerators beginning 1889. Turbogenerator output quickly jumped from 100 kW to 25 megawatts in two decades. Prior to efficient turbogenerators, hydroelectric projects were a significant source of large amounts of power requiring transmission infrastructure.
became interested in electricity, he quickly and correctly concluded that Edison's low voltages were too inefficient to be scaled up for transmission needed for large systems. He further understood that long-distance transmission needed high voltage and that inexpensive conversion technology only existed for alternating current. Transformers would play the decisive role in the victory of alternating current over direct current for transmission and distribution systems. In 1876, Pavel Yablochkov
patented his mechanism of using induction coils to serve as a step up transformer prior to the Paris Exposition demonstrating his arc lights. Lucien Gaulard
and John Dixon Gibbs later developed more efficient, less expensive AC transformers.
The birth of the first transformer
Between 1884 and 1885, Hungarian
engineers Zipernowsky
, Bláthy
and Déri
from the Ganz company in Budapest
created the efficient "Z.B.D." closed-core coils, as well as the modern electric distribution system. The three had discovered that all former coreless or open-core devices were incapable of regulating voltage, and were therefore impracticable. Their joint patent described two versions of a design with no poles: the "closed-core transformer" and the "shell-core transformer". Ottó Bláthy suggested the use of closed-cores, Károly Zipernowsky the use of shunt connections
, and Miksa Déri performed the experiments.
In the closed-core transformer the iron core is a closed ring around which the two coils are wound. In the shell type transformer, the windings are passed through the core. In both designs, the magnetic flux linking the primary and secondary windings travels almost entirely within the iron core, with no intentional path through air. The core consists of iron strands or sheets. These revolutionary design elements would finally make it technically and economically feasible to provide electric power for lighting in homes, businesses and public spaces. Zipernowsky, Bláthy and Déri also discovered the transformer formula, Vs/Vp = Ns/Np. Electrical and electronic systems the world over rely on the principles of the original Ganz
transformers. The inventors are also credited with the first use of the word "transformer" to describe a device for altering the EMF
of an electric current.
The concept that is the basis of modern transmission using inexpensive step up and step down transformers was first implemented by Westinghouse, Stanley and Franklin Leonard Pope
in 1886 in Great Barrington, Massachusetts
. There were still problems with efficient generators and high voltage transformers. At an AIEE meeting on May 16, 1888, Nikola Tesla
delivered a lecture entitled A New System of Alternating Current Motors and Transformers, describing the equipment which allowed efficient generation and use of alternating current
s. Westinghouse needed Telsa's better step up transformer technology and bought patents for it along with the highly efficient and inexpensive polyphase
design for AC generators and motors used today. The utter simplicity of polyphase generators and motors meant that besides their efficiency they could be manufactured cheaply, compactly and would required little attention to maintain. Simple economics would drive the expensive, balky and mechanically complex DC dynamos to their ultimate extinction. As it turned out, the deciding factor in the War of Currents
was the availability of low cost step up and step down transformers that meant that all customers regardless of their specialized voltage requirements could be served at minimal cost of conversion. This "universal system" is today regarded as one of the most influential innovations for the use of electricity.
who had spent six months at Edison's Menlo park facility understood his problem with transmission and was convinced that moving electricity over great distances was possible using direct current. He was familiar with the work of Marcel Deprez, who did early work on high voltage transmission after being inspired by the capability of arc light generators to support lights over great distances. Deprez avoided transformers by placing generators and loads in series as arc light
systems of Charles F. Brush
did. Thury developed this idea into the first commercial system for high-voltage DC transmission. Like Brush's dynamos, current is kept constant, and when increasing load demands more pressure, voltage is increased. The Thury System was successfully used on several DC transmission projects from Hydro generators. The first in 1885 was a low voltage system in Bözingen
, and the first high voltage system went into service in 1889 in Genoa
, Italy
by the Acquedotto de Ferrari-Galliera company. This system transmitted 630 kW at 14 kV DC over a circuit 120 km long. The largest Thury System was the Lyon Moutiers project
that was 230 km in length, eventually delivering 20 Megawatts, at 125kV.
s. The AC "universal system" won by force of numbers, proliferating systems with transformers both to couple generators to high-voltage transmission lines, and to connect transmission to local distribution circuits. By a suitable choice of utility frequency
, both lighting and motor loads could be served. Rotary converter
s and later mercury-arc valves and other rectifier equipment allowed DC load to be served by local conversion where needed. Even generating stations and loads using different frequencies could also be interconnected using rotary converters. By using common generating plants for every type of load, important economies of scale were achieved, lower overall capital investment was required, load factor
on each plant was increased allowing for higher efficiency, allowing for a lower cost of energy to the consumer and increased overall use of electric power.
By allowing multiple generating plants to be interconnected over a wide area, electricity production cost was reduced. The most efficient available plants could be used to supply the varying loads during the day. Reliability was improved and capital investment cost was reduced, since stand-by generating capacity could be shared over many more customers and a wider geographic area. Remote and low-cost sources of energy, such as hydroelectric power or mine-mouth coal, could be exploited to lower energy production cost.
The first transmission of three-phase alternating current using high voltage took place in 1891 during the international electricity exhibition
in Frankfurt
. A 25 kV transmission line, approximately 175 kilometers long, connected Lauffen on the Neckar
and Frankfurt.
Initially transmission lines were supported by porcelain pin-and-sleeve insulators similar to those used for telegraphs
and telephone
lines. However, these had a practical limit of 40 kV. In 1907, the invention of the disc insulator by Harold W. Buck of the Niagara Falls Power Corporation and Edward M. Hewlett of General Electric
allowed practical insulators of any length to be constructed for higher voltages.
The first large scale hydroelectric generators in the USA were installed in 1895 at Niagara Falls
and provided electricity to Buffalo, New York
via power transmission lines. A statue of Tesla stands at Niagara Falls today in tribute to his contributions.
and Grand Rapids, Michigan
. Voltages of 100 kV and more where not established technology until around 5 years later, with for example the first 110 kV line in Europe between Lauchhammer
and Riesa
, Germany
in 1912.
In the early 1920s the Pit River
– Cottonwood
– Vaca-Dixon line was built for 220 kV transporting power from hydroelectric plants in the Sierra Nevada to the San Francisco Bay Area
, at the same time the Big Creek
- Los Angeles
lines where upgraded to the same voltage. Both of those systems entered commercial service in 1923. On April 17, 1929 the first 220 kV line in Germany
was completed, running from Brauweiler
near Cologne
, over Kelsterbach
near Frankfurt, Rheinau
near Mannheim
, Ludwigsburg
–Hoheneck near Austria
. This line comprises the North-South interconnect
, at the time one of the world's largest power systems. The masts of this line were designed for eventual upgrade to 380 kV. However the first transmission at 380 kV in Germany was on October 5, 1957 between the substations in Rommerskirchen
and Ludwigsburg
–Hoheneck.
The world's first 380 kV power line was built in Sweden
, the 952 km Harsprånget - Hallsberg
line in 1952. In 1965, the first extra-high-voltage transmission at 735 kV took place on a Hydro-Québec
transmission line. In 1982 the first transmission at 1200 kV was in the Soviet Union
.
The rapid industrialization in the 20th century made electrical transmission lines and grids a critical part of the economic infrastructure in most industrialized nations. Interconnection of local generation plants and small distribution networks was greatly spurred by the requirements of World War I
, where large electrical generating plants were built by governments to provide power to munitions factories; later these plants were connected to supply civil load through long-distance transmission.
Small municipal electrical utilities did not necessarily desire to reduce the cost of each unit of electricity sold; to some extent, especially during the period 1880–1890, electrical lighting was considered a luxury product and electric power was not substituted for steam power. Engineers such as Samuel Insull
in the United States and Sebastian Z. De Ferranti
in the United Kingdom were instrumental in overcoming technical, economic, regulatory and political difficulties in development of long-distance electric power transmission. By introduction of electric power transmission networks, in the city of London the cost of a kilowatt-hour was reduced to one-third in a ten-year period.
In 1926 electrical networks
in the United Kingdom began to be interconnected in the National Grid, initially operating at 132,000 volts.
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
), and the delivery of electricity ("distribution
Electricity distribution
File:Electricity grid simple- North America.svg|thumb|380px|right|Simplified diagram of AC electricity distribution from generation stations to consumers...
") to individual customers. The distinction between the two terms did not exist in early years and were used interchangeably.
Early transmission
Prior to electricity, various systems have been used for transmission of power across large distances. Chief among them were telodynamic (cable in motion), pneumatic (pressurized air), and hydraulic (pressurized fluid) transmission. Cable cars were the most frequent example of telodynamic transmission, whose lines could extend for several miles for a single section. Pneumatic transmission was used for city power transmission systems in Paris, Birmingham, Rixdorf, Offenbach, Dresden and Buenos Aires at the beginning of the twentieth century. Cities in the 19th century also used hydraulic transmissionHydraulic transmission
Hydraulic transmission may refer to:* Hydrostatic transmission, see Hydraulic drive system and Hydraulic machinery* Hydrokinetic transmission, see Torque converter...
using high pressure water mains to deliver power to factory motors. London's system
London Hydraulic Power Company
The London Hydraulic Power Company was set up by an Act of Parliament in 1883 to install a hydraulic power network of high-pressure cast iron water mains under London. It was the successor to the Steam Wharf and Warehouse Company, founded in 1871 by Edward B Ellington...
delivered 7000 hp (5Megawatts) over a 180 miles (289.7 km) network of pipes carrying water at 800psi. These systems were replaced by cheaper and more versatile electrical systems, but by the end of the 19th century, city planners and financiers well aware of the benefits, economics, and process of establishing power transmission systems.
In the early days electric power usage, widespread transmission of electric power
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
had two obstacles. Firstly, devices requiring different voltages required specialized generators with their own separate lines. Street lights, electric motors in factories, power for streetcars and lights in homes are examples of the diversity of devices with voltages requiring separate systems. Secondly, generators had to be relatively nearby their loads (a mile or less for low voltage devices). It was known that long distance transmission was possible the higher the voltage was raised, so both problems could be solved if transforming voltages could be cheaply performed from a single universal power line.
Specialized systems
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
, which could not easily be increased or decreased in voltage either for long-distance transmission or for sharing a common line to be used with multiple types of electric devices. Companies simply ran different lines for the different classes of loads their inventions required, for example, Charles Brush
Charles F. Brush
Charles Francis Brush was a U.S. inventor, entrepreneur and philanthropist.-Biography:Born in Euclid Township, Ohio, Brush was raised on a farm about 10 miles from downtown Cleveland...
's New York voltaic arc lights required up to 10,000 volts, Edison's incandescent lights used 110 volts, streetcars built by Siemens
Ernst Werner von Siemens
Ernst Werner Siemens, von Siemens since 1888, was a German inventor and industrialist. Siemens' name has been adopted as the SI unit of electrical conductance, the siemens...
or Sprague
Frank J. Sprague
Frank Julian Sprague was an American naval officer and inventor who contributed to the development of the electric motor, electric railways, and electric elevators...
required large motors in the 500 volt range, whereas industrial motors in factories used still other voltages. Due to this specialization of lines and because transmission was so inefficient that generators needed to be close by their loads, it seemed at the time that the industry would develop into what is now known as a distributed generation
Distributed generation
Distributed generation, also called on-site generation, dispersed generation, embedded generation, decentralized generation, decentralized energy or distributed energy, generates electricity from many small energy sources....
system with large numbers of small generators located nearby their loads.
Early high voltage and commercial systems
High voltage was of interest to early researchers working on the problem of transmission over distance. They know from elementary electricity principle that the same amount of power could be transferred on a cable by doubling the voltage and halving the current. Due to Joule's LawJoule's law
Joule's laws are a pair of laws concerning the heat produced by a current and the energy dependence of an ideal gas to that of pressure, volume, and temperature, respectively...
, they also knew that the capacity of a wire is proportionate to the square of the current traveling on it, regardless the voltage, and so by doubling the voltage, the same cable would be capable of transmitting the same amount of power four times the distance.
At the Paris Exposition of 1878
Exposition Universelle (1878)
The third Paris World's Fair, called an Exposition Universelle in French, was held from 1 May through to 10 November 1878. It celebrated the recovery of France after the 1870 Franco-Prussian War.-Construction:...
, electric arc lighting
Arc lamp
"Arc lamp" or "arc light" is the general term for a class of lamps that produce light by an electric arc . The lamp consists of two electrodes, first made from carbon but typically made today of tungsten, which are separated by a gas...
had been installed along the Avenue de l'Opera and the Place de l'Opera, using electric Yablochkov arc lamps
Yablochkov candle
A Yablochkov candle is a type of electric carbon arc lamp, invented in 1876 by Pavel Yablochkov.-Design:A Yablochkov candle consists of a sandwich of two long carbon blocks, approximately 6 by 12 millimetres in cross-section, separated by a block of inert material such as plaster of paris or kaolin...
, powered by Zénobe Gramme
Zénobe Gramme
Zénobe Théophile Gramme was a Belgian electrical engineer. He invented the Gramme machine, a type of direct current dynamo capable of generating smoother and much higher voltages than the dynamos known to that point.In 1873 he and Hippolyte Fontaine accidentally discovered that the device was...
alternating current dynamos. Yablochkov candles required high voltage, and it was not long before experimenters reported that the arc lights could be powered on a 7 miles (11.3 km) circuit. Within a decade scores of cities would have lighting systems using a central power plant that provided electricity to multiple customers via electrical transmission lines. These systems were in direct competition with the dominant gaslight
Gas lighting
Gas lighting is production of artificial light from combustion of a gaseous fuel, including hydrogen, methane, carbon monoxide, propane, butane, acetylene, ethylene, or natural gas. Before electricity became sufficiently widespread and economical to allow for general public use, gas was the most...
utilities of the period.
 |
| Brush Electric Company's central power plant dynamos powered arc lamps for public lighting in New York. Beginning operation in December 1880 at 133 West Twenty-Fifth Street, it powered a 2 miles (3.2 km) long circuit. |
The idea of investing in a central plant and a network to deliver energy produced to customers who pay a recurring fee for service was familiar business model for investors: it was identical to the lucrative gaslight business, or the hydraulic and pneumatic power transmission systems. The only difference was the stuff being delivered was electricity not gas, and the "pipes" doing the delivering were flexible.
The California Electric Company
Pacific Gas and Electric Company
The Pacific Gas and Electric Company , commonly known as PG&E, is the utility that provides natural gas and electricity to most of the northern two-thirds of California, from Bakersfield almost to the Oregon border...
(now PG&E) in San Francisco in 1879 used two direct current generators from Charles Brush's company to supply multiple customers with power for their arc lights. This San Francisco system was the first case of a utility
Electric utility
An electric utility is a company that engages in the generation, transmission, and distribution of electricity for sale generally in a regulated market. The electrical utility industry is a major provider of energy in most countries. It is indispensable to factories, commercial establishments,...
selling electricity from a central plant to multiple customers via transmission
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
lines. CEC soon opened a second plant with 4 additional generators. Service charges for light from sundown to midnight was $10 per lamp per week.
In December 1880, Brush Electric Company set up a central station to supply a 2 miles (3.2 km) length of Broadway with arc lighting. By the end of 1881, New York, Boston, Philadelphia, Baltimore, Montreal, Buffalo, San Francisco, Cleveland and other cities had Brush arc light systems, producing public light well into the 20th century. By 1893 there were 1500 arc lights illuminating New York streets.
The first electricity system supplying incandescent lights was built by Edison Electric Illuminating Company in lower Manhattan eventually serving one square mile with 6 "jumbo dynamos" housed at Pearl Street Station
Pearl Street Station
Pearl Street Station was the first central power plant in the United States. It was located at 255-257 Pearl Street in Manhattan on a site measuring 50 by 100 feet, just south of Fulton Street. It began with one direct current generator, and it started generating electricity on September 4, 1882,...
. When service began in September 1882, there were 85 customers with 400 light bulbs. Each dynamo produced 100 kW- enough for 1200 incandescent lights, and transmission was at 110 volts via underground conduits. The system cost $300,000 to build with installation of the 100000 feet (30,480 m) of underground conduits one of the most expensive parts of the project. Operating expenses exceeded income in the first two years and fire destroyed the plant in 1890. Edison's lights were cheaper, provided light that was warmer and operated at much lower voltages than the arc lights. Further, Edison had a three wire system so that either 110 volts or 220 volts could be supplied to power some motors.
Availability of large scale generation
Availability of large amounts of power from diverse locations would become possible after Charles ParsonsCharles Algernon Parsons
Sir Charles Algernon Parsons OM KCB FRS was an Anglo-Irish engineer, best known for his invention of the steam turbine. He worked as an engineer on dynamo and turbine design, and power generation, with great influence on the naval and electrical engineering fields...
' production of turbogenerators beginning 1889. Turbogenerator output quickly jumped from 100 kW to 25 megawatts in two decades. Prior to efficient turbogenerators, hydroelectric projects were a significant source of large amounts of power requiring transmission infrastructure.
Induction coils advantage of alternating current
When George WestinghouseGeorge Westinghouse
George Westinghouse, Jr was an American entrepreneur and engineer who invented the railway air brake and was a pioneer of the electrical industry. Westinghouse was one of Thomas Edison's main rivals in the early implementation of the American electricity system...
became interested in electricity, he quickly and correctly concluded that Edison's low voltages were too inefficient to be scaled up for transmission needed for large systems. He further understood that long-distance transmission needed high voltage and that inexpensive conversion technology only existed for alternating current. Transformers would play the decisive role in the victory of alternating current over direct current for transmission and distribution systems. In 1876, Pavel Yablochkov
Pavel Yablochkov
Pavel Nikolayevich Yablochkov was a Russian electrical engineer, the inventor of the Yablochkov candle and businessman.-Biography:...
patented his mechanism of using induction coils to serve as a step up transformer prior to the Paris Exposition demonstrating his arc lights. Lucien Gaulard
Lucien Gaulard
Lucien Gaulard invented devices for the transmission of alternating current electrical energy.-Biography:Gaulard was born in Paris, France....
and John Dixon Gibbs later developed more efficient, less expensive AC transformers.
The birth of the first transformer
Between 1884 and 1885, Hungarian
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
engineers Zipernowsky
Károly Zipernowsky
Károly Zipernowsky was a Hungarian electrical engineer of Jewish descent. He was the co-inventor of the transformer and other AC technologies.-Biography:...
, Bláthy
Ottó Bláthy
Ottó Titusz Bláthy was a Hungarian electrical engineer. In his career, he became the co-inventor of the modern electric transformer, the tension regulator, , the AC watt-hour meter, the single-phase alternating current electric motor, the turbo generator, and the high efficiency turbo...
and Déri
Miksa Déri
Miksa Déri was a Hungarian electrical engineer. He was, with his partners Károly Zipernowsky and Ottó Bláthy, co-inventor of the closed iron core transformer and the ZBD model AC electrical generator....
from the Ganz company in Budapest
Budapest
Budapest is the capital of Hungary. As the largest city of Hungary, it is the country's principal political, cultural, commercial, industrial, and transportation centre. In 2011, Budapest had 1,733,685 inhabitants, down from its 1989 peak of 2,113,645 due to suburbanization. The Budapest Commuter...
created the efficient "Z.B.D." closed-core coils, as well as the modern electric distribution system. The three had discovered that all former coreless or open-core devices were incapable of regulating voltage, and were therefore impracticable. Their joint patent described two versions of a design with no poles: the "closed-core transformer" and the "shell-core transformer". Ottó Bláthy suggested the use of closed-cores, Károly Zipernowsky the use of shunt connections
Shunt (electrical)
In electronics, a shunt is a device which allows electric current to pass around another point in the circuit. The term is also widely used in photovoltaics to describe an unwanted short circuit between the front and back surface contacts of a solar cell, usually caused by wafer damage.-Defective...
, and Miksa Déri performed the experiments.
In the closed-core transformer the iron core is a closed ring around which the two coils are wound. In the shell type transformer, the windings are passed through the core. In both designs, the magnetic flux linking the primary and secondary windings travels almost entirely within the iron core, with no intentional path through air. The core consists of iron strands or sheets. These revolutionary design elements would finally make it technically and economically feasible to provide electric power for lighting in homes, businesses and public spaces. Zipernowsky, Bláthy and Déri also discovered the transformer formula, Vs/Vp = Ns/Np. Electrical and electronic systems the world over rely on the principles of the original Ganz
Ganz
The Ganz electric works in Budapest is probably best known for the manufacture of tramcars, but was also a pioneer in the application of three-phase alternating current to electric railways. Ganz also made / makes: ships , bridge steel structures , high voltage equipment...
transformers. The inventors are also credited with the first use of the word "transformer" to describe a device for altering the EMF
Electromotive force
In physics, electromotive force, emf , or electromotance refers to voltage generated by a battery or by the magnetic force according to Faraday's Law, which states that a time varying magnetic field will induce an electric current.It is important to note that the electromotive "force" is not a...
of an electric current.
The concept that is the basis of modern transmission using inexpensive step up and step down transformers was first implemented by Westinghouse, Stanley and Franklin Leonard Pope
Franklin Leonard Pope
Franklin Leonard Pope was an American engineer, explorer, and inventor.-Biography:He was born in Great Barrington, Massachusetts, the son of Ebenezer Pope and Electra Wainwright. He was a telegrapher, electrical engineer, explorer, inventor, and patent attorney.He was also a major contributor to...
in 1886 in Great Barrington, Massachusetts
Great Barrington, Massachusetts
Great Barrington is a town in Berkshire County, Massachusetts, United States. It is part of the Pittsfield, Massachusetts Metropolitan Statistical Area. The population was 7,104 at the 2010 census. Both a summer resort and home to Ski Butternut, Great Barrington includes the villages of Van...
. There were still problems with efficient generators and high voltage transformers. At an AIEE meeting on May 16, 1888, Nikola Tesla
Nikola Tesla
Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...
delivered a lecture entitled A New System of Alternating Current Motors and Transformers, describing the equipment which allowed efficient generation and use of alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
s. Westinghouse needed Telsa's better step up transformer technology and bought patents for it along with the highly efficient and inexpensive polyphase
Polyphase system
A polyphase system is a means of distributing alternating current electrical power. Polyphase systems have three or more energized electrical conductors carrying alternating currents with a definite time offset between the voltage waves in each conductor. Polyphase systems are particularly useful...
design for AC generators and motors used today. The utter simplicity of polyphase generators and motors meant that besides their efficiency they could be manufactured cheaply, compactly and would required little attention to maintain. Simple economics would drive the expensive, balky and mechanically complex DC dynamos to their ultimate extinction. As it turned out, the deciding factor in the War of Currents
War of Currents
In the "War of Currents" era in the late 1880s, George Westinghouse and Thomas Edison became adversaries due to Edison's promotion of direct current for electric power distribution over alternating current advocated by several European companies and Westinghouse Electric based out of Pittsburgh,...
was the availability of low cost step up and step down transformers that meant that all customers regardless of their specialized voltage requirements could be served at minimal cost of conversion. This "universal system" is today regarded as one of the most influential innovations for the use of electricity.
High voltage direct current transmission
The case for alternating current was not clear at the turn of the century and high voltage direct current transmission systems were successfully installed without the benefit of transformers. Rene ThuryRené Thury
René Thury was a Swiss pioneer in electrical engineering. He was known for his work with high voltage direct current electricity transmission and was known in the professional world as the "King of DC." -Biography:...
who had spent six months at Edison's Menlo park facility understood his problem with transmission and was convinced that moving electricity over great distances was possible using direct current. He was familiar with the work of Marcel Deprez, who did early work on high voltage transmission after being inspired by the capability of arc light generators to support lights over great distances. Deprez avoided transformers by placing generators and loads in series as arc light
Arc Light
Arc Light is the debut novel by Eric L. Harry, a techno-thriller about limited nuclear war published in 1994 and written in 1991-2.As China and Russia clash in Siberia in June 1999, nuclear missiles strike the United States. The U.S. retaliates against Russia, and World War III begins...
systems of Charles F. Brush
Charles F. Brush
Charles Francis Brush was a U.S. inventor, entrepreneur and philanthropist.-Biography:Born in Euclid Township, Ohio, Brush was raised on a farm about 10 miles from downtown Cleveland...
did. Thury developed this idea into the first commercial system for high-voltage DC transmission. Like Brush's dynamos, current is kept constant, and when increasing load demands more pressure, voltage is increased. The Thury System was successfully used on several DC transmission projects from Hydro generators. The first in 1885 was a low voltage system in Bözingen
Biel/Bienne
Biel/Bienne is a city in the district of the Biel/Bienne administrative district in the canton of Bern in Switzerland.It is located on the language boundary and is throughout bilingual. Biel is the German name for the town, Bienne its French counterpart. The town is often referred to in both...
, and the first high voltage system went into service in 1889 in Genoa
Genoa
Genoa |Ligurian]] Zena ; Latin and, archaically, English Genua) is a city and an important seaport in northern Italy, the capital of the Province of Genoa and of the region of Liguria....
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
by the Acquedotto de Ferrari-Galliera company. This system transmitted 630 kW at 14 kV DC over a circuit 120 km long. The largest Thury System was the Lyon Moutiers project
Lyon-Moutiers DC transmission scheme
The Lyon–Moutiers DC transmission scheme was the most powerful mechanical high voltage direct current electric power transmission scheme ever built...
that was 230 km in length, eventually delivering 20 Megawatts, at 125kV.
Victory for AC
Ultimately, the versatility of the Thury system was hampered the fragility of series distribution, and the lack of a reliable DC conversion technology that would not show up until the 1940s with improvements in mercury arc valveMercury arc valve
A mercury-arc valve is a type of electrical rectifier used for converting high-voltage or high-current alternating current into direct current . Rectifiers of this type were used to provide power for industrial motors, electric railways, streetcars, and electric locomotives, as well as for...
s. The AC "universal system" won by force of numbers, proliferating systems with transformers both to couple generators to high-voltage transmission lines, and to connect transmission to local distribution circuits. By a suitable choice of utility frequency
Utility frequency
The utility frequency, line frequency or mains frequency is the frequency at which alternating current is transmitted from a power plant to the end-user. In most parts of the world this is 50 Hz, although in the Americas it is typically 60 Hz...
, both lighting and motor loads could be served. Rotary converter
Rotary converter
A rotary converter is a type of electrical machine which acts as a mechanical rectifier or inverter. It was used to convert AC to DC or DC to AC power before the advent of chemical or solid state power rectification...
s and later mercury-arc valves and other rectifier equipment allowed DC load to be served by local conversion where needed. Even generating stations and loads using different frequencies could also be interconnected using rotary converters. By using common generating plants for every type of load, important economies of scale were achieved, lower overall capital investment was required, load factor
Load factor
Load factor may refer to:* Load factor , the ratio of the lift of an aircraft to its weight* Load factor , the ratio of the number of records to the number of addresses within a data structure...
on each plant was increased allowing for higher efficiency, allowing for a lower cost of energy to the consumer and increased overall use of electric power.
By allowing multiple generating plants to be interconnected over a wide area, electricity production cost was reduced. The most efficient available plants could be used to supply the varying loads during the day. Reliability was improved and capital investment cost was reduced, since stand-by generating capacity could be shared over many more customers and a wider geographic area. Remote and low-cost sources of energy, such as hydroelectric power or mine-mouth coal, could be exploited to lower energy production cost.
The first transmission of three-phase alternating current using high voltage took place in 1891 during the international electricity exhibition
International Electro-Technical Exhibition - 1891
The 1891 International Electro-Technical Exhibition was held between 16 May and 19 October on the disused site of the three former “Westbahnhöfe” in Frankfurt am Main. The exhibition featured the first long distance transmission of high-power, three-phase electrical current, which was generated...
in Frankfurt
Frankfurt
Frankfurt am Main , commonly known simply as Frankfurt, is the largest city in the German state of Hesse and the fifth-largest city in Germany, with a 2010 population of 688,249. The urban area had an estimated population of 2,300,000 in 2010...
. A 25 kV transmission line, approximately 175 kilometers long, connected Lauffen on the Neckar
Neckar
The Neckar is a long river, mainly flowing through the southwestern state of Baden-Württemberg, but also a short section through Hesse, in Germany. The Neckar is a major right tributary of the River Rhine...
and Frankfurt.
Initially transmission lines were supported by porcelain pin-and-sleeve insulators similar to those used for telegraphs
Telegraphy
Telegraphy is the long-distance transmission of messages via some form of signalling technology. Telegraphy requires messages to be converted to a code which is known to both sender and receiver...
and telephone
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
lines. However, these had a practical limit of 40 kV. In 1907, the invention of the disc insulator by Harold W. Buck of the Niagara Falls Power Corporation and Edward M. Hewlett of General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
allowed practical insulators of any length to be constructed for higher voltages.
The first large scale hydroelectric generators in the USA were installed in 1895 at Niagara Falls
Niagara Falls
The Niagara Falls, located on the Niagara River draining Lake Erie into Lake Ontario, is the collective name for the Horseshoe Falls and the adjacent American Falls along with the comparatively small Bridal Veil Falls, which combined form the highest flow rate of any waterfalls in the world and has...
and provided electricity to Buffalo, New York
Buffalo, New York
Buffalo is the second most populous city in the state of New York, after New York City. Located in Western New York on the eastern shores of Lake Erie and at the head of the Niagara River across from Fort Erie, Ontario, Buffalo is the seat of Erie County and the principal city of the...
via power transmission lines. A statue of Tesla stands at Niagara Falls today in tribute to his contributions.
Modern Period
Voltages used for electric power transmission increased throughout the 20th century. The first electric power transmission line in North America operated at 4000V. It was constructed in 1889 between the generating station at Willamette Falls in Oregon City, Oregon, and downtown Portland, Oregon, a distance of around 13 miles. By 1914 fifty-five transmission systems operating at more than 70,000 V were in service, and the highest voltage then used was 150,000 volts. The first three-phase alternating current power transmission at 110 kV took place in 1907 between CrotonCroton Dam (Michigan)
Croton Dam is a dam and powerplant complex on the Muskegon River in Croton Township, Newaygo County, Michigan. It was built in 1907 under the direction of William D. Fargo by the Grand Rapids - Muskegon Power Company, a predecessor of Consumers Energy...
and Grand Rapids, Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
. Voltages of 100 kV and more where not established technology until around 5 years later, with for example the first 110 kV line in Europe between Lauchhammer
Lauchhammer
Lauchhammer is a town in the Oberspreewald-Lausitz district, in southern Brandenburg, Germany. It is situated on the river Schwarze Elster, approx. 17 km west of Senftenberg, and 50 km north of Dresden....
and Riesa
Riesa
Riesa is a town in the district of Meißen in the Free State of Saxony, Germany. It is located at the river Elbe, approx. 40 km northwest of Dresden.The world's first 110 kV power line was inaugurated between Riesa and Lauchhammer in 1912....
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
in 1912.
In the early 1920s the Pit River
Pit River
The Pit River is a major river draining from northeastern California into the state's Central Valley. The Pit, the Klamath and the Columbia are the only three rivers in the U.S...
– Cottonwood
Cottonwood, California
Cottonwood is a census-designated place in Shasta County, California, United States. The population was 3,316 at the 2010 census, up from 2,960 at the 2000 census. Cottonwood is a stagecoach town founded in 1882. Cottonwood is equidistant between Redding and Red Bluff , in both directions...
– Vaca-Dixon line was built for 220 kV transporting power from hydroelectric plants in the Sierra Nevada to the San Francisco Bay Area
San Francisco Bay Area
The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...
, at the same time the Big Creek
Big Creek, California
Big Creek is a small census-designated place in Fresno County, California located in the Sierra Nevada Mountains on the north bank of Big Creek. It lies at an elevation of 4984 feet . Its population is 175...
- Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
lines where upgraded to the same voltage. Both of those systems entered commercial service in 1923. On April 17, 1929 the first 220 kV line in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
was completed, running from Brauweiler
Brauweiler
Brauweiler is a part of Pulheim, west of Cologne, North Rhine-Westphalia in Germany.The former Benedictine abbey, Brauweiler Abbey, founded 1024, is used today by the Rhein Department for the Care of Historic Monuments....
near Cologne
Cologne
Cologne is Germany's fourth-largest city , and is the largest city both in the Germany Federal State of North Rhine-Westphalia and within the Rhine-Ruhr Metropolitan Area, one of the major European metropolitan areas with more than ten million inhabitants.Cologne is located on both sides of the...
, over Kelsterbach
Kelsterbach
Kelsterbach is a town in Groß-Gerau district in Hessen, Germany. It lies on Frankfurt's southwestern outskirts at a bend on the left bank of the river Main, right where a small brook, called the Kelster empties into the river...
near Frankfurt, Rheinau
Rheinau (Baden)
Rheinau is a town in southwestern Baden-Württemberg, Germany and is part of the district of Ortenau.-Geography:Rheinau is located in the Upper Rhine River Plains directly on the Rhine and as such at the German-French border...
near Mannheim
Mannheim
Mannheim is a city in southwestern Germany. With about 315,000 inhabitants, Mannheim is the second-largest city in the Bundesland of Baden-Württemberg, following the capital city of Stuttgart....
, Ludwigsburg
Ludwigsburg
Ludwigsburg is a city in Baden-Württemberg, Germany, about north of Stuttgart city centre, near the river Neckar. It is the largest and primary city of the Ludwigsburg urban district with about 87,000 inhabitants...
–Hoheneck near Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
. This line comprises the North-South interconnect
North-South Powerline
The North–South Powerline, or Nord–Süd-Leitung, is the world's oldest interconnection for electric current. It was built between 1924 and 1929 by RWE AG, to transport electricity produced in the hydro-electric power plants in Vorarlberg, Austria and the southern Black Forest to the Ruhr...
, at the time one of the world's largest power systems. The masts of this line were designed for eventual upgrade to 380 kV. However the first transmission at 380 kV in Germany was on October 5, 1957 between the substations in Rommerskirchen
Rommerskirchen
Rommerskirchen is the southernmost municipality in the Rhein-Kreis Neuss, in North Rhine-Westphalia, Germany.-Notable places:Rommerskirchen possesses rich historical inheritances, including numerous remains of the Roman Villae Rusticae, and those from several Frankish settlements. The town centre...
and Ludwigsburg
Ludwigsburg
Ludwigsburg is a city in Baden-Württemberg, Germany, about north of Stuttgart city centre, near the river Neckar. It is the largest and primary city of the Ludwigsburg urban district with about 87,000 inhabitants...
–Hoheneck.
The world's first 380 kV power line was built in Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, the 952 km Harsprånget - Hallsberg
Hallsberg
Hallsberg is a bimunicipal locality and the seat of Hallsberg Municipality, Örebro County, Sweden with 7,122 inhabitants in 2005. It is also partly located in Kumla Municipality.-Overview:...
line in 1952. In 1965, the first extra-high-voltage transmission at 735 kV took place on a Hydro-Québec
Hydro-Québec
Hydro-Québec is a government-owned public utility established in 1944 by the Government of Quebec. Based in Montreal, the company is in charge of the generation, transmission and distribution of electricity across Quebec....
transmission line. In 1982 the first transmission at 1200 kV was in the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
.
The rapid industrialization in the 20th century made electrical transmission lines and grids a critical part of the economic infrastructure in most industrialized nations. Interconnection of local generation plants and small distribution networks was greatly spurred by the requirements of World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
, where large electrical generating plants were built by governments to provide power to munitions factories; later these plants were connected to supply civil load through long-distance transmission.
Small municipal electrical utilities did not necessarily desire to reduce the cost of each unit of electricity sold; to some extent, especially during the period 1880–1890, electrical lighting was considered a luxury product and electric power was not substituted for steam power. Engineers such as Samuel Insull
Samuel Insull
Samuel Insull was an Anglo-American innovator and investor based in Chicago who greatly contributed to creating an integrated electrical infrastructure in the United States. Insull was notable for purchasing utilities and railroads using holding companies, as well as the abuse of them...
in the United States and Sebastian Z. De Ferranti
Sebastian Ziani de Ferranti
Sebastian Pietro Innocenzo Adhemar Ziani de Ferranti was an electrical engineer and inventor.-Personal life:...
in the United Kingdom were instrumental in overcoming technical, economic, regulatory and political difficulties in development of long-distance electric power transmission. By introduction of electric power transmission networks, in the city of London the cost of a kilowatt-hour was reduced to one-third in a ten-year period.
In 1926 electrical networks
Grid (electricity)
An electrical grid is a vast, interconnected network for delivering electricity from suppliers to consumers. It consists of three main components: 1) generating plants that produce electricity from combustible fuels or non-combustible fuels ; 2) transmission lines that carry electricity from power...
in the United Kingdom began to be interconnected in the National Grid, initially operating at 132,000 volts.