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127-516: Approved: [REDACTED] The Navi Mumbai Metro is a rapid transit system in the city of Navi Mumbai , Maharashtra , India . The planning and construction of the Navi Mumbai Metro was overseen by the City and Industrial Development Corporation (CIDCO). The system is planned to consist of five rail lines covering a total distance of 106.4 kilometres (66.1 mi), out of which one

254-403: A balanced signaling system, so that the two wires carry equal but opposite currents. Each wire in a twisted pair radiates a signal, but it is effectively cancelled by radiation from the other wire, resulting in almost no radiation loss. Coaxial cables are commonly used at audio frequencies and above for convenience. A coaxial cable has a conductive wire inside a conductive tube, separated by

381-448: A dielectric layer. The current flowing on the surface of the inner conductor is equal and opposite to the current flowing on the inner surface of the outer tube. The electromagnetic field is thus completely contained within the tube, and (ideally) no energy is lost to radiation or coupling outside the tube. Coaxial cables have acceptably small losses for frequencies up to about 5 GHz. For microwave frequencies greater than 5 GHz,

508-477: A power plant , energy is generated at a convenient voltage for the design of a generator , and then stepped up to a high voltage for transmission. Near the loads, the transmission voltage is stepped down to the voltages used by equipment. Consumer voltages vary somewhat depending on the country and size of load, but generally motors and lighting are built to use up to a few hundred volts between phases. The voltage delivered to equipment such as lighting and motor loads

635-425: A body of water), which are potential congestion sites but also offer an opportunity for transfers between lines. Ring lines provide good coverage, connect between the radial lines and serve tangential trips that would otherwise need to cross the typically congested core of the network. A rough grid pattern can offer a wide variety of routes while still maintaining reasonable speed and frequency of service. A study of

762-454: A code for its stations. Unlike that of Singapore's MRT, it is mostly numbers. Based on the line number, for example Sinyongsan station, is coded as station 429. Being on Line 4, the first number of the station code is 4. The last two numbers are the station number on that line. Interchange stations can have multiple codes. Like City Hall station in Seoul which is served by Line 1 and Line 2. It has

889-651: A code of 132 and 201 respectively. The Line 2 is a circle line and the first stop is City Hall, therefore, City Hall has the station code of 201. For lines without a number like Bundang line it will have an alphanumeric code. Lines without a number that are operated by KORAIL will start with the letter 'K'. With widespread use of the Internet and cell phones globally, transit operators now use these technologies to present information to their users. In addition to online maps and timetables, some transit operators now offer real-time information which allows passengers to know when

1016-440: A compromise between low frequency for traction and heavy induction motors, while still allowing incandescent lighting to operate (although with noticeable flicker). Most of the 25 Hz residential and commercial customers for Niagara Falls power were converted to 60 Hz by the late 1950s, although some 25 Hz industrial customers still existed as of the start of the 21st century. 16.7 Hz power (formerly 16 2/3 Hz)

1143-583: A conventional track is often provided in case of flat tires and for switching . There are also some rubber-tired systems that use a central guide rail , such as the Sapporo Municipal Subway and the NeoVal system in Rennes , France. Advocates of this system note that it is much quieter than conventional steel-wheeled trains, and allows for greater inclines given the increased traction of

1270-405: A dedicated right-of-way are typically used only outside dense areas, since they create a physical barrier in the urban fabric that hinders the flow of people and vehicles across their path and have a larger physical footprint. This method of construction is the cheapest as long as land values are low. It is often used for new systems in areas that are planned to fill up with buildings after the line

1397-490: A direct current does not create electromagnetic waves. At very high frequencies, the current no longer flows in the wire, but effectively flows on the surface of the wire, within a thickness of a few skin depths . The skin depth is the thickness at which the current density is reduced by 63%. Even at relatively low frequencies used for power transmission (50 Hz – 60 Hz), non-uniform distribution of current still occurs in sufficiently thick conductors . For example,

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1524-437: A form of dielectric waveguides, can be used. For such frequencies, the concepts of voltages and currents are no longer used. Alternating currents are accompanied (or caused) by alternating voltages. An AC voltage v can be described mathematically as a function of time by the following equation: where The peak-to-peak value of an AC voltage is defined as the difference between its positive peak and its negative peak. Since

1651-459: A higher voltage requires less loss-producing current than for the same power at a lower voltage. Power is often transmitted at hundreds of kilovolts on pylons , and transformed down to tens of kilovolts to be transmitted on lower level lines, and finally transformed down to 100 V – 240 V for domestic use. High voltages have disadvantages, such as the increased insulation required, and generally increased difficulty in their safe handling. In

1778-418: A large number of factors, including geographical barriers, existing or expected travel patterns, construction costs, politics, and historical constraints. A transit system is expected to serve an area of land with a set of lines , which consist of shapes summarized as "I", "L", "U", "S", and "O" shapes or loops. Geographical barriers may cause chokepoints where transit lines must converge (for example, to cross

1905-652: A large part of the network, for example, in outer suburbs, runs at ground level. In most of Britain , a subway is a pedestrian underpass . The terms Underground and Tube are used for the London Underground . The North East England Tyne and Wear Metro , mostly overground, is known as the Metro . In Scotland , the Glasgow Subway underground rapid transit system is known as the Subway . In Ireland ,

2032-957: A lighting system where sets of induction coils were installed along a high voltage AC line. Instead of changing voltage, the primary windings transferred power to the secondary windings which were connected to one or several 'electric candles' (arc lamps) of his own design, used to keep the failure of one lamp from disabling the entire circuit. In 1878, the Ganz factory , Budapest, Hungary, began manufacturing equipment for electric lighting and, by 1883, had installed over fifty systems in Austria-Hungary . Their AC systems used arc and incandescent lamps, generators, and other equipment. Alternating current systems can use transformers to change voltage from low to high level and back, allowing generation and consumption at low voltages but transmission, possibly over great distances, at high voltage, with savings in

2159-452: A line is obtained by multiplying the car capacity, the train length, and the service frequency . Heavy rapid transit trains might have six to twelve cars, while lighter systems may use four or fewer. Cars have a capacity of 100 to 150 passengers, varying with the seated to standing ratio  – more standing gives higher capacity. The minimum time interval between trains is shorter for rapid transit than for mainline railways owing to

2286-615: A metro. In Spain, such systems are present in Madrid , Barcelona , Bilbao and Valencia . In Portugal, Lisbon has a metro. The Italian cities of Catania , Genoa , Milan , Naples , Rome and Turin also have metro lines. In Germany and Austria they rapid transit is known as U-Bahn , which are often supported by S-Bahn systems. In Germany, U-Bahn systems exist in Berlin , Hamburg , Munich and Nuremberg , while in Austria such

2413-725: A public hearing on 21 May 2010 reported no major objections to the plan. CIDCO was named as the implementing agency of the Belapur–Pendhar–Kalamboli–Khandeshwar line, under the Indian Tramway Act 1886, by the Government of Maharashtra on 30 September 2010. The metro's foundation stone was laid on 1 May 2011 by Chief Minister Prithviraj Chavan , and general foundation work on the system's first phase commenced in October 2011. In March 2012, CIDCO released

2540-401: A rapid transit setting. Alternating current Alternating current ( AC ) is an electric current that periodically reverses direction and changes its magnitude continuously with time ranging between some maximum and minimum values, in contrast to direct current (DC), which flows only in one direction. Alternating current is the type of electric current through which electric power

2667-522: A single center-tapped transformer giving two live conductors, is a common distribution scheme for residential and small commercial buildings in North America. This arrangement is sometimes incorrectly referred to as "two phase". A similar method is used for a different reason on construction sites in the UK. Small power tools and lighting are supposed to be supplied by a local center-tapped transformer with

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2794-565: A specialized transit police may be established. These security measures are normally integrated with measures to protect revenue by checking that passengers are not travelling without paying. Some subway systems, such as the Beijing Subway , which is ranked by Worldwide Rapid Transit Data as the "World's Safest Rapid Transit Network" in 2015, incorporates airport-style security checkpoints at every station. Rapid transit systems have been subject to terrorism with many casualties, such as

2921-608: A system exists in Vienna . In addition, the small, car-free town of Serfaus in the Austrian state of Tyrol also features a short U-Bahn line. There are no U-Bahn systems in the German-speaking part of Switzerland, but the city of Lausanne has its own, small metro system. In Zurich, Switzerland's largest city, a project for a U-Bahn network was stopped by a referendum in the 1970s and instead its S-Bahn system

3048-555: A voltage of 55 V between each power conductor and earth. This significantly reduces the risk of electric shock in the event that one of the live conductors becomes exposed through an equipment fault whilst still allowing a reasonable voltage of 110 V between the two conductors for running the tools. A third wire , called the bond (or earth) wire, is often connected between non-current-carrying metal enclosures and earth ground. This conductor provides protection from electric shock due to accidental contact of circuit conductors with

3175-403: A wire that is made of a non-perfect conductor (a conductor with finite, rather than infinite, electrical conductivity) pushes the alternating current, along with their associated electromagnetic fields, away from the wire's center. The phenomenon of alternating current being pushed away from the center of the conductor is called skin effect , and a direct current does not exhibit this effect, since

3302-470: Is 230 × R × W × 2 {\displaystyle 230\times R\times W\times 2} , that is 460 RW. During the course of one cycle (two cycle as the power) the voltage rises from zero to 325 V, the power from zero to 460 RW, and both falls through zero. Next, the voltage descends to reverse direction, -325 V, but the power ascends again to 460 RW, and both returns to zero. Alternating current

3429-645: Is a sine wave , whose positive half-period corresponds with positive direction of the current and vice versa (the full period is called a cycle ). In certain applications, like guitar amplifiers , different waveforms are used, such as triangular waves or square waves . Audio and radio signals carried on electrical wires are also examples of alternating current. These types of alternating current carry information such as sound (audio) or images (video) sometimes carried by modulation of an AC carrier signal. These currents typically alternate at higher frequencies than those used in power transmission. Electrical energy

3556-801: Is a shortened reference to a metropolitan area . Rapid transit systems such as the Washington Metrorail , Los Angeles Metro Rail , the Miami Metrorail , and the Montreal Metro are generally called the Metro . In Philadelphia , the term "El" is used for the Market–Frankford Line which runs mostly on an elevated track, while the term "subway" applies to the Broad Street Line which is almost entirely underground. Chicago 's commuter rail system that serves

3683-608: Is a single corporate image for the entire transit authority, but the rapid transit uses its own logo that fits into the profile. A transit map is a topological map or schematic diagram used to show the routes and stations in a public transport system. The main components are color-coded lines to indicate each line or service, with named icons to indicate stations. Maps may show only rapid transit or also include other modes of public transport. Transit maps can be found in transit vehicles, on platforms , elsewhere in stations, and in printed timetables . Maps help users understand

3810-506: Is built. Most rapid transit trains are electric multiple units with lengths from three to over ten cars. Crew sizes have decreased throughout history, with some modern systems now running completely unstaffed trains. Other trains continue to have drivers, even if their only role in normal operation is to open and close the doors of the trains at stations. Power is commonly delivered by a third rail or by overhead wires . The whole London Underground network uses fourth rail and others use

3937-530: Is called Litz wire . This measure helps to partially mitigate skin effect by forcing more equal current throughout the total cross section of the stranded conductors. Litz wire is used for making high-Q inductors , reducing losses in flexible conductors carrying very high currents at lower frequencies, and in the windings of devices carrying higher radio frequency current (up to hundreds of kilohertz), such as switch-mode power supplies and radio frequency transformers . As written above, an alternating current

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4064-462: Is delivered to businesses and residences, and it is the type of electric current that consumers typically use when they plug kitchen appliances , televisions , fans and electric lamps into a wall socket . The abbreviations AC and DC are often used to mean simply Alternating Current and Direct Current , respectively, as when they modify current or voltage . The usual waveform of alternating current in most electric power circuits

4191-505: Is distributed as alternating current because AC voltage may be increased or decreased with a transformer . This allows the power to be transmitted through power lines efficiently at high voltage , which reduces the energy lost as heat due to resistance of the wire, and transformed to a lower, safer voltage for use. Use of a higher voltage leads to significantly more efficient transmission of power. The power losses ( P w {\displaystyle P_{\rm {w}}} ) in

4318-439: Is double of the one of the voltage's. To illustrate these concepts, consider a 230 V AC mains supply used in many countries around the world. It is so called because its root mean square value is 230 V. This means that the time-averaged power delivered P average {\displaystyle P_{\text{average}}} is equivalent to the power delivered by a DC voltage of 230 V. To determine

4445-469: Is made of electric charge under periodic acceleration , which causes radiation of electromagnetic waves . Energy that is radiated is lost. Depending on the frequency, different techniques are used to minimize the loss due to radiation. At frequencies up to about 1 GHz, pairs of wires are twisted together in a cable, forming a twisted pair . This reduces losses from electromagnetic radiation and inductive coupling . A twisted pair must be used with

4572-416: Is necessary, rolling stock with a smaller loading gauge from one sub network may be transported along other lines that use larger trains. On some networks such operations are part of normal services. Most rapid transit systems use conventional standard gauge railway track . Since tracks in subway tunnels are not exposed to rain , snow , or other forms of precipitation , they are often fixed directly to

4699-500: Is operational and the other four are being planned. The foundation stone for the project was laid on 1 May 2011, with a target completion date of 2014. After over 9 years of delays, due to slowdowns in construction caused by lack of labour and adequate funding, along with land acquisition issues, the Line-1 of the metro commenced operations on 17 November 2023. The Navi Mumbai Metro projects received formal approval on 29 April 2010, and

4826-521: Is probably by Guillaume Duchenne , inventor and developer of electrotherapy . In 1855, he announced that AC was superior to direct current for electrotherapeutic triggering of muscle contractions. Alternating current technology was developed further by the Hungarian Ganz Works company (1870s), and in the 1880s: Sebastian Ziani de Ferranti , Lucien Gaulard , and Galileo Ferraris . In 1876, Russian engineer Pavel Yablochkov invented

4953-555: Is referred to simply as "the subway", despite 40% of the system running above ground. The term "L" or "El" is not used for elevated lines in general as the lines in the system are already designated with letters and numbers. The "L" train or L (New York City Subway service) refers specifically to the 14th Street–Canarsie Local line, and not other elevated trains. Similarly, the Toronto Subway is referred to as "the subway", with some of its system also running above ground. These are

5080-412: Is serviced by at least one specific route with trains stopping at all or some of the line's stations. Most systems operate several routes, and distinguish them by colors, names, numbering, or a combination thereof. Some lines may share track with each other for a portion of their route or operate solely on their own right-of-way. Often a line running through the city center forks into two or more branches in

5207-446: Is standardized, with an allowable range of voltage over which equipment is expected to operate. Standard power utilization voltages and percentage tolerance vary in the different mains power systems found in the world. High-voltage direct-current (HVDC) electric power transmission systems have become more viable as technology has provided efficient means of changing the voltage of DC power. Transmission with high voltage direct current

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5334-568: Is still used in some European rail systems, such as in Austria , Germany , Norway , Sweden and Switzerland . Off-shore, military, textile industry, marine, aircraft, and spacecraft applications sometimes use 400 Hz, for benefits of reduced weight of apparatus or higher motor speeds. Computer mainframe systems were often powered by 400 Hz or 415 Hz for benefits of ripple reduction while using smaller internal AC to DC conversion units. A direct current flows uniformly throughout

5461-748: Is the most commonly used term for underground rapid transit systems used by non-native English speakers. Rapid transit systems may be named after the medium by which passengers travel in busy central business districts ; the use of tunnels inspires names such as subway , underground , Untergrundbahn ( U-Bahn ) in German, or the Tunnelbana (T-bana) in Swedish. The use of viaducts inspires names such as elevated ( L or el ), skytrain , overhead , overground or Hochbahn in German. One of these terms may apply to an entire system, even if

5588-422: Is therefore V peak − ( − V peak ) = 2 V peak {\displaystyle V_{\text{peak}}-(-V_{\text{peak}})=2V_{\text{peak}}} . Below an AC waveform (with no DC component ) is assumed. The RMS voltage is the square root of the mean over one cycle of the square of the instantaneous voltage. The relationship between voltage and

5715-425: Is used to transmit information , as in the cases of telephone and cable television . Information signals are carried over a wide range of AC frequencies. POTS telephone signals have a frequency of about 3 kHz, close to the baseband audio frequency. Cable television and other cable-transmitted information currents may alternate at frequencies of tens to thousands of megahertz. These frequencies are similar to

5842-627: The Dublin Area Rapid Transit is despite the name considered a commuter rail due to usage of mainline railways. In France, large cities, such as Paris , Marseille and Lyon , feature a Métro . Also the smaller cities of Lille Rennes have a light metro. Furthermore, Brussels in Belgium, and Amsterdam and Rotterdam in the Netherlands have metro systems in place. Several Southern European contries also have

5969-752: The Hudson and Manhattan Railroad K-series cars from 1958, the New York City Subway R38 and R42 cars from the late-1960s, and the Nagoya Municipal Subway 3000 series , Osaka Municipal Subway 10 series and MTR M-Train EMUs from the 1970s, were generally only made possible largely due to the relatively generous loading gauges of these systems and also adequate open-air sections to dissipate hot air from these air conditioning units. Especially in some rapid transit systems such as

6096-477: The Khandeshwar railway station , terminating at the proposed Navi Mumbai International Airport . In mid-2012, CIDCO awarded the ₹ 321 crore (US$ 38 million) contract for the construction of the 11.1 km (6.9 mi) section from Belapur to Pendhar to a consortium of Sanjose (Spain), Mahavira Road and Infrastructure (Navi Mumbai), and Supreme Infrastructure (Mumbai). The original deadline to complete

6223-429: The London Underground . In 1868, New York opened the elevated West Side and Yonkers Patent Railway , initially a cable-hauled line using stationary steam engines . As of 2021 , China has the largest number of rapid transit systems in the world  – 40 in number, running on over 4,500 km (2,800 mi) of track – and was responsible for most of the world's rapid-transit expansion in

6350-740: The Metropolitan Railway opened publicly in London in 1863. High capacity monorails with larger and longer trains can be classified as rapid transit systems. Such monorail systems recently started operating in Chongqing and São Paulo . Light metro is a subclass of rapid transit that has the speed and grade separation of a "full metro" but is designed for smaller passenger numbers. It often has smaller loading gauges, lighter train cars and smaller consists of typically two to four cars. Light metros are typically used as feeder lines into

6477-578: The Montreal Metro (opened 1966) and Sapporo Municipal Subway (opened 1971), their entirely enclosed nature due to their use of rubber-tyred technology to cope with heavy snowfall experienced by both cities in winter precludes any air-conditioning retrofits of rolling stock due to the risk of heating the tunnels to temperatures that would be too hot for passengers and for train operations. In many cities, metro networks consist of lines operating different sizes and types of vehicles. Although these sub-networks may not often be connected by track, in cases when it

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6604-589: The Prague Metro . The London Underground and Paris Métro are densely built systems with a matrix of crisscrossing lines throughout the cities. The Chicago 'L' has most of its lines converging on The Loop , the main business, financial, and cultural area. Some systems have a circular line around the city center connecting to radially arranged outward lines, such as the Moscow Metro 's Koltsevaya Line and Beijing Subway 's Line 10 . The capacity of

6731-685: The Singapore MRT , Changi Airport MRT station has the alphanumeric code CG2, indicating its position as the 2nd station on the Changi Airport branch of the East West Line. Interchange stations have at least two codes, for example, Raffles Place MRT station has two codes, NS26 and EW14, the 26th station on the North South Line and the 14th station on the East West Line. The Seoul Metro is another example that utilizes

6858-849: The Westinghouse Electric in Pittsburgh, Pennsylvania, on January 8, 1886. The new firm became active in developing alternating current (AC) electric infrastructure throughout the United States. The Edison Electric Light Company held an option on the US rights for the Ganz ZBD transformers, requiring Westinghouse to pursue alternative designs on the same principles. George Westinghouse had bought Gaulard and Gibbs' patents for $ 50,000 in February 1886. He assigned to William Stanley

6985-450: The deep tube lines . Historically, rapid transit trains used ceiling fans and openable windows to provide fresh air and piston-effect wind cooling to riders. From the 1950s to the 1990s (and in most of Europe until the 2000s), many rapid transit trains from that era were also fitted with forced-air ventilation systems in carriage ceiling units for passenger comfort. Early rapid transit rolling stock fitted with air conditioning , such as

7112-409: The linear motor for propulsion. Some urban rail lines are built to a loading gauge as large as that of main-line railways ; others are built to a smaller one and have tunnels that restrict the size and sometimes the shape of the train compartments. One example is most of the London Underground , which has acquired the informal term "tube train" due to the cylindrical shape of the trains used on

7239-432: The 15 world largest subway systems suggested a universal shape composed of a dense core with branches radiating from it. Rapid transit operators have often built up strong brands , often focused on easy recognition – to allow quick identification even in the vast array of signage found in large cities – combined with the desire to communicate speed, safety, and authority. In many cities, there

7366-488: The 1995 Tokyo subway sarin gas attack and the 2005 " 7/7 " terrorist bombings on the London Underground. Some rapid transport trains have extra features such as wall sockets, cellular reception, typically using a leaky feeder in tunnels and DAS antennas in stations, as well as Wi-Fi connectivity. The first metro system in the world to enable full mobile phone reception in underground stations and tunnels

7493-621: The 2010s. The world's longest single-operator rapid transit system by route length is the Shanghai Metro . The world's largest single rapid transit service provider by number of stations (472 stations in total) is the New York City Subway . The busiest rapid transit systems in the world by annual ridership are the Shanghai Metro, Tokyo subway system , Seoul Metro and the Moscow Metro . The term Metro

7620-532: The 21st century, most new expansions and systems are located in Asia, with China becoming the world's leader in metro expansion, operating some of the largest and busiest systems while possessing almost 60 cities that are operating, constructing or planning a rapid transit system . Rapid transit is used for local transport in cities , agglomerations , and metropolitan areas to transport large numbers of people often short distances at high frequency . The extent of

7747-752: The AC system at the Grosvenor Gallery power station in 1886 for the London Electric Supply Corporation (LESCo) including alternators of his own design and open core transformer designs with serial connections for utilization loads - similar to Gaulard and Gibbs. In 1890, he designed their power station at Deptford and converted the Grosvenor Gallery station across the Thames into an electrical substation , showing

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7874-526: The CIDCO head office and all development projects in the region. These will include the metro project and any progress on the airport project". The Navi Mumbai Metro is planned to consist of five lines, totaling 106.4 kilometres (66.1 mi) in length. As of 2017, Line 1 of the metro was slated to commence operations in November 2023, which it ultimately did on the 17th of that month. [REDACTED] All

8001-797: The Chinese company CSR Zhuzhou signed a contract with CIDCO to supply rolling stock for the first phase of the metro's Line 1. The three-car trainsets are 64.6 metres (212 ft) long and 3.1 metres (10 ft 2 in) wide, with a passenger capacity of around 1,100 and a maximum speed of 90 km/h (56 mph). The trains feature stainless steel bodies, air-conditioning and LED lighting. Rapid transit Modern services on rapid transit systems are provided on designated lines between stations typically using electric multiple units on railway tracks . Some systems use guided rubber tires , magnetic levitation ( maglev ), or monorail . The stations typically have high platforms, without steps inside

8128-428: The beginning of rapid transit. Initial experiences with steam engines, despite ventilation, were unpleasant. Experiments with pneumatic railways failed in their extended adoption by cities. In 1890, the City & South London Railway was the first electric-traction rapid transit railway, which was also fully underground. Prior to opening, the line was to be called the "City and South London Subway", thus introducing

8255-413: The biggest difference being that waveguides have no inner conductor. Waveguides can have any arbitrary cross section, but rectangular cross sections are the most common. Because waveguides do not have an inner conductor to carry a return current, waveguides cannot deliver energy by means of an electric current , but rather by means of a guided electromagnetic field . Although surface currents do flow on

8382-547: The city of Pomona, California , which was 14 miles away. Meanwhile, the possibility of transferring electrical power from a waterfall at a distance was explored at the Grängesberg mine in Sweden. A 45  m fall at Hällsjön, Smedjebackens kommun, where a small iron work had been located, was selected. In 1893, a three-phase 9.5  kv system was used to transfer 400 horsepower a distance of 15  km , becoming

8509-454: The cost of conductors and energy losses. A bipolar open-core power transformer developed by Lucien Gaulard and John Dixon Gibbs was demonstrated in London in 1881, and attracted the interest of Westinghouse . They also exhibited the invention in Turin in 1884. However, these early induction coils with open magnetic circuits are inefficient at transferring power to loads . Until about 1880,

8636-514: The cross-section of a homogeneous electrically conducting wire. An alternating current of any frequency is forced away from the wire's center, toward its outer surface. This is because an alternating current (which is the result of the acceleration of electric charge ) creates electromagnetic waves (a phenomenon known as electromagnetic radiation ). Electric conductors are not conducive to electromagnetic waves (a perfect electric conductor prohibits all electromagnetic waves within its boundary), so

8763-411: The cross-sectional area. A conductor's AC resistance is higher than its DC resistance, causing a higher energy loss due to ohmic heating (also called I R loss). For low to medium frequencies, conductors can be divided into stranded wires, each insulated from the others, with the relative positions of individual strands specially arranged within the conductor bundle. Wire constructed using this technique

8890-476: The design of electric motors, particularly for hoisting, crushing and rolling applications, and commutator-type traction motors for applications such as railways . However, low frequency also causes noticeable flicker in arc lamps and incandescent light bulbs . The use of lower frequencies also provided the advantage of lower transmission losses, which are proportional to frequency. The original Niagara Falls generators were built to produce 25 Hz power, as

9017-414: The display of the transit network. Often this has the effect of compressing the distance between stations in the outer area of the system, and expanding distances between those close to the center. Some systems assign unique alphanumeric codes to each of their stations to help commuters identify them, which briefly encodes information about the line it is on, and its position on the line. For example, on

9144-508: The electrical system to a safe state. All bond wires are bonded to ground at the main service panel, as is the neutral/identified conductor if present. The frequency of the electrical system varies by country and sometimes within a country; most electric power is generated at either 50 or 60  Hertz . Some countries have a mixture of 50 Hz and 60 Hz supplies, notably electricity power transmission in Japan . A low frequency eases

9271-522: The electromagnetic wave frequencies often used to transmit the same types of information over the air . The first alternator to produce alternating current was an electric generator based on Michael Faraday 's principles constructed by the French instrument maker Hippolyte Pixii in 1832. Pixii later added a commutator to his device to produce the (then) more commonly used direct current. The earliest recorded practical application of alternating current

9398-611: The entire metropolitan area is called Metra (short for Met ropolitan Ra il), while its rapid transit system that serves the city is called the "L" . Boston's subway system is known locally as "The T". In Atlanta , the Metropolitan Atlanta Rapid Transit Authority goes by the acronym "MARTA." In the San Francisco Bay Area , residents refer to Bay Area Rapid Transit by its acronym "BART". The New York City Subway

9525-414: The experiments; In their joint 1885 patent applications for novel transformers (later called ZBD transformers), they described two designs with closed magnetic circuits where copper windings were either wound around a ring core of iron wires or else surrounded by a core of iron wires. In both designs, the magnetic flux linking the primary and secondary windings traveled almost entirely within the confines of

9652-479: The first commercial application. In 1893, Westinghouse built an alternating current system for the Chicago World Exposition . In 1893, Decker designed the first American commercial three-phase power plant using alternating current—the hydroelectric Mill Creek No. 1 Hydroelectric Plant near Redlands, California . Decker's design incorporated 10 kV three-phase transmission and established

9779-516: The floor rather than resting on ballast , such as normal railway tracks. An alternate technology, using rubber tires on narrow concrete or steel roll ways , was pioneered on certain lines of the Paris Métro and Mexico City Metro , and the first completely new system to use it was in Montreal , Canada. On most of these networks, additional horizontal wheels are required for guidance, and

9906-564: The inner walls of the waveguides, those surface currents do not carry power. Power is carried by the guided electromagnetic fields. The surface currents are set up by the guided electromagnetic fields and have the effect of keeping the fields inside the waveguide and preventing leakage of the fields to the space outside the waveguide. Waveguides have dimensions comparable to the wavelength of the alternating current to be transmitted, so they are feasible only at microwave frequencies. In addition to this mechanical feasibility, electrical resistance of

10033-439: The interconnections between different parts of the system; for example, they show the interchange stations where passengers can transfer between lines. Unlike conventional maps, transit maps are usually not geographically accurate, but emphasize the topological connections among the different stations. The graphic presentation may use straight lines and fixed angles, and often a fixed minimum distance between stations, to simplify

10160-511: The iron core, with no intentional path through air (see toroidal cores ). The new transformers were 3.4 times more efficient than the open-core bipolar devices of Gaulard and Gibbs. The Ganz factory in 1884 shipped the world's first five high-efficiency AC transformers. This first unit had been manufactured to the following specifications: 1,400 W, 40 Hz, 120:72 V, 11.6:19.4 A, ratio 1.67:1, one-phase, shell form. The ZBD patents included two other major interrelated innovations: one concerning

10287-625: The limitations of the direct current system. In 1886, the ZBD engineers designed the world's first power station that used AC generators to power a parallel-connected common electrical network, the steam-powered Rome-Cerchi power plant. The reliability of the AC technology received impetus after the Ganz Works electrified a large European metropolis: Rome in 1886. Building on the advancement of AC technology in Europe, George Westinghouse founded

10414-602: The lines of the Lyon Metro includes a section of rack (cog) railway , while the Carmelit , in Haifa, is an underground funicular . For elevated lines, another alternative is the monorail , which can be built either as straddle-beam monorails or as a suspended monorail . While monorails have never gained wide acceptance outside Japan, there are some such as Chongqing Rail Transit 's monorail lines which are widely used in

10541-429: The losses (due mainly to the dielectric separating the inner and outer tubes being a non-ideal insulator) become too large, making waveguides a more efficient medium for transmitting energy. Coaxial cables often use a perforated dielectric layer to separate the inner and outer conductors in order to minimize the power dissipated by the dielectric. Waveguides are similar to coaxial cables, as both consist of tubes, with

10668-419: The lower speed is preferable for larger machines. If the load on a three-phase system is balanced equally among the phases, no current flows through the neutral point . Even in the worst-case unbalanced (linear) load, the neutral current will not exceed the highest of the phase currents. Non-linear loads (e.g. the switch-mode power supplies widely used) may require an oversized neutral bus and neutral conductor in

10795-557: The main rapid transit system. For instance, the Wenhu Line of the Taipei Metro serves many relatively sparse neighbourhoods and feeds into and complements the high capacity metro lines. Some systems have been built from scratch, others are reclaimed from former commuter rail or suburban tramway systems that have been upgraded, and often supplemented with an underground or elevated downtown section. Ground-level alignments with

10922-484: The main street of Great Barrington. The spread of Westinghouse and other AC systems triggered a push back in late 1887 by Thomas Edison (a proponent of direct current), who attempted to discredit alternating current as too dangerous in a public campaign called the " war of the currents ". In 1888, alternating current systems gained further viability with introduction of a functional AC motor , something these systems had lacked up till then. The design, an induction motor ,

11049-538: The maximum value of sin ⁡ ( x ) {\displaystyle \sin(x)} is +1 and the minimum value is −1, an AC voltage swings between + V peak {\displaystyle +V_{\text{peak}}} and − V peak {\displaystyle -V_{\text{peak}}} . The peak-to-peak voltage, usually written as V pp {\displaystyle V_{\text{pp}}} or V P-P {\displaystyle V_{\text{P-P}}} ,

11176-469: The metal chassis of portable appliances and tools. Bonding all non-current-carrying metal parts into one complete system ensures there is always a low electrical impedance path to ground sufficient to carry any fault current for as long as it takes for the system to clear the fault. This low impedance path allows the maximum amount of fault current, causing the overcurrent protection device (breakers, fuses) to trip or burn out as quickly as possible, bringing

11303-590: The metro's complete master plan, including a proposed connection to the Mumbai Metro . In February 2017, RITES submitted an interim detailed project report (DPR) for Lines II, III and IV of the Navi Mumbai Metro. In February 2013, thousands of villagers in the Navi Mumbai area protested against CIDCO's inaction on local housing developments and its failure to provide restitution for locals affected by infrastructure projects. The protesters pledged to "shut down

11430-418: The network map "readable" by illiterate people, this system has since become an "icon" of the system. Compared to other modes of transport, rapid transit has a good safety record, with few accidents. Rail transport is subject to strict safety regulations , with requirements for procedure and maintenance to minimize risk. Head-on collisions are rare due to use of double track, and low operating speeds reduce

11557-402: The next vehicle will arrive, and expected travel times. The standardized GTFS data format for transit information allows many third-party software developers to produce web and smartphone app programs which give passengers customized updates regarding specific transit lines and stations of interest. Mexico City Metro uses a unique pictogram for each station. Originally intended to help make

11684-425: The non-ideal metals forming the walls of the waveguide causes dissipation of power (surface currents flowing on lossy conductors dissipate power). At higher frequencies, the power lost to this dissipation becomes unacceptably large. At frequencies greater than 200 GHz, waveguide dimensions become impractically small, and the ohmic losses in the waveguide walls become large. Instead, fiber optics , which are

11811-902: The occurrence and severity of rear-end collisions and derailments . Fire is more of a danger underground, such as the King's Cross fire in London in November 1987, which killed 31 people. Systems are generally built to allow evacuation of trains at many places throughout the system. High platforms , usually over 1 meter / 3 feet, are a safety risk, as people falling onto the tracks have trouble climbing back. Platform screen doors are used on some systems to eliminate this danger. Rapid transit facilities are public spaces and may suffer from security problems: petty crimes , such as pickpocketing and baggage theft, and more serious violent crimes , as well as sexual assaults on tightly packed trains and platforms. Security measures include video surveillance , security guards , and conductors . In some countries

11938-603: The only two North American systems that are primarily called "subways". In most of Southeast Asia and in Taiwan , rapid transit systems are primarily known by the acronym MRT . The meaning varies from one country to another. In Indonesia , the acronym stands for Moda Raya Terpadu or Integrated Mass [Transit] Mode in English. In the Philippines , it stands for Metro Rail Transit . Two underground lines use

12065-587: The outset. Budapest , Chicago , Glasgow , Boston and New York City all converted or purpose-designed and built electric rail services. Advancements in technology have allowed new automated services. Hybrid solutions have also evolved, such as tram-train and premetro , which incorporate some of the features of rapid transit systems. In response to cost, engineering considerations and topological challenges some cities have opted to construct tram systems, particularly those in Australia, where density in cities

12192-435: The paradigm for AC power transmission from a high voltage supply to a low voltage load was a series circuit. Open-core transformers with a ratio near 1:1 were connected with their primaries in series to allow use of a high voltage for transmission while presenting a low voltage to the lamps. The inherent flaw in this method was that turning off a single lamp (or other electric device) affected the voltage supplied to all others on

12319-431: The peak voltage (amplitude), we can rearrange the above equation to: For 230 V AC, the peak voltage V peak {\displaystyle V_{\text{peak}}} is therefore 230  V × 2 {\displaystyle 230{\text{ V}}\times {\sqrt {2}}} , which is about 325 V, and the peak power P peak {\displaystyle P_{\text{peak}}}

12446-549: The phases of Line 1 will be constructed and funded by CIDCO. Lines 2 and 3 will be funded by the Navi Mumbai Municipal Corporation and Mumbai Metropolitan Region Development Authority respectively. The total cost of Line 1 is estimated to be ₹ 4,068 crore (US$ 490 million). The 23.40-kilometre (14.54 mi) Line 1 consists of 20 stations. The proposed route will link CBD Belapur , Kharghar , Taloja , Taloja MIDC, Kalamboli , Kamothe and

12573-610: The power delivered is: where R {\displaystyle R} represents a load resistance. Rather than using instantaneous power, p ( t ) {\displaystyle p(t)} , it is more practical to use a time-averaged power (where the averaging is performed over any integer number of cycles). Therefore, AC voltage is often expressed as a root mean square (RMS) value, written as V rms {\displaystyle V_{\text{rms}}} , because For this reason, AC power's waveform becomes Full-wave rectified sine, and its fundamental frequency

12700-502: The project was in 2016. This was later extended to mid-2017, and then mid-2018. By January 2017, only 60% of the work on the stations had been completed. Finding the progress of work to be unsatisfactory, CIDCO sent a notice terminating the contract to the consortium on 11 January 2017. On 1 March 2017, CIDCO floated new tenders to construct 11 stations along the Belapur-Pendhar section. The previous contractors had completed 60% of

12827-908: The rapid transit system varies greatly between cities, with several transport strategies. Some systems may extend only to the limits of the inner city, or to its inner ring of suburbs with trains making frequent station stops. The outer suburbs may then be reached by a separate commuter rail network where more widely spaced stations allow higher speeds. In some cases the differences between urban rapid transit and suburban systems are not clear. Rapid transit systems may be supplemented by other systems such as trolleybuses , regular buses , trams , or commuter rail. This combination of transit modes serves to offset certain limitations of rapid transit such as limited stops and long walking distances between outside access points. Bus or tram feeder systems transport people to rapid transit stops. Each rapid transit system consists of one or more lines , or circuits. Each line

12954-542: The rubber tires. However, they have higher maintenance costs and are less energy efficient. They also lose traction when weather conditions are wet or icy, preventing above-ground use of the Montréal Metro and limiting it on the Sapporo Municipal Subway, but not rubber-tired systems in other cities. Some cities with steep hills incorporate mountain railway technologies in their metros. One of

13081-492: The same circuit. Many adjustable transformer designs were introduced to compensate for this problematic characteristic of the series circuit, including those employing methods of adjusting the core or bypassing the magnetic flux around part of a coil. The direct current systems did not have these drawbacks, giving it significant advantages over early AC systems. In the UK, Sebastian de Ferranti , who had been developing AC generators and transformers in London since 1882, redesigned

13208-414: The same phases with reverse polarity and so can be simply wired together. In practice, higher "pole orders" are commonly used. For example, a 12-pole machine would have 36 coils (10° spacing). The advantage is that lower rotational speeds can be used to generate the same frequency. For example, a 2-pole machine running at 3600 rpm and a 12-pole machine running at 600 rpm produce the same frequency;

13335-411: The skin depth of a copper conductor is approximately 8.57 mm at 60 Hz, so high current conductors are usually hollow to reduce their mass and cost. This tendency of alternating current to flow predominantly in the periphery of conductors reduces the effective cross-section of the conductor. This increases the effective AC resistance of the conductor, since resistance is inversely proportional to

13462-585: The standards for the complete system of generation, transmission and motors used in USA today. The original Niagara Falls Adams Power Plant with three two-phase generators was put into operation in August 1895, but was connected to the remote transmission system only in 1896. The Jaruga Hydroelectric Power Plant in Croatia was set in operation two days later, on 28 August 1895. Its generator (42 Hz, 240 kW)

13589-663: The suburbs, allowing a higher service frequency in the center. This arrangement is used by many systems, such as the Copenhagen Metro , the Milan Metro , the Oslo Metro , the Istanbul Metro and the New York City Subway . Alternatively, there may be a single central terminal (often shared with the central railway station), or multiple interchange stations between lines in the city center, for instance in

13716-410: The supply side. For smaller customers (just how small varies by country and age of the installation) only a single phase and neutral, or two phases and neutral, are taken to the property. For larger installations all three phases and neutral are taken to the main distribution panel. From the three-phase main panel, both single and three-phase circuits may lead off. Three-wire single-phase systems, with

13843-646: The task of redesigning the Gaulard and Gibbs transformer for commercial use in United States. On March 20, 1886, Stanley conducted a demonstrative experiment in Great Barrington : A Siemens generator's voltage of 500 volts was converted into 3000 volts, and then the voltage was stepped down to 500 volts by six Westinghouse transformers. With this setup, the Westinghouse company successfully powered thirty 100-volt incandescent bulbs in twenty shops along

13970-714: The term subway . In Thailand , it stands for Metropolitan Rapid Transit , previously using the Mass Rapid Transit name. Outside of Southeast Asia, Kaohsiung and Taoyuan, Taiwan , have their own MRT systems which stands for Mass Rapid Transit , as with Singapore and Malaysia . In general rapid transit is a synonym for "metro" type transit, though sometimes rapid transit is defined to include "metro", commuter trains and grade separated light rail . Also high-capacity bus-based transit systems can have features similar to "metro" systems. The opening of London's steam-hauled Metropolitan Railway in 1863 marked

14097-414: The term Subway into railway terminology. Both railways, alongside others, were eventually merged into London Underground . The 1893 Liverpool Overhead Railway was designed to use electric traction from the outset. The technology quickly spread to other cities in Europe , the United States, Argentina, and Canada, with some railways being converted from steam and others being designed to be electric from

14224-511: The trains, requiring custom-made trains in order to minimize gaps between train and platform. They are typically integrated with other public transport and often operated by the same public transport authorities . Some rapid transit systems have at-grade intersections between a rapid transit line and a road or between two rapid transit lines. The world's first rapid transit system was the partially underground Metropolitan Railway which opened in 1863 using steam locomotives , and now forms part of

14351-403: The upstream distribution panel to handle harmonics . Harmonics can cause neutral conductor current levels to exceed that of one or all phase conductors. For three-phase at utilization voltages a four-wire system is often used. When stepping down three-phase, a transformer with a Delta (3-wire) primary and a Star (4-wire, center-earthed) secondary is often used so there is no need for a neutral on

14478-601: The use of communications-based train control : the minimum headway can reach 90 seconds, but many systems typically use 120 seconds to allow for recovery from delays. Typical capacity lines allow 1,200 people per train, giving 36,000 passengers per hour per direction . However, much higher capacities are attained in East Asia with ranges of 75,000 to 85,000 people per hour achieved by MTR Corporation 's urban lines in Hong Kong. Rapid transit topologies are determined by

14605-578: The use of parallel connected, instead of series connected, utilization loads, the other concerning the ability to have high turns ratio transformers such that the supply network voltage could be much higher (initially 1400 V to 2000 V) than the voltage of utilization loads (100 V initially preferred). When employed in parallel connected electric distribution systems, closed-core transformers finally made it technically and economically feasible to provide electric power for lighting in homes, businesses and public spaces. The other essential milestone

14732-519: The way to integrate older plants into a universal AC supply system. In the autumn of 1884, Károly Zipernowsky , Ottó Bláthy and Miksa Déri (ZBD), three engineers associated with the Ganz Works of Budapest, determined that open-core devices were impractical, as they were incapable of reliably regulating voltage. Bláthy had suggested the use of closed cores, Zipernowsky had suggested the use of parallel shunt connections , and Déri had performed

14859-477: The wire are a product of the square of the current ( I ) and the resistance (R) of the wire, described by the formula: This means that when transmitting a fixed power on a given wire, if the current is halved (i.e. the voltage is doubled), the power loss due to the wire's resistance will be reduced to one quarter. The power transmitted is equal to the product of the current and the voltage (assuming no phase difference); that is, Consequently, power transmitted at

14986-582: The work on the stations. The new contract with worth ₹ 141 crore (US$ 17 million). Line 1 is planned to be developed in 3 phases: An international consortium of companies including Ansaldo STS , Tata Projects and CSR Zhuzhou will provide the electrical and mechanical systems for the first phase of Line 1. Ansaldo will conduct systems integration and supply train control systems, telecoms, fare collection systems and equipment storage. The metro's standard gauge network would be electrified at 25 kV AC , with power provided via an overhead catenary . In 2014,

15113-559: Was Singapore's Mass Rapid Transit (MRT) system, which launched its first underground mobile phone network using AMPS in 1989. Many metro systems, such as the Hong Kong Mass Transit Railway (MTR) and the Berlin U-Bahn, provide mobile data connections in their tunnels for various network operators. The technology used for public, mass rapid transit has undergone significant changes in the years since

15240-899: Was developed further. Other Central European countries also have metro lines, for example in the cities of Budapest (Hungary), Prague (Czech Republic) and Warsaw (Poland). In Eastern Europe , metro systems are in operation in Minsk (Belarus), Kyiv (Ukraine), Riga (Latvia), Vilnius (Lithuania) and Moscow (Russia). In Southeastern European countries, there are metro systems in Athens and Thessaloniki (Greece), Belgrade (Serbia), Sofia (Bulgaria) and Istanbul (Turkey). In Northern Europe , rapid transit systems exist in Copenhagen (Denmark), Oslo (Norway), Stockholm (Sweden) and Helsinki (Finland). Various terms are used for rapid transit systems around North America . The term metro

15367-560: Was independently invented by Galileo Ferraris and Nikola Tesla (with Tesla's design being licensed by Westinghouse in the US). This design was independently further developed into the modern practical three-phase form by Mikhail Dolivo-Dobrovolsky and Charles Eugene Lancelot Brown in Germany on one side, and Jonas Wenström in Sweden on the other, though Brown favoured the two-phase system. A long-distance alternating current transmission

15494-547: Was installed in Telluride Colorado. The first three-phase system was established in 1891 in Frankfurt , Germany. The Tivoli – Rome transmission was completed in 1892. The San Antonio Canyon Generator was the third commercial single-phase hydroelectric AC power plant in the United States to provide long-distance electricity. It was completed on December 31, 1892, by Almarian William Decker to provide power to

15621-702: Was low and suburbs tended to spread out . Since the 1970s, the viability of underground train systems in Australian cities, particularly Sydney and Melbourne , has been reconsidered and proposed as a solution to over-capacity. Melbourne had tunnels and stations developed in the 1970s and opened in 1980. The first line of the Sydney Metro was opened in 2019. Since the 1960s, many new systems have been introduced in Europe , Asia and Latin America . In

15748-507: Was made and installed by the Hungarian company Ganz , while the transmission line from the power plant to the City of Šibenik was 11.5 kilometers (7.1 mi) long, and the municipal distribution grid 3000 V/110 V included six transforming stations. Alternating current circuit theory developed rapidly in the latter part of the 19th and early 20th century. Notable contributors to

15875-596: Was not feasible in the early days of electric power transmission , as there was then no economically viable way to step the voltage of DC down for end user applications such as lighting incandescent bulbs. Three-phase electrical generation is very common. The simplest way is to use three separate coils in the generator stator , physically offset by an angle of 120° (one-third of a complete 360° phase) to each other. Three current waveforms are produced that are equal in magnitude and 120° out of phase to each other. If coils are added opposite to these (60° spacing), they generate

16002-506: Was the introduction of 'voltage source, voltage intensive' (VSVI) systems' by the invention of constant voltage generators in 1885. In early 1885, the three engineers also eliminated the problem of eddy current losses with the invention of the lamination of electromagnetic cores. Ottó Bláthy also invented the first AC electricity meter . The AC power system was developed and adopted rapidly after 1886 due to its ability to distribute electricity efficiently over long distances, overcoming

16129-754: Was used in 1883 for the Metropolitan Railway station lighting in London , while the single-phase 1884 system in Turin , Italy, was the first multiple-user AC distribution system in the world. The Ames Hydroelectric Generating Plant , constructed in 1890, was among the first hydroelectric alternating current power plants. A long distance transmission of single-phase electricity from a hydroelectric generating plant in Oregon at Willamette Falls sent power fourteen miles downriver to downtown Portland for street lighting in 1890. In 1891, another transmission system

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