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79-420: In order for current to flow within a closed electrical circuit , one charged particle does not need to travel from the component producing the current (the current source ) to those consuming it (the loads ). Instead, the charged particle simply needs to nudge its neighbor a finite amount, who will nudge its neighbor, and on and on until a particle is nudged into the consumer, thus powering it. Essentially what

158-557: A battery or a generator . Active elements can inject power to the circuit, provide power gain, and control the current flow within the circuit. Passive networks do not contain any sources of electromotive force. They consist of passive elements like resistors and capacitors. A network is linear if its signals obey the principle of superposition ; otherwise it is non-linear. Passive networks are generally taken to be linear, but there are exceptions. For instance, an inductor with an iron core can be driven into saturation if driven with

237-447: A bus plus some circuit breakers . The largest transmission substations can cover a large area (several acres/hectares) with multiple voltage levels, many circuit breakers, and a large amount of protection and control equipment ( voltage and current transformers , relays and SCADA systems). Modern substations may be implemented using international standards such as IEC Standard 61850 . A distribution substation transfers power from

316-401: A contractor or alternately all phases of its development may be handled by the electrical utility . Most commonly, the utility does the engineering and procurement while hiring a contractor for actual construction. Major design constraints for construction of substations include land availability and cost, limitations on the construction period, transportation restrictions, and the need to get

395-451: A conductor of uniform cross section, therefore, can be computed as where ℓ {\displaystyle \ell } is the length of the conductor, measured in metres [m], A is the cross-section area of the conductor measured in square metres [m], σ ( sigma ) is the electrical conductivity measured in siemens per meter (S·m), and ρ ( rho ) is the electrical resistivity (also called specific electrical resistance ) of

474-706: A disconnection of the load supplied by the circuit break from the feeding point. This seeks to isolate the fault point from the rest of the system, and allow the rest of the system to continue operating with minimal impact. Both switches and circuit breakers may be operated locally (within the substation) or remotely from a supervisory control center. With overhead transmission lines , the propagation of lightning and switching surges can cause insulation failures into substation equipment. Line entrance surge arrestors are used to protect substation equipment accordingly. Insulation Coordination studies are carried out extensively to ensure equipment failure (and associated outages )

553-418: A few hundred amperes. Aside from the geometry of the wire, temperature also has a significant effect on the efficacy of conductors. Temperature affects conductors in two main ways, the first is that materials may expand under the application of heat. The amount that the material will expand is governed by the thermal expansion coefficient specific to the material. Such an expansion (or contraction) will change

632-410: A given material, the resistance is inversely proportional to the cross-sectional area. For example, a thick copper wire has lower resistance than an otherwise-identical thin copper wire. Also, for a given material, the resistance is proportional to the length; for example, a long copper wire has higher resistance than an otherwise-identical short copper wire. The resistance R and conductance G of

711-442: A large enough current. In this region, the behaviour of the inductor is very non-linear. Discrete passive components (resistors, capacitors and inductors) are called lumped elements because all of their, respectively, resistance, capacitance and inductance is assumed to be located ("lumped") at one place. This design philosophy is called the lumped-element model and networks so designed are called lumped-element circuits . This

790-457: A large substation, circuit breakers are used to interrupt any short circuits or overload currents that may occur on the network. Smaller distribution stations may use recloser circuit breakers or fuses for protection of distribution circuits. Substations themselves do not usually have generators, although a power plant may have a substation nearby. Other devices such as capacitors , voltage regulators , and reactors may also be located at

869-522: A long lease such as a renewable 99-year lease, giving the utility company security of tenure . The first step in planning a substation layout is the preparation of a one-line diagram , which shows in simplified form the switching and protection arrangement required, as well as the incoming supply lines and outgoing feeders or transmission lines. It is a usual practice by many electrical utilities to prepare one-line diagrams with principal elements (lines, switches, circuit breakers, transformers) arranged on

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948-454: A model of such an interconnection, consisting of electrical elements (e.g., voltage sources , current sources , resistances , inductances , capacitances ). An electrical circuit is a network consisting of a closed loop, giving a return path for the current. Thus all circuits are networks, but not all networks are circuits (although networks without a closed loop are often imprecisely referred to as "circuits"). Linear electrical networks,

1027-416: A reducing atmosphere, then oxygen-free high conductivity copper (CW008A or ASTM designation C10100) may be used. Because of its ease of connection by soldering or clamping, copper is still the most common choice for most light-gauge wires. Silver is 6% more conductive than copper, but due to cost it is not practical in most cases. However, it is used in specialized equipment, such as satellites , and as

1106-690: A ring bus, double bus, or so-called "breaker and a half" setup can be used, so that the failure of any one circuit breaker does not interrupt power to other circuits, and so that parts of the substation may be de-energized for maintenance and repairs. Substations feeding only a single industrial load may have minimal switching provisions, especially for small installations. Because of the risk of electrical shock, substations are inherently dangerous to electrical workers. To mitigate this hazard, substations are designed with various safety features. Live conductors and bare equipment are kept separate, either with protected equipment, or using screens or distance. Based on

1185-439: A special type consisting only of sources (voltage or current), linear lumped elements (resistors, capacitors, inductors), and linear distributed elements (transmission lines), have the property that signals are linearly superimposable . They are thus more easily analyzed, using powerful frequency domain methods such as Laplace transforms , to determine DC response , AC response , and transient response . A resistive network

1264-679: A substation. Substations may be on the surface in fenced enclosures, underground, or special-purpose buildings. High-rise buildings may have several indoor substations. Indoor substations are usually found in urban areas to reduce the noise from transformers, improve appearance, or protect switchgear from extreme climate or pollution. Substations often use busbars as conductors between electrical equipment. Busbars may be aluminum tubing 3–6 inches (76–152 mm) thick, or else wires (strain bus). Outdoor, above-ground substation structures include wood pole, lattice metal tower, and tubular metal structures, although other variants are available. Where space

1343-574: A thin plating to mitigate skin effect losses at high frequencies. Famously, 14,700 short tons (13,300 t) of silver on loan from the United States Treasury were used in the making of the calutron magnets during World War II due to wartime shortages of copper. Aluminum wire is the most common metal in electric power transmission and distribution . Although only 61% of the conductivity of copper by cross-sectional area, its lower density makes it twice as conductive by mass. As aluminum

1422-422: A transmission line or a transformer. To maintain reliability of supply, companies aim at keeping the system up and running while performing maintenance. All work to be performed, from routine testing to adding entirely new substations, should be done while keeping the whole system running. Unplanned switching events are caused by a fault in a transmission line or any other component, for example: The function of

1501-493: Is a network containing only resistors and ideal current and voltage sources. Analysis of resistive networks is less complicated than analysis of networks containing capacitors and inductors. If the sources are constant ( DC ) sources, the result is a DC network. The effective resistance and current distribution properties of arbitrary resistor networks can be modeled in terms of their graph measures and geometrical properties. A network that contains active electronic components

1580-467: Is a part of an electrical generation , transmission , and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Between the generating station and consumer, electric power may flow through several substations at different voltage levels. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at

1659-602: Is aimed at minimizing cost while ensuring power availability and reliability, and enabling changes to the substation in the future. Substations may be built outdoors, indoors, or underground or in a combination of these locations. Selection of the location of a substation must consider many factors. Sufficient land area is required for installation of equipment with necessary clearances for electrical safety, and for access to maintain large apparatus such as transformers. The site must have room for expansion due to load growth or planned transmission additions. Environmental effects of

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1738-419: Is called a semi-lumped design. An example of a semi-lumped circuit is the combline filter . Sources can be classified as independent sources and dependent sources. An ideal independent source maintains the same voltage or current regardless of the other elements present in the circuit. Its value is either constant (DC) or sinusoidal (AC). The strength of voltage or current is not changed by any variation in

1817-465: Is common in the area. The output is a number of feeders. Distribution voltages are typically medium voltage, between 2.4 kV and 33 kV, depending on the size of the area served and the practices of the local utility. The feeders run along streets overhead (or underground, in some cases) and power the distribution transformers at or near the customer premises. In addition to transforming voltage, distribution substations also isolate faults in either

1896-433: Is known as an electronic circuit . Such networks are generally nonlinear and require more complex design and analysis tools. An active network contains at least one voltage source or current source that can supply energy to the network indefinitely. A passive network does not contain an active source. An active network contains one or more sources of electromotive force . Practical examples of such sources include

1975-402: Is minimal. Once past the switching components, the lines of a given voltage connect to one or more buses . These are sets of busbars , usually in multiples of three, since three-phase electrical power distribution is largely universal around the world. The arrangement of switches, circuit breakers, and buses used affects the cost and reliability of the substation. For important substations

2054-474: Is necessary to work on parts of the substation while energized, but employees must maintain a safe distance of at least 3 metres (9.8 ft). The aim to reduce substation footprints comes into conflict with ease of maintenance enhanced by including gaps where employees can safely work. Underneath a substation, a mat or grid of conductors laid around 0.5 or 0.6 metres (1 ft 8 in or 2 ft 0 in) underground provides grounding . This grid, which

2133-404: Is not exact: It assumes the current density is totally uniform in the conductor, which is not always true in practical situation. However, this formula still provides a good approximation for long thin conductors such as wires. Another situation this formula is not exact for is with alternating current (AC), because the skin effect inhibits current flow near the center of the conductor. Then,

2212-473: Is occurring is a long chain of momentum transfer between mobile charge carriers ; the Drude model of conduction describes this process more rigorously. This momentum transfer model makes metal an ideal choice for a conductor; metals, characteristically, possess a delocalized sea of electrons which gives the electrons enough mobility to collide and thus affect a momentum transfer. As discussed above, electrons are

2291-404: Is passed through it. Liquids made of compounds with only covalent bonds cannot conduct electricity. Certain organic ionic liquids , by contrast, can conduct an electric current. While pure water is not an electrical conductor, even a small portion of ionic impurities, such as salt , can rapidly transform it into a conductor. Wires are measured by their cross sectional area. In many countries,

2370-472: Is plentiful and appearance of the station is not a factor, steel lattice towers provide low-cost supports for transmission lines and apparatus. Low-profile substations may be specified in suburban areas where appearance is more critical. Indoor substations may be gas insulated substations (GIS) (at high voltages, with gas insulated switchgear), or use metal-enclosed or metal-clad switchgear at lower voltages. Urban and suburban indoor substations may be finished on

2449-650: Is roughly one-third the cost of copper by weight, the economic advantages are considerable when large conductors are required. The disadvantages of aluminum wiring lie in its mechanical and chemical properties. It readily forms an insulating oxide, making connections heat up. Its larger coefficient of thermal expansion than the brass materials used for connectors causes connections to loosen. Aluminum can also "creep", slowly deforming under load, which also loosens connections. These effects can be mitigated with suitably designed connectors and extra care in installation, but they have made aluminum building wiring unpopular past

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2528-503: Is the conventional approach to circuit design. At high enough frequencies, or for long enough circuits (such as power transmission lines ), the lumped assumption no longer holds because there is a significant fraction of a wavelength across the component dimensions. A new design model is needed for such cases called the distributed-element model . Networks designed to this model are called distributed-element circuits . A distributed-element circuit that includes some lumped components

2607-574: Is the international standard to which all other electrical conductors are compared; the International Annealed Copper Standard conductivity is 58 MS/m , although ultra-pure copper can slightly exceed 101% IACS. The main grade of copper used for electrical applications, such as building wire, motor windings, cables and busbars , is electrolytic-tough pitch (ETP) copper (CW004A or ASTM designation C100140). If high conductivity copper must be welded or brazed or used in

2686-451: Is typically copper although it may be galvanized iron in some countries, is used to ground circuits that are being worked on to prevent accidental re-energization while workers are in contact with a de-energized circuit. Often, earth rods are driven deeper into the ground from the grounding grid for lower resistance grounding, and may be surrounded by bentonite or marconite to further reduce resistance and ensure effective grounding for

2765-410: Is used as a protection device to interrupt fault currents automatically, and may be used to switch loads on and off, or to cut off a line when power is flowing in the 'wrong' direction. When a large fault current flows through the circuit breaker, this is detected through the use of current transformers . The magnitude of the current transformer outputs may be used to trip the circuit breaker resulting in

2844-404: Is usually insulated with PVC insulation that is only rated to operate to about 60 °C, therefore, the current in such wires must be limited so that it never heats the copper conductor above 60 °C, causing a risk of fire . Other, more expensive insulation such as Teflon or fiberglass may allow operation at much higher temperatures. If an electric field is applied to a material, and

2923-618: Is where all transmission lines have the same voltage. In such cases, substation contains high-voltage switches that allow lines to be connected or isolated for fault clearance or maintenance. A transmission station may have transformers to convert between two transmission voltages, voltage control / power factor correction devices such as capacitors, reactors or static VAR compensators and equipment such as phase shifting transformers to control power flow between two adjacent power systems. Transmission substations can range from simple to complex. A small "switching station" may be little more than

3002-536: The PLECS interface to Simulink uses piecewise-linear approximation of the equations governing the elements of a circuit. The circuit is treated as a completely linear network of ideal diodes . Every time a diode switches from on to off or vice versa, the configuration of the linear network changes. Adding more detail to the approximation of equations increases the accuracy of the simulation, but also increases its running time. Electrical substation A substation

3081-483: The geometrical cross-section is different from the effective cross-section in which current actually flows, so the resistance is higher than expected. Similarly, if two conductors are near each other carrying AC current, their resistances increase due to the proximity effect . At commercial power frequency , these effects are significant for large conductors carrying large currents, such as busbars in an electrical substation , or large power cables carrying more than

3160-416: The microprocessor made for an exponential increase in the number of points that could be economically controlled and monitored. Today, standardized communication protocols such as DNP3 , IEC 61850 and Modbus , to list a few, are used to allow multiple intelligent electronic devices to communicate with each other and supervisory control centers. Distributed automatic control at substations is one element of

3239-440: The service drop . Organic compounds such as octane, which has 8 carbon atoms and 18 hydrogen atoms, cannot conduct electricity. Oils are hydrocarbons, since carbon has the property of tetracovalency and forms covalent bonds with other elements such as hydrogen, since it does not lose or gain electrons, thus does not form ions. Covalent bonds are simply the sharing of electrons. Hence, there is no separation of ions when electricity

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3318-458: The Czech Republic, where power is collected from nearby lignite -fired power plants. If no transformers are required for increasing the voltage to transmission level, the substation is a switching station. Converter substations may be associated with HVDC converter plants, traction current , or interconnected non-synchronous networks. These stations contain power electronic devices to change

3397-591: The amps exceed a certain amount over a period of time. Reclosers will attempt to re-energize the circuit after a delay. If unsuccessful for a few times, the recloser will have to be manually reset by an electrical worker. Capacitor banks are used in substations to balance the lagging current draw from inductive loads (such as motors, transformers, and some industrial equipment) with their reactive load . Additional capacitor capacity may be needed if dispersed generation (such as small diesel generators, rooftop photovoltaic solar panels , or wind turbines ) are added to

3476-489: The circuit conform to the voltage/current equations governing that element. Once the steady state solution is found, the operating points of each element in the circuit are known. For a small signal analysis, every non-linear element can be linearized around its operation point to obtain the small-signal estimate of the voltages and currents. This is an application of Ohm's Law. The resulting linear circuit matrix can be solved with Gaussian elimination . Software such as

3555-587: The complexity of distribution networks grew, it became economically necessary to automate supervision and control of substations from a centrally attended point, to allow overall coordination in case of emergencies and to reduce operating costs. Early efforts to remote control substations used dedicated communication wires, often run alongside power circuits. Power-line carrier , microwave radio , fiber optic cables as well as dedicated wired remote control circuits have all been applied to Supervisory Control and Data Acquisition (SCADA) for substations. The development of

3634-462: The conductor is made from (as described above) and the conductor's size. For a given material, conductors with a larger cross-sectional area have less resistance than conductors with a smaller cross-sectional area. For bare conductors, the ultimate limit is the point at which power lost to resistance causes the conductor to melt. Aside from fuses , most conductors in the real world are operated far below this limit, however. For example, household wiring

3713-1341: The connected network. Dependent sources depend upon a particular element of the circuit for delivering the power or voltage or current depending upon the type of source it is. A number of electrical laws apply to all linear resistive networks. These include: Applying these laws results in a set of simultaneous equations that can be solved either algebraically or numerically. The laws can generally be extended to networks containing reactances . They cannot be used in networks that contain nonlinear or time-varying components. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] To design any electrical circuit, either analog or digital , electrical engineers need to be able to predict

3792-477: The current to back-up lines or for parallelizing circuits in case of failure. An example is the switching stations for the HVDC Inga–Shaba transmission line. A switching station may also be known as a switchyard, and these are commonly located directly adjacent to or nearby a power station . In this case the generators from the power station supply their power into the yard onto the generator bus on one side of

3871-446: The days before the distribution system became a grid . As central generation stations became larger, smaller generating plants were converted to distribution stations, receiving their energy supply from a larger plant instead of using their own generators. The first substations were connected to only one power station , where the generators were housed, and were subsidiaries of that power station. Substations may be designed and built by

3950-416: The equipment used to monitor, control, and protect the rest of the substation equipment. It often contains protective relays, meters, breaker controls, communications, batteries, and recorders that save detailed data about substation operations, particularly when there is any unusual activity, to help reconstruct what happened after the fact. These control rooms typically are heated and air conditioned to ensure

4029-425: The frequency of current, or else convert from alternating to direct current or the reverse. Formerly rotary converters changed frequency to interconnect two systems; nowadays such substations are rare. A switching station is a substation without transformers and operating only at a single voltage level. Switching stations are sometimes used as collector and distribution stations. Sometimes they are used for switching

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4108-425: The geometry of the conductor and therefore its characteristic resistance. However, this effect is generally small, on the order of 10. An increase in temperature will also increase the number of phonons generated within the material. A phonon is essentially a lattice vibration, or rather a small, harmonic kinetic movement of the atoms of the material. Much like the shaking of a pinball machine, phonons serve to disrupt

4187-474: The interconnection of two different transmission voltages. They are a common component of the infrastructure. There are 55,000 substations in the United States. Substations may be owned and operated by an electrical utility, or may be owned by a large industrial or commercial customer. Generally substations are unattended, relying on SCADA for remote supervision and control. The word substation comes from

4266-408: The jurisdiction or company, there are safety standards with minimum required clearance between different live equipment or conductors or between live metal and the ground, which often varies with higher clearance being required for higher voltages because of the greater ability to generate flashover . To this is added the necessary space for employees to work safely and vehicles to pass. Sometimes it

4345-590: The lifetime of the substation. Above ground, the grounding conductors may be steel, aluminum, or copper. They must be thick enough to carry the expected current of a fault for 1-3 seconds and remain undamaged. Substation fences, typically at least 2 metres (6 ft 7 in) in height, both protect the public from electrical hazards and also protect the substation from vandalism. Internal fences can also be incorporated to protect employees from areas that are unsafe when energized. Substations generally have switching, protection and control equipment, and transformers. In

4424-411: The low-voltage side. More typical distribution substations have a switch, one transformer, and minimal facilities on the low-voltage side. In distributed generation projects such as a wind farm or photovoltaic power station , a collector substation may be required. It resembles a distribution substation although power flow is in the opposite direction, from many wind turbines or inverters up into

4503-443: The material, measured in ohm-metres (Ω·m). The resistivity and conductivity are proportionality constants, and therefore depend only on the material the wire is made of, not the geometry of the wire. Resistivity and conductivity are reciprocals : ρ = 1 / σ {\displaystyle \rho =1/\sigma } . Resistivity is a measure of the material's ability to oppose electric current. This formula

4582-411: The outside so as to blend in with other buildings in the area. A compact substation is generally an outdoor substation built in a metal enclosure, in which each item of the electrical equipment is located very near to each other to create a relatively smaller footprint size of the substation. High-voltage circuit breakers are commonly used to interrupt the flow of current in substation equipment. At

4661-407: The page similarly to the way the apparatus would be laid out in the actual station. In a common design, incoming lines have a disconnect switch and a circuit breaker . In some cases, the lines will not have both, with either a switch or a circuit breaker being all that is considered necessary. A disconnect switch is used to provide isolation, since it cannot interrupt load current. A circuit breaker

4740-427: The path of electrons, causing them to scatter. This electron scattering will decrease the number of electron collisions and therefore will decrease the total amount of current transferred. Conduction materials include metals , electrolytes , superconductors , semiconductors , plasmas and some nonmetallic conductors such as graphite and conductive polymers . Copper has a high conductivity . Annealed copper

4819-425: The primary mover in metals; however, other devices such as the cationic electrolyte (s) of a battery , or the mobile protons of the proton conductor of a fuel cell rely on positive charge carriers. Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents. The resistance of a given conductor depends on the material it is made of, and on its dimensions. For

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4898-661: The public grid. Sometimes they are also transmission substations or collector substations if the railway network also operates its own grid and generators to supply the other stations. A mobile substation is a substation on wheels, containing a transformer, breakers and buswork mounted on a self-contained semi-trailer , meant to be pulled by a truck . They are designed to be compact for travel on public roads, and are used for temporary backup in times of natural disaster or war . Mobile substations are usually rated much lower than permanent installations, and may be built in several units to meet road travel limitations. Substation design

4977-411: The reliable operation of this equipment. Additional equipment is necessary to handle power surges associated with intermittent renewable energy such as dispersed generation from wind or solar. Most transformers lose between 5 and 1.5 percent of their input as heat and noise. Iron losses are no-load and constant whenever the transformer is energized, while copper and auxiliary losses are proportionate to

5056-486: The resulting induced electric current is in the same direction, the material is said to be an isotropic electrical conductor . If the resulting electric current is in a different direction from the applied electric field, the material is said to be an anisotropic electrical conductor . Electrical network An electrical network is an interconnection of electrical components (e.g., batteries , resistors , inductors , capacitors , switches , transistors ) or

5135-408: The size is expressed in square millimetres. In North America, conductors are measured by American wire gauge for smaller ones, and circular mils for larger ones. The ampacity of a conductor, that is, the amount of current it can carry, is related to its electrical resistance: a lower-resistance conductor can carry a larger value of current. The resistance, in turn, is determined by the material

5214-430: The square of the current. Auxiliary losses are due to running fans and pumps which is noisy when the transformer is operating at maximum capacity. To reduce noise, enclosures are often built around the transformer and can also be added after the substation is built. Oil-based transformers are often built with bunded areas to prevent the escape of flaming or leaking oil. Fire separation areas or firewalls are built around

5293-451: The substation must be considered, such as drainage , noise and road traffic effects. The substation site must be reasonably central to the distribution area to be served. The site must be secure from intrusion by passers-by, both to protect people from injury by electric shock or arcs, and to protect the electrical system from misoperation due to vandalism. If not owned and operated by a utility company, substations are typically occupied on

5372-400: The substation running quickly. Prefabrication is a common way to reduce the construction cost. For connecting the new substation, a partial outage at another substation may be required, but the utility often tries to minimize downtime. Substations typically serve at least one of the following purposes: A transmission substation connects two or more transmission lines. The simplest case

5451-454: The substation where electrical energy is being converted to heat, which indicates a problem and can cause additional damage from the high heat. Dissolved gas analysis can tell when an oil-insulated transformer needs to have the oil filtered or replace, and also detect other issues. Early electrical substations required manual switching or adjustment of equipment, and manual collection of data for load, energy consumption, and abnormal events. As

5530-554: The switching station is to isolate the faulty portion of the system in the shortest possible time. De-energizing faulty equipment protects it from further damage, and isolating a fault helps keep the rest of the electrical grid operating with stability. Electrified railways also use substations, often distribution substations. In some cases a conversion of the current type takes place, commonly with rectifiers for direct current (DC) trains, or rotary converters for trains using alternating current (AC) at frequencies other than that of

5609-436: The system. Capacitors can reduce the current in wires, helping stem system losses from voltage drop or enabling extra power to be sent through the conductors. Capacitors may be left on in response to constant inductive load or turned on when inductive load is increased, such as in the summer for air conditioners . The switching may be remote and can be done manually or automatically. Larger substations have control rooms for

5688-466: The time of interruption, current could be normal, too high due to excessive load, unusual due to a fault, or tripped by protective relays prior to anticipated trouble. The most common technologies to extinguish the power arc from separating the conductors in the breaker include: Reclosers are similar to breakers, and can be cheaper because they do not require separate protective relays. Often used in distribution, they often are programmed to trip when

5767-428: The time, cost and risk of error involved in building circuit prototypes. More complex circuits can be analyzed numerically with software such as SPICE or GNUCAP , or symbolically using software such as SapWin . When faced with a new circuit, the software first tries to find a steady state solution , that is, one where all nodes conform to Kirchhoff's current law and the voltages across and through each element of

5846-429: The transformer to stop the spread of fire. Firefighting vehicles are allowed a path to access the area. Maintenance of substations involves inspections, data collection and analysis, and routine scheduled work. Using methods such as infrared scanning and dissolved gas analysis, it can be predicted when the substation will need maintenance and predict dangers before they materialize. Infrared technology finds hot spots in

5925-707: The transmission grid. Usually for economy of construction the collector system operates around 35 kV, although some collector systems are 12 kV, and the collector substation steps up voltage to a transmission voltage for the grid. The collector substation can also provide power factor correction if it is needed, metering, and control of the wind farm. In some special cases a collector substation can also contain an HVDC converter station. Collector substations also exist where multiple thermal or hydroelectric power plants of comparable output power are in proximity. Examples for such substations are Brauweiler in Germany and Hradec in

6004-401: The transmission or distribution systems. Distribution substations are typically the points of voltage regulation , although on long distribution circuits (of several miles/kilometers), voltage regulation equipment may also be installed along the line. The downtown areas of large cities feature complicated distribution substations, with high-voltage switching, and switching and backup systems on

6083-454: The transmission system to the distribution system of an area. It is uneconomical to directly connect electricity consumers to the main transmission network, unless they use large amounts of power, so the distribution station reduces voltage to a level suitable for local distribution. The input for a distribution substation is typically at least two transmission or sub-transmission lines. Input voltage may be, for example, 115 kV, or whatever

6162-462: The voltages and currents at all places within the circuit. Simple linear circuits can be analyzed by hand using complex number theory . In more complex cases the circuit may be analyzed with specialized computer programs or estimation techniques such as the piecewise-linear model. Circuit simulation software, such as HSPICE (an analog circuit simulator), and languages such as VHDL-AMS and verilog-AMS allow engineers to design circuits without

6241-462: The yard, and the transmission lines take their power from a Feeder Bus on the other side of the yard. An important function performed by a substation is switching , which is the connecting and disconnecting of transmission lines or other components to and from the system. Switching events may be planned or unplanned. A transmission line or other component may need to be de-energized for maintenance or for new construction, for example, adding or removing

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