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Explore a preview version of Power System Operation and Control right now. Power System Operation and Control is a comprehensive text designed for undergraduate and postgraduate courses in electrical engineering. This book aims to meet the requirements of electrical engineering students of universities all over India. This text is written in a simple and easy-to-understand manner and is valuable both as a textbook as well as a reference book for engineering students and practicing engineers. The essential guide that combines power system fundamentals with the practical aspects of equipment design and ….
An electric power system is a network of electrical components deployed to supply, transfer, and use electric power. An example of a power system is the electrical grid that provides power to homes and industry within an extended area. The electrical grid can be broadly divided into the generators that supply the power, the transmission system that carries the power from the generating centers to the load centers, and the distribution system that feeds the power to nearby homes and industries.
Smaller power systems are also found in industry, hospitals, commercial buildings and homes. The majority of these systems rely upon three-phase AC power —the standard for large-scale power transmission and distribution across the modern world. Specialized power systems that do not always rely upon three-phase AC power are found in aircraft, electric rail systems, ocean liners, submarines and automobiles. In , two electricians built the world's first power system at Godalming in England.
It was powered by two waterwheels and produced an alternating current that in turn supplied seven Siemens arc lamps at volts and 34 incandescent lamps at 40 volts. The Pearl Street Station initially powered around 3, lamps for 59 customers. Direct current power could not be transformed easily or efficiently to the higher voltages necessary to minimize power loss during long-distance transmission, so the maximum economic distance between the generators and load was limited to around half a mile m.
That same year in London, Lucien Gaulard and John Dixon Gibbs demonstrated the "secondary generator"—the first transformer suitable for use in a real power system. Perhaps the most serious was connecting the primaries of the transformers in series so that active lamps would affect the brightness of other lamps further down the line. The system lit more than carbon filament lamps and operated successfully from May until November of that year.
Also in George Westinghouse , an American entrepreneur, obtained the patent rights to the Gaulard-Gibbs transformer and imported a number of them along with a Siemens generator, and set his engineers to experimenting with them in hopes of improving them for use in a commercial power system. In , one of Westinghouse's engineers, William Stanley , independently recognized the problem with connecting transformers in series as opposed to parallel and also realized that making the iron core of a transformer a fully enclosed loop would improve the voltage regulation of the secondary winding.
In , Westinghouse licensed Nikola Tesla 's patents for a polyphase AC induction motor and transformer designs. By , the electric power industry was flourishing, and power companies had built thousands of power systems both direct and alternating current in the United States and Europe. These networks were effectively dedicated to providing electric lighting.
During this time the rivalry between Thomas Edison and George Westinghouse's companies had grown into a propaganda campaign over which form of transmission direct or alternating current was superior, a series of events known as the " war of the currents ".
In , after a protracted decision-making process, alternating current was chosen as the transmission standard with Westinghouse building the Adams No. Developments in power systems continued beyond the nineteenth century. In the first experimental high voltage direct current HVDC line using mercury arc valves was built between Schenectady and Mechanicville, New York.
It consisted of a layer of selenium applied on an aluminum plate. In that same year, Siemens demonstrated a solid-state rectifier, but it was not until the early s that solid-state devices became the standard in HVDC, when GE emerged as one of the top suppliers of thyristor-based HVDC.
In recent times, many important developments have come from extending innovations in the information and communications technology ICT field to the power engineering field. For example, the development of computers meant load flow studies could be run more efficiently allowing for much better planning of power systems. Advances in information technology and telecommunication also allowed for effective remote control of a power system's switchgear and generators.
Electric power is the product of two quantities: current and voltage. These two quantities can vary with respect to time AC power or can be kept at constant levels DC power. Most refrigerators, air conditioners, pumps and industrial machinery use AC power whereas most computers and digital equipment use DC power digital devices plugged into the mains typically have an internal or external power adapter to convert from AC to DC power. AC power has the advantage of being easy to transform between voltages and is able to be generated and utilised by brushless machinery.
DC power remains the only practical choice in digital systems and can be more economical to transmit over long distances at very high voltages see HVDC. The ability to easily transform the voltage of AC power is important for two reasons: Firstly, power can be transmitted over long distances with less loss at higher voltages.
So in power systems where generation is distant from the load, it is desirable to step-up increase the voltage of power at the generation point and then step-down decrease the voltage near the load. Secondly, it is often more economical to install turbines that produce higher voltages than would be used by most appliances, so the ability to easily transform voltages means this mismatch between voltages can be easily managed.
Solid state devices , which are products of the semiconductor revolution, make it possible to transform DC power to different voltages , build brushless DC machines and convert between AC and DC power. Nevertheless, devices utilising solid state technology are often more expensive than their traditional counterparts, so AC power remains in widespread use.
All power systems have one or more sources of power. For some power systems, the source of power is external to the system but for others, it is part of the system itself—it is these internal power sources that are discussed in the remainder of this section. Direct current power can be supplied by batteries , fuel cells or photovoltaic cells. Alternating current power is typically supplied by a rotor that spins in a magnetic field in a device known as a turbo generator.
There have been a wide range of techniques used to spin a turbine's rotor, from steam heated using fossil fuel including coal, gas and oil or nuclear energy to falling water hydroelectric power and wind wind power.
The speed at which the rotor spins in combination with the number of generator poles determines the frequency of the alternating current produced by the generator. All generators on a single synchronous system, for example, the national grid , rotate at sub-multiples of the same speed and so generate electric current at the same frequency.
If the load on the system increases, the generators will require more torque to spin at that speed and, in a steam power station, more steam must be supplied to the turbines driving them. Thus the steam used and the fuel expended directly relate to the quantity of electrical energy supplied. An exception exists for generators incorporating power electronics such as gearless wind turbines or linked to a grid through an asynchronous tie such as a HVDC link — these can operate at frequencies independent of the power system frequency.
Depending on how the poles are fed, alternating current generators can produce a variable number of phases of power. A higher number of phases leads to more efficient power system operation but also increases the infrastructure requirements of the system.
There are a range of design considerations for power supplies. These range from the obvious: How much power should the generator be able to supply? What is an acceptable length of time for starting the generator some generators can take hours to start?
Is the availability of the power source acceptable some renewables are only available when the sun is shining or the wind is blowing? To the more technical: How should the generator start some turbines act like a motor to bring themselves up to speed in which case they need an appropriate starting circuit? What is the mechanical speed of operation for the turbine and consequently what are the number of poles required?
What type of generator is suitable synchronous or asynchronous and what type of rotor squirrel-cage rotor, wound rotor, salient pole rotor or cylindrical rotor? Power systems deliver energy to loads that perform a function. These loads range from household appliances to industrial machinery. Most loads expect a certain voltage and, for alternating current devices, a certain frequency and number of phases.
An exception exists for larger centralized air conditioning systems as in some countries these are now typically three-phase because this allows them to operate more efficiently. All electrical appliances also have a wattage rating, which specifies the amount of power the device consumes.
At any one time, the net amount of power consumed by the loads on a power system must equal the net amount of power produced by the supplies less the power lost in transmission. Making sure that the voltage, frequency and amount of power supplied to the loads is in line with expectations is one of the great challenges of power system engineering.
However it is not the only challenge, in addition to the power used by a load to do useful work termed real power many alternating current devices also use an additional amount of power because they cause the alternating voltage and alternating current to become slightly out-of-sync termed reactive power. The reactive power like the real power must balance that is the reactive power produced on a system must equal the reactive power consumed and can be supplied from the generators, however it is often more economical to supply such power from capacitors see "Capacitors and reactors" below for more details.
A final consideration with loads has to do with power quality. In addition to sustained overvoltages and undervoltages voltage regulation issues as well as sustained deviations from the system frequency frequency regulation issues , power system loads can be adversely affected by a range of temporal issues. These include voltage sags, dips and swells, transient overvoltages, flicker, high-frequency noise, phase imbalance and poor power factor.
Power quality issues can be especially important when it comes to specialist industrial machinery or hospital equipment. Conductors carry power from the generators to the load. In a grid , conductors may be classified as belonging to the transmission system , which carries large amounts of power at high voltages typically more than 69 kV from the generating centres to the load centres, or the distribution system , which feeds smaller amounts of power at lower voltages typically less than 69 kV from the load centres to nearby homes and industry.
Choice of conductors is based on considerations such as cost, transmission losses and other desirable characteristics of the metal like tensile strength. Copper , with lower resistivity than aluminum , was once the conductor of choice for most power systems.
However, aluminum has a lower cost for the same current carrying capacity and is now often the conductor of choice. Overhead line conductors may be reinforced with steel or aluminium alloys.
Conductors in exterior power systems may be placed overhead or underground. Overhead conductors are usually air insulated and supported on porcelain, glass or polymer insulators. Cables used for underground transmission or building wiring are insulated with cross-linked polyethylene or other flexible insulation. Conductors are often stranded for to make them more flexible and therefore easier to install. Conductors are typically rated for the maximum current that they can carry at a given temperature rise over ambient conditions.
As current flow increases through a conductor it heats up. For insulated conductors, the rating is determined by the insulation. The majority of the load in a typical AC power system is inductive; the current lags behind the voltage.
Since the voltage and current are out-of-phase, this leads to the emergence of an "imaginary" form of power known as reactive power. Reactive power does no measurable work but is transmitted back and forth between the reactive power source and load every cycle. This reactive power can be provided by the generators themselves but it is often cheaper to provide it through capacitors, hence capacitors are often placed near inductive loads i.
Reactors consume reactive power and are used to regulate voltage on long transmission lines. In light load conditions, where the loading on transmission lines is well below the surge impedance loading , the efficiency of the power system may actually be improved by switching in reactors.
Reactors installed in series in a power system also limit rushes of current flow, small reactors are therefore almost always installed in series with capacitors to limit the current rush associated with switching in a capacitor. Series reactors can also be used to limit fault currents. Capacitors and reactors are switched by circuit breakers, which results in moderately large step changes of reactive power. A solution to this comes in the form of synchronous condensers , static VAR compensators and static synchronous compensators.
Briefly, synchronous condensers are synchronous motors that spin freely to generate or absorb reactive power. This provides a far more refined response than circuit-breaker-switched capacitors. Static synchronous compensators take this a step further by achieving reactive power adjustments using only power electronics.
Power electronics are semiconductor based devices that are able to switch quantities of power ranging from a few hundred watts to several hundred megawatts.
Despite their relatively simple function, their speed of operation typically in the order of nanoseconds  means they are capable of a wide range of tasks that would be difficult or impossible with conventional technology. The classic function of power electronics is rectification , or the conversion of AC-to-DC power, power electronics are therefore found in almost every digital device that is supplied from an AC source either as an adapter that plugs into the wall see photo or as component internal to the device.
HVDC is used because it proves to be more economical than similar high voltage AC systems for very long distances hundreds to thousands of kilometres.
Such an application will result in a more economical, more convenient and higher service quality operation and in less inconvenience in the case of abnormal conditions. For its analytical treatment, control system design generally requires the determination of a mathematical model from which the control strategy can be derived. While much of the control theory postulates that a model of the system is available, it is also necessary to have a suitable technique to determine the models for the process to be controlled. It is therefore essential to model and identify power system components using both physical relationships and experimental or normal operating data. The objective of system identification is the determination of a mathematical model that characterizes the operation of a system in some form. The available information is either system output or a function of the system output.
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New Technologies for Power System Operation and Analysis considers the very latest developments in renewable energy integration and system operation, including electricity markets and wide-area monitoring systems and forecasting. Helping readers quickly grasp the essential information needed to address renewable energy integration challenges, this new book looks at basic power system mathematical models, advanced renewable integration and system optimizations from transmission and distribution system sides. Sections cover wind, solar, gas and petroleum, making this a useful reference for all engineers interested in power system operation. Power system basic Mathematical model Power flow computation Static security analysis.
- У нее кольцо, которое принадлежит. Я готов заплатить. Очень. Двухцветный застыл на месте и зашелся в истерическом хохоте.
Фонтейн погрузился в раздумья. Джабба терпеливо ждал, наконец не выдержал и крикнул ассистентке: - Соши. Немедленно.
Неужели он ее трогает. Она не сразу поняла, что он пытается застегнуть верхнюю пуговицу ее блузки. - Сьюзан, - позвал он, задыхаясь. - Ты должна помочь мне выбраться отсюда. Она ничего не понимала. Все это было лишено всякого смысла. - Сьюзан, ты должна мне помочь.
Через пять гудков он услышал ее голос. - Здравствуйте, Это Сьюзан Флетчер. Извините, меня нет дома, но если вы оставите свое сообщение… Беккер выслушал все до конца.
- Тебе удалось стереть электронную почту Хейла. - Нет, - сконфуженно ответила. - Ты нашла ключ.
Да, да, прямо. К тому же у нас вышел из строя генератор. Я требую направить сюда всю энергию из внешних источников.
D.P. Kothari and I.J. Nagrath, 'Modern Power System Analysis', Third Edition, Tata The main objective of power system operation and control is to maintain Electric power is generated by converting mechanical energy into electrical energy.Hoxbotsmindsearch 31.03.2021 at 10:33
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The matter presented here is prepared by the author for their respective teaching assignments by referring the text books and reference books.Elda N. 03.04.2021 at 20:31
An electric power system is a network of electrical components deployed to supply, transfer, and use electric power.Barlaan A. 04.04.2021 at 20:05
Such an application will result in a more economical, more convenient and higher service quality operation and in less inconvenience in the case of abnormal conditions.