HISTORY
Electricity generation is the process of generating electric power from sources of energy. The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday. His basic method is still used today: electricity is generated by the movement of a loop of wire or disc of copper between the poles of a magnet.
For electric utilities, it is the first process in the delivery of electricity to consumers. The other processes, electricity transmission, distribution, and electrical power storage and recovery using pumped-storage methods are normally carried out by the electric power industry.
Electricity is most often generated at a power station by electromechanical generators, primarily driven by engines fueled by chemical combustion or nuclear fission but also by other means such as the kinetic energy of flowing water and wind. Other energy sources include solar photovoltaic and geothermal power.
Central power stations became economically practical with the development of alternating current power transmission, using power transformers to transmit power at high voltage and with low loss. Electricity has been generated at central stations since 1881. The first power plants were run on water power or coal, and today we rely mainly on coal, nuclear, natural gas, hydroelectric, wind generators, and petroleum, with a small amount from solar energy, tidal power, and geothermal sources.
The use of power lines and power poles has been significantly important in the distribution of electricity.
INTRODUCTION
When you start out with electronics, you’ll hear a lot about power supplies – they’re in every electronics project and they are the backbone of everything! A good power supply will make your project hum along nicely. A bad power supply will make life frustrating: stuff will work sometimes but not others, inconsistent results, motors not working, and sensor data always off. Understanding power supplies is the key to making things work.
Electric power systems are comprised of components that produce electrical energy and transmit this energy to consumers. A modern electric power system has mainly six main components:
1) Power plants that generate electric power
2) Transformers that raise or lower the voltages as needed
3) Transmission lines to carry power
4) Substations at which the voltage is stepped down for carrying power over the distribution lines
5) Distribution lines
6) Distribution transformers which lower the voltage to the level needed for the consumer equipment. The production and transmission of electricity are relatively efficient and inexpensive, although, unlike other forms of energy, electricity is not easily stored, and thus, must be produced based on the demand.
ELECTRIC POWER SUPPLY SYSTEMS IN THE WORLD
Electrical systems differ around the world – both in voltage and less critically, frequency. The physical interfaces (plugs and sockets) are also different and often incompatible. However, travelers with electrical appliances can take a few steps to ensure that they can be safely used at their destination.
Total energy consumed at all power plants for the generation of electricity was 4,398,768 ktoe (kilo ton of oil equivalent) which was 36% of the total for primary energy sources (TPES) of 2008.
Electricity output (gross) was 1,735,579 ktoe (20,185 TWh), efficiency was 39%, and the balance of 61% was generated heat. A small part (145,141 ktoe, which was 3% of the input total) of the heat was utilized at co-generation heat and power plants. The in-house consumption of electricity and power transmission losses were 289,681 ktoe.
| Source of Electricity (World total year 2008) | |||||||
| Coal | Oil | Natural Gas | Nuclear | Hydro | other | Total | |
| Average electric power (TWh/year) | 8,263 | 1,111 | 4,301 | 2,731 | 3,288 | 568 | 20,261 |
| Average electric power (GW) | 942.6 | 126.7 | 490.7 | 311.6 | 375.1 | 64.8 | 2311.4 |
| Proportion | 41% | 5% | 21% | 13% | 16% | 3% | 100% |
Electric power delivery throughout the United States was designated by the National Academy of Engineering as the leading engineering development of the 20th century. Since electricity was first delivered to private citizens in the late 19th century, the value of reliable electric power to our economy has been obvious. Our world has been transformed by countless technologies enabled by the widespread delivery of secure, high-quality electric power. However, the transmission and distribution infrastructure in the United States is aging, and the need for modernization has become urgent.
2020, a Different Kind of Power System
By 2020 USA anticipates that wind, water, and solar energy (WWS) will be dependably integrated with efficient, conventional-fuel power plants that are cleaner than ever (Jacobson and Delucchi, 2009). In addition, the transmission grid will be greatly expanded, and new monitoring and control systems will help keep it reliable.
In individual homes, dishwashers and clothes washers, more efficient than ever, will turn on to take advantage of low-cost power that the utility has signaled is available; hybrid electric cars will also be recharged in off-peak hours. Electric outages will be very rare because intelligent systems will identify deteriorating power-delivery apparatus and dispatch crews for repair before outages occur. When a major fault or accident does happen, the electricity system will automatically reconfigure itself and restore power with a barely noticeable blink of the lights.
Widespread deployment of these advanced technologies is within their grasp. But to make these systems economical, dependable, maintainable, and operationally independent of excessive human oversight will require additional research and much good engineering. A plentiful, educated, and experienced workforce is the key to USA’s electric-power future.
| County | Fossil Fuel | Nuclear | rank | Renewable | |||||||||||
| Coal | Oil | Gas | sub total | rank | Hydro | Geo Thermal | Solar PV* | Solar Thermal | Wind | Tide | sub total | rank | |||
| USA | 2,133 | 58 | 911 | 3,101 | 1 | 838 | 1 | 282 | 17 | 1.6 | 0.88 | 56 | – | 357 | 4 |
Composition of Electricity in USA by Resources (TWh per the year 2008)
Hydropower provides about 96 percent of the renewable energy in the United States. Other renewable resources include geothermal, wave power, tidal power, wind power, and solar power. In Washington State, hydroelectric power plants provided approximately 80 percent of the electrical power during 2002. In contrast, in Ohio during the same year, almost 87 percent of the electrical power came from coal-fired power plants due to the area’s ample supply of coal.
POWER SUPPLY
A power supply is a device that supplies electric power to an electrical load. The term is most commonly applied to electric power converters that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy (mechanical, chemical, solar) to electrical energy. A regulated power supply is one that controls the output voltage or current to a specific value; the controlled value is held nearly constant despite variations in either load current or the voltage supplied by the power supply’s energy source.
Every power supply must obtain the energy it supplies to its load, as well as any energy it consumes while performing that task, from an energy source. Depending on its design, a power supply may obtain energy from:
• Electrical energy transmission systems. Common examples of this include power supplies that convert AC line voltage to DC voltage.
• Energy storage devices such as batteries and fuel cells.
• Electromechanical systems such as generators and alternators.
• Solar power.
This is a massive power supply that’s in a PC, usually, you don’t see this unless you open up the PC and look inside for the big metal box.
POWER SUPPLY TYPES
Power supplies for electronic devices can be broadly divided into line-frequency (or “conventional”) and switching power supplies. The line-frequency supply is usually a relatively simple design, but it becomes increasingly bulky and heavy for high-current equipment due to the need for large mains-frequency transformers and heatsinked electronic regulation circuitry. Conventional line-frequency power supplies are sometimes called “linear,” but that is not accurate because the conversion from AC voltage to DC is fundamentally non-linear when the rectifiers feed into capacitive reservoirs. Linear voltage regulators produce regulated output voltage by means of an active voltage divider that consumes energy, thus making efficiency low. A switched-mode supply of the same rating as a line-frequency supply will be smaller, and is usually more efficient but would be more complex
Battery: A battery is a device that converts stored chemical energy to electrical energy. Batteries are commonly used as energy sources in many household and industrial applications. There are two types of batteries: primary batteries (disposable batteries), which are designed to be used once and discarded, and secondary batteries (rechargeable batteries), which are designed to be recharged and used multiple times. Batteries come in many sizes, from miniature cells used in hearing aids and wristwatches to room-size battery banks that serve as backup power supplies in telephone exchanges and computer data centers.
DC Power Supply: An AC-powered unregulated power supply usually uses a transformer to convert the voltage from the wall outlet (mains) to a different, nowadays usually lower, voltage. If it is used to produce DC, a rectifier is used to convert alternating voltage to a pulsating direct voltage, followed by a filter, comprising one or more capacitors, resistors, and sometimes inductors, to filter out (smooth) most of the pulsation. A small remaining unwanted alternating voltage component at mains or twice mains power frequency (depending upon whether half- or full-wave rectification is used)—ripple—is unavoidably superimposed on the direct output voltage.
For purposes such as charging batteries, the ripple is not a problem, and the simplest unregulated mains-powered DC power supply circuit consists of a transformer driving a single diode in series with a resistor.
Before the introduction of solid-state electronics, equipment used valves (vacuum tubes) which required high voltages; power supplies used step-up transformers, rectifiers, and filters to generate one or more direct voltages of some hundreds of volts and a low alternating voltage for filaments. Only the most advanced equipment used expensive and bulky regulated power supplies.
AC Power Supply: An AC power supply typically takes the voltage from a wall outlet (mains supply) and lowers it to the desired voltage. Some filtering may take place as well.
Linear Regulated Power Supply: The voltage produced by an unregulated power supply will vary depending on the load and on variations in the AC supply voltage. For critical electronics applications, a linear regulator may be used to set the voltage to a precise value, stabilized against fluctuations in input voltage and load. The regulator also greatly reduces the ripple and noise in the output direct current. Linear regulators often provide current limiting, protecting the power supply and attached circuit from overcurrent.
AC/DC Supply: In the past, mains electricity was supplied as DC in some regions, AC in others. Transformers cannot be used for DC, but a simple, cheap unregulated power supply could run directly from either AC or DC mains without using a transformer. The power supply consisted of a rectifier and a filter capacitor. When operating from DC, the rectifier was essentially a conductor, having no effect; it was included to allow operation from AC or DC without modification.
POWER SUPPLY APPLICATIONS
Computer Power Supply: A modern computer power supply is a switch-mode power supply that converts AC power from the mains supply to several DC voltages. Switch-mode supplies replaced linear supplies due to cost, weight, and size improvement.
Welding Power Supply: Arc welding uses electricity to melt the surfaces of the metals in order to join them together through coalescence. The electricity is provided by a welding power supply, and can either be AC or DC. Arc welding typically requires high currents typically between 100 and 350 amps. Some types of welding can use as few as 10 amps, while some applications of spot welding employ currents as high as 60,000 amps for an extremely short time. Older welding power supplies consisted of transformers or engines driving generators. More recent supplies use semiconductors and microprocessors reducing their size and weight.
Here is the power supply that is used in many apple products
ELECTRIC POWER SYSTEM
An electric power system is a network of electrical components used to supply, transmit and use electric power. An example of an electric power system is the network that supplies a region’s homes and industry with power – for sizable regions, this power system is known as the grid and 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, and automobiles.
ELECTRICAL GRID
An electrical grid is an interconnected network for delivering electricity from suppliers to consumers. It consists of generating stations that produce electrical power, high-voltage transmission lines that carry power from distant sources to demand centers, and distribution lines that connect individual customers.
Power stations may be located near a fuel source, at a dam site, or to take advantage of renewable energy sources, and are often located away from heavily populated areas. They are usually quite large to take advantage of the economies of scale. The electric power which is generated is stepped up to a higher voltage at which it connects to the transmission network.
The transmission network will move the power long distances, sometimes across international boundaries, until it reaches its wholesale customer (usually the company that owns the local distribution network).
On arrival at a substation, the power will be stepped down from a transmission level voltage to a distribution level voltage. As it exits the substation, it enters the distribution wiring. Finally, upon arrival at the service location, the power is stepped down again from the distribution voltage to the required service voltage(s).
The general layout of electricity networks, voltages, and depictions of electrical lines are typical for Germany and other European systems.
POWER STATIONS
A power station (also referred to as a generating station, power plant, powerhouse, or generating plant) is an industrial facility for the generation of electric power. At the center of nearly all power stations is a generator, a rotating machine that converts mechanical power into electrical power by creating relative motion between a magnetic field and a conductor.
The energy source harnessed to turn the generator varies widely. It depends chiefly on which fuels are easily available, cheap enough, and on the types of technology that the power company has access to. Most power stations in the world burn fossil fuels such as coal, oil, and natural gas to generate electricity, and some use nuclear power, but there is increasing use of cleaner renewable sources such as solar, wind, wave, and hydroelectric.
Thermal Power Stations: In thermal power stations, mechanical power is produced by a heat engine that transforms thermal energy, often from the combustion of a fuel, into rotational energy. Most thermal power stations produce steam, and these are sometimes called steam power stations. Not all thermal energy can be transformed into mechanical power, according to the second law of thermodynamics.
Therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for industrial processes or district heating, the power plant is referred to as a cogeneration power plant or CHP (combined heat-and-power) plant. In countries where district heating is common, there are dedicated heat plants called heat-only boiler stations. An important class of power stations in the Middle East uses by-product heat for the desalination of water.
ELECTRICAL SUBSTATIONS
A substation 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 the consumer, electric power may flow through several substations at different voltage levels.
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 (supervisory control and data acquisition) for remote supervision and control.
A substation has a metallic fence; it must be properly grounded to protect people from high voltages that may occur during a fault in the network. Earth faults at a substation can cause a ground potential rise. Currents flowing in the Earth’s surface during a fault can cause metal objects to have a significantly different voltage than the ground under a person’s feet
TYPES
- Transmission Substation: A transmission substation connects two or more transmission lines. The simplest case is where all transmission lines have the same voltage. In such cases, the 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, and equipment such as phase shifting transformers to control power flow between two adjacent power systems.
- Distribution Substation: A distribution substation transfers power from 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 the voltage to a level suitable for local distribution.
A 50 Hz electrical substation in Melbourne. This is showing three of the five 220 kV/66 kV transformers, each with a capacity of 150 MVA. This substation is constructed using steel lattice structures to support strain bus wires and apparatus
TRANSFORMER
Transformers work over the principle of magnetic induction. There are two types of winding namely primary and secondary. When a current is supplied to the primary winding a magnetic flux is generated in the coil and by the law of magnetic induction and continuous change in magnetic flux, a voltage is induced at the secondary coil which is used as the output.
The number of turns of the coil usually contributes by increasing or decreasing the output voltage. This is known as:
* Step-up transformer: where voltage is increased at the output terminal.
* Step-down transformer: that reduces the voltage at the output terminal.
Transformers range in size from thumbnail-sized units hidden inside microphones to units weighing hundreds of tons interconnecting the power grid. A wide range of transformer designs are used in electronic and electric power applications. Transformers are essential for the transmission, distribution, and utilization of electrical energy.
AGING INFRASTRUCTURE
Despite the novel institutional arrangements and network designs of the electrical grid, its power delivery infrastructures suffer aging across the developed world. Four contributing factors to the current state of the electric grid and its consequences include:
1. Aging power equipment – older equipment has higher failure rates, leading to customer interruption rates affecting the economy and society; also, older assets and facilities lead to higher inspection maintenance costs and further repair/restoration costs.
2. Obsolete system layout – older areas require serious additional substation sites and rights-of-way that cannot be obtained in the current area and are forced to use existing, insufficient facilities.
3. Outdated engineering – traditional tools for power delivery planning and engineering are ineffective in addressing current problems of aged equipment, obsolete system layouts, and modern deregulated loading levels
4. Old cultural value – planning, engineering, and operating of systems using concepts and procedures that worked in vertically integrated industries impair the problem under a deregulated industry.
MODERN TRENDS
With everything interconnected, and open competition occurring in a free market economy, it starts to make sense to allow and even encourage distributed generation (DG). Smaller generators, usually not owned by the utility, can be brought online to help supply the need for power. The smaller generation facility might be a homeowner with excess power from their solar panel or wind turbine. It might be a small office with a diesel generator.
Furthermore, numerous efforts are underway to develop a “smart grid”. In the U.S., the Energy Policy Act of 2005 and Title XIII of the Energy Independence and Security Act of 2007 are providing funding to encourage smart grid development. The hope is to enable utilities to better predict their needs for excess power from their solar panel or wind turbine. It might be a small office with a diesel generator. Funds have also been allocated to develop more strong energy control technologies. Various planned and proposed systems to dramatically increase transmission capacity are known as super, or mega grids.
FUTURE TRENDS
Recently, U.K’s National Grid, the largest private electric utility in the world, bought New England’s electric system for $3.2 billion. Also, Scottish Power purchased Pacific Energy for $12.8 billion. Domestically, local electric and gas firms begin to merge operations as they see the advantage of joint affiliation, especially with the reduced cost of joint metering. Technological advances will take place in the competitive wholesale electric markets examples already being utilized include fuel cells used in space flight, aero-derivative gas turbines used in jet aircraft, solar engineering, photovoltaic systems, and off-shore wind farms.
EMERGING SMART GRIDS
The electrical grid is expected to evolve into a new grid model–smart grid, an enhancement of the 20th-century electrical grid. Traditional electrical grids are generally used to carry power from a few central generators to a large number of users or customers. In contrast, the new emerging smart grid uses two-way flows of electricity and information to create an automated and distributed advanced energy delivery network. Many research projects have been conducted to explore the concept of a smart grid. According to the newest survey on smart grids, the research is mainly focused on three systems in the smart grid- the infrastructure system, the management system, and the protection system.
The infrastructure system is the energy, information, and communication infrastructure underlying the smart grid that supports
1) advanced electricity generation, delivery, and consumption;
2) advanced information metering, monitoring, and management. In the transition from the conventional power grid to the smart grid, we will replace a physical infrastructure with a digital one.
- The management system is the subsystem in the smart grid that provides advanced management and control services.
- The protection system is the subsystem in the smart grid that provides advanced grid reliability analysis, failure protection, and security and privacy protection services.
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