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62-460: The site employs 1,680 regular employees. As of 2 August 2010, it became the second nuclear station anywhere in the world to produce over one thousand terawatt-hours of electricity, following Bruce Nuclear Generating Station in Ontario, Canada, which passed that milestone in 2009. The reactors of Units 5 and 6 were initially intended for export to Iran , but the order was cancelled after

124-428: A battery is usually expressed indirectly by its capacity in ampere-hours ; to convert ampere-hour (Ah) to watt-hours (Wh), the ampere-hour value must be multiplied by the voltage of the power source. This value is approximate, since the battery voltage is not constant during its discharge, and because higher discharge rates reduce the total amount of energy that the battery can provide. In the case of devices that output

186-401: A change over time. For example: miles per hour, kilometres per hour, dollars per hour. Power units, such as kW, already measure the rate of energy per unit time (kW= kJ / s ). Kilowatt-hours are a product of power and time, not a rate of change of power with time. Watts per hour (W/h) is a unit of a change of power per hour, i.e. an acceleration in the delivery of energy. It is used to measure

248-562: A current that is always in phase with and at the same frequency as the line voltage. Another switched-mode converter inside the power supply produces the desired output voltage from the DC bus. This approach requires additional semiconductor switches and control electronics but permits cheaper and smaller passive components. It is frequently used in practice. For a three-phase SMPS, the Vienna rectifier configuration may be used to substantially improve

310-442: A different voltage than the battery, it is the battery voltage (typically 3.7 V for Li-ion ) that must be used to calculate rather than the device output (for example, usually 5.0 V for USB portable chargers). This results in a 500 mA USB device running for about 3.7 hours on a 2,500 mAh battery, not five hours. The Board of Trade unit (B.T.U.) is an obsolete UK synonym for kilowatt-hour. The term derives from

372-462: A factor of three. While smaller customer loads are usually billed only for energy, transmission services, and the rated capacity, larger consumers also pay for peak power consumption, the greatest power recorded in a fairly short time, such as 15 minutes. This compensates the power company for maintaining the infrastructure needed to provide peak power. These charges are billed as demand changes. Industrial users may also have extra charges according to

434-422: A fraction of the period later. Electrical circuits containing predominantly resistive loads ( incandescent lamps , devices using heating elements like electric toasters and ovens ) have a power factor of almost 1, but circuits containing inductive or capacitive loads (electric motors, solenoid valves, transformers, fluorescent lamp ballasts , and others) can have a power factor well below 1. A circuit with

496-452: A kilowatt-hour over an eight-hour day. To convert a quantity measured in a unit in the left column to the units in the top row, multiply by the factor in the cell where the row and column intersect. All the SI prefixes are commonly applied to the watt-hour: a kilowatt-hour is 1,000 Wh (kWh); a megawatt-hour is 1 million Wh (MWh); a milliwatt-hour is 1/1,000 Wh (mWh) and so on. The kilowatt-hour

558-424: A load to improve the power factor. Some types of the active PFC are buck , boost , buck-boost and synchronous condenser . Active power factor correction can be single-stage or multi-stage. In the case of a switched-mode power supply, a boost converter is inserted between the bridge rectifier and the main input capacitors. The boost converter attempts to maintain a constant voltage at its output while drawing

620-452: A low power factor will use a greater amount of current to transfer a given quantity of real power than a circuit with a high power factor thus causing increased losses due to resistive heating in power lines, and requiring the use of higher-rated conductors and transformers. AC power has two components: Together, they form the complex power ( S {\displaystyle S} ) expressed as volt-amperes (VA). The magnitude of

682-417: A non-linear device look more like a linear load. An example of passive PFC is a valley-fill circuit . A disadvantage of passive PFC is that it requires larger inductors or capacitors than an equivalent power active PFC circuit. Also, in practice, passive PFC is often less effective at improving the power factor. Active PFC is the use of power electronics to change the waveform of current drawn by

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744-569: A non-zero current in the neutral wire . This could overload the neutral wire in some cases and create error in kilowatt-hour metering systems and billing revenue. The presence of current harmonics in a transformer also result in larger eddy currents in the magnetic core of the transformer. Eddy current losses generally increase as the square of the frequency, lowering the transformer's efficiency, dissipating additional heat, and reducing its service life. Negative-sequence harmonics (5th, 11th, 17th, etc.) combine 120 degrees out of phase, similarly to

806-504: A period of one year. In 2020, the average household in the United States consumed 893 kWh per month. Raising the temperature of 1 litre of water from room temperature to the boiling point with an electric kettle takes about 0.1 kWh. A 12 watt LED lamp lit constantly uses about 0.3 kW⋅h per 24 hours and about 9 kWh per month. In terms of human power , a healthy adult male manual laborer performs work equal to about half

868-402: A physical quantity as used. The power factor is defined as the ratio of real power to apparent power. As power is transferred along a transmission line, it does not consist purely of real power that can do work once transferred to the load, but rather consists of a combination of real and reactive power, called apparent power. The power factor describes the amount of real power transmitted along

930-421: A power factor of less than 1. A negative power factor (0 to −1) can result from returning active power to the source, such as in the case of a building fitted with solar panels when surplus power is fed back into the supply. A high power factor is generally desirable in a power delivery system to reduce losses and improve voltage regulation at the load. Compensating elements near an electrical load will reduce

992-420: A regulator that measures power factor in an electrical network. Depending on the load and power factor of the network, the power factor controller will switch the necessary blocks of capacitors in steps to make sure the power factor stays above a selected value. In place of a set of switched capacitors , an unloaded synchronous motor can supply reactive power. The reactive power drawn by the synchronous motor

1054-406: A sinusoidal response to the sinusoidal line voltage. A linear load does not change the shape of the input waveform but may change the relative timing (phase) between voltage and current, due to its inductance or capacitance. In a purely resistive AC circuit, voltage and current waveforms are in step (or in phase ), changing polarity at the same instant in each cycle. All the power entering the load

1116-410: A transmission line relative to the total apparent power flowing in the line. The power factor can also be computed as the cosine of the angle θ by which the current waveform lags or leads the voltage waveform. [REDACTED] One can relate the various components of AC power by using the power triangle in vector space. Real power extends horizontally in the real axis and reactive power extends in

1178-485: A yearly basis, in units such as megawatt-hours per year (MWh/yr) gigawatt-hours/year (GWh/yr) or terawatt-hours per year (TWh/yr). These units have dimensions of energy divided by time and thus are units of power. They can be converted to SI power units by dividing by the number of hours in a year, about 8760 h/yr . Thus, 1 GWh/yr = 1 GWh/8760 h ≈ 114.12 kW . Many compound units for various kinds of rates explicitly mention units of time to indicate

1240-453: Is a function of its field excitation. It is referred to as a synchronous condenser . It is started and connected to the electrical network . It operates at a leading power factor and puts vars onto the network as required to support a system's voltage or to maintain the system power factor at a specified level. The synchronous condenser's installation and operation are identical to those of large electric motors . Its principal advantage

1302-482: Is commonly used by electrical energy providers for purposes of billing, since the monthly energy consumption of a typical residential customer ranges from a few hundred to a few thousand kilowatt-hours. Megawatt-hours (MWh), gigawatt-hours (GWh), and terawatt-hours (TWh) are often used for metering larger amounts of electrical energy to industrial customers and in power generation. The terawatt-hour and petawatt-hour (PWh) units are large enough to conveniently express

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1364-457: Is consumed (or dissipated). Where reactive loads are present, such as with capacitors or inductors , energy storage in the loads results in a phase difference between the current and voltage waveforms. During each cycle of the AC voltage, extra energy, in addition to any energy consumed in the load, is temporarily stored in the load in electric or magnetic fields then returned to the power grid

1426-413: Is described as leading if the current waveform is advanced in phase concerning voltage, or lagging when the current waveform is behind the voltage waveform. A lagging power factor signifies that the load is inductive, as the load will consume reactive power. The reactive component Q {\displaystyle Q} is positive as reactive power travels through the circuit and is consumed by

1488-425: Is interrupted by a switching action, the current contains frequency components that are multiples of the power system frequency. Distortion power factor is a measure of how much the harmonic distortion of a load current decreases the average power transferred to the load. In linear circuits having only sinusoidal currents and voltages of one frequency, the power factor arises only from the difference in phase between

1550-765: Is just energy moving back and forth on each AC cycle. The reactive elements in power factor correction devices can create voltage fluctuations and harmonic noise when switched on or off. They will supply or sink reactive power regardless of whether there is a corresponding load operating nearby, increasing the system's no-load losses. In the worst case, reactive elements can interact with the system and with each other to create resonant conditions, resulting in system instability and severe overvoltage fluctuations. As such, reactive elements cannot simply be applied without engineering analysis. An automatic power factor correction unit consists of some capacitors that are switched by means of contactors . These contactors are controlled by

1612-544: Is located next to the power station. Kilowatt hour#Watt hour multiples and billing units A kilowatt-hour ( unit symbol : kW⋅h or kW h ; commonly written as kWh ) is a non-SI unit of energy equal to 3.6 megajoules (MJ) in SI units, which is the energy delivered by one kilowatt of power for one hour . Kilowatt-hours are a common billing unit for electrical energy supplied by electric utilities . Metric prefixes are used for multiples and submultiples of

1674-450: Is measured in watts , or joules per second . For example, a battery stores energy. When the battery delivers its energy, it does so at a certain power, that is, the rate of delivery of the energy. The higher the power, the quicker the battery's stored energy is delivered. A higher power output will cause the battery's stored energy to be depleted in a shorter time period. Electric energy production and consumption are sometimes reported on

1736-567: Is the ease with which the amount of correction can be adjusted; it behaves like a variable capacitor. Unlike with capacitors, the amount of reactive power furnished is proportional to voltage, not the square of voltage; this improves voltage stability on large networks. Synchronous condensers are often used in connection with high-voltage direct-current transmission projects or in large industrial plants such as steel mills . For power factor correction of high-voltage power systems or large, fluctuating industrial loads, power electronic devices such as

1798-450: Is typically sold to consumers in kilowatt-hours. The cost of running an electrical device is calculated by multiplying the device's power consumption in kilowatts by the operating time in hours, and by the price per kilowatt-hour. The unit price of electricity charged by utility companies may depend on the customer's consumption profile over time. Prices vary considerably by locality. In the United States prices in different states can vary by

1860-467: Is used with loads or output that vary during the year but whose annual totals are similar from one year to the next. For example, it is useful to compare the energy efficiency of household appliances whose power consumption varies with time or the season of the year. Another use is to measure the energy produced by a distributed power source. One kilowatt-hour per year equals about 114.08 milliwatts applied constantly during one year. The energy content of

1922-702: The International System of Units (SI). Other representations of the unit may be encountered: The hour is a unit of time listed among the non-SI units accepted by the International Bureau of Weights and Measures for use with the SI. An electric heater consuming 1,000 watts (1 kilowatt) operating for one hour uses one kilowatt-hour of energy. A television consuming 100 watts operating continuously for 10 hours uses one kilowatt-hour. A 40-watt electric appliance operating continuously for 25 hours uses one kilowatt-hour. Electrical energy

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1984-625: The Iranian Revolution in 1979. Their design, known as CPY , was the basis for the Chinese CPR-1000 . An intermediate derivative is called the M310. The cooling water that carries waste heat from the plant is used for aquaculture in a location named Route De L'aquaculture. A local commune of aquafarmers who raise European seabass and gilt-head breams . The warm water helps them grow faster. A major OVH datacentre

2046-433: The annual electricity generation for whole countries and the world energy consumption . A kilowatt is a unit of power (rate of flow of energy per unit of time). A kilowatt-hour is a unit of energy. Kilowatt per hour would be a rate of change of power flow with time. Work is the amount of energy transferred to a system; power is the rate of delivery of energy. Energy is measured in joules , or watt-seconds . Power

2108-413: The power factor of an AC power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit. Real power is the average of the instantaneous product of voltage and current and represents the capacity of the electricity for performing work. Apparent power is the product of root mean square (RMS) current and voltage. Due to energy stored in

2170-405: The power factor of their load. Major energy production or consumption is often expressed as terawatt-hours (TWh) for a given period that is often a calendar year or financial year . A 365-day year equals 8,760 hours, so over a period of one year, power of one gigawatt equates to 8.76 terawatt-hours of energy. Conversely, one terawatt-hour is equal to a sustained power of about 114 megawatts for

2232-502: The static VAR compensator or STATCOM are increasingly used. These systems are able to compensate sudden changes of power factor much more rapidly than contactor-switched capacitor banks and, being solid-state, require less maintenance than synchronous condensers. Examples of non-linear loads on a power system are rectifiers (such as used in a power supply), and arc discharge devices such as fluorescent lamps , electric welding machines, or arc furnaces . Because current in these systems

2294-530: The apparent power demand on the supply system. Power factor correction may be applied by an electric power transmission utility to improve the stability and efficiency of the network. Individual electrical customers who are charged by their utility for low power factor may install correction equipment to increase their power factor to reduce costs. Power factor correction brings the power factor of an AC power circuit closer to 1 by supplying or absorbing reactive power, adding capacitors or inductors that act to cancel

2356-450: The basic unit, the watt-hour (3.6 kJ). The kilowatt-hour is a composite unit of energy equal to one kilowatt (kW) sustained for (multiplied by) one hour. The International System of Units (SI) unit of energy meanwhile is the joule (symbol J). Because a watt is by definition one joule per second , and because there are 3,600 seconds in an hour, one kWh equals 3,600  kilojoules or 3.6 MJ. A widely used representation of

2418-417: The complex power is the apparent power ( | S | {\displaystyle |S|} ), also expressed in volt-amperes (VA). The VA and var are non-SI units dimensionally similar to the watt but are used in engineering practice instead of the watt to state what quantity is being expressed. The SI explicitly disallows using units for this purpose or as the only source of information about

2480-418: The corresponding current in place of total current). This definition with respect to total harmonic distortion assumes that the voltage stays undistorted (sinusoidal, without harmonics). This simplification is often a good approximation for stiff voltage sources (not being affected by changes in load downstream in the distribution network). Total harmonic distortion of typical generators from current distortion in

2542-492: The costs of larger equipment and wasted energy, electrical utilities will usually charge a higher cost to industrial or commercial customers with a low power factor. Power-factor correction increases the power factor of a load, improving efficiency for the distribution system to which it is attached. Linear loads with a low power factor (such as induction motors ) can be corrected with a passive network of capacitors or inductors . Non-linear loads, such as rectifiers , distort

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2604-620: The current and voltage. This is displacement power factor . Non-linear loads change the shape of the current waveform from a sine wave to some other form. Non-linear loads create harmonic currents in addition to the original (fundamental frequency) AC current. This is of importance in practical power systems that contain non-linear loads such as rectifiers , some forms of electric lighting, electric arc furnaces , welding equipment, switched-mode power supplies , variable speed drives and other devices. Filters consisting of linear capacitors and inductors can prevent harmonic currents from entering

2666-431: The current drawn from the system. In such cases, active or passive power factor correction may be used to counteract the distortion and raise the power factor. The devices for correction of the power factor may be at a central substation , spread out over a distribution system, or built into power-consuming equipment. In a linear circuit , consisting of combinations of resistors, inductors, and capacitors, current flow has

2728-421: The current waveform lagging the voltage. Capacitive loads such as capacitor banks or buried cables generate reactive power with the current phase leading the voltage. Both types of loads will absorb energy during part of the AC cycle, which is stored in the device's magnetic or electric field, only to return this energy back to the source during the rest of the cycle. For example, to get 1 kW of real power, if

2790-558: The daily variation of demand (e.g. the slope of the duck curve ), or ramp-up behavior of power plants . For example, a power plant that reaches a power output of 1 MW from 0 MW in 15 minutes has a ramp-up rate of 4 MW/h . Other uses of terms such as watts per hour are likely to be errors. Several other units related to kilowatt-hour are commonly used to indicate power or energy capacity or use in specific application areas. Average annual energy production or consumption can be expressed in kilowatt-hours per year. This

2852-494: The direction of the imaginary axis. Complex power (and its magnitude, apparent power) represents a combination of both real and reactive power, and therefore can be calculated by using the vector sum of these two components. We can conclude that the mathematical relationship between these components is: As the angle θ increases with fixed total apparent power, current and voltage are further out of phase with each other. Real power decreases, and reactive power increases. Power factor

2914-410: The fundamental harmonic but in a reversed sequence. In generators and motors, these currents produce magnetic fields which oppose the rotation of the shaft and sometimes result in damaging mechanical vibrations. The simplest way to control the harmonic current is to use a filter that passes current only at line frequency (50 or 60 Hz). The filter consists of capacitors or inductors and makes

2976-502: The inductive load. A leading power factor signifies that the load is capacitive, as the load supplies reactive power, and therefore the reactive component Q {\displaystyle Q} is negative as reactive power is being supplied to the circuit. [REDACTED] If θ is the phase angle between the current and voltage, then the power factor is equal to the cosine of the angle, cos ⁡ θ {\displaystyle \cos \theta } : Since

3038-489: The inductive or capacitive effects of the load, respectively. In the case of offsetting the inductive effect of motor loads, capacitors can be locally connected. These capacitors help to generate reactive power to meet the demand of the inductive loads. This will keep that reactive power from having to flow from the utility generator to the load. In the electricity industry, inductors are said to consume reactive power, and capacitors are said to supply it, even though reactive power

3100-413: The kilowatt-hour is kWh , derived from its component units, kilowatt and hour. It is commonly used in billing for delivered energy to consumers by electric utility companies, and in commercial, educational, and scientific publications, and in the media. It is also the usual unit representation in electrical power engineering. This common representation, however, does not comply with the style guide of

3162-404: The load and is subject to losses in the production and transmission processes. Electrical loads consuming alternating current power consume both real power and reactive power. The vector sum of real and reactive power is the complex power, and its magnitude is the apparent power. The presence of reactive power causes the real power to be less than the apparent power, and so, the electric load has

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3224-404: The load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power may be greater than the real power, so more current flows in the circuit than would be required to transfer real power alone. A power factor magnitude of less than one indicates the voltage and current are not in phase, reducing the average product of

3286-449: The load current. I 1 {\displaystyle I_{1}} is the fundamental component of the current, I r m s {\displaystyle I_{rms}} is the total current, and I h {\displaystyle I_{h}} is the current on the h harmonic; all are root mean square values (distortion power factor can also be used to describe individual order harmonics, using

3348-540: The name of the Board of Trade which regulated the electricity industry until 1942 when the Ministry of Power took over. This should not be confused with a British Thermal Unit (BTU) which is 1055 J. In India, the kilowatt-hour is often simply called a unit of energy. A million units, designated MU , is a gigawatt-hour and a BU (billion units) is a terawatt-hour. Power factor In electrical engineering ,

3410-409: The network is on the order of 1–2%, which can have larger scale implications but can be ignored in common practice. The result when multiplied with the displacement power factor is the overall, true power factor or just power factor (PF): In practice, the local effects of distortion current on devices in a three-phase distribution network rely on the magnitude of certain order harmonics rather than

3472-405: The power factor is unity, 1 kVA of apparent power needs to be transferred (1 kW ÷ 1 = 1 kVA). At low values of power factor, more apparent power needs to be transferred to get the same real power. To get 1 kW of real power at 0.2 power factor, 5 kVA of apparent power needs to be transferred (1 kW ÷ 0.2 = 5 kVA). This apparent power must be produced and transmitted to

3534-428: The power factor. SMPSs with passive PFC can achieve power factor of about 0.7–0.75, SMPSs with active PFC, up to 0.99 power factor, while a SMPS without any power factor correction have a power factor of only about 0.55–0.65. Due to their very wide input voltage range, many power supplies with active PFC can automatically adjust to operate on AC power from about 100 V (Japan) to 240 V (Europe). That feature

3596-459: The sign of the phase angle. Capacitive loads are leading (current leads voltage), and inductive loads are lagging (current lags voltage). If a purely resistive load is connected to a power supply, current and voltage will change polarity in step, the power factor will be 1, and the electrical energy flows in a single direction across the network in each cycle. Inductive loads such as induction motors (any type of wound coil) consume reactive power with

3658-409: The supplying system. To measure the real power or reactive power, a wattmeter designed to work properly with non-sinusoidal currents must be used. The distortion power factor is the distortion component associated with the harmonic voltages and currents present in the system. THD i {\displaystyle {\mbox{THD}}_{i}} is the total harmonic distortion of

3720-436: The total harmonic distortion. For example, the triplen , or zero-sequence, harmonics (3rd, 9th, 15th, etc.) have the property of being in-phase when compared line-to-line. In a delta-wye transformer , these harmonics can result in circulating currents in the delta windings and result in greater resistive heating . In a wye-configuration of a transformer, triplen harmonics will not create these currents, but they will result in

3782-435: The two. A negative power factor occurs when the device (normally the load) generates real power, which then flows back towards the source. In an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred. The larger currents increase the energy lost in the distribution system and require larger wires and other equipment. Because of

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3844-443: The units are consistent, the power factor is by definition a dimensionless number between -1 and 1. When the power factor is equal to 0, the energy flow is entirely reactive, and stored energy in the load returns to the source on each cycle. When the power factor is 1, referred to as the unity power factor, all the energy supplied by the source is consumed by the load. Power factors are usually stated as leading or lagging to show

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