1512:, for example, can be made smaller because the magnetic core can be much smaller for the same power level. Induction motors turn at a speed proportional to frequency, so a high-frequency power supply allows more power to be obtained for the same motor volume and mass. Transformers and motors for 400 Hz are much smaller and lighter than at 50 or 60 Hz, which is an advantage in aircraft and ships. A United States military standard
235:. For very slow prime mover speeds, it would be costly to build a generator with enough poles to provide a high AC frequency. As well, synchronizing two generators to the same speed was found to be easier at lower speeds. While belt drives were common as a way to increase speed of slow engines, in very large ratings (thousands of kilowatts) these were expensive, inefficient, and unreliable. After about 1906, generators driven directly by
3439:
665:
4018:
1532:
159:. When large central generating stations became practical, the choice of frequency was made based on the nature of the intended load. Eventually improvements in machine design allowed a single frequency to be used both for lighting and motor loads. A unified system improved the economics of electricity production, since system load was more uniform during the course of a day.
844:. Industrial plants and mines in North America and Australia sometimes were built with 40 Hz electrical systems which were maintained until too uneconomic to continue. Although frequencies near 40 Hz found much commercial use, these were bypassed by standardized frequencies of 25, 50 and 60 Hz preferred by higher volume equipment manufacturers.
1506:, military equipment, and hand-held machine tools. Such high frequencies cannot be economically transmitted long distances; the increased frequency greatly increases series impedance due to the inductance of transmission lines, making power transmission difficult. Consequently, 400 Hz power systems are usually confined to a building or vehicle.
45:
903:(VDE), in the first standard for electrical machines and transformers in 1902, recommended 25 Hz and 50 Hz as standard frequencies. VDE did not see much application of 25 Hz, and dropped it from the 1914 edition of the standard. Remnant installations at other frequencies persisted until well after the Second World War.
754:
that frequency was chosen. The operation of Tesla's induction motor, licensed by
Westinghouse in 1888, required a lower frequency than the 133 Hz common for lighting systems at that time. In 1893 General Electric Corporation, which was affiliated with AEG in Germany, built a generating project at
2099:
that limits the RoCoF. Since the IBRs are not electromechanically coupled into the power grid, a system with high VRE penetration might exhibit large RoCoF values that can cause problems with the operation of the system due to stress placed onto the remaining synchronous generators, triggering of the
1010:
In Japan, the western part of the country (Nagoya and west) uses 60 Hz and the eastern part (Tokyo and east) uses 50 Hz. This originates in the first purchases of generators from AEG in 1895, installed for Tokyo, and
General Electric in 1896, installed in Osaka. The boundary between the two
753:
decided to standardize on a higher frequency to permit operation of both electric lighting and induction motors on the same generating system. Although 50 Hz was suitable for both, in 1890 Westinghouse considered that existing arc-lighting equipment operated slightly better on 60 Hz, and so
130:
In practice, the exact frequency of the grid varies around the nominal frequency, reducing when the grid is heavily loaded, and speeding up when lightly loaded. However, most utilities will adjust generation onto the grid over the course of the day to ensure a constant number of cycles occur. This is
991:
had standardized on 50 Hz. Much of
Southern California operated on 50 Hz and did not completely change frequency of their generators and customer equipment to 60 Hz until around 1948. Some projects by the Au Sable Electric Company used 30 Hz at transmission voltages up to 110,000
722: Hz were used on different systems. For example, the city of Coventry, England, in 1895 had a unique 87 Hz single-phase distribution system that was in use until 1906. The proliferation of frequencies grew out of the rapid development of electrical machines in the period 1880 through 1900.
111:
During the development of commercial electric power systems in the late-19th and early-20th centuries, many different frequencies (and voltages) had been used. Large investment in equipment at one frequency made standardization a slow process. However, as of the turn of the 21st century, places that
2183:
rate to be the same as the local mains supply frequency. This helped to prevent power line hum and magnetic interference from causing visible beat frequencies in the displayed picture of early analogue TV receivers particularly from the mains transformer. Although some distortion of the picture was
1332:
Even by the middle of the 20th century, utility frequencies were still not entirely standardized at the now-common 50 Hz or 60 Hz. In 1946, a reference manual for designers of radio equipment listed the following now obsolete frequencies as in use. Many of these regions also had 50-cycle,
1779:
Smaller power systems, not extensively interconnected with many generators and loads, will not maintain frequency with the same degree of accuracy. Where system frequency is not tightly regulated during heavy load periods, system operators may allow system frequency to rise during periods of light
2197:
Another use of this side effect is as a forensic tool. When a recording is made that captures audio near an AC appliance or socket, the hum is also incidentally recorded. The peaks of the hum repeat every AC cycle (every 20 ms for 50 Hz AC, or every 16.67 ms for 60 Hz AC). The
983:
Rotating-machine frequency changers used to convert between 25 Hz and 60 Hz systems were awkward to design; a 60 Hz machine with 24 poles would turn at the same speed as a 25 Hz machine with 10 poles, making the machines large, slow-speed, and expensive. A ratio of 60/30 would
621:
can be used to step down high transmission voltages to lower customer utilization voltage. The transformer is effectively a voltage conversion device with no moving parts and requiring little maintenance. The use of AC eliminated the need for spinning DC voltage conversion motor-generators that
223:
was found to work well on frequencies around 50 to 60 Hz, but with the materials available in the 1890s would not work well at a frequency of, say, 133 Hz. There is a fixed relationship between the number of magnetic poles in the induction motor field, the frequency of the alternating
1562:
Today, AC power network operators regulate the daily average frequency so that clocks stay within a few seconds of the correct time. In practice the nominal frequency is raised or lowered by a specific percentage to maintain synchronization. Over the course of a day, the average frequency is
139:
Several factors influence the choice of frequency in an AC system. Lighting, motors, transformers, generators, and transmission lines all have characteristics which depend on the power frequency. All of these factors interact and make selection of a power frequency a matter of considerable
2028:
or other generation-load mismatch, then adjacent generators would observe a decrease in frequency but a counterbalancing increase in outward tieline power flow, giving no ACE. They would thus make no governor adjustments in the (presumed) brief period before the failed region recovered.
1624:
Real-time frequency meters for power generation in the United
Kingdom are available online – an official one for the National Grid, and an unofficial one maintained by Dynamic Demand. Real-time frequency data of the synchronous grid of Continental Europe is available on websites such as
975:
for 60 Hz distribution. Converters for production of DC from alternating current were available in larger sizes and were more efficient at 25 Hz compared with 60 Hz. Remnant fragments of older systems may be tied to the standard frequency system via a rotary converter or
884:
allowed international trade in electrical equipment. Much later, the use of standard frequencies allowed interconnection of power grids. It was not until after World War II – with the advent of affordable electrical consumer goods – that more uniform standards were enacted.
879:
In the early days of electrification, so many frequencies were used that no single value prevailed (London in 1918 had ten different frequencies). As the 20th century continued, more power was produced at 60 Hz (North
America) or 50 Hz (Europe and most of Asia).
2198:
exact frequency of the hum should match the frequency of a forensic recording of the hum at the exact date and time that the recording is alleged to have been made. Discontinuities in the frequency match or no match at all will betray the authenticity of the recording.
1000:, intended to bring the whole country under 50 Hz within eight years. The law did not work, and in the early 1960s it was decided that Brazil would be unified under 60 Hz standard, because most developed and industrialized areas used 60 Hz; and a new law
2107:
As of 2017, regulations for some grids required the power plants to tolerate RoCoF of 1–4 Hz/s, the upper limit being a very high value, an order of magnitude higher than the design target of a typical older gas turbine generator. Testing high-power (multiple
778:
power transmission had been definitively selected. Westinghouse would have selected a low frequency of 30 Hz to drive motor loads, but the turbines for the project had already been specified at 250 RPM. The machines could have been made to deliver
807: Hz. Eventually a compromise of 25 Hz, with 12-pole 250 RPM generators, was chosen. Because the Niagara project was so influential on electric power systems design, 25 Hz prevailed as the North American standard for low-frequency AC.
819:
study concluded that 40 Hz would have been a good compromise between lighting, motor, and transmission needs, given the materials and equipment available in the first quarter of the 20th century. Several 40 Hz systems were built. The
2364:
frequencies originated in the 19th century practice that gave frequencies in terms of alternations per minute, instead of alternations (cycles) per second. For example, a machine which produced 8,000 alternations per minute is operating at
1743:
Small, temporary frequency changes are an unavoidable consequence of changing demand, but dramatic, rapid frequency shifts often signal that a distribution network is near capacity limits. Exceptional examples have occurred before major
2140:). It is usually produced by motor and transformer core laminations vibrating in time with the magnetic field. This hum can also appear in audio systems, where the power supply filter or signal shielding of an amplifier is not adequate.
1659:(NERC) discussed a proposed experiment that would relax frequency regulation requirements for electrical grids which would reduce the long-term accuracy of clocks and other devices that use the 60 Hz grid frequency as a time base.
116:, and those that now use 60 Hz tend to use 100–127 V. Both frequencies coexist today (Japan uses both) with no great technical reason to prefer one over the other and no apparent desire for complete worldwide standardization.
1780:
load to maintain a daily average frequency of acceptable accuracy. Portable generators, not connected to a utility system, need not tightly regulate their frequency because typical loads are insensitive to small frequency deviations.
1480:. In the 19th century, frequencies as low as 8 Hz were contemplated for operation of electric railways with commutator motors. Some outlets in trains carry the correct voltage, but using the original train network frequency like
995:
Initially in Brazil, electric machinery were imported from Europe and United States, implying the country had both 50 Hz and 60 Hz standards according to each region. In 1938, the federal government made a law,
1937:
popularized the practice in a series of articles, arguing that load-frequency control minimized the adjustment necessary for changes in load. In particular, Cohn supposed that all regions of the grid shared a common
3106:
Mathematically, the derivative can vary with location as long as each generation control system has only one neighbor generating plant. That is only possible on a grid with the unrealistically few one or two
645:
Generators can only be interconnected to operate in parallel if they are of the same frequency and wave-shape. By standardizing the frequency used, generators in a geographic area can be interconnected in a
3214:
918:. In the 1950s, many 25 Hz systems, from the generators right through to household appliances, were converted and standardized. Until 2006, some 25 Hz generators were still in existence at the
151:, so as to economize on transformer materials and to reduce visible flickering of the lamps, but would pick a lower frequency for systems with long transmission lines or feeding primarily motor loads or
2022:
930:
to provide power for large industrial customers who did not want to replace existing equipment; and some 25 Hz motors and a 25 Hz power station exist in New
Orleans for floodwater pumps. The
625:
Since, for a given power level, the dimensions of a transformer are roughly inversely proportional to frequency, a system with many transformers would be more economical at a higher frequency.
906:
Because of the cost of conversion, some parts of the distribution system may continue to operate on original frequencies even after a new frequency is chosen. 25 Hz power was used in
1643:
measures the frequency of the interconnections within the North
American power grid, as well as in several other parts of the world. These measurements are displayed on the FNET website.
2188:, and other changes to set design helped minimise the effect and some countries now use a vertical rate that is an approximation to the supply frequency (most notably 60 Hz areas).
1892:
892:
starting in 1926 compelled the standardization of frequencies among the many interconnected electrical service providers. The 50 Hz standard was completely established only after
980:
frequency changer. These allow energy to be interchanged between two power networks at different frequencies, but the systems are large, costly, and waste some energy in operation.
283:
182:
If an incandescent lamp is operated on a low-frequency current, the filament cools on each half-cycle of the alternating current, leading to perceptible change in brightness and
888:
In the United
Kingdom, a standard frequency of 50 Hz was declared as early as 1904, but significant development continued at other frequencies. The implementation of the
725:
In the early incandescent lighting period, single-phase AC was common and typical generators were 8-pole machines operated at 2,000 RPM, giving a frequency of 133 hertz.
4054:
231:
Generators operated by slow-speed reciprocating engines will produce lower frequencies, for a given number of poles, than those operated by, for example, a high-speed steam
1579:. The target frequency is then adjusted by up to ±0.01 Hz (±0.02%) from 50 Hz as needed, to ensure a long-term frequency average of exactly 50 Hz × 60
1748:. During a severe failure of generators or transmission lines, the ensuing load-generation imbalance will induce variation in local power system frequencies. Loss of an
198:. Open arc lamps made an audible buzz on alternating current, leading to experiments with high-frequency alternators to raise the sound above the range of human hearing.
2081:
3243:
2848:
2841:
1656:
1606:
919:
3290:
2565:
2112:) equipment for RoCoF tolerance is hard, as a typical test setup is powered off the grid, and the frequency thus cannot be arbitrarily varied. In the US, the
3963:
602:
Direct-current power was not entirely displaced by alternating current and was useful in railway and electrochemical processes. Prior to the development of
2579:
1473:'s traction power systems in the United States. Other AC railway systems are energized at the local commercial power frequency, 50 Hz or 60 Hz.
793: Hz power suitable for heavy commutator-type motors, but the Westinghouse company objected that this would be undesirable for lighting and suggested
3223:
3205:
1915:
traditionally has a negative value, so that when the frequency is lower than the target, area power production should increase; its magnitude is usually
1559:
also depends on a synchronous AC clock motor to maintain the correct speed of its internal "tone wheel" generator, thus keeping all notes pitch-perfect.
2928:
739:(descended from a company founded by Edison in Germany) built the first German generating facility to run at 50 Hz. At the time, AEG had a virtual
179:. Both devices operate well on DC, but DC could not be easily changed in voltage, and was generally only produced at the required utilization voltage.
2390:
821:
744:
2168:
1438:
2703:
1466:
3234:
2157:
2146:
1969:
2511:
1564:
1470:
2688:
2192:
825:
640:
2958:
609:, rotary converters were used to produce DC power from AC. Like other commutator-type machines, these worked better with lower frequencies.
4021:
2812:
2117:
1652:
1024:
631:
over long lines favors lower frequencies. The effects of the distributed capacitance and inductance of the line are less at low frequency.
3860:
2167:
1028:
971:
In some cases, where most load was to be railway or motor loads, it was considered economic to generate power at 25 Hz and install
771:
2805:
2156:
2145:
4040:
3968:
3438:
3283:
755:
743:
and their standard spread to the rest of Europe. After observing flicker of lamps operated by the 40 Hz power transmitted by the
3588:
3067:
2982:
2498:
2455:
1476:
Traction power may be derived from commercial power supplies by frequency converters, or in some cases may be produced by dedicated
837:
824:
used 40 Hz to transmit power 175 km in 1891. A large interconnected 40 Hz network existed in north-east
England (the
750:
1621:, a correction of ±0.02 Hz (0.033%) is applied. Time error corrections start and end either on the hour or on the half-hour.
2909:
1847:
1016:
931:
3751:
3676:
3547:
1552:
1752:
causes system frequency to increase (due to excess generation) upstream of the loss, but may cause a collapse in frequency or
4047:
2491:
Electricity Supply in the United
Kingdom: A Chronology from the beginnings of the industry to 31 December 1985 Fourth Edition
3923:
3855:
3845:
3721:
3621:
3276:
1736:
discovered that solar plants could respond to the signal faster than traditional generators, because they did not need to
889:
829:
3776:
3736:
3313:
1695:
1544:
1503:
105:
2166:
1004:
was declared in 1964. Brazil underwent a frequency conversion program to 60 Hz that was not completed until 1978.
4003:
3998:
3716:
3691:
3681:
3657:
3652:
3358:
2217:
2155:
2144:
1012:
628:
224:
current, and the rotation speed; so, a given standard speed limits the choice of frequency (and the reverse). Once AC
125:
1007:
In Mexico, areas operating on 50 Hz grid were converted during the 1970s, uniting the country under 60 Hz.
840:, still produces electric power at 40 Hz and supplies power to the local 60 Hz transmission system through
239:
favored higher frequencies. The steadier rotation speed of high-speed machines allowed for satisfactory operation of
3918:
3636:
3606:
3383:
3252:
1764:
too low, depending on the system's disturbance tolerance and the severity of protection measures). These initiate
1667:
1568:
1086:
988:
923:
81:
2806:"Western Electricity Coordinating Council Regional Reliability Standard Regarding Automatic Time Error Correction"
762:
using 50 Hz, but changed to 60 Hz a year later to maintain market share with the Westinghouse standard.
3973:
3462:
3423:
2088:
1687:
1572:
2869:
3948:
3756:
3696:
3353:
2630:
C. Linder (2002), "Umstellung der Sollfrequenz im zentralen Bahnstromnetz von 16 2/3 Hz auf 16,70 Hz (English:
2212:
1421:
209:-type motors do not operate well on high-frequency AC, because the rapid changes of current are opposed by the
1355:
Canada (Southern Ontario), Panama Canal Zone(*), France, Germany, Sweden, UK, China, Hawaii, India, Manchuria
984:
have simplified these designs, but the installed base at 25 Hz was too large to be economically opposed.
899:
By about 1900, European manufacturers had mostly standardized on 50 Hz for new installations. The German
219:
motors are common in AC household appliances and power tools, they are small motors, less than 1 kW. The
4134:
3887:
3877:
3867:
2184:
present, it went mostly un-noticed because it was stationary. The elimination of transformers by the use of
2092:
2083:), usually measured in Hz per second, Hz/s. The importance of this parameter increases when the traditional
1640:
1618:
1610:
1372:
Lots Road Power station, Chelsea, London (for London Underground and Trolley busses after conversion to DC)
915:
729:
168:
2397:
249:
3808:
3671:
3454:
3343:
2583:
1729:
1674:
to coordinate generators connected the network. The practice arose because the frequency of a mechanical
1444:
1298:
1229:
1202:
1183:
977:
228:
became common, it was important to standardize frequency for compatibility with the customer's equipment.
3943:
3711:
3706:
3686:
3022:
2632:
Switching the frequency in train electric power supply network from 16 2/3 Hz to 16,70 Hz
2185:
1614:
1539:
Regulation of power system frequency for timekeeping accuracy was not commonplace until after 1916 with
1502:
Power frequencies as high as 400 Hz are used in aircraft, spacecraft, submarines, server rooms for
1477:
774:, built by Westinghouse in 1895, were 25 Hz, because the turbine speed had already been set before
240:
206:
172:
1796:
for power provision or consumption to surrounding areas. The automatic generation scheme described in
832:
in the late 1920s, and projects in Italy used 42 Hz. The oldest continuously operating commercial
3537:
3299:
1737:
759:
736:
2515:
3908:
3741:
3641:
3616:
3569:
3378:
3368:
3333:
2600:, copyright American Technical Book Company 1897, published by P.F. Collier and Sons New York, 1902
1904:
1829:
775:
659:
77:
2929:"First Solar Proves That PV Plants Can Rival Frequency Response Services From Natural Gas Peakers"
2756:
3782:
3393:
3057:
2892:
2659:
2313:
1699:
1675:
691:
647:
191:
143:
In the late 19th century, designers would pick a relatively high frequency for systems featuring
2816:
2279:
2257:
2870:"Power-grid experiment could confuse clocks – Technology & science – Innovation – NBC News"
2048:
4087:
3933:
3813:
3063:
2978:
2684:
2639:
2494:
2451:
2275:
2253:
2207:
2180:
2096:
1749:
1462:
1443:
Other power frequencies are still used. Germany, Austria, Switzerland, Sweden, and Norway use
841:
682:
Very early isolated AC generating schemes used arbitrary frequencies based on convenience for
603:
3169:
3882:
3823:
3527:
3522:
3499:
3408:
3348:
2443:
2426:
2137:
1757:
1671:
972:
833:
816:
195:
152:
61:
2514:. Louisiana Department of Transportation and Development. September 5, 2005. Archived from
2347:, Transactions AIEE January 1918, reprinted in the Baltimore Amateur Radio Club newsletter
1698:(AGC) maintains scheduled frequency and interchange power flows by adjusting the generator
3913:
3872:
3850:
3731:
3701:
3666:
3626:
3428:
3261:
3183:
3026:
2101:
1930:
1916:
1769:
1683:
1540:
1388:
Czechoslovakia, Hungary, Italy, Monaco(*), Portugal, Romania, Yugoslavia, Libya (Tripoli)
1130:
881:
220:
69:
2545:, 4th Ed., Westinghouse Electric Corporation, East Pittsburgh Pennsylvania, 1950, no ISBN
1694:
of the generated current; excess force deposits rotational energy, increasing frequency.
2716:
1429:
Where regions are marked (*), this is the only utility frequency shown for that region.
732:, there is little certitude in the details of the history of 60 Hz vs. 50 Hz.
4063:
3938:
3928:
3726:
3338:
2994:
2936:
2676:
1789:
1721:
1380:
Jamaica, Belgium, Switzerland, UK, Federated Malay States, Egypt, Western Australia(*)
225:
214:
176:
156:
104:
it is typically 60 Hz. Current usage by country or region is given in the list of
2662:
systems also used 415 Hz power systems within a computer room. Robert B. Hickey,
2252:, Industry Applications Magazine, IEEE, Sep/Oct 2000, Volume 6, Issue 5, Pages 12–14,
243:
in rotary converters. The synchronous speed N in RPM is calculated using the formula,
17:
4128:
3958:
3746:
3631:
3611:
3542:
3532:
3489:
3373:
3328:
2267:, AIEE Transactions, Volume 31, 1912, pages 955–983, and discussion on pages 974–978.
2025:
1939:
1765:
1556:
927:
687:
236:
85:
2272:
Electrification of a Major Steel Mill – Part II Development of the 25 Hz System
296:
Synchronous speeds of AC motors for some current and historical utility frequencies
4108:
4103:
3978:
3953:
3818:
3787:
3601:
3403:
1745:
1548:
893:
683:
664:
38:
2611:
4113:
3803:
3771:
3564:
3552:
3472:
3398:
3388:
3318:
2121:
1934:
1725:
1703:
1576:
1513:
1509:
943:
618:
144:
1531:
3766:
3761:
3574:
3557:
3413:
2619:(2nd ed.). New York: Federal Telephone and Radio Corporation. p. 26.
2177:
2084:
2042:
1717:
1020:
848:
210:
2643:
1756:(due to excess load) downstream of the loss. Consequently many power system
1563:
maintained at a nominal value within a few hundred parts per million. In the
1461: Hz or 16.7 Hz. A frequency of 25 Hz is used for the Austrian
140:
importance. The best frequency is a compromise among competing requirements.
4077:
4032:
3482:
3477:
3363:
3323:
2532:, private printing, Chicago 1915, available on the Internet Archive, page 72
2222:
2133:
1923:
1773:
1691:
606:
73:
31:
2770:
3062:. IEE Control Engineering. Stevenage: Peter Peregrinus. pp. 193–198.
2743:
3596:
1919:
1822:
1793:
1713:
1709:
1551:
demonstrated the concept of clocks synchronized by line frequency at the
900:
740:
187:
148:
97:
89:
2430:
2417:
Owen, Edward (1997-11-01). "The Origins of 60-Hz as a Power Frequency".
3517:
3507:
3268:
2132:
AC-powered appliances can give off a characteristic hum, often called "
1929:
Tie-line bias LFC was known since 1930s, but was rarely used until the
1908:
1828:
LFC incorporates power transfer between different areas, known as "net
1801:
1753:
939:
935:
907:
232:
113:
2136:", at the multiples of the frequencies of AC power that they use (see
3512:
2897:(International Student ed.). Tata-McGraw Hill. pp. 562–565.
2877:
2095:(IBR). The design of a synchronous generator inherently provides the
1584:
1580:
951:
947:
911:
2638:(in German), vol. Book 12, Munich: Oldenbourg-Industrieverlag,
2541:
Central Station Engineers of the Westinghouse Electric Corporation,
2120:
is the only facility that allows testing of multi-MW units (up to 7
747:
in 1891, AEG raised their standard frequency to 50 Hz in 1891.
44:
37:"ROCOF" redirects here. For the rate of occurrence of failures, see
2683:(Eleventh ed.). New York: McGraw-Hill. pp. 16–15, 16–16.
2391:"City of Coventry Single and Two Phase Generation and Distribution"
2300:
Electrical Transmission and Distribution Reference Book 4th Edition
1942:, with location-invariant frequency change per additional loading (
1911:, and governors adjusted to counteract its value. The coefficient
3151:
3149:
2361:
2274:, Industry Applications Magazine, IEEE, Sep/Oct 2005, Pages 9–12,
2164:
2153:
2142:
1821:
refers to the difference between measured and desired values, and
1733:
1679:
1627:
1530:
663:
289:
93:
43:
3215:
European Network of Transmission System Operators for Electricity
1337:
Frequencies in use in 1946 (as well as 50 Hz and 60 Hz)
3467:
2474:
50-Hz frequency: how the standard emerged from a European jungle
2109:
1636:
1588:
679:
Many different power frequencies were used in the 19th century.
101:
4036:
3272:
3001:, vol. 1, John Wiley and Sons, New York, 1948 pg. 189
2910:"Battery Storage: A Clean Alternative for Frequency Regulation"
2448:
Networks of Power: Electrification in Western Society 1880–1930
851:
of Hungary had standardized on 5000 alternations per minute (41
3222:
Miller, Nicholas; Lew, Debra; Barnes, Steven (April 9, 2017).
2656:
1592:
2788:
48:
The waveform of 230 V and 50 Hz compared with 120 V and 60 Hz
3017:, pp. 48–49. Note that an older notation instead uses
2975:
Standard Handbook for Electrical Engineers, Eleventh Edition
1903:
refers to tie-line power. This instantaneous error is then
30:"60 cycles" redirects here. For the 1965 Canadian film, see
2891:
Grainger, John J.; Stevenson, William D. (1994).
2757:"National Grid: Real Time Frequency Data – Last 60 Minutes"
1655:
made time error correction mandatory in 2009. In 2011, The
1221:
AEG, Oerlikon, and other manufacturers, eventual standard
1097:
Many manufacturers, becoming "increasingly common" in 1897
27:
Frequency used on standard electricity grid in a given area
2017:{\displaystyle B={\frac {1}{2}}{\frac {dL}{df}}{\text{,}}}
1844:(ACE) associated with LFC at any moment in time is simply
1760:
automatically trigger on severe underfrequency (typically
1732:
to follow the frequency signal. Indeed, a 2017 trial for
1702:
to counteract frequency changes, typically within several
1121:
General Electric at Portland Oregon for rotary converters
112:
now use the 50 Hz frequency tend to use 220–240
1804:
that minimizes the magnitude of average frequency error,
1575:) is calculated at 08:00 each day in a control center in
728:
Though many theories exist, and quite a few entertaining
167:
The first applications of commercial electric power were
3207:
Rate of Change of Frequency (ROCOF) withstand capability
2704:
Entsoe Load Frequency Control and Performance, chapter D
1141:
Westinghouse Niagara Falls 2-phase—for operating motors
871: Hz systems that in some cases ran for many years.
3225:
Advisory on Equipment Limits associated with High RoCoF
3025:
of the frequency bias as defined here, and sometimes a
2543:
Electrical Transmission and Distribution Reference Book
1832:
power", into the minimized quantity. For a particular
131:
used by some clocks to accurately maintain their time.
1774:
preserve the operation of at least part of the network
2450:, The Johns Hopkins University Press, Baltimore 1983
2051:
1972:
1850:
252:
2960:
Transmission and Distribution Electrical Engineering
1792:
that restores the system frequency while respecting
861: Hz) for their products, so Ganz clients had 41
4096:
4070:
3987:
3897:
3834:
3796:
3650:
3587:
3498:
3453:
3446:
3306:
2124:). Testing of large thermal units is not possible.
1015:substations which convert the frequency; these are
2075:
2016:
1886:
277:
3046:5th Edition. Cengage Learning. 2012. pp. 663–664.
1257:Municipal power station, Frankfurt am Main, 1893
186:of the lamps; the effect is more pronounced with
2957:Bayliss, Colin; Hardy, Brian (14 October 2022).
2302:, Westinghouse Electric Corporation 1950, page 6
1609:, whenever the error exceeds 10 seconds for the
1290:Lauffen am Neckar, hydroelectric, 1891, to 1925
3244:North American Electric Reliability Corporation
3155:
3140:
2849:North American Electric Reliability Corporation
2842:"Time error correction and reliability (draft)"
1657:North American Electric Reliability Corporation
1567:, the deviation between network phase time and
922:(these were retrofitted to 60 Hz) and the
1516:exists for aircraft use of 400 Hz power.
1447:for railways, distributing single-phase AC at
92:. In large parts of the world this is 50
4048:
3284:
2973:Donald G. Fink and H. Wayne Beaty,
2468:
2466:
2464:
1318:St. James and Soho Electric Light Co. London
1166:Single-phase lighting systems, UK and Europe
8:
1174:Single-phase lighting system, UK and Europe
1035:Utility frequencies in North America in 1897
622:require regular maintenance and monitoring.
1887:{\displaystyle \Delta (P_{T}-Bf){\text{,}}}
1213:Single phase lighting, Germany, 1891, 1893
826:Newcastle-upon-Tyne Electric Supply Company
213:of the motor field. Though commutator-type
4055:
4041:
4033:
3450:
3291:
3277:
3269:
2985:, pp. 16‑15–16‑21
2681:Standard Handbook for Electrical Engineers
1788:Load-frequency control (LFC) is a type of
650:, providing reliability and cost savings.
2963:(4th ed.). Newnos. pp. 344–345.
2598:Recent Types of Dynamo-Electric Machinery
2339:
2337:
2335:
2333:
2065:
2060:
2052:
2050:
2009:
1989:
1979:
1971:
1879:
1861:
1849:
274:
259:
251:
3033:is included in the area control formula.
2412:
2410:
2236:The Evolution of Power-Line Frequencies
1340:
1151:
1038:
294:
3128:
3116:
3094:
3014:
2927:St. John, Jeff (19 January 2017).
2664:Electrical engineer's portable handbook
2291:
2024:and one region experienced a temporary
1797:
1724:-linked power supplies. However, such
1690:from the generator shaft, reducing the
1439:List of railway electrification systems
4078:Synchronous Motor and the Master Clock
3228:. General Electric International, Inc.
2596:Edwin J. Houston and Arthur Kennelly,
2345:The Technical Story of the Frequencies
1565:synchronous grid of Continental Europe
1333:60-cycle, or direct current supplies.
914:, the northern United States, and for
3254:On the load-frequency control problem
3056:Sterling, M. J. H. (1978).
2193:Electrical network frequency analysis
1547:and self-starting synchronous motor.
1148:Utility frequencies in Europe to 1900
641:Synchronization (alternating current)
278:{\displaystyle N={\frac {120f}{P}}\,}
7:
3082:
3010:
2813:Federal Energy Regulatory Commission
2118:National Renewable Energy Laboratory
1686:experienced. Excess load withdraws
1670:use precise frequency control as an
1653:Federal Energy Regulatory Commission
1326:Single phase lighting, Germany 1897
1194:Single-phase lighting, Germany 1891
836:power station in the United States,
3184:"The hum that helps to fight crime"
1637:Frequency Monitoring Network (FNET)
1029:Higashi-Shimizu Frequency Converter
1011:regions contains four back-to-back
3969:Renewable energy commercialization
2613:Reference Data for Radio Engineers
2037:Rate of change of frequency (also
1851:
1265:Ganz customers, also Germany 1898
25:
3251:Bratton, Timothy Lee (May 1971).
3044:Power System Analysis and Design.
2298:A.C. Monteith, C.F. Wagner (ed),
1545:Warren Power Station Master Clock
838:Mechanicville Hydroelectric Plant
828:, NESCO) until the advent of the
4017:
4016:
3437:
2530:Central-Station Electric Service
1668:Modern alternating-current grids
1105:General Electric Lachine Rapids
668:Japan's utility frequencies are
3236:Balancing and Frequency Control
2977:, McGraw-Hill, New York, 1978,
2312:Wald, Matthew L. (2011-01-07).
822:Lauffen-Frankfurt demonstration
3260:(MSc thesis). Houston, Texas:
2876:. 25 June 2011. Archived from
2815:. May 21, 2009. Archived from
2717:"Manual Time Error Correction"
2478:IEEE Power and Energy Magazine
2419:Industry Applications Magazine
2128:Audible noise and interference
1876:
1854:
1232:Kilwangen generating station,
1069:General Electric single-phase
926:(until its 2006 closure) near
292:and P is the number of poles.
1:
3964:Renewable Energy Certificates
3924:Cost of electricity by source
3846:Arc-fault circuit interrupter
3722:High-voltage shore connection
3170:"Controllable Grid Interface"
3156:Miller, Lew & Barnes 2017
3141:Miller, Lew & Barnes 2017
613:Transmission and transformers
3979:Spark/Dark/Quark/Bark spread
3777:Transmission system operator
3737:Mains electricity by country
3314:Automatic generation control
2908:Lombardo, Tom (6 May 2016).
2582:(in Spanish). Archived from
2480:, July/August 2011 pp. 66–81
1966:). If the utility selected
1696:Automatic generation control
770:The first generators at the
694:design. Frequencies between
288:where f is the frequency in
106:mains electricity by country
4004:List of electricity sectors
3999:Electric energy consumption
3717:High-voltage direct current
3692:Electric power transmission
3682:Electric power distribution
3359:Energy return on investment
2610:H.T. Kohlhaas, ed. (1946).
2218:Network analyzer (AC power)
2176:Most countries chose their
2114:controllable grid interface
2033:Rate of change of frequency
1525:Time error correction (TEC)
1182:Single phase, Ferranti UK,
924:Rankine generating stations
629:Electric power transmission
126:Time error correction (TEC)
4151:
3919:Carbon offsets and credits
3637:Three-phase electric power
2679:; Beaty, H. Wayne (1978).
2190:
2045:of the utility frequency (
1728:or storage systems can be
1712:physics does not apply to
1651:In the United States, the
1494: Hz or 16.7 Hz.
1436:
989:Southern California Edison
968: Hz or 16.7 Hz.
901:Verband der Elektrotechnik
657:
638:
123:
82:wide area synchronous grid
36:
29:
4064:Electric clock technology
4012:
3974:Renewable Energy Payments
3463:Fossil fuel power station
3435:
3204:ENTSO-E (29 March 2017).
3042:Glover, Duncan J. et al.
2631:
2489:The Electricity Council,
2425:(6). IEEE: 8, 10, 12–14.
2089:variable renewable energy
2076:{\displaystyle {df}/{dt}}
1798:§ Frequency and load
1772:interconnection lines to
1573:International Atomic Time
1053:Wood arc-lighting dynamo
3757:Single-wire earth return
3697:Electrical busbar system
3354:Energy demand management
2213:Maximum demand indicator
2181:vertical synchronization
2093:inverter-based resources
1825:indicate time averages.
1553:1893 Chicago Worlds fair
758:to bring electricity to
3888:Residual-current device
3878:Power system protection
3868:Generator interlock kit
2775:www.dynamicdemand.co.uk
2100:protection devices and
1641:University of Tennessee
1619:Western Interconnection
1617:, or 2 seconds for the
1611:Eastern Interconnection
1445:traction power networks
1404:Italy, Libya (Tripoli)
934:rail networks, used in
916:railway electrification
76:of the oscillations of
4071:Powerline synchronized
3672:Distributed generation
3344:Electric power quality
2999:Power System Stability
2518:on September 23, 2005.
2173:
2162:
2151:
2085:synchronous generators
2077:
2018:
1905:numerically integrated
1888:
1784:Load-frequency control
1678:varies with the input
1536:
1478:traction powerstations
1282:Ganz Company, Hungary
1184:Deptford Power Station
1077:Stanley-Kelly Company
1061:Stanley-Kelly Company
987:In the United States,
745:Lauffen-Frankfurt link
676:
635:System interconnection
279:
58:(power) line frequency
49:
18:Load-frequency control
3944:Fossil fuel phase-out
3712:Electricity retailing
3707:Electrical substation
3687:Electric power system
3233:NERC (May 11, 2021).
2995:Edward Wilson Kimbark
2931:. Grid Optimization.
2894:Power system analysis
2744:Time Error Correction
2566:"Padrões brasileiros"
2314:"Hold That Megawatt!"
2171:
2160:
2149:
2078:
2019:
1889:
1738:accelerate a rotating
1615:Texas Interconnection
1534:
772:Niagara Falls project
751:Westinghouse Electric
667:
280:
169:incandescent lighting
47:
3300:Electricity delivery
3059:Power System Control
2822:on December 21, 2016
2270:Blalock, Thomas J.,
2087:are replaced by the
2049:
1970:
1848:
1613:, 3 seconds for the
1543:'s invention of the
1129:Crocker-Wheeler for
760:Redlands, California
692:electrical generator
250:
3909:Availability factor
3861:Sulfur hexafluoride
3742:Overhead power line
3642:Virtual power plant
3617:Induction generator
3570:Sustainable biofuel
3379:Home energy storage
3369:Grid energy storage
3334:Droop speed control
3190:. 12 December 2012.
2564:Atitude Editorial.
2431:10.1109/2943.628099
2351:January -March 2007
2041:) is simply a time
1605:cycles per day. In
1422:British East Africa
954:, still operate at
776:alternating current
735:The German company
660:War of the currents
297:
192:mercury-vapor lamps
84:transmitted from a
78:alternating current
3783:Transmission tower
3394:Nameplate capacity
2880:on August 4, 2020.
2660:mainframe computer
2636:Elektrische Bahnen
2472:Gerhard Neidhofer
2379:cycles per second.
2174:
2163:
2152:
2073:
2014:
1884:
1842:area control error
1672:out-of-band signal
1663:Frequency and load
1537:
1240:Rome, Geneva 1900
1085:General Electric "
932:15 kV AC
842:frequency changers
830:National Grid (UK)
677:
295:
275:
96:, although in the
50:
4122:
4121:
4088:Synchronous motor
4083:Utility frequency
4030:
4029:
3934:Environmental tax
3814:Cascading failure
3583:
3582:
3419:Utility frequency
3119:, pp. 48–49.
2690:978-0-07-020974-9
2389:Gordon Woodward.
2208:Mains electricity
2169:
2158:
2147:
2097:inertial response
2012:
2007:
1987:
1933:. In the 1950s,
1907:to give the time
1882:
1758:protective relays
1688:rotational energy
1463:Mariazell Railway
1427:
1426:
1330:
1329:
1145:
1144:
1113:General Electric
973:rotary converters
604:mercury arc valve
600:
599:
326:RPM at 25 Hz
323:RPM at 40 Hz
320:RPM at 50 Hz
317:RPM at 60 Hz
272:
202:Rotating machines
196:fluorescent lamps
153:rotary converters
135:Operating factors
72:) is the nominal
54:utility frequency
16:(Redirected from
4142:
4057:
4050:
4043:
4034:
4020:
4019:
3929:Energy subsidies
3883:Protective relay
3824:Rolling blackout
3451:
3441:
3409:Power-flow study
3349:Electrical fault
3293:
3286:
3279:
3270:
3265:
3259:
3247:
3241:
3229:
3218:
3212:
3192:
3191:
3180:
3174:
3173:
3165:
3159:
3153:
3144:
3138:
3132:
3126:
3120:
3114:
3108:
3104:
3098:
3092:
3086:
3080:
3074:
3073:
3053:
3047:
3040:
3034:
3032:
3020:
3013:, p. 11 or
3008:
3002:
2992:
2986:
2971:
2965:
2964:
2954:
2948:
2947:
2945:
2943:
2924:
2918:
2917:
2905:
2899:
2898:
2888:
2882:
2881:
2866:
2860:
2859:
2857:
2855:
2846:
2838:
2832:
2831:
2829:
2827:
2821:
2810:
2802:
2796:
2795:
2792:
2790:
2785:
2779:
2778:
2771:"Dynamic Demand"
2767:
2761:
2760:
2753:
2747:
2741:
2735:
2734:
2732:
2730:
2721:
2713:
2707:
2701:
2695:
2694:
2673:
2667:
2653:
2647:
2646:
2633:
2627:
2621:
2620:
2618:
2607:
2601:
2594:
2588:
2587:
2576:
2570:
2569:
2561:
2555:
2552:
2546:
2539:
2533:
2526:
2520:
2519:
2508:
2502:
2487:
2481:
2470:
2459:
2444:Thomas P. Hughes
2441:
2435:
2434:
2414:
2405:
2404:
2402:
2396:. Archived from
2395:
2386:
2380:
2378:
2377:
2373:
2370:
2358:
2352:
2341:
2328:
2327:
2325:
2324:
2309:
2303:
2296:
2263:Rushmore, D.B.,
2249:
2248:
2244:
2241:
2172:400 Hz power hum
2170:
2159:
2148:
2138:Magnetostriction
2082:
2080:
2079:
2074:
2072:
2064:
2059:
2023:
2021:
2020:
2015:
2013:
2010:
2008:
2006:
1998:
1990:
1988:
1980:
1965:
1964:
1962:
1961:
1955:
1952:
1914:
1902:
1893:
1891:
1890:
1885:
1883:
1880:
1866:
1865:
1839:
1820:
1816:
1812:
1811:
1790:integral control
1763:
1634:
1631:
1629:
1604:
1603:
1600:
1535:TEC availability
1493:
1492:
1488:
1485:
1460:
1459:
1455:
1452:
1369:
1368:
1364:
1341:
1315:
1314:
1310:
1279:
1278:
1274:
1254:
1253:
1249:
1152:
1039:
1025:Minami-Fukumitsu
967:
966:
962:
959:
870:
869:
865:
860:
859:
855:
817:General Electric
806:
805:
801:
798:
792:
791:
787:
784:
721:
720:
716:
713:
707:
706:
702:
699:
675:
671:
570:
569:
565:
558:
557:
553:
546:
545:
541:
338:
337:
333:
313:
312:
308:
298:
284:
282:
281:
276:
273:
268:
260:
190:, and the later
62:American English
21:
4150:
4149:
4145:
4144:
4143:
4141:
4140:
4139:
4125:
4124:
4123:
4118:
4092:
4066:
4061:
4031:
4026:
4008:
3992:
3990:
3983:
3914:Capacity factor
3902:
3900:
3893:
3873:Numerical relay
3851:Circuit breaker
3839:
3837:
3830:
3792:
3732:Load management
3702:Electrical grid
3667:Demand response
3660:
3655:
3646:
3627:Microgeneration
3579:
3494:
3442:
3433:
3429:Vehicle-to-grid
3302:
3297:
3262:Rice University
3257:
3250:
3239:
3232:
3221:
3210:
3203:
3200:
3195:
3182:
3181:
3177:
3167:
3166:
3162:
3158:, p. 2-16.
3154:
3147:
3143:, p. 3-17.
3139:
3135:
3131:, pp. 3–4.
3127:
3123:
3115:
3111:
3105:
3101:
3097:, pp. 4–5.
3093:
3089:
3081:
3077:
3070:
3055:
3054:
3050:
3041:
3037:
3030:
3027:unit conversion
3018:
3009:
3005:
2993:
2989:
2972:
2968:
2956:
2955:
2951:
2941:
2939:
2926:
2925:
2921:
2914:Engineering.com
2907:
2906:
2902:
2890:
2889:
2885:
2868:
2867:
2863:
2853:
2851:
2844:
2840:
2839:
2835:
2825:
2823:
2819:
2808:
2804:
2803:
2799:
2787:
2786:
2782:
2769:
2768:
2764:
2755:
2754:
2750:
2742:
2738:
2728:
2726:
2719:
2715:
2714:
2710:
2702:
2698:
2691:
2677:Fink, Donald G.
2675:
2674:
2670:
2654:
2650:
2629:
2628:
2624:
2616:
2609:
2608:
2604:
2595:
2591:
2578:
2577:
2573:
2563:
2562:
2558:
2554:Hughes as above
2553:
2549:
2540:
2536:
2528:Samuel Insull,
2527:
2523:
2510:
2509:
2505:
2488:
2484:
2471:
2462:
2442:
2438:
2416:
2415:
2408:
2400:
2393:
2388:
2387:
2383:
2375:
2371:
2368:
2366:
2359:
2355:
2342:
2331:
2322:
2320:
2311:
2310:
2306:
2297:
2293:
2289:
2246:
2242:
2239:
2237:
2234:Furfari, F.A.,
2231:
2229:Further reading
2204:
2195:
2186:AC/DC receivers
2165:
2161:60 Hz power hum
2154:
2150:50 Hz power hum
2143:
2130:
2047:
2046:
2035:
1999:
1991:
1968:
1967:
1956:
1953:
1947:
1946:
1944:
1943:
1931:post-war period
1917:on the order of
1912:
1900:
1895:
1857:
1846:
1845:
1837:
1818:
1814:
1806:
1805:
1786:
1761:
1750:interconnection
1665:
1649:
1630:.mainsfrequency
1626:
1601:
1598:
1596:
1527:
1522:
1500:
1490:
1486:
1483:
1481:
1457:
1453:
1450:
1448:
1441:
1435:
1366:
1362:
1361:
1312:
1308:
1307:
1276:
1272:
1271:
1251:
1247:
1246:
1131:calcium carbide
998:Decreto-Lei 852
992:volts in 1914.
978:static inverter
964:
960:
957:
955:
920:Sir Adam Beck 1
882:Standardization
877:
875:Standardization
867:
863:
862:
857:
853:
852:
813:
803:
799:
796:
794:
789:
785:
782:
780:
768:
718:
714:
711:
709:
704:
700:
697:
695:
673:
669:
662:
656:
643:
637:
615:
567:
563:
562:
555:
551:
550:
543:
539:
538:
335:
331:
330:
310:
306:
305:
261:
248:
247:
226:electric motors
221:induction motor
204:
177:electric motors
165:
137:
128:
122:
120:Electric clocks
70:British English
66:mains frequency
42:
35:
28:
23:
22:
15:
12:
11:
5:
4148:
4146:
4138:
4137:
4135:Electric power
4127:
4126:
4120:
4119:
4117:
4116:
4111:
4106:
4100:
4098:
4094:
4093:
4091:
4090:
4085:
4080:
4074:
4072:
4068:
4067:
4062:
4060:
4059:
4052:
4045:
4037:
4028:
4027:
4025:
4024:
4013:
4010:
4009:
4007:
4006:
4001:
3995:
3993:
3989:Statistics and
3988:
3985:
3984:
3982:
3981:
3976:
3971:
3966:
3961:
3956:
3951:
3946:
3941:
3939:Feed-in tariff
3936:
3931:
3926:
3921:
3916:
3911:
3905:
3903:
3898:
3895:
3894:
3892:
3891:
3885:
3880:
3875:
3870:
3865:
3864:
3863:
3858:
3848:
3842:
3840:
3835:
3832:
3831:
3829:
3828:
3827:
3826:
3816:
3811:
3806:
3800:
3798:
3794:
3793:
3791:
3790:
3785:
3780:
3774:
3769:
3764:
3759:
3754:
3749:
3744:
3739:
3734:
3729:
3727:Interconnector
3724:
3719:
3714:
3709:
3704:
3699:
3694:
3689:
3684:
3679:
3677:Dynamic demand
3674:
3669:
3663:
3661:
3651:
3648:
3647:
3645:
3644:
3639:
3634:
3629:
3624:
3619:
3614:
3609:
3607:Combined cycle
3604:
3599:
3593:
3591:
3585:
3584:
3581:
3580:
3578:
3577:
3572:
3567:
3562:
3561:
3560:
3555:
3550:
3545:
3540:
3530:
3525:
3520:
3515:
3510:
3504:
3502:
3496:
3495:
3493:
3492:
3487:
3486:
3485:
3480:
3475:
3470:
3459:
3457:
3448:
3444:
3443:
3436:
3434:
3432:
3431:
3426:
3421:
3416:
3411:
3406:
3401:
3396:
3391:
3386:
3384:Load-following
3381:
3376:
3371:
3366:
3361:
3356:
3351:
3346:
3341:
3339:Electric power
3336:
3331:
3326:
3321:
3316:
3310:
3308:
3304:
3303:
3298:
3296:
3295:
3288:
3281:
3273:
3267:
3266:
3248:
3230:
3219:
3199:
3196:
3194:
3193:
3175:
3160:
3145:
3133:
3121:
3109:
3099:
3087:
3075:
3068:
3048:
3035:
3003:
2987:
2966:
2949:
2937:Wood Mackenzie
2919:
2900:
2883:
2861:
2833:
2797:
2780:
2762:
2748:
2736:
2708:
2696:
2689:
2668:
2648:
2622:
2602:
2589:
2586:on 2009-12-13.
2571:
2556:
2547:
2534:
2521:
2512:"News in DOTD"
2503:
2482:
2460:
2436:
2406:
2403:on 2007-10-31.
2381:
2353:
2329:
2304:
2290:
2288:
2285:
2284:
2283:
2268:
2261:
2230:
2227:
2226:
2225:
2220:
2215:
2210:
2203:
2200:
2191:Main article:
2129:
2126:
2071:
2068:
2063:
2058:
2055:
2034:
2031:
2005:
2002:
1997:
1994:
1986:
1983:
1978:
1975:
1898:
1878:
1875:
1872:
1869:
1864:
1860:
1856:
1853:
1834:frequency bias
1817:is frequency,
1800:establishes a
1785:
1782:
1762:0.5–2 Hz
1664:
1661:
1648:
1647:US regulations
1645:
1587:× 60 min/
1526:
1523:
1521:
1518:
1504:computer power
1499:
1496:
1437:Main article:
1434:
1431:
1425:
1424:
1418:
1414:
1413:
1410:
1406:
1405:
1402:
1398:
1397:
1394:
1390:
1389:
1386:
1382:
1381:
1378:
1374:
1373:
1370:
1357:
1356:
1353:
1349:
1348:
1345:
1328:
1327:
1324:
1320:
1319:
1316:
1303:
1302:
1296:
1292:
1291:
1288:
1284:
1283:
1280:
1267:
1266:
1263:
1259:
1258:
1255:
1242:
1241:
1238:
1234:
1233:
1227:
1223:
1222:
1219:
1215:
1214:
1211:
1207:
1206:
1200:
1196:
1195:
1192:
1188:
1187:
1180:
1176:
1175:
1172:
1168:
1167:
1164:
1160:
1159:
1156:
1143:
1142:
1139:
1135:
1134:
1127:
1123:
1122:
1119:
1115:
1114:
1111:
1107:
1106:
1103:
1099:
1098:
1095:
1091:
1090:
1083:
1079:
1078:
1075:
1071:
1070:
1067:
1063:
1062:
1059:
1055:
1054:
1051:
1047:
1046:
1043:
876:
873:
812:
809:
767:
764:
655:
652:
639:Main article:
636:
633:
614:
611:
598:
597:
594:
591:
588:
585:
582:
579:
575:
574:
571:
559:
547:
535:
532:
529:
525:
524:
521:
518:
515:
512:
509:
506:
502:
501:
498:
495:
492:
489:
486:
483:
479:
478:
475:
472:
469:
466:
463:
460:
456:
455:
452:
449:
446:
443:
440:
437:
433:
432:
429:
426:
423:
420:
417:
414:
410:
409:
406:
403:
400:
397:
394:
391:
387:
386:
383:
380:
377:
374:
371:
368:
364:
363:
360:
357:
354:
351:
348:
345:
341:
340:
327:
324:
321:
318:
315:
302:
286:
285:
271:
267:
264:
258:
255:
237:steam turbines
203:
200:
164:
161:
157:direct current
155:for producing
136:
133:
124:Main article:
121:
118:
26:
24:
14:
13:
10:
9:
6:
4:
3:
2:
4147:
4136:
4133:
4132:
4130:
4115:
4112:
4110:
4107:
4105:
4102:
4101:
4099:
4095:
4089:
4086:
4084:
4081:
4079:
4076:
4075:
4073:
4069:
4065:
4058:
4053:
4051:
4046:
4044:
4039:
4038:
4035:
4023:
4015:
4014:
4011:
4005:
4002:
4000:
3997:
3996:
3994:
3986:
3980:
3977:
3975:
3972:
3970:
3967:
3965:
3962:
3960:
3959:Pigouvian tax
3957:
3955:
3952:
3950:
3947:
3945:
3942:
3940:
3937:
3935:
3932:
3930:
3927:
3925:
3922:
3920:
3917:
3915:
3912:
3910:
3907:
3906:
3904:
3896:
3889:
3886:
3884:
3881:
3879:
3876:
3874:
3871:
3869:
3866:
3862:
3859:
3857:
3856:Earth-leakage
3854:
3853:
3852:
3849:
3847:
3844:
3843:
3841:
3833:
3825:
3822:
3821:
3820:
3817:
3815:
3812:
3810:
3807:
3805:
3802:
3801:
3799:
3797:Failure modes
3795:
3789:
3786:
3784:
3781:
3778:
3775:
3773:
3770:
3768:
3765:
3763:
3760:
3758:
3755:
3753:
3750:
3748:
3747:Power station
3745:
3743:
3740:
3738:
3735:
3733:
3730:
3728:
3725:
3723:
3720:
3718:
3715:
3713:
3710:
3708:
3705:
3703:
3700:
3698:
3695:
3693:
3690:
3688:
3685:
3683:
3680:
3678:
3675:
3673:
3670:
3668:
3665:
3664:
3662:
3659:
3654:
3649:
3643:
3640:
3638:
3635:
3633:
3632:Rankine cycle
3630:
3628:
3625:
3623:
3620:
3618:
3615:
3613:
3612:Cooling tower
3610:
3608:
3605:
3603:
3600:
3598:
3595:
3594:
3592:
3590:
3586:
3576:
3573:
3571:
3568:
3566:
3563:
3559:
3556:
3554:
3551:
3549:
3546:
3544:
3541:
3539:
3536:
3535:
3534:
3531:
3529:
3526:
3524:
3521:
3519:
3516:
3514:
3511:
3509:
3506:
3505:
3503:
3501:
3497:
3491:
3488:
3484:
3481:
3479:
3476:
3474:
3471:
3469:
3466:
3465:
3464:
3461:
3460:
3458:
3456:
3455:Non-renewable
3452:
3449:
3445:
3440:
3430:
3427:
3425:
3422:
3420:
3417:
3415:
3412:
3410:
3407:
3405:
3402:
3400:
3397:
3395:
3392:
3390:
3387:
3385:
3382:
3380:
3377:
3375:
3374:Grid strength
3372:
3370:
3367:
3365:
3362:
3360:
3357:
3355:
3352:
3350:
3347:
3345:
3342:
3340:
3337:
3335:
3332:
3330:
3329:Demand factor
3327:
3325:
3322:
3320:
3317:
3315:
3312:
3311:
3309:
3305:
3301:
3294:
3289:
3287:
3282:
3280:
3275:
3274:
3271:
3263:
3256:
3255:
3249:
3245:
3238:
3237:
3231:
3227:
3226:
3220:
3216:
3209:
3208:
3202:
3201:
3197:
3189:
3185:
3179:
3176:
3171:
3164:
3161:
3157:
3152:
3150:
3146:
3142:
3137:
3134:
3130:
3125:
3122:
3118:
3113:
3110:
3103:
3100:
3096:
3091:
3088:
3085:, p. 20.
3084:
3079:
3076:
3071:
3069:0-906048-01-X
3065:
3061:
3060:
3052:
3049:
3045:
3039:
3036:
3028:
3024:
3016:
3012:
3007:
3004:
3000:
2996:
2991:
2988:
2984:
2983:0-07-020974-X
2980:
2976:
2970:
2967:
2962:
2961:
2953:
2950:
2938:
2934:
2930:
2923:
2920:
2915:
2911:
2904:
2901:
2896:
2895:
2887:
2884:
2879:
2875:
2871:
2865:
2862:
2850:
2843:
2837:
2834:
2818:
2814:
2807:
2801:
2798:
2794:
2784:
2781:
2776:
2772:
2766:
2763:
2758:
2752:
2749:
2745:
2740:
2737:
2725:
2718:
2712:
2709:
2705:
2700:
2697:
2692:
2686:
2682:
2678:
2672:
2669:
2665:
2661:
2658:
2652:
2649:
2645:
2641:
2637:
2626:
2623:
2615:
2614:
2606:
2603:
2599:
2593:
2590:
2585:
2581:
2575:
2572:
2567:
2560:
2557:
2551:
2548:
2544:
2538:
2535:
2531:
2525:
2522:
2517:
2513:
2507:
2504:
2500:
2499:0-85188-105-X
2496:
2492:
2486:
2483:
2479:
2475:
2469:
2467:
2465:
2461:
2457:
2456:0-8018-2873-2
2453:
2449:
2445:
2440:
2437:
2432:
2428:
2424:
2420:
2413:
2411:
2407:
2399:
2392:
2385:
2382:
2363:
2357:
2354:
2350:
2349:The Modulator
2346:
2343:B. G. Lamme,
2340:
2338:
2336:
2334:
2330:
2319:
2315:
2308:
2305:
2301:
2295:
2292:
2286:
2281:
2277:
2273:
2269:
2266:
2262:
2259:
2255:
2251:
2250:to 25 Hz
2233:
2232:
2228:
2224:
2221:
2219:
2216:
2214:
2211:
2209:
2206:
2205:
2201:
2199:
2194:
2189:
2187:
2182:
2179:
2141:
2139:
2135:
2127:
2125:
2123:
2119:
2115:
2111:
2105:
2103:
2102:load shedding
2098:
2094:
2090:
2086:
2069:
2066:
2061:
2056:
2053:
2044:
2040:
2032:
2030:
2027:
2003:
2000:
1995:
1992:
1984:
1981:
1976:
1973:
1960:
1951:
1941:
1940:linear regime
1936:
1932:
1927:
1925:
1921:
1918:
1910:
1906:
1901:
1873:
1870:
1867:
1862:
1858:
1843:
1835:
1831:
1826:
1824:
1810:
1803:
1799:
1795:
1791:
1783:
1781:
1777:
1775:
1771:
1767:
1766:load shedding
1759:
1755:
1751:
1747:
1741:
1739:
1735:
1731:
1727:
1723:
1719:
1715:
1711:
1707:
1705:
1701:
1697:
1693:
1689:
1685:
1681:
1677:
1673:
1669:
1662:
1660:
1658:
1654:
1646:
1644:
1642:
1638:
1633:
1622:
1620:
1616:
1612:
1608:
1607:North America
1594:
1590:
1586:
1582:
1578:
1574:
1570:
1566:
1560:
1558:
1557:Hammond Organ
1554:
1550:
1546:
1542:
1533:
1529:
1524:
1519:
1517:
1515:
1511:
1507:
1505:
1497:
1495:
1479:
1474:
1472:
1468:
1465:, as well as
1464:
1446:
1440:
1432:
1430:
1423:
1419:
1416:
1415:
1412:Gibraltar(*)
1411:
1408:
1407:
1403:
1400:
1399:
1395:
1392:
1391:
1387:
1384:
1383:
1379:
1376:
1375:
1371:
1359:
1358:
1354:
1351:
1350:
1346:
1343:
1342:
1339:
1338:
1334:
1325:
1322:
1321:
1317:
1305:
1304:
1300:
1297:
1294:
1293:
1289:
1286:
1285:
1281:
1269:
1268:
1264:
1261:
1260:
1256:
1244:
1243:
1239:
1236:
1235:
1231:
1228:
1225:
1224:
1220:
1217:
1216:
1212:
1209:
1208:
1204:
1201:
1198:
1197:
1193:
1190:
1189:
1185:
1181:
1178:
1177:
1173:
1170:
1169:
1165:
1162:
1161:
1157:
1154:
1153:
1150:
1149:
1140:
1137:
1136:
1132:
1128:
1125:
1124:
1120:
1117:
1116:
1112:
1109:
1108:
1104:
1101:
1100:
1096:
1093:
1092:
1088:
1084:
1081:
1080:
1076:
1073:
1072:
1068:
1065:
1064:
1060:
1057:
1056:
1052:
1049:
1048:
1044:
1041:
1040:
1037:
1036:
1032:
1030:
1026:
1022:
1018:
1014:
1008:
1005:
1003:
999:
993:
990:
985:
981:
979:
974:
969:
953:
949:
945:
941:
937:
933:
929:
928:Niagara Falls
925:
921:
917:
913:
909:
904:
902:
897:
895:
891:
890:National Grid
886:
883:
874:
872:
850:
845:
843:
839:
835:
834:hydroelectric
831:
827:
823:
818:
811:40 Hz origins
810:
808:
777:
773:
766:25 Hz origins
765:
763:
761:
757:
752:
748:
746:
742:
738:
733:
731:
730:urban legends
726:
723:
708: Hz and
693:
689:
688:water turbine
685:
680:
666:
661:
653:
651:
649:
642:
634:
632:
630:
626:
623:
620:
612:
610:
608:
605:
595:
592:
589:
586:
583:
580:
577:
576:
572:
560:
548:
536:
533:
530:
527:
526:
522:
519:
516:
513:
510:
507:
504:
503:
499:
496:
493:
490:
487:
484:
481:
480:
476:
473:
470:
467:
464:
461:
458:
457:
453:
450:
447:
444:
441:
438:
435:
434:
430:
427:
424:
421:
418:
415:
412:
411:
407:
404:
401:
398:
395:
392:
389:
388:
384:
381:
378:
375:
372:
369:
366:
365:
361:
358:
355:
352:
349:
346:
343:
342:
328:
325:
322:
319:
316:
303:
300:
299:
293:
291:
269:
265:
262:
256:
253:
246:
245:
244:
242:
238:
234:
229:
227:
222:
218:
217:
212:
208:
201:
199:
197:
193:
189:
185:
180:
178:
174:
170:
162:
160:
158:
154:
150:
146:
141:
134:
132:
127:
119:
117:
115:
109:
107:
103:
100:and parts of
99:
95:
91:
87:
86:power station
83:
79:
75:
71:
67:
63:
59:
55:
46:
40:
33:
19:
4109:Atomic clock
4104:Quartz clock
4082:
3954:Net metering
3901:and policies
3819:Power outage
3788:Utility pole
3752:Pumped hydro
3658:distribution
3653:Transmission
3602:Cogeneration
3418:
3404:Power factor
3253:
3235:
3224:
3206:
3187:
3178:
3163:
3136:
3129:ENTSO-E 2017
3124:
3117:Bratton 1971
3112:
3102:
3095:Bratton 1971
3090:
3078:
3058:
3051:
3043:
3038:
3015:Bratton 1971
3006:
2998:
2990:
2974:
2969:
2959:
2952:
2940:. Retrieved
2932:
2922:
2913:
2903:
2893:
2886:
2878:the original
2873:
2864:
2852:. Retrieved
2836:
2824:. Retrieved
2817:the original
2800:
2783:
2774:
2765:
2751:
2739:
2727:. Retrieved
2723:
2711:
2699:
2680:
2671:
2663:
2651:
2635:
2625:
2612:
2605:
2597:
2592:
2584:the original
2574:
2559:
2550:
2542:
2537:
2529:
2524:
2516:the original
2506:
2490:
2485:
2477:
2473:
2458:pgs. 282–283
2447:
2439:
2422:
2418:
2398:the original
2384:
2356:
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1591:× 24 h/
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1541:Henry Warren
1538:
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1510:Transformers
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1336:
1335:
1331:
1158:Description
1147:
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1045:Description
1034:
1033:
1017:Shin Shinano
1009:
1006:
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681:
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4114:Radio clock
3949:Load factor
3804:Black start
3772:Transformer
3473:Natural gas
3424:Variability
3399:Peak demand
3389:Merit order
3319:Backfeeding
3107:generators.
2360:Fractional
1935:Nathan Cohn
1718:solar farms
1716:-connected
1704:decaseconds
1682:and output
1577:Switzerland
1514:MIL-STD-704
1205:Bellinzona
944:Switzerland
241:commutators
4097:Electronic
3991:production
3836:Protective
3767:Super grid
3762:Smart grid
3589:Generation
3523:Geothermal
3414:Repowering
3029:factor of
2942:20 January
2789:fnetpublic
2666:, page 401
2655:Formerly,
2580:"Historia"
2323:2020-10-16
2318:Green Blog
2287:References
2178:television
2043:derivative
1730:programmed
1571:(based on
1420:Malta(*),
1396:Argentina
1087:monocyclic
1027:, and the
1021:Sakuma Dam
756:Mill Creek
658:See also:
607:rectifiers
304:RPM at 133
211:inductance
207:Commutator
173:commutator
149:arc lights
80:(AC) in a
3899:Economics
3622:Micro CHP
3500:Renewable
3483:Petroleum
3478:Oil shale
3364:Grid code
3324:Base load
3083:NERC 2021
3011:NERC 2021
2724:naesb.org
2644:0013-5437
2501:, page 41
2280:1077-2618
2265:Frequency
2258:1077-2618
2223:Telechron
2134:mains hum
1868:−
1852:Δ
1836:constant
1823:overlines
1794:contracts
1720:or other
1692:frequency
1676:generator
1520:Stability
1186:, London
1133:furnaces
1002:Lei 4.454
617:With AC,
339: Hz
329:RPM at 16
216:universal
188:arc lamps
74:frequency
32:60 Cycles
4129:Category
4022:Category
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3597:AC power
3307:Concepts
3188:BBC News
3023:opposite
3021:for the
2874:NBC News
2854:June 23,
2826:June 23,
2202:See also
1830:tie-line
1813:, where
1714:inverter
1710:Flywheel
1700:governor
1433:Railways
741:monopoly
314: Hz
163:Lighting
98:Americas
90:end-user
3838:devices
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3508:Biofuel
3490:Nuclear
3447:Sources
3198:Sources
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1498:400 Hz
1467:Amtrak
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952:Norway
950:, and
948:Sweden
912:Quebec
690:, and
573:111.1
500:142.9
485:1142.9
477:166.7
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301:Poles
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3553:Tidal
3528:Hydro
3258:(PDF)
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2845:(PDF)
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2809:(PDF)
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1680:force
1471:SEPTA
674:60 Hz
670:50 Hz
531:888.9
520:187.5
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494:342.8
491:428.6
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