|
Geomagnetically Induced Current
Geomagnetically induced currents (GIC) are electrical currents induced at the Earth's surface by rapid changes in the geomagnetic field caused by space weather events. GICs can affect the normal operation of long electrical conductor systems such as electric transmission grids and buried pipelines. The geomagnetic disturbances which induce GICs include geomagnetic storms and substorms where the most severe disturbances occur at high geomagnetic latitudes. Background The Earth's magnetic field varies over a wide range of timescales. The longer-term variations, typically occurring over decades to millennia, are predominantly the result of dynamo action in the Earth's core. Geomagnetic variations on timescales of seconds to years also occur, due to dynamic processes in the ionosphere, magnetosphere and heliosphere. These changes are ultimately tied to variations associated with the solar activity (or sunspot) cycle and are manifestations of space weather. The fact that the geomagn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Current
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell's equations. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others. The presence of an electric charge, which can be either positive or negative, produces an electric field. The movement of electric charges is an electric current and produces a magnetic field. When a charge is placed in a location with a non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. If the charge moves, the electric field would be doing work on the electric charge. Thus we can speak of electric potential at a certain point in space, which is equal to the work done by an external agent in carrying a unit of p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Direct Current
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for this type of current was galvanic current. The abbreviations ''AC'' and ''DC'' are often used to mean simply ''alternating'' and ''direct'', as when they modify ''current'' or '' voltage''. Direct current may be converted from an alternating current supply by use of a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be converted into alternating current via an inverter. Direct current has many uses, from the charging of batteries to large power ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protective Relay
In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, overvoltage, reverse power flow, over-frequency, and under-frequency. Microprocessor-based solid-state digital protection relays now emulate the original devices, as well as providing types of protection and supervision impractical with electromechanical relays. Electromechanical relays provide only rudimentary indication of the location and origin of a fault. In many cases a single microprocessor relay provides functions that would take two or more electromechanical devices. By combining several functions in one case, numerical relays also save capital cost and maintenance cost over electromechanical relays. However, due to their very long life span, tens of thousands of these "si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydro-Québec Power Grid
Hydro-Québec is a public utility that manages the generation, transmission and distribution of electricity in the Canadian province of Quebec, as well as the export of power to portions of the Northeast United States. It was established by the Government of Quebec in 1944 from the expropriation of private firms. This was followed by massive investment in hydro-electric projects like the James Bay Project. Today, with 63 hydroelectric power stations, the combined output capacity is 37,370 megawatts. Extra power is exported from the province and Hydro-Québec supplies 10 per cent of New England's power requirements. Hydro-Québec is a Crown corporation ( state-owned enterprise) based in Montreal. In 2018, it paid CAD$2.39 billion in dividends to its sole shareholder, the Government of Québec. Its residential power rates are among the lowest in North America. More than 40 percent of Canada’s water resources are in Québec and Hydro-Québec is the fourth largest hydropow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
March 1989 Geomagnetic Storm
The March 1989 geomagnetic storm occurred as part of severe to extreme solar storms during early to mid March 1989, the most notable being a geomagnetic storm that struck Earth on March 13. This geomagnetic storm caused a nine-hour outage of Hydro-Québec's electricity transmission system. The onset time was exceptionally rapid. Other historically significant solar storms occurred later in 1989, during a very active period of solar cycle 22. Geomagnetic storm and auroras The geomagnetic storm causing this event is believed to be the result of two separate events known as coronal mass ejections (CME) on March 10 and 12, 1989. A few days before, on March 6, a very large X15-class solar flare also occurred. Several days later, at 01:27 UT on March 13, a severe geomagnetic storm struck Earth. The storm began on Earth with extremely intense auroras at the poles. The aurora could be seen as far south as Texas and Florida. As this occurred during the Cold War, an unknown number of peop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reactive Power
Reactive may refer to: *Generally, capable of having a reaction (other) *An adjective abbreviation denoting a bowling ball coverstock made of reactive resin *Reactivity (chemistry) *Reactive mind *Reactive programming See also *Reactance (other) Reactance may refer to: * Electrical reactance, the opposition to a change in voltage due to capacitance (capacitive reactance) or in current due to inductance (inductive reactance); the imaginary component of AC impedance * Magnetic reactance, a ... * Reactivity (other) {{disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harmonics
A harmonic is a wave with a frequency that is a positive integer multiple of the '' fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', the other harmonics are known as ''higher harmonics''. As all harmonics are periodic at the fundamental frequency, the sum of harmonics is also periodic at that frequency. The set of harmonics forms a '' harmonic series''. The term is employed in various disciplines, including music, physics, acoustics, electronic power transmission, radio technology, and other fields. For example, if the fundamental frequency is 50 Hz, a common AC power supply frequency, the frequencies of the first three higher harmonics are 100 Hz (2nd harmonic), 150 Hz (3rd harmonic), 200 Hz (4th harmonic) and any addition of waves with these frequencies is periodic at 50 Hz. In music, harmonics are used on string instruments and wind i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saturation (magnetic)
Seen in some magnetic materials, saturation is the state reached when an increase in applied external magnetic field ''H'' cannot increase the magnetization of the material further, so the total magnetic flux density ''B'' more or less levels off. (Though, magnetization continues to increase very slowly with the field due to paramagnetism.) Saturation is a characteristic of ferromagnetic and ferrimagnetic materials, such as iron, nickel, cobalt and their alloys. Different ferromagnetic materials have different saturation levels. Description Saturation is most clearly seen in the ''magnetization curve'' (also called ''BH'' curve or hysteresis curve) of a substance, as a bending to the right of the curve (see graph at right). As the ''H'' field increases, the ''B'' field approaches a maximum value asymptotically, the saturation level for the substance. Technically, above saturation, the ''B'' field continues increasing, but at the paramagnetic rate, which is several ord ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transformer
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force (EMF) across any other coils wound around the same core. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits. Faraday's law of induction, discovered in 1831, describes the induced voltage effect in any coil due to a changing magnetic flux encircled by the coil. Transformers are used to change AC voltage levels, such transformers being termed step-up or step-down type to increase or decrease voltage level, respectively. Transformers can also be used to provide galvanic isolation between circuits as well as to couple stages of signal-processing circuits. Since the invention of the first constant-potential transfo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imperial College Press
Imperial College Press (ICP) was formed in 1995 as a partnership between Imperial College of Science, Technology and Medicine in London and World Scientific publishing. This publishing house was awarded the rights, by The Nobel Foundation, Sweden, to publish ''The Nobel Prize: The First 100 years'', edited by Agneta Wallin Levinovitz and Nils Ringertz. They publish areas of teaching and research at Imperial College: Chemistry, Computer Science, Economics, Finance & Management, Engineering, Environmental Science, Life Sciences, Mathematics, Medicine & Healthcare, and Physics. As of August 2016, ICP has been fully incorporated into World Scientific under the new imprint, ''World Scientific Europe''. Selected journals * ''Journal of Bioinformatics and Computational Biology'' * ''Journal of Integrative Neuroscience'' * ''International Journal of Innovation Management'' * ''Journal of Environmental Assessment Policy and Management A journal, from the Old French ''journal'' ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Cycle 9
Solar cycle 9 was the ninth solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 12.4 years, beginning in July 1843 and ending in December 1855. The maximum smoothed sunspot number observed during the solar cycle was 219.9 (February 1848), and the starting minimum was 17.6.SIDC Monthly Smoothed Sunspot Number. During the solar cycle minimum transit from solar cycle 9 to solar cycle 10, there were a total of 655 days with no sunspots.Spotless Days.Solaemon's Spotless Days Page. Solar cycle 9 began in 1843, the year that Heinrich Schwabe discovered the sunspot cycle. During this cycle, Edward Sabine, Rudolf Wolf, and other scientists recognized that solar disturbances affected the Earth's magnetic environment, so that solar cycles are identical to the Earth's geomagnetic cycles. Wolf also introduced the Wolf number during this period. The phenomenon now known as geomagnetically induced current was seen for the first time during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Telegraph
Electrical telegraphs were point-to-point text messaging systems, primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems called ''telegraphs'', that were devised to communicate text messages quicker than physical transportation. Electrical telegraphy can be considered to be the first example of electrical engineering. Text telegraphy consisted of two or more geographically separated stations, called telegraph offices. The offices were connected by wires, usually supported overhead on utility poles. Many different electrical telegraph systems were invented, but the ones that became widespread fit into two broad categories. The first category consists of needle telegraphs in which a needle pointer is made to move electromagnetically with an electric current sent down the telegraph line. Early systems used multiple needles requiring multiple wires. The firs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
