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Grid Oscillations
The grid oscillations are oscillations in an electric grid manifesting themselves in low-frequency (mostly below 1 Hz) periodic changes of the power flow. These oscillations are a natural effect of negative feedback used in the power system control algorithms. During the normal operation of the power grid, these oscillations, triggered by some change in the system, decay with time (are "damped" within few tens of seconds), and are mostly not noticeable. If the damping in the system is not sufficient, the amplitude of oscillations can grow eventually leading to a blackout. For example, shortly before the 1996 Western North America blackouts the grid after each disturbance was oscillating with a frequency of 0.26 Hz for about 30 seconds. At some point a sequence of faults and operations of automatic protection relays caused loss of damping, eventually breaking the system into disconnected "islands" with many customers losing power. The other notable events involving oscillations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Line Power Flow During The 10 August 19906 Blackout
Transmission or transmit may refer to: Science and technology * Power transmission ** Electric power transmission ** Transmission (mechanical device), technology that allows controlled application of power *** Automatic transmission *** Manual transmission * Signal transmission, the process of sending and propagating an analogue or digital information signal ** Analogue transmission, the process of sending and propagating an analogue signal ** Data communication, Data transmission, the process of sending and propagating digital information ** Signaling (telecommunications), transmission of meta-information related to the actual transmission * Monetary transmission mechanism, process by which asset prices and general economic conditions are affected as a result of monetary policy decisions * Pathogen transmission, the passing of a disease from an infected host individual or group to a particular individual or group * Cellular signaling, transmission of signals within or between livin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subcycle Overvoltage
The subcycle overvoltage condition describes the electrical generation fault mode that is associated with the inverter-based resources (IBR, like solar photovoltaics and wind turbines) and can cause a massive and instantaneous loss of electricity generation. When the overvoltage condition is detected, the IBR devices self-protect by disconnecting from the grid and can only come back online once the voltage returns to the design limits. In the meantime, a cascading failure can be triggered due to lack of generation capacity that remains online. The typical fault scenario is two-stage: # A line-to-ground or line-to-line fault occurs on a transmission line far away from the generator. This condition, if short-lived, is not very unusual. The inverter electronics cannot tolerate the resulting low-voltage condition and enters the " momentary cessation" (MC) mode where the unit stops providing the power but remains connected to the grid; # Once the fault clears, the line voltage might ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Power System Stabilizer
Power may refer to: Common meanings * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power, a type of energy * Power (social and political), the ability to influence people or events Mathematics, science and technology Computing * IBM POWER (software), an IBM operating system enhancement package * IBM POWER architecture, a RISC instruction set architecture * Power ISA, a RISC instruction set architecture derived from PowerPC * IBM Power microprocessors, made by IBM, which implement those RISC architectures * Power.org, a predecessor to the OpenPOWER Foundation Mathematics * Exponentiation, "''x'' to the power of ''y''" * Power function * Power of a point * Statistical power Physics * Magnification, the factor by which an optical system enlarges an image * Optical power, the degree to which a lens converges or diverges light Social sciences and politics * Economic power, encompassing several concepts that economists use, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Damper Winding
The damper winding (also amortisseur winding) is a squirrel-cage-like winding on the rotor of a typical synchronous electric machine. It is used to dampen the transient oscillations and facilitate the start-up operation. Since the design of a damper winding is similar to that of a asynchronous motor, the winding technically enables the direct-on-line start and can even be used for the motor operation in the asynchronous mode. Originally the damper winding was invented by Maurice Leblanc in France and Benjamin G. Lamme in the US to deal with the problem of hunting oscillations due to the early generators being driven by the directly connected steam engines with their pulsating torque. In the modern designs the generators are driven by turbines and the issue of hunting is less important, although pulsating torque is still encountered by motors, for example, while driving the piston compressors. The construction of the damper windings is complex and largely based on empirical kno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hunting Oscillation
Hunting oscillation is a self-oscillation, usually unwanted, about an Mechanical equilibrium, equilibrium. The expression came into use in the 19th century and describes how a system "hunts" for equilibrium. The expression is used to describe phenomena in such diverse fields as electronics, aviation, biology, and railway engineering. Railway wheelsets A classical hunting oscillation is a swaying motion of a railway vehicle (often called ''truck hunting'' or ''bogie hunting'') caused by the Adhesion railway#Directional stability and hunting instability, coning action on which the directional Directional stability, stability of an adhesion railway depends. It arises from the interaction of adhesion forces and inertial forces. At low speed, adhesion dominates but, as the speed increases, the adhesion forces and inertial forces become comparable in magnitude and the oscillation begins at a critical speed. Above this speed, the motion can be violent, damaging track and wheels and pote ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pendulum
A pendulum is a device made of a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force acting on the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. The period depends on the length of the pendulum and also to a slight degree on the amplitude, the width of the pendulum's swing. Pendulums were widely used in early mechanical clocks for timekeeping. The regular motion of pendulums was used for timekeeping and was the world's most accurate timekeeping technology until the 1930s. The pendulum clock invented by Christiaan Huygens in 1656 became the world's standard timekeeper, used in homes and offices for 270 years, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turbine Generator
In electricity generation, a generator, also called an ''electric generator'', ''electrical generator'', and ''electromagnetic generator'' is an electromechanical device that converts mechanical energy to electrical energy for use in an external circuit. In most generators which are rotating machines, a source of kinetic power rotates the generator's shaft, and the generator produces an electric current at its output terminals which flows through an external circuit, powering electrical loads. Sources of mechanical energy used to drive generators include steam turbines, gas turbines, water turbines, internal combustion engines, wind turbines and even hand cranks. Generators produce nearly all of the electric power for worldwide electric power grids. The first electromagnetic generator, the Faraday disk, was invented in 1831 by British scientist Michael Faraday. The reverse conversion of electrical energy into mechanical energy is done by an electric motor, and motors and gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage Compensation
Voltage control and reactive power management are two facets of an ancillary service that enables reliability of the transmission networks and facilitates the electricity market on these networks. Both aspects of this activity are intertwined (voltage change in an alternating current (AC) network is effected through production or absorption of reactive power), so within this article the term ''voltage control'' will be primarily used to designate this essentially single activity, as suggested by Kirby & Hirst (1997). Voltage control does not include reactive power injections to dampen the grid oscillations; these are a part of a separate ancillary service, so-called system stability service. The transmission of reactive power is limited by its nature, so the voltage control is provided through pieces of equipment distributed throughout the power grid, unlike the frequency control that is based on maintaining the overall active power balance in the system. Need for voltage con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line Frequency
The utility frequency, (power) line frequency (American English) or mains frequency (British English) is the nominal frequency of the oscillations of alternating current (AC) in a wide area synchronous grid transmitted from a power station to the end-user. In large parts of the world this is 50 Hz, although in the Americas and parts of Asia it is typically 60 Hz. Current usage by country or region is given in the list of mains electricity by country. 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 now use the 50 Hz frequency tend to use 220–240 V, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grid Balancing
Grid balancing ensures that electricity consumption matches electricity production of an electrical grid at any moment. Electricity is by its nature difficult to store and has to be available on demand, so the supply shall match the demand very closely at any time despite the continuous variations of both. In a deregulated grid, a transmission system operator is responsible for the balancing (in the US electric system smaller entities, so called balancing authorities, are in charge, overseen by reliability coordinators). In a wide area synchronous grid the short-term balancing is coupled with frequency control: as long as the balance is maintained, the frequency stays constant (at the ''scheduled frequency''), whenever a small mismatch between aggregate demand and aggregate supply occurs, it is restored due to both supply and demand being frequency-sensitive: lower frequency increases the supply, and higher frequency increases the demand. As of the beginning of 2020s, the act ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotor Angle
A power system consists of a number of synchronous machines operating synchronously under all operating conditions. Under normal operating conditions, the relative position of the rotor axis and the resultant magnetic field axis is fixed. The angle between the two is known as the power angle, torque angle, or rotor angle. During any disturbance, the rotor decelerates or accelerates with respect to the synchronously rotating air gap magnetomotive force, creating relative motion. The equation describing the relative motion is known as the swing equation, which is a non-linear second order differential equation that describes the swing of the rotor of synchronous machine. The power exchange between the mechanical rotor and the electrical grid due to the rotor swing (acceleration and deceleration) is called Inertial response. Derivation A synchronous generator is driven by a prime mover. The equation governing the rotor motion is given by: J\frac = T_a = T_\text - T_\text, where: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American Electric Reliability Corporation
The North American Electric Reliability Corporation (NERC) is a nonprofit corporation based in Atlanta, Georgia, and formed on March 28, 2006, as the successor to the North American Electric Reliability Council (also known as NERC). The original NERC was formed on June 1, 1968, by the electric utility industry to promote the reliability and adequacy of bulk power transmission in the electric utility systems of North America. NERC's mission states that it "is to assure the effective and efficient reduction of risks to the reliability and security of the grid". NERC oversees six regional reliability entities and encompasses all of the interconnected power systems of Canada and the contiguous United States, as well as a portion of the Mexican state of Baja California. NERC's major responsibilities include working with all stakeholders to develop standards for power system operation, monitoring and enforcing compliance with those standards, assessing resource adequacy, and prov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
