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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. 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".
An electricity market is a system that enables the exchange of electrical energy, through an electrical grid. Historically, electricity has been primarily sold by companies that operate electric generators, and purchased by consumers or electricity retailers.
Grid energy storage is a collection of methods used for energy storage on a large scale within an electrical power grid. Electrical energy is stored during times when electricity is plentiful and inexpensive or when demand is low, and later returned to the grid when demand is high, and electricity prices tend to be higher.
A regional transmission organization (RTO) in the United States is an electric power transmission system operator (TSO) that coordinates, controls, and monitors a multi-state electric grid. The transfer of electricity between states is considered interstate commerce, and electric grids spanning multiple states are therefore regulated by the Federal Energy Regulatory Commission (FERC). The voluntary creation of RTOs was initiated by FERC in December 1999. The purpose of the RTO is to promote economic efficiency, reliability, and non-discriminatory practices while reducing government oversight.
Demand response is a change in the power consumption of an electric utility customer to better match the demand for power with the supply. Until the 21st century decrease in the cost of pumped storage and batteries, electric energy could not be easily stored, so utilities have traditionally matched demand and supply by throttling the production rate of their power plants, taking generating units on or off line, or importing power from other utilities. There are limits to what can be achieved on the supply side, because some generating units can take a long time to come up to full power, some units may be very expensive to operate, and demand can at times be greater than the capacity of all the available power plants put together. Demand response, a type of energy demand management, seeks to adjust in real-time the demand for power instead of adjusting the supply.
A transmission system operator (TSO) is an entity entrusted with transporting energy in the form of natural gas or electrical power on a national or regional level, using fixed infrastructure. The term is defined by the European Commission. The certification procedure for transmission system operators is listed in Article 10 of the Electricity and Gas Directives of 2009.
The Eastern Interconnection is one of the two major alternating-current (AC) electrical grids in the North American power transmission grid. The other major interconnection is the Western Interconnection. The three minor interconnections are the Quebec, Alaska, and Texas interconnections.
A load-following power plant, regarded as producing mid-merit or mid-priced electricity, is a power plant that adjusts its power output as demand for electricity fluctuates throughout the day. Load-following plants are typically in between base load and peaking power plants in efficiency, speed of start-up and shut-down, construction cost, cost of electricity and capacity factor.
An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids consist of power stations, electrical substations to step voltage up or down, electric power transmission to carry power over long distances, and finally electric power distribution to customers. In that last step, voltage is stepped down again to the required service voltage. Power stations are typically built close to energy sources and far from densely populated areas. Electrical grids vary in size and can cover whole countries or continents. From small to large there are microgrids, wide area synchronous grids, and super grids. The combined transmission and distribution network is part of electricity delivery, known as the power grid.
Inertial response is a property of large synchronous generators, which contain large synchronous rotating masses, and which acts to overcome any immediate imbalance between power supply and demand for electric power systems, typically the electrical grid. Due to the ever existing power imbalance between mechanical power supply and electric power demand the rotational frequency of the rotating masses in all synchronous generators in the grid either speed up and thus absorb the extra power in case of an excess power supply, or slow down and provide additional power in case of an excess power demand. This response in case of a synchronous generator is built-in into the design and happens without any external intervention or coordination, providing the automatic generation control and the grid operator with valuable time to rebalance the system The grid frequency is the combined result of the detailed motions of all individual synchronous rotors in the grid, which are modeled by a general equation of motion called the swing equation.
Variable renewable energy (VRE) or intermittent renewable energy sources (IRES) are renewable energy sources that are not dispatchable due to their fluctuating nature, such as wind power and solar power, as opposed to controllable renewable energy sources, such as dammed hydroelectricity or bioenergy, or relatively constant sources, such as geothermal power.
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 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, 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.
The electrical power grid that powers Northern America is not a single grid, but is instead divided into multiple wide area synchronous grids. The Eastern Interconnection and the Western Interconnection are the largest. Three other regions include the Texas Interconnection, the Quebec Interconnection, and the Alaska Interconnection. Each region delivers power at a nominal 60 Hz frequency.
Capacity credit is the fraction of the installed capacity of a power plant which can be relied upon at a given time, frequently expressed as a percentage of the nameplate capacity. A conventional (dispatchable) power plant can typically provide the electricity at full power as long as it has a sufficient amount of fuel and is operational, therefore the capacity credit of such a plant is close to 100%; it is exactly 100% for some definitions of the capacity credit. The output of a variable renewable energy (VRE) plant depends on the state of an uncontrolled natural resource, therefore a mechanically and electrically sound VRE plant might not be able to generate at the rated capacity when needed, so its CC is much lower than 100%. The capacity credit is useful for a rough estimate of the firm power a system with weather-dependent generation can reliably provide. For example, with a low, but realistic wind power capacity credit of 5%, 20 gigawatts (GW) worth of wind power needs to be added to the system in order to permanently retire a 1 GW fossil fuel plant while keeping the electrical grid reliability at the same level.
Reliability index is an attempt to quantitatively assess the reliability of a system using a single numerical value. The set of reliability indices varies depending on the field of engineering, multiple different indices may be used to characterize a single system. In the simple case of an object that cannot be used or repaired once it fails, a useful index is the mean time to failure representing an expectation of the object's service lifetime. Another cross-disciplinary index is forced outage rate (FOR), a probability that a particular type of a device is out of order. Reliability indices are extensively used in the modern electricity regulation.
Loss of load in an electrical grid is a term used to describe the situation when the available generation capacity is less than the system load. Multiple probabilistic reliability indices for the generation systems are using loss of load in their definitions, with the more popular being Loss of Load Probability (LOLP) that characterizes a probability of a loss of load occurring within a year. Loss of load events are calculated before the mitigating actions are taken, so a loss of load does not necessarily cause a blackout.
Power system operations is a term used in electricity generation to describe the process of decision-making on the timescale from one day to minutes prior to the power delivery. The term power system control describes actions taken in response to unplanned disturbances in order to provide reliable electric supply of acceptable quality. The corresponding engineering branch is called Power System Operations and Control. Electricity is hard to store, so at any moment the supply (generation) shall be balanced with demand. In an electrical grid the task of real-time balancing is performed by a regional-based control center, run by an electric utility in the traditional electricity market. In the restructured North American power transmission grid, these centers belong to balancing authorities numbered 74 in 2016, the entities responsible for operations are also called independent system operators, transmission system operators. The other form of balancing resources of multiple power plants is a power pool. The balancing authorities are overseen by reliability coordinators.
Resource adequacy in the field of electric power is the ability of the electric grid to satisfy the end-user power demand at any time. RA is a component of the electrical grid reliability. For example, sufficient unused generation capacity shall be available to the electrical grid at any time to accommodate major equipment failures and drops in variable renewable energy sources. The adequacy standard should satisfy the chosen reliability index, typically the loss of load expectation (LOLE) of 1 day in 10 years.
In an electrical grid, contingency is an unexpected failure of a single principal component that causes the change of the system state large enough to endanger the grid security. Some protective relays are set up in a way that multiple individual components are disconnected due to a single fault, in this case, taking out of all the units in a group counts as a single contingency. A scheduled outage is not a contingency.
Power resilience refers to a company's ability to adapt to power outages. Frequent outages have forced businesses to take into account the "cost of not having access to power" in addition to the traditional "cost of power". Climate-related issues have intensified the attention on energy sustainability and resilience. In the United States, electric utility firms have registered over 2500 significant power outages since 2002, with almost half of them attributed to weather events, including storms, hurricanes, and other unspecified severe weather occurrences. These incidents often lead to significant economic losses.
References
- 1 2 Heylen et al. 2018, p. 22.
- 1 2 Heylen et al. 2018, p. 21.
- ↑ Prada 2017, p. 5.
- 1 2 3 4 Geocaris 2022.
- 1 2 3 Tezak 2005, p. 2.
- ↑ Tezak 2005, p. 16.
