A-C | D-E | F-I | L-N| O-Q | R | S-Z | Acronyms
day-ahead - The calendar day immediately preceding an operating day.
day-ahead energy market - a market that produces financially binding schedules for the production and consumption of electricity one day before the operating day (see energy market and real-time Energy Market).
day-ahead load obligation (DALO) - For each hour, the requirement that each market participant has for providing electric energy (megawatt-hours) at each node, external node, load zone, or the Hub equal to the megawatt-hours of its demand bids, decrement bids, and external transaction sales accepted in the day-ahead energy market at that location.
deactivation - The "mothballing" of a facility, such that with reconditioning it could be brought back into service in a relatively short time.
dead bus - An inactive bus; a point on the transmission system where electric energy is not available for transmission.
dead-bus logic - A procedure for assigning a price for electric energy from the nearest active bus to the dead (inactive) bus.
decrement bid - A financial bid to buy electricity at a specified location in the day-ahead energy market; virtual demand not associated with a physical load. In speaking, sometimes referred to as a "dec" (pronounced "deck").
demand - Load; the amount of electrical power used; the level of electricity consumption at a particular time measured in megawatts.
demand bid - A request to purchase an amount of electric energy at a specific location.
Demand resource, demand-side resource - A source of capacity whereby a customer reduces the demand for electricity from the bulk power system, such as by using energy-efficient equipment, shutting off equipment, and using electricity generated on site.
derate - A reduction in claimed capability, usually temporary and due to physical problems.
dispatch - When a control room operator issues electronic or verbal instructions to generators, transmission facilities, and other market participants to start up, shut down, raise or lower generation, change interchange schedules, or change the status of a dispatchable load in accordance with applicable contracts or demand bid parameters.
dispatchable asset-related demand (DARD) - Demand that can be modified on the basis of the physical load's ability to respond to remote dispatch instructions from the ISO.
distributed generation (DG) -Generation provided by relatively small installations directly connected to distribution facilities or retail customer facilities. A small (24 kilowatt) solar photovoltaic system installed by a retail customer is an example of distributed generation.
distribution - The delivery of electricity to end users via low-voltage electric power lines (typically <69 kV) (see transmission); the transfer of electricity from high-voltage lines to lower-voltage lines.
disturbance - An unplanned event that produces an abnormal system condition; any perturbation to the electric system. Also, the unexpected change in the area control error caused by the sudden failure of generation or an interruption of load.
Disturbance Control Standard (DCS) - The reliability standard that sets the time limit following a disturbance within which a Balancing Authority must return its area control error to within a specified range.
dual-fuel capability - When a generator has the flexibility and storage capacity to use oil as well as natural gas.
Eastern Interconnection - One of two major AC power grids in North America that spans from central Canada eastward to the Atlantic coast (excluding Qubec), south to Florida, and west to the foot of the Rocky Mountains (excluding most of Texas). The electric utilities within the Eastern Interconnection are electrically tied together during normal system conditions and operate at a synchronized frequency of 60 Hz average. The Eastern Interconnection is tied to the Western Interconnection, the Texas Interconnection, and the Qubec Interconnection, and other systems in Canada through numerous high-voltage DC transmission lines.
economic dispatch - The selection of generating resources to cover load as inexpensively as possible.
Economic Maximum (EcoMax) - The highest unrestricted level of electric energy (MW) a resource is ableto generate, representing the highest megawatt output available from the resource for economic dispatch.
economic-merit order - When the generators with the lowest-price offers are committed and dispatched first, and increasingly higher-priced generators are brought on line as demand increases.
Economic Minimum (EcoMin) - The minimum amount of electric energy (MW) that a generating resource must be allowed to produce while under economic dispatch. A generator may request to self-schedule and increase its offered Economic Minimum to the desired level of MW.
electric energy, electrical energy - The ability of an electric current to produce work (heat, light, another form of energy); the generation or use of electric power over a specified time, usually expressed in gigawatt-hours (GWh), megawatt-hours (MWh), or kilowatt-hours (kWh).
electric energy market, energy market - A system for purchasing and selling electric energy using supply and demand to set the price (see electricity market and wholesale electric energy market). The energy markets operated by ISO are the Day-Ahead Energy Market and the Real-Time Energy Market.
electricity market - A system for purchasing and selling electricity using supply and demand to set the price (see electric energy market and wholesale electric energy market). In general, electricity markets include electric energy markets, capacity markets, and ancillary services markets, a part of which are regulation markets and operating reserve markets.
electric power - The rate at which electric energy is transferred or used to do work, measured in kilowatts (or watts or megawatts).
eMarket - A Web-based software application for use by market participants for submitting supply offers, demand bids, increment offers, decrement bids, and regulation offers into the Day-Ahead Energy Market and the Real-Time Energy Market.
Emergency - Abnormal condition of an electric system requiring manual or automatic action to maintain system frequency or to prevent the involuntary loss of load, equipment damage, or tripping of system elements that could adversely affect the reliability of the system or the safety of people or property. Could also be a fuel shortage requiring departure from normal operating procedures to minimize the use of such scarce fuel or any condition that requires the implementation of emergency procedures by ISO.
emergency maximum limit (or Emergency Max) - The maximum generation amount (MW) that a generating resource can deliver for a limited amount of time without exceeding the specified limits of equipment stability and operating permits.
emergency minimum limit (or Emergency Min) - The minimum generation amount (MW) that a generating resource can deliver for a limited amount of time without exceeding the specified limits of equipment stability and operating permits.
emergency outage - A type of unplanned outage when a piece of transmission equipment has a failure and comes out of service on its own or requires immediate operator intervention to remove it from service.
energy - see electric energy, electrical energy
energy efficiency - A type of other demand resource that is an installed measure or a system on an end-use customer's facility that reduces the total amount of electrical energy and capacity that otherwise would have been needed to deliver an equivalent or improved level of end-use service. Such measures or systems include the use of more efficient lighting, motors, refrigeration, HVAC equipment and control systems, and industrial process equipment.
energy market - See electric energy market and electricity market.
equivalent demand forced-outage rate (EFORd) - The portion of time a unit is in demand but is unavailable due to forced outages. See forced outage.
external node - A proxy location on the transmission system that is used for establishing prices for electricity that is being sold to or bought from outside of New England.
external transaction - A transfer of electric energy that crosses control area (balancing authority area) borders.