A-C | D-E | F-I | L-N| O-Q | R | S-Z | Acronyms
scheduled outage - When a power system element is intentionally shut down, usually to allow for maintenance or other preplanned activities.
seams - The interface between two control areas, systems, and markets (see seams issues).
seams issues - Trading barriers between adjoining wholesale electricity markets resulting from the use of different rules and procedures by the neighboring markets, which can obstruct the trading or sharing of electric capacity and energy between the two markets and affect the reliability of each system.
second contingency - The loss of the facility that would have the largest impact on the system after the first facility is lost. A system constraint met by maintaining an operating reserve that can increase output when the first contingency occurs. See N-1-1, N-2.
self-schedule - Is the action of a market participant to commit or schedule its resource at a determined output level to provide generation within an hour, regardless of price or whether the ISO could have scheduled or dispatched the resource to provide the service.
self-supply - When a participant provides itself with a market product from its own resources rather than purchasing it from the market.
settlements model - Computer-based software used to determine financial settlements in ISO New England.
Settlement Market System (SMS) - A Web-based system that allows market participants to submit internal bilateral transactions (IBTs) and meter readings..
settlement-only generator (SOG), settlement-only unit - A unit that generates less than 5 MW and is entitled to receive capacity credit but is not centrally dispatched by the ISO control room and is not monitored in real time.
shortage event - A designated period (hours) of system stress during which capacity resources are most needed on the basis of system conditions.
sink, sink point - The point on the transmission system where electric energy is withdrawn. A Financial Transmission Right delivery point.
source, source point - The point on the transmission system where electric energy is injected. A Financial Transmission Right location of origin.
special protection system - Equipment installed on a power system used to perform functions other than isolating electrical faults.
spinning - On-line capacity electrically synchronized to the system.
spinning reserve - The reserve capability that a generator can fully convert into electric energy within 10 minutes after receiving a request from ISO New England to do so.
spot market - A market that typically involves short-term, often interruptible contracting and immediate delivery of specified volumes of electric energy, as opposed to bilateral trading. In New England, the Real-Time Energy Market is a spot market.
Standard Market Design - New England's wholesale electricity market structure that incorporates locational marginal pricing, day-ahead and real-time energy markets, and risk-management tools to hedge against the adverse impacts of having to pay higher locational marginal prices when transmission congestion occurs.
Start-Up Fee - The dollar amount that must be paid to an owner each time the generating resource is scheduled to start-up.
step-down transformer -A transformer, usually located on the distribution system, that converts electricity from a higher to a lower voltage.
step-up transformers - A transformer, usually located at a generator site, that converts electricity from a lower to a higher voltage.
strike price - The price at which an option contract entitles a buyer to purchase energy.
Supervisory Control and Data Acquisition (SCADA) - A type of equipment that can remotely control, communicate with, and monitor the generation, transmission, and distribution of electric energy.
supply - Electricity delivered to the system; generation.
supply margin - Available generation (megawatts) beyond the amount needed to meet demand.
supply offer - A resource's proposal to furnish electric energy at a node or provide regulation, which includes a dollar price and megawatt quantity along with other information.
supply stack - Generator offers ordered by ascending price.
synchronous condenser - Either a combustion turbine or hydro resource that is synchronized to the New England transmission system and operates as a motor (i.e., it is consuming energy). Also, rotating equipment (or a generator with 0 MW output) that can provide dynamic voltage support, typically designed and operated as separate equipment from generating units.
synchronous generator - A typical type of generator connected to the network.
system operating limit (SOL) - A value (such as MW, MVar, ampere, frequency, or volt) for the most limiting of the prescribed operating criteria for a specified bulk electric power system configuration that ensures operation within acceptable reliability criteria. (Also see interconnection-reliability operating limit.)
through-or-out service - Delivery of electricity through or from New England to another control area.
tie line - A transmission line that connects two control areas; an interconnection.
transfer capability - The amount of megawatts that interconnected electricity systems under specified conditions can reliably transfer from one system to the other over all transmission lines that connect the systems.
transmission - The transporting of electricity through high-voltage lines to distribution lines (see distribution).
transmission congestion - see congestion.
transmission line -Any line with a voltage greater than or equal to 69 kV that carries bulk power over long distances. Typical industry voltages are 69 kV, 115 kV, 138 kV, 230 kV, and 345 kV.
Transmission Operating Agreement - An agreement between an RTO and a utility whereby the RTO will pay the utility for its transmission system costs in exchange for control of the transmission.
transmission operator (TOP) - An entity responsible for the reliability of its "local" transmission system and that operates or directs the operations of the transmission facilities. The ISO has registered with NERC as a TOP and is responsible for complying with NERC standards applicable to a TOP.
transmission owner (TO) - An entity that owns and maintains transmission facilities.
transmission planner (TP) - An entity that develops a long-term plan (generally one year and beyond) for the reliability (adequacy) of the interconnected bulk electric transmission systems within its portion of the Planning Authority area. The ISO has registered with NERC as a TP and is responsible for complying with NERC standards applicable to a TP.
transmission service provider (TSP) - An entity that administers the transmission tariff and provides transmission service to transmission customers under applicable transmission service agreements. The ISO has registered with NERC as a TSP and is responsible for complying with NERC standards applicable to a TSP.
unplanned outage - When equipment is forced out of operation due to a problem that was discovered, and the request for the outage did not meet the timing requirements for it to be considered a planned outage. Unplanned outages are categorized as emergency outages or forced outages.
uplift - Payments to resources operated out of merit. See Net Commitment-Period Compensation.
virtual demand - See decrement bid.
virtual supply - See increment offer.
voltage regulation - When an electrical system provides constant voltage over a range of
wheel through - see through-or-out service
wholesale electric energy market - The buying, selling, and reselling of the electric energy generated by a bulk power system to meet the system's demand for electric energy. New England's wholesale electric energy markets are the Day-Ahead or Real-Time Energy Market. (Also see energy market.)
wholesale electricity - Power that is bought and sold among generators, utilities, municipalities, and other wholesale entities (see market participants).
wholesale electricity markets, wholesale electric power market - The buying, selling and reselling of electric energy, ancillary services and capacity at the transmission level.
withdrawal - The location where power is taken off (withdrawn) from the system, see sink, sink point.
zone - An aggregation of nodes in the New England Balancing Authority Area. There are 8 load zones in New England.
zonal price - The hourly price for electric energy received in a defined load zone calculated using a load-weighted average of the locational marginal prices for the nodes within the load zone.