Glossary - S

For your convenience, this page contains an alphabetically organized list of terms, definitions and common acronyms used in the electric utility industry.


Term/Acronym Definition
SASM Supplemental Ancillary Services Market
SCADA Supervisory Control And Data Acquisition
SCED Security-Constrained Economic Dispatch
SCUC Security-Constrained Unit Commitment
SDRAMP SCED Down Ramp Rate
SE State Estimator
SFT Simultaneous Feasibility Test
SGIA Standard Generation Interconnection Agreement
SMOG Settlement Metering Operating Guides
SPS Special Protection Systems
SRR Statewide RPS Requirement
STEC South Texas Electric Cooperative
STLF Short-Term Load Forecast
STPPF Short-Term PhotoVoltaic Power Forecast
STWPF Short-Term Wind Power Forecast
SWCAP System-Wide Offer Cap
Sampling The process of selecting a subset of a population of Customers that statistically represents the entire population.
Scheduled Power Consumption Expected Load, in MW, reported by a QSE for a Controllable Load Resource pursuant to Section, Operational Data Requirements.
Scheduled Power Consumption Snapshot A snapshot, taken by ERCOT, of the Scheduled Power Consumption provided by the QSE for a Controllable Load Resource at the end of the adjustment period and used in determining the Controllable Load Resource Desired Load.
Scheduling Process The process through which schedules for energy and Ancillary Services are submitted by QSEs to ERCOT as further described in Section 4, Scheduling.
Season or Seasonal Winter months are December, January, and February; Spring months are March, April, and May; Summer months are June, July, and August; Fall months are September, October, and November.

Seasonal Operation Period

The period in which a Generation Resource has identified it is available for operation.

Security-Constrained Economic Dispatch (SCED) The determination of desirable Generation Resource output levels using Energy Offer Curves while considering State Estimator (SE) output for Load at transmission-level Electrical Buses, Generation Resource limits, and transmission limits to provide the least offer-based cost dispatch of the ERCOT System.

Self-Arranged Ancillary Service Quantity

The quantity of an Ancillary Service that a QSE secures for itself using Resources represented by that QSE and Ancillary Service Trades.

Self-Schedule Information for Real-Time Settlement purposes that specifies the amount of energy supply at a specified source Settlement Point used to meet an energy obligation at a specified sink Settlement Point for the QSE submitting the information.
Service Address The street address associated with an ESI ID as recorded in the Customer Registration Database. This address shall conform to United States Postal Service Publication 28.
Service Delivery Point The specific point on the system where electricity flows from the TSP or DSP to a Customer.
Settlement The process used to resolve financial obligations between a Market Participant and ERCOT.
Settlement Calendar A calendar that provides information on when Settlement Statements and Invoices shall be posted, payment due dates, and dispute deadlines. Additional information is provided in Section 9.1.2, Settlement Calendar.
Settlement Interval The time period for which markets are settled.
Settlement Invoice A notice for payment or credit due rendered by ERCOT based on data contained in Settlement Statements.
Settlement Meter Generation and end-use consumption meters used for allocation of ERCOT charges and wholesale and retail Settlements.
Settlement Point A Resource Node, Load Zone, or Hub.
Settlement Point Price A price calculated for a Settlement Point for each Settlement Interval using LMP data and the formulas detailed in Section 4.6, DAM Settlement, and Section 6.6, Settlement Calculations for the Real-Time Energy Operations.
Settlement Quality Meter Data Data that has been edited, validated, and is appropriate for ERCOT to use for Settlement and billing purposes.

Settlement Statement

A statement issued by ERCOT reflecting a breakdown of administrative, miscellaneous, and market charges for the applicable market services, as further described in Section 9.2, Settlement Statements for the Day-Ahead Market, and Section 9.5, Settlement Statements for Real-Time Market.

Day-Ahead Market (DAM) Resettlement Statement
The Settlement Statement issued for a particular DAM using corrected Settlement data, in accordance with Section 9.2.5, DAM Resettlement Statement.

Day-Ahead Market (DAM) Statement
The Settlement Statement issued for a particular DAM, as further described in Section 9.2.4, DAM Statement.

Real-Time Market (RTM) Final Statement
The RTM Settlement Statement issued at the end of the 55th calendar day following the Operating Day, as described in Section 9.5.5, RTM Final Statement.

Real-Time Market (RTM) Initial Statement
The first iteration of an RTM Settlement Statement issued for a particular Operating Day, as further described in Section 9.5.4, RTM Initial Statement.

Real-Time Market (RTM) Resettlement Statement
The RTM Settlement Statement using corrected Settlement data, in accordance with Section 9.5.6, RTM Resettlement Statement.

Real-Time Market (RTM) True-Up Statement
The RTM Settlement Statement issued 180 days following the Operating Day, as further described in Section 9.5.8, RTM True-Up Statement.

Shadow Price A price for a commodity that measures the marginal value of this commodity; that is, the rate at which system costs could be decreased or increased by slightly increasing or decreasing, respectively, the amount of the commodity being made available.
Shift Factor A measure of the flow on a particular Transmission Element due to a unit injection of power from a particular Electrical Bus to a fixed reference Electrical Bus.

Short-Term PhotoVoltaic Power Forecast (STPPF)

An ERCOT produced hourly 50% probability of exceedance forecast of the generation in MWh per hour from each PVGR that could be generated from all available units of that Resource.

Short-Term Wind Power Forecast (STWPF) An ERCOT produced hourly 50% probability of exceedance forecast of the generation in MWh per hour from each WGR that could be generated from all available units of that Resource.
Simple Transmission Outage See Outage
Special Protection Systems (SPS) Automatic protective relay systems designed to detect abnormal or pre-determined ERCOT System conditions and take pre-planned corrective action, other than the isolation of faulted Transmission Facilities, to provide acceptable ERCOT System performance. SPS actions include, but are not limited to generation or transmission system configuration to maintain system stability, acceptable voltages, or acceptable Facility loadings. An SPS does not include under-frequency or under frequency Load shedding, fault conditions that must be isolated, or out-of-step relaying (not designed as an integral part of an SPS). An SPS owner can be a TSP or Resource Entity.
Split Generation Resource Where a Generation Resource has been split to function as two or more independent Generation Resources in accordance with Section, Generation Resource Meter Splitting, and Section, Modeling of Resources and Transmission Loads, each such functionality independent Generation Resource is a Split Generation Resource.

Startup Cost

All costs incurred by a Generation Resource in starting up and reaching Low Sustained Limit (LSL), as described in the Verifiable Cost Manual. The Startup Cost is in dollars per start.

Startup Loading Failure An event that results when a Generation Resource is unable to operate at Low Sustained Limit (LSL) at the time scheduled in the Current Operating Plan (COP) which occurs while the unit is ramping up to its scheduled MW output. A Startup Loading Failure ends when the Resource:
  1. Achieves its LSL;
  2. Is scheduled to go Off-Line; or
  3. Enters a Forced Outage.

Startup Offer

An offer for all costs incurred by a Generation Resource in starting up and reaching Low Sustained Limit (LSL). The Startup Offer is in dollars per start.

State Estimator (SE) A computational algorithm that uses Real-Time inputs from the network’s Supervisory Control and Data Acquisition (SCADA) system that measure the network’s electrical parameters, including its topology, voltage, power flows, etc., to estimate electrical parameters (such as line flows and Electrical Bus voltages and Loads) in the ERCOT Transmission Grid. The SE’s output is a description of the network and all of the values (topology, voltage, power flow, etc.) to describe each Electrical Bus and line included in the system model.
State Estimator (SE) Bus An electrical node of common voltage at a substation that consists of one or more Electrical Buses tied together with closed breakers or switches.

Sustained Response Period

The period of time beginning ten minutes after ERCOT’s issuance of a VDI deploying ERS-10 or 30 minutes after ERCOT’s issuance of a VDI deploying ERS-30 and ending with ERCOT’s issuance of a VDI releasing ERS Resources from the deployment.

Switch Request A request submitted by a CR on behalf of a Customer to switch service from the Customer's current CR to the requesting CR.
Switchable Generation Resource A Generation Resource that can be connected to either the ERCOT Transmission Grid or a non-ERCOT Control Area.
Synchronous Condenser Unit A unit operated under the terms of an annual Agreement with ERCOT that is only capable of supplying Volt-Amperes reactive (VArs) that would not otherwise be operated except as necessary to provide voltage support under Credible Single Contingency criteria.
System Lambda The cost of providing one MWh of energy at the reference Electrical Bus, i.e. the Shadow Price for the power balance constraint, which is equal to the change in the objective function obtained by relaxing the power balance constraint by one MW. The System Lambda is the energy component of LMP at each Settlement Point in ERCOT.
System Operator An Entity that supervises the collective Transmission Facilities of a power region. This Entity is charged with coordination of market transactions, system-wide transmission planning, and network reliability.

System-Wide Offer Cap (SWCAP)

The SWCAP shall be determined in accordance with PUCT Substantive Rules.