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30-Minute Reserve Service

can be satisfied by online or offline resources that are able to respond in 30 minutes or less.

Adequacy

The ability to supply the demand and energy requirements of the end-use customers.

Ancillary Services

Services necessary to support the transmission of electric power.

Area Control Error

ACE. The instantaneous difference between net actual and scheduled interchange.

Area, Zone, Region

Some geographical concepts in power systems

Automatic Generation Control

AGC. Automatic regulation of the power output of generators

Balancing Authoritiy

The responsible entity within a Balancing Authority Area.

Bilateral Transaction

A direct contract between a seller and buyer outside of a centralized market.

black-start

Establishing the voltage from around zero

Bulk Electric System

BES. Transmission Elements and Power resources 100 kV or higher.

Bulk Power System

BPS. Facilities and control systems for an transmission network.

Capacity Markets

A market for trading capacity credits.

Cascading

The uncontrolled successive loss of System Elements triggered by an incident

Co-Located Load

Load connected to the an existing or planned facility.

Common Information Model

CIM. A set of open standards for representing power system components

Compliance Factor

CF.

Contingency Analysis

A list of network elements to be simulated as disconnected.

Contingency List

A list of network elements to be simulated as disconnected.

Contingency Reserve Service

A.k.a. Primary Reserve. Can be satisfied in 10 minutes or less.

Contingency Reserve

Capacity deployed by the Balancing Authority to meet the Disturbance Control Standard.

Contingency

The unexpected failure or outage of a system component.

Control Performance Standard 1

CPS1. A standard that measures impact on frequency error

Control Performance Standard 2

CPS2. A standard intended to limit unscheduled flows

Converter-Driven Stability

Converter-interfaced generation's impact on stability

Critical Clearing Time

CCT. The maximum permissible duration of the fault.

Critical Inertia

Minimum level of system inertia necessary to ensure deployment of frequency responsive reserves.

Day Ahead Energy Market

Forward markets for electricity to be supplied the following day.

Digital Twin

A virtual representation to reflect a physical object accurately.

DER

Distributed Energy Resources

Distribution Provider

Provides and operates the “wires” between the transmission system and the end-use customer.

Distribution

The act of distributing gas or electric power to customers.

Disturbance

Any perturbation or sudden loss of generation or interruption of load

Electrical Resonance

The behavior of power systems with conventional turbine-generators and variable speed induction generators.

Emergency

Abnormal system condition that requires automatic or immediate manual action.

Energy Market

Equal Area Criterion

EAC and EEAC. A method to determine the stability.

Expected Unserved Energy

EUE. A measure of the capability to continuously serve loads.

Factors

Some sensitivity matrices, such as GSF, PTDF, LODF, BODF, OTDF, etc.

Fast Frequency Response

FFR. Power in response to frequency changes during the arresting phase

Fault

An event such as a short circuit, a broken wire, or an intermittent connection.

Financial Markets

Trading financially settled products.

Financial Transmission Right

FTR. Compensation contract for transmission charges due to grid congestion.

Flexibility

The ability to respond to system changes and uncertainties.

Flowgate

Portion of the transmission system used to analyze power flow impact.

Frequency Deviation

A change in Interconnection frequency.

Frequency Regulation

The ability of a Balancing Authority to help maintain Scheduled Frequency.

Frequency Response Measure

The median of all Frequency Response observations reported annually.

Frequency Stability

The ability of a power system to maintain steady frequency following a severe system upset.

Frequency Response

The ability of a system to react to a change in system frequency.

Futures Market

For contracts for future delivery of a commodity or security.

Generation Redispatch

Generators are adjusted away (off-cost) from their normal assignments (on-cost).

Horizon

Time span

Interchange

Energy transfers that cross Balancing Authority boundaries.

Interconnection Reliability Operating Limit

A System Operating Limit that, if violated, could lead to instability or cascading outages.

Interconnection

A geographic area where BPS components are synchronized.

Interruptible Demand

Customer demand that can be interrupted by control or request of the system operator.

IBR

Inverter-based Resources

Localtional Marginal Price

LMP. Marginal price for energy at the location delivered or received.

Loss-of-Load Expectation

LOLE. The number of days per year for which the available generation capacity is insufficient.

Loss-of-Load Hour

LOLH. The number of hours per year where demand will exceed the generating capacity.

Markets

Some electricity markets in North America

Non-Spinning Reserve

Unconnected to the system but capable of serving demand within a specified time.

Non-Synchronized Reserve

Reserve capability within 10 minutes not electrically synchronized to the system

Operating Reliability

The ability to withstand sudden disturbances while avoiding uncontrolled cascading blackouts or damage to equipment.

Operating Reserve – Spinning

Generation synchronized to the system and fully available to serve load within the Disturbance Recovery Period.

Operating Reserve – Supplemental

Generation or load available to serve load within the Disturbance Recovery Period.

Operating Reserve

Capability above firm system demand required for regulation, load forecasting error, and outages.

Oscillation

A repetitive motion that can be either undamped, positively damped, or negatively damped.

Primary Control

A.k.a. Frequency Response.

Primary Frequency Response

PFR. Immediate proportional response to system Frequency Deviations.

Ramp

A.k.a. Ramp Rate. The rate at which the interchange schedule or generator output is attained.

Real Time Energy Market

Real-Time Reliability Model

A.k.a. EMS model. A computer representation of the power system facilities.

Regulating Reserve

Reserve for AGC to provide normal regulating margin.

Reliability

The probability of satisfactory operation of a power system over the long run.

Remedial Action Scheme

RAS.

Reserve

The generating capability that is “standing by” ready for service in the event that something happens on the power system.

Resilience

Concepts and its metrics.

Resonance Stability

The behavior of power systems under oscillatory energy exchange conditions.

Response Rate

The Ramp Rate that a generating unit can achieve under normal conditions.

Ride-through

Ability to withstand voltage or frequency disturbances and continue operating.

Rotating Blackouts

When each set of distribution feeders is interrupted for a limited time and then rotated among individual feeders.

Rotor Angle Stability

The ability to remain in synchronism under normal and disturbed conditions.

Secondary Control

Associated with Load-Frequency Control and Automatic Generation Control. Balancing services deployed in the “minutes” time frame.

Secondary Reserve

Reserve capability within a 10-to-30 minute interval.

Security Constraiend Economic Dispatch

SCED. Allocation of generating units for economical production.

Security Constrained Unit Commitment

SCUC. Resource Scheduling and Commitment

Security

The degree of risk in a power system's ability to survive imminent disturbances.

Severity Risk Index

SRI. A daily metric that indicates performance of the BES.

Small Signal Stability

The ability to maintain synchronism when subjected to small disturbances.

Spinning Reserve

A.k.a. Synchronized Reserve. Synchronized generation and ready to serve additional demand.

Spot Market

For short-term contractual commitments.

Stability Limit

The maximum power flow possible while maintaining system stability.

Stability Limits

Stability related transmission limits

Stability

The ability to maintain equilibrium during normal and abnormal conditions.

Subsynchronous Resonance

SSR. A condition involving energy exchange at natural frequencies below the synchronous frequency.

synchronization

Aligning a device's terminal voltage with another voltage source

Synchronized Reserve Service

Can be satisfied by online resources in 10 minutes or less.

Synchronous Machine

SM. An AC electrical machine operated with a constant electromagnetic field.

Tertiary Control

Actions taken to handle current and future contingencies.

Thermal Limit Operation Criteria

Techniques to control contingency or system violations.

Torsional Resonance

The SSR due to torsional interactions between series compensated lines and turbine-generator mechanical shafts.

Transient Stability Assessment

Monitor and determine transient stability of the system

Transmission Expansion

The addition or modification of facilities of the Transmission System.

Uncertainty

Two types of uncertainty.

Vendors

Power system vendors

Virtual Synchronous Machine

VSM. Equipment that includes a DC/AC converter controlled to mimic a conventional synchronous machine.

Voltage Dip

Voltage Sag. Short-duration decreases in RMS voltage.

Voltage Limits

Voltage limits to protect against wide area voltage collapse.

Voltage Reductions

A.k.a brownouts

Voltage Stability

The ability of a power system to maintain steady voltages close to nominal value.

Waveform Measurement Unit

WMU, SMU. Sensor device to record synchro-waveforms.

Wholesale Markets

The purchase and sale from generators to resellers.

Zonal Price

A pricing mechanism for a specific zone within a control area.