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Firm Demand
- NERC GLOSSARY
- That portion of the Demand that a power supplier is obligated to provide except when system reliability is threatened or during emergency conditions.
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Firm Transmission Service
- NERC GLOSSARY
- The highest quality (priority) service offered to customers under a filed rate schedule that anticipates no planned interruption.
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Frequency Bias
- NERC GLOSSARY
- A value, usually expressed in megawatts per 0.1 Hertz (MW/0.1 Hz), associated with a Balancing Authority Area that approximates the Balancing Authority Area’s response to Interconnection frequency error.
- NERC GLOSSARY – WECC REGIONAL TERM
- Means a value, usually given in megawatts per 0.1 Hertz, associated with a Control Area that relates the difference between scheduled and actual frequency to the amount of generation required to correct the difference.
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Frequency Bias Setting
- NERC GLOSSARY
- A number, either fixed or variable, usually expressed in MW/0.1 Hz, included in a Balancing Authority’s Area Control Error equation to account for the Balancing Authority’s inverse Frequency Response contribution to the Interconnection, and discourage response withdrawal through secondary control systems.
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Frequency Deviation
- NERC GLOSSARY
- A change in Interconnection frequency.
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Frequency Error
- NERC GLOSSARY
- The difference between the actual and scheduled frequency. (FA – FS)
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Frequency Regulation
- NERC GLOSSARY
- The ability of a Balancing Authority to help the Interconnection maintain Scheduled Frequency. This assistance can include both turbine governor response and Automatic Generation Control.
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Frequency Response
- NERC GLOSSARY
- (Equipment) The ability of a system or elements of the system to react or respond to a change in system frequency.
- (System) The sum of the change in demand, plus the change in generation, divided by the change in frequency, expressed in megawatts per 0.1 Hertz (MW/0.1 Hz).
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Inadvertent Interchange
- NERC GLOSSARY
- The difference between the Balancing Authority’s Net Actual Interchange and Net Scheduled Interchange. (IA – IS)
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IEEE
- NERC GLOSSARY
- Institute of Electrical and Electronics Engineers, Inc.
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Interchange
- NERC GLOSSARY
- Energy transfers that cross Balancing Authority boundaries.
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Interchange Meter Error (IME)
- NERC GLOSSARY
- A term used in the Reporting ACE calculation to compensate for data or equipment errors affecting any other components of the Reporting ACE calculation.
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Interchange Schedule
- NERC GLOSSARY
- An agreed-upon Interchange Transaction size (megawatts), start and end time, beginning and ending ramp times and rate, and type required for delivery and receipt of power and energy between the Source and Sink Balancing Authorities involved in the transaction.
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Interchange Transaction
- NERC GLOSSARY
- An agreement to transfer energy from a seller to a buyer that crosses one or more Balancing Authority Area boundaries.
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Interchange Transaction Tag or Tag
- NERC GLOSSARY
- The details of an Interchange Transaction required for its physical implementation.
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Interconnection
- NERC GLOSSARY
- A geographic area in which the operation of Bulk Power System components is synchronized such that the failure of one or more of such components may adversely affect the ability of the operators of other components within the system to maintain Reliable Operation of the Facilities within their control. When capitalized, any one of the four major electric system networks in North America: Eastern, Western, ERCOT and Quebec.
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IROL
- Interconnection Reliability Operating Limit
- NERC GLOSSARY
- A System Operating Limit that, if violated, could lead to instability, uncontrolled separation, or Cascading outages that adversely impact the reliability of the Bulk Electric System.
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Interruptible Load or Interruptible Demand
- NERC GLOSSARY
- Demand that the end-use customer makes available to its Load-Serving Entity via contract or agreement for curtailment.
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LSE
- NERC GLOSSARY
- Load-Serving Entity
- Secures energy and Transmission Service (and related Interconnected Operations Services) to serve the electrical demand and energy requirements of its end-use customers.
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MSSC
- Most Severe Single Contingency
- NERC GLOSSARY
- The Balancing Contingency Event, due to a single contingency identified using system models maintained within the Reserve Sharing Group (RSG) or a Balancing Authority’s area that is not part of a Reserve Sharing Group, that would result in the greatest loss (measured in MW) of resource output used by the RSG or a Balancing Authority that is not participating as a member of a RSG at the time of the event to meet Firm Demand and export obligation (excluding export obligation for which Contingency Reserve obligations are being met by the Sink Balancing Authority).
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Net Actual Interchange
- NERC GLOSSARY
- The algebraic sum of all metered interchange over all interconnections between two physically Adjacent Balancing Authority Areas.
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Net Interchange Schedule
- NERC GLOSSARY
- The algebraic sum of all Interchange Schedules with each Adjacent Balancing Authority.
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Net Scheduled Interchange
- NERC GLOSSARY
- The algebraic sum of all Interchange Schedules across a given path or between Balancing
- Authorities for a given period or instant in time.
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NFTS
- NERC GLOSSARY
- Non-Firm Transmission Service
- Transmission service that is reserved on an as-available basis and is subject to curtailment or interruption.
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Non-Spinning Reserve
- 1) That generating reserve not connected to the system but capable of serving demand within a specified time.
- 2) Interruptible load that can be removed from the system in a specified time.
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OASIS
- Open Access Same Time Information Service
- NERC GLOSSARY
- An electronic posting system that the Transmission Service Provider maintains for transmission
- access data and that allows all transmission customers to view the data simultaneously.
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OATT
- Open Access Transmission Tariff
- NERC GLOSSARY
- Electronic transmission tariff accepted by the U.S. Federal Energy Regulatory Commission requiring the Transmission Service Provider to furnish to all shippers with non-discriminating service comparable to that provided by Transmission Owners to themselves.
- Operating Reserve
- NERC GLOSSARY
- That capability above firm system demand required to provide for regulation, load forecasting error, equipment forced and scheduled outages and local area protection. It consists of spinning and non spinning reserve.
- NERC GLOSSARY – WECC REGIONAL TERM
- Means that capability above firm system demand required to provide for regulation, load-forecasting error, equipment forced and scheduled outages and local area protection. Operating Reserve consists of Spinning Reserve and Non-spinning Reserve.
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Operating Voltage
- NERC GLOSSARY
- The voltage level by which an electrical system is designated and to which certain operating
- characteristics of the system are related; also, the effective (root-mean-square) potential
- difference between any two conductors or between a conductor and the ground. The actual
- voltage of the circuit may vary somewhat above or below this value.
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Operations Support Personnel
- NERC GLOSSARY
- Individuals who perform current day or next day outage coordination or assessments, or who determine SOLs, IROLs, or operating nomograms,1 in direct support of Real-time operations of the Bulk Electric System.
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PSP
- NERC GLOSSARY
- Physical Security Perimeter
- The physical border surrounding locations in which BES Cyber Assets, BES Cyber Systems, or Electronic Access Control or Monitoring Systems reside, and for which access is controlled.
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POD
- Point of Delivery
- NERC GLOSSARY
- A location that the Transmission Service Provider specifies on its transmission system where an Interchange Transaction leaves or a Load-Serving Entity receives its energy.
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POR
- Point of Receipt
- NERC GLOSSARY
- A location that the Transmission Service Provider specifies on its transmission system where an Interchange Transaction enters or a generator delivers its output.
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Protection System
- NERC GLOSSARY
- - Protective relays which respond to electrical quantities,
- - Communications systems necessary for correct operation of protective functions
- - Voltage and current sensing devices providing inputs to protective relays,
- - Station dc supply associated with protective functions (including station batteries, battery
- - chargers, and non-battery-based dc supply), and
- - Control circuitry associated with protective functions through the trip coil(s) of the circuit breakers or other interrupting devices.
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Pseudo-Tie
- NERC GLOSSARY
- A time-varying energy transfer that is updated in Real-time and included in the Actual Net Interchange term (NIA) in the same manner as a Tie Line in the affected Balancing Authorities’ Reporting ACE equation (or alternate control processes).
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PSE
- Purchasing-Selling Entity
- NERC GLOSSARY
- The entity that purchases or sells, and takes title to, energy, capacity, and Interconnected Operations Services. Purchasing-Selling Entities may be affiliated or unaffiliated merchants and may or may not own generating facilities.
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Ramp Rate or Ramp
- NERC GLOSSARY
- (Schedule) The rate, expressed in megawatts per minute, at which the interchange schedule is attained during the ramp period.
- (Generator) The rate, expressed in megawatts per minute, that a generator changes its output.
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Rating
- NERC GLOSSARY
- The operational limits of a transmission system element under a set of specified conditions.
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Reactive Power
- NERC GLOSSARY
- The portion of electricity that establishes and sustains the electric and magnetic fields of alternating-current equipment. Reactive Power must be supplied to most types of magnetic equipment, such as motors and transformers. It also must supply the reactive losses on transmission facilities. Reactive Power is provided by generators, synchronous condensers, or electrostatic equipment such as capacitors and directly influences electric system voltage. It is usually expressed in kilovars (kvar) or megavars (Mvar).
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Real Power
- NERC GLOSSARY
- The portion of electricity that supplies energy to the Load.
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Regulating Reserve
- NERC GLOSSARY
- An amount of reserve responsive to Automatic Generation Control, which is sufficient to provide normal regulating margin.
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