Glossary by "R"

  • 449


    See: Radial circuit
  • 450

    Radial circuit

    A transmission line, distribution line, or transmission/distribution subsystem which is not interconnected with other systems. So named because it radiates outward from another transmission system without bridging any other systems.

  • 451


    See: Ramp rate


    Source: ESA Technical Working Group
  • 452

    Ramp rate

    1. The rate at which power output can be changed. Typically ramp rate is expressed in units of MW/minute. 2. The rate at which output from a generator or demand associated with loads varies. Ramp rates can involve variation ranging from several percent over a few seconds to significant percentages over timeframes of one or a few minutes. 3. The rate at which power output can be changed. Typically ramp rate is expressed in units % of maximum power per minute. 4. (Schedule) The rate, expressed in megawatts per minute, at which the interchange schedule is attained during the ramp period. 5. (Generator) The rate, expressed in megawatts per minute, that a generator changes its output.

    Source: ESA Technical Working Group
  • 453

    Ramping service

    A proposed ancillary service that involves electric resources whose output can be varied rapidly to offset ramping of other resources. See also ramp rate and ramping.

    Source: ESA Technical Working Group
  • 454

    Rate base

    The asset (property) value of a given utility. Rate base is used as a benchmark value to determine how much a utility can be permitted to earn (its rate of return). Whether public or private, utilities will likely have debts investments that must be repaid over time, and without a rate base, it is impossible to determine how much income a public utility will require to sustain itself. Rate bases may also used to determine the point at which a private utility in a regulated environment graduates from reasonable profitability to obscene profitability, or to calculate a utility’s worthiness for funds which may be needed for expansion or upgrading of equipment.  

  • 455

    Rate case

    An administrative proceeding—and related documents—used by a regulated entity to justify and apply for cost-recovery and rate changes.  Rate case proceedings take place before the relevant regulatory agency or committee thereof.

    Source: ESA Technical Working Group
  • 456

    Rate class

    A group of utility customers that is categorized based on the type of rate structure (tariff) they are subject to.

    Source: ESA Technical Working Group
  • 457

    Rated electrical operating conditions

    The specified or reasonably anticipated conditions under which the electrical system or an individual electrical circuit is intended/designed to operate.

  • 458


    The operational limits of a transmission system element under a set of specified conditions.

  • 459

    Reactive power

    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 kiloVoltAmp-reactive (kVARs or MegaVoltAmp-reactive (MVARs).

  • 460

    Reactive supply and voltage control from generation service

    Electric supply resources used to supply reactive power to the grid to manage the grid voltage. Typically generators used for this service are equipped with a synchronous condenser. One of six ancillary services specified by the FERC under Order 888. See voltage support.  

    Source: ESA Technical Working Group
  • 461

    Real power

    The portion of electricity that supplies energy to the load.

  • 462

    Real time pricing

    Acronym(s): RTP

    Prices for wholesale electricity that are specific to the time when the electricity is purchased.

    Source: ESA Technical Working Group
  • 463


    Present time as opposed to future time. (From Interconnection Reliability Operating Limits standard.)

  • 464

    Real-time market

    The competitive generation market controlled and coordinated by the ISO for arranging real-time imbalance power. 

  • 465

    Receiving balancing authority

    The balancing authority importing the Interchange.

  • 466


    Cells or batteries that can be recharged.

    Source: ESA Technical Working Group
  • 467


    A somewhat sophisticated circuit breaker that protects electrical T&D systems from overloading, voltage surges and other undesirable phenomena and that can “reclose” once the problem is cleared to restore normal operation. The reclosure process is typically designed so they are prevented from reclosing if the same fault occurs several times in succession over a short period. That reduces the chance of repetitive line faults (i.e. so electric service is not turned off repeatedly, in part to reduce damage to or accelerated wear of electrical equipment. and to avoided temporary outages caused by short duration phenomena like lightning strikes or transmission switching.

    Source: ESA Technical Working Group
  • 468


    State in which the gases normally formed within the battery cell during its operation, are recombined to form water.

  • 469


    A chemical process that results in the acceptance of electrons by an electrode’s active material. The opposite of oxidation.

    Source: ESA Technical Working Group
  • 471

    Regional entities

    Eight organizations in North America with delegated authority from North American Electric Reliability Corporation (NERC) to safeguard the reliability of the bulk power systems throughout North America. (WECC, MRO, SPP, TRE, FRCC, SERC, RFC and NPCC).

    Source: ESA Technical Working Group
  • 472

    Regional reliability organization

    1.  An entity that ensures that a defined area of the Bulk Electric System is reliable, adequate and secure. 2.  A member of the North American Electric Reliability Council. The Regional Reliability Organization can serve as the Compliance Monitor.

  • 475

    Regional reliability plan

    The plan that specifies the Reliability Coordinators and Balancing Authorities within the Regional Reliability Organization, and explains how reliability coordination will be accomplished.  

  • 476

    Regional transmission organization

    Acronym(s): RTO

    Regional transmission organizations are established to operate the high-voltage interstate transmission system in a reliable, non-discriminatory manner, and to coordinate with other critical entities, such as participating utilities and generators, neighboring RTOs/ISOs and power exchanges. See also Regional Transmission Organizations/Independent System Operators.

  • 478

    Regional Transmission Organizations/Independent System Operators

    Acronym(s): RTO/ISO

    Independent System Operators grew out of FERC Orders Nos. 888/889 where the Commission suggested the concept of an Independent System Operator ISO) as one way for existing tight power pools to satisfy the requirement of providing non-discriminatory access to transmission. Subsequently, in Order No. 2000, the Commission encouraged the voluntary formation of Regional Transmission Organizations to administer the transmission grid on a regional basis throughout North America (including Canada). Order No. 2000 delineated twelve characteristics and functions that an entity must satisfy in order to become a Regional Transmission Organization. RTO/ISO regions in the U.S.: CAISO, ERCOT, SPP, MISO, PJM, NYISO and ISO-NE. RTO/ISO regions in Canada: AESO, NBSO and OIESO.

  • 479

    Regulating reserve

    An amount of reserve responsive to Automatic Generation Control, which is sufficient to provide normal regulating margin.

  • 480

    Regulation and frequency response service

    See: Frequency response

    One of six ancillary services specified by the FERC under Order 888.

    Source: ESA Technical Working Group
  • 481

    Regulation service

    The process whereby one Balancing Authority contracts to provide corrective response to all or a portion of the ACE of another Balancing Authority.  The Balancing Authority providing the response assumes the obligation of meeting all applicable control criteria as specified by North American Electric Reliability Corporation (NERC) for itself and the Balancing Authority for which it is providing the Regulation Service.

  • 482


    The degree of performance of the elements of the bulk electric system that results in electricity being delivered to customers within accepted standards and in the amount desired. May be measured by the frequency, duration and magnitude of adverse effects on the electric supply.

  • 484

    Reliability coordinator

    The entity that is the highest level of authority who is responsible for the reliable operation of the Bulk Electric System, has the Wide Area view of the Bulk Electric System, and has the operating tools, processes and procedures, including the authority to prevent or mitigate emergency operating situations in both next- day analysis and real-time operations. The Reliability Coordinator has the purview that is broad enough to enable the calculation of Interconnection Reliability Operating Limits, which may be based on the operating parameters of transmission systems beyond any Transmission Operator

  • 485

    Reliability coordinator area

    The collection of generation, transmission, and loads within the boundaries of the Reliability Coordinator. Its boundary coincides with one or more Balancing Authority Areas.  

  • 486

    ReliabilityFirst Inc.

    Acronym(s): RFC

    A not-for-profit company whose mission is to preserve and enhance electric service reliability and security for the interconnected electric systems within the ReliabilityFirst geographic area. See also regional entities.

    Source: RFC
  • 487

    Replacement reserve

    Contingency operation that provides capacity (power) if a generator or transmission line fails unexpectedly, called after Non-spinning Reserve.  Response is typically required 30-60 minutes after the failure. Also known as Supplemental Reserve.

  • 489

    Reserve sharing group

    A group whose members consist of two or more Balancing Authorities that collectively maintain, allocate, and supply operating reserves required for each Balancing Authority  

  • 491

    Resistive losses

    See: I
    Source: ESA Technical Working Group
  • 492

    Resource adequacy

    Acronym(s): RA

    The degree to which electric supply resources are capable of delivering the needed energy and power.  

    Source: ESA Technical Working Group
  • 494

    Resource planner

    The entity that develops a long-term (generally one year and beyond) plan for the resource adequacy of specific loads (customer demand and energy requirements) within a Planning Authority Area.  

  • 495

    Response rate

    The Ramp Rate that a generating unit can achieve under normal operating conditions expressed in megawatts per minute (MW/Min).  

  • 497

    Response time

    The amount of time required for a storage system output to transition from no discharge to full discharge.

    Source: ESA Technical Working Group
  • 498

    Retail wheeling

    The practice by retail electricity end-users of purchasing electricity from a supplier other than the retail utility and then using utility transmission systems to “wheel in” the purchased energy.

    Source: ESA Technical Working Group
  • 499

    Revenue requirement

    The amount of revenue required to cover all utility costs—including those related to electric supply, transmission, distribution and customer service—including capital-related expenditures, operating expenses, taxes, interest on and return of debt, and, if applicable, the authorized rate of return on and return of stockholder equity.

    Source: ESA Technical Working Group
  • 500

    Right-of-way (row)

    A corridor of land on which electric lines may be located. The Transmission Owner may own the land in fee, own an easement, or have certain franchise, prescription, or license rights to construct and maintain lines.  

  • 501


    Exposure to or the existence of potential danger, harm, or loss related to something of value.

    Source: ESA Technical Working Group
  • 502

    Round trip efficiency

    The amount of energy that a storage system can deliver relative to the amount of energy injected into the system during the immediately preceding charge. (Also referred to as efficiency.)  

    Source: ESA Technical Working Group
  • 503

    Rural electric cooperative

    See: Electric cooperative
    Source: ESA Technical Working Group
  • 504

    Rural Utilities Service

    Acronym(s): RUS

    An organization within the U.S. Department of Agriculture whose purpose is to be the U.S. federal government’s lead agency regarding matters related to rural infrastructure (electricity, water and telecommunications).  

    Source: ESA Technical Working Group