Glossary by "R"

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.

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.

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.  

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

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

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.  

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

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

Cells or batteries that can be recharged.

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

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).

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

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.

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

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.

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

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.

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.  

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

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.

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