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See tesla.
The canal or channel that carries water away from a dam.
The water surface immediately downstream from a dam.
A power sales contract provision where the sale price is contingent on a customer’s committing to purchase a certain amount of power from BPA, even if the customer actually uses less power.
See Transmission Agency of Northern California.
To tie a substation into an existing line by running a new single-circuit line from the substation to the line.
A mechanism on a power transformer that permits a tap connection to be changed to adjust the voltage ratio of the transformer. A tap-changer can be a load tap-changer which changes taps with the transformer energized or a no-load tap-changer which requires de-energization of the transformer to change taps.
The point on a transmission line where a tap from a substation is tied in.
BPA’s approach to acquiring conservation that focuses on individual customer's unique opportunities for programs tailored to their needs; such acquisitions, together with competitive acquisitions, allow innovation and flexibility in acquiring new resources.
The agreement between BPA and a contractor that describes a specific job and estimates its cost.
See testing automation unit.
See transmission control and dispatch system.
In conservation, refers to the maximum amount of electric energy savings theoretically available if all consumers in an end-use sector implement all cost-effective conservation measures.
A measure of the interfering effects of voltage and current in a power system on voice communications.
Pulling the conductors to the correct sag so that proper ground clearance is maintained. Also insures that supporting structures are not overloaded under ice and wind.
The equipment used to connect a line or transformer into a substation.
A unit of measurement of magnetic field strength. A smaller unit, the gauss, is also used (one tesla equals 10,000 gauss).
A computer system programmed to simulate inputs and outputs of a unit under test. A TAU output is the equivalent of a field input to the unit under test; a TAU input reads the outputs of the field unit under test.
A unit of heat equal to 100,000 British thermal units (Btu). One therm converts to 105.5 megajoules.
1) Refers to heating and cooling characteristics of building structures. 2) Refers to a type of electric generating station or power plant, such as coal and nuclear plants, in which the source of energy for the prime mover is heat.
A factor that describes the heat conduction process in solids, liquids, and gases. The amount of heat in one Btu that will flow through one square foot of a material, one inch thick, in one hour, when there is a temperature difference of one degree F.
The ratio of the electric power produced by a power plant to the amount of heat produced by the fuel. A measure of the efficiency with which the plant converts thermal to electric energy.
Energy in the form of heat.
The maximum power or current that can be permitted to flow in a transmission line conductor, device, or electrical machine without a failure or damage caused by excessive temperature.
The excessive raising of water temperature above normal seasonal ranges in streams, lakes, estuaries, or coastal ocean water as the result of discharge of hot effluents, frequently from the discharge of cooling waters from industrial processes, and particularly from thermal generating plants.
A generating plant that converts heat energy into electrical energy, by the burning of coal, oil, or gas, or by nuclear fusion.
In reservoirs, the vertical layering of water during summer months into lighter, warmer water on the surface and cold oxygen-deficient water on the bottom.
A semiconductor device whose resistance changes (usually decreases) with the temperature in a definite manner. Used in circuits to compensate for temperature variations in other components.
A pair of dissimilar metals so joined at two points that a voltage is developed when the junctions are at different temperatures.
A parallel reinforcement of the two existing alternating-current parts of the Pacific Northwest-Pacific Southwest Intertie to increase power transfer capabilities between the Northwest and California. The 500-kV, Third AC line extends from Alvey Substation (south of Eugene, Oregon) to Tesla Substation (east of San Francisco).
See financing.
Sources of funds, other than bonds issued to the U.S. Treasury and congressional appropriations, that may issue debt to finance Federal Columbia River Power System investments for generation, conservation, transmission, and fish and wildlife projects. Third party sources can be either tax exempt (such as State and local government entities) or taxable (such as corporations). BPA may, in some cases, act as guarantor or security for bonds that the third party issues.
A volume of water sufficient to provide a flow of 1,000 cubic feet per second for a 24-hour period (28 cubic meters/second/day).
As defined in the Endangered Species Act, those species likely to become endangered within the foreseeable future throughout all or a significant portion of their range.
A bearing that resists a thrust in the direction of the axis of a shaft. In a vertical turbine the thrust bearing is required to support the shaft weight plus the axial hydraulic pressure on the runner.
A semiconductor switch with “on” and “off” states. May be uni-directional or bi-directional, and may be a triggered three-terminal device (a controlled rectifier), or a two-terminal device (diode).
A transmission line connecting two or more power systems.
A method of automatically matching generation to load in a power system. Also see automatic generation control.
See telephone influence factor.
The difference between actual system time as derived from system frequency and standard time from the U.S. Bureau of Standards. Adjustments in control of system frequency are made when needed to compensate for the deviation.
Rates imposing higher charges during those periods of the day when the higher costs to the utility are incurred.
The top 25 percent of the direct-service industry load that is served with nonfirm energy and that BPA may interrupt or the DSIs may curtail, for any reason.
In law, a claim alleging property damage, personal injury, or death caused by a negligent or wrongful act or omission other than a contractual or criminal wrong.
All matter in solid or liquid form contained in a sample of air, regardless of the sample’s particle size or chemical composition.
A broad-base latticed steel support for line conductors (as differentiated from a wood or steel pole structure or line).
A heavy tower designed for use where the transmission line loads the tower primarily in tension (pull) rather than compression (downward push), such as in turning large angles along a line or bringing a line into a substation.
A tower designed to support conductors strung along a virtually straight line with only small turning or descending or ascending angles. Approximately five suspension towers are used to a mile; tangent towers have no turn angle; angle towers have light or heavy turning abilities.
1.       tower body — the main or center part of the tower, designed in standard heights to which the leg extensions are attached.
2.       crossarm or bridge — the uppermost part of the tower to which the insulator strings are attached.
3.       leg extensions — the lower parts of the tower which form the tower support and are designed in various lengths to permit different height towers and allow tower installation on non-level ground.
4.       ground-wire bracket — a bracket attached to the crossarm of the tower for supporting the overhead ground wire.
5.       step bolt — galvanized steel bolts attached to a corner tower leg to permit climbing.
1.       horizontal crossarm — a single-circuit tower designed with all insulators attached in a horizontal plane. Generally self-supporting (does not require guys and has four footings); may be square (the footings are set square in the direction of the line); or are rotated (the footings are set in the shape of a diamond in the direction of the line).
2.       delta — a tower with the two outside insulator strings in the same horizontal plane and the center string supported at a higher level. Can be guyed from a single support or self-supporting with four legs; the self-supporting delta tower is used for most 500-kV line construction.
3.       lattice pole — a tower formed by a network of light steel angles assembled to form poles and a crossarm; requires guys for support; single-circuit.
4.       double-circuit — a tower with three crossarms, each supporting two phases; all three phases of one circuit are usually located on one side of the tower.
1.       grillage — footing made of framework of galvanized steel with wide-flange beams and channels; attached to footing stub angle and attaching leg extension.
2.       pressed plate — footing consisting of galvanized steel plate, ranging in size from 610 millimeters (24 inches) to 1321 millimeters (52 inches) square; multiple plates are also used.
3.       rock — footing consisting of stub angles cemented into a hole in solid rock; anchor dowels are optional.
4.       concrete — a footing designed for special conditions and consisting of buried reinforced concrete.
The center part of the tower body through which the center conductor passes.
A Federal law that requires identification and control of chemicals, such as polychlorinated biphenyls, that pose an unreasonable risk to human health or the environment through their manufacture, processing, commercial distribution, use, or disposal.
Agreements, with various Pacific Northwest utilities, that the transferor utility will use its system to deliver power and energy to a customer of another utility. The power transferred is replaced, and the transferor is compensated in cash or kilowatthour credits.
The amount of power, usually the maximum amount, that can be transmitted between one system and another; power flow and stability studies determine transfer capability under various outage, system loading, and system operating conditions.
See relay.
A device for transferring electrical energy from one circuit to another by magnetic induction, usually between circuits of different voltages. Consists of a magnetic core on which there are two or more windings. In power systems, most frequently used for changing voltage levels.
A transformer that uses a common winding for both the primary and secondary windings, giving it distinct advantages, both in economy and size, over two-winding transformers when the ratio of transformation is in the order of three-to-one or less (for example, from 500 kV to 230 kV and from 230 kV to 115 kV).
An instrument transformer using two or more capacitors to divide and reduce the primary voltage to the lower secondary voltage levels required for metering and relaying circuits.
An instrument transformer, with its primary winding connected in series with the conductor carrying the current to be measured, which gives an accurate low-current (five-ampere) indication in its secondary winding of the high-amperage current in its primary winding. The low-current output is used for relaying, metering, and indication.
A transformer used to change the voltage level for power transmission and distribution.
Used to lower voltages at the appropriate points in the transmission system and at the load for ultimate use.
Used to increase voltage at generating plants for transmission.
An instrument transformer, with its primary winding connected in shunt with the voltage that is to be measured, which gives an accurate low-voltage (115 volts) indication of the high-voltage system it is measuring. The low-voltage output is used for relaying, metering, and indication.
A sudden short-time disturbance or change in an electrical quantity in a circuit.
The bulk transport of electricity from large generation centers over significant distances to interchanges with large industries and distribution networks of utilities.
See Federal Columbia River Transmission System Act.
A consortium of 15 publicly owned California utilities managing the California/Ore-gon Transmission Project, a 300-mile transmission line increasing Pacific Northwest-Pacific Southwest intertie capacity.
A computer-based system located in the Dittmer Control Center that gathers data from remotes at all the major BPA substations and allows the Dittmer dispatchers to remotely operate power equipment in the substation.
An interconnected network of transmission lines including associated equipment for the transfer of electric energy in bulk between points of supply and points of demand. The BPA transmission grid includes some 22 500 circuit kilometers (14,000 circuit miles) of lines connecting more than 400 substations in the Pacific Northwest. The main grid consists of 500-kV, 345- kV, and 230-kV lines.
A high-voltage, extra-high-voltage, or ultra-high-voltage power line used to carry electric power efficiently over long distances.
See line losses.
See tower.
The interchanging of positions of conductors along a transmission line to reduce inductive influence and power loss.
See financing.
The 19.1 cubic kilometers (15.5 million acre-feet) of water storage that Canada agreed to build under the 1964 Columbia River Treaty. The treaty dams are Mica, Duncan, and Arrow.
The opening of a circuit breaker. The opening can be automatic by protective relays or manual by means of a control switch.
A three-fingered or pyramid-shaped arrangement of cast or welded steel plates installed in a line to permit dead-ending a parallel conductor to three strings of insulators.
A plan for disconnecting a potentially unstable area from the rest of a system if sensors detect the beginnings of electrical instability in the area that might spread to, or damage, other areas.
Advance deposits received from non-government entities to finance work performed by BPA pursuant to letter agreements, memorandums of understanding, or other contractual agreements. Also called advance funding, customer deposits.
A fund set up under the Comprehensive Environmental Response, Compensation, and Liability Act to help pay for cleaning up hazardous waste sites and for legal action to force those responsible for the sites to clean them up.
See Toxic Substances Control Act.
See total suspended particulates.
Haziness in air or water caused by the presence of particles or pollutants. Specifically, a measure of the optical clarity of water, which depends on the light scattering and absorption characteristics of both suspended and dissolved material in the water.
An enclosed rotary type of prime mover that drives an electric generator to produce power.
An electrical generator powered by exhaust gases from an oil- or gas-fired turbine rather than by heat-created steam.
A turbine in which the flow of water acts upon vanes of a runner.
A combustion turbine that converts energy of hot compressed gases (produced by burning fuel in compressed air) into mechanical energy that can be used to generate electricity and compress more air. Often used interchangeably with combustion turbine.
A turbine in which the force of water directed against blades fastened to a vertical or horizontal shaft produces mechanical energy.
A turbine in which the flow of water is exposed to atmospheric pressure. The Pelton turbine, or wheel, is generally used on high heads.
A prime mover with propeller-shaped blades, used at low-head dams.
A turbine in which the flow of water acts upon blades on a hub. The blades may be fixed or adjustable (for example, the Kaplan turbine has a variable-pitch blade).
A turbine in which the flow of water is under pressure.
A turbine in which heat energy in steam is converted into mechanical energy by the force of a high velocity flow of steam directed against successive rows of radial blades fastened to a central shaft.
The maximum amount of water that can be passed through the turbines of a dam at any instant.
A rotary-type unit consisting of a turbine and an electric generator. Also called a turbine generator.



The U-factor of a component times the area of that component, eliminating area from the equation.
A measurement of the heat-conducting properties of a material.
Refers to transmission lines with voltage levels above the 800-kV class. Also see extra-high voltage, high voltage.
Long-term contracts between BPA and utility customers which set forth generic terms for scheduling, billing, and other administrative matters and enable those parties to buy, sell, store, or exchange power in specific instances with letters of agreement.
An unexpected or uncontrollable event that upsets plans or releases from obligation. Same as force majeure.
A written offer to perform a proposed task or effort, initiated and submitted to BPA by a prospective offeror without a solicitation by BPA, with the objective of obtaining a contract or financial assistance.
The amount of capital expenditures against which BPA has not borrowed. A BPA policy is to limit cumulative U.S. Treasury borrowing (net of amortization of BPA bonds) to the amount of estimated cumulative capital expenditures.
The overall heat loss rate (UA) of all components in a building divided by the total area of all components.
Increases in the capacity of existing electrical facilities, including transmission lines and equipment, by increasing the operating voltage.
Increases in the capacity of existing electrical facilities, including transmission lines and equipment, by increasing the operating current.
Compensation to owners of upstream projects on the Columbia River System for benefits that accrue at downstream generating plants due to storage and scheduled releases at upstream reservoirs.
See storage.
The builder and now the owner-operator of many of the Federal dams in the Columbia River Basin (as well as elsewhere in the U.S.).
A Bureau within the Department of the Interior responsible for managing public lands, including resources such as timber, minerals, oil and gas, geothermal energy, wildlife habitat, endangered species, recreation and cultural values, and open space.
A Bureau within the Department of the Interior responsible for operating and maintaining Grand Coulee and Hungry Horse dams and numerous water resource projects in the Columbia River Basin, for such purposes as irrigation and power production.
A Department established in 1977 by the Department of Energy Organization Act to consolidate the major Federal energy functions into one cabinet-level department that would formulate a comprehensive, balanced national energy policy. Responsible for regulatory, research, and marketing programs related to energy production and use. BPA is an agency of DOE.
See sector.
The Federal agency created in 1970 to permit coordinated and effective governmental action for protecting the environment by the systematic abatement and control of pollution by integrating research, monitoring, standard setting, and enforcement activities.
An agency within the Department of the Interior responsible for guiding conservation, development, and management of U.S. fish and wildlife resources.
A public or private organization created for the purpose of selling or supplying for general public use water, electric energy, telephone service, or other items or services.
The two classifications of utilities, publicly and privately owned, that BPA serves and whose basic service and rates are established by legislation. See generating utility, non-generating utility, public utility, investor-owned utility.



See volts.
See voltamperes.
1) The relative monetary worth of power at the market as measured by the cost of producing and delivering equivalent alternative power to the market. 2) The monetary worth of power at the site of the generating station as measured by the at-market worth minus the cost of transmission facilities and losses from generating station to market.
That part of the at-site or at-market value of electric power that is assigned to capacity.
That part of the at-site or at-market value of electric energy, usually hydro, that may be substituted for energy generated in a fossil fuel or nuclear plant, in terms of the incremental cost of producing energy in the latter.
A material that retards the transmission of water vapor. It is rated in perms and should have a permeance of one perm or less.
The unit of measurement of reactive power in a circuit. Equal to the product of volts and amperes 90 degrees out of phase (kvar = kilovar, or 1,000 var; Mvar = megavar, or 1,000 kilovar).
See costs.
The January-through-July portion of the energy content curve; based on the forecasted amount of spring runoff.
See rates.
See rates, variable industrial.
See variable energy content curve.
A mathematical representation of a quantity having both magnitude and direction.
The release of limited amounts of gases or vapors to maintain pressures within design limits in tanks, pipes, and other equipment.
A device attached to a conductor to prevent damage caused by wind-induced vibration.
Variable industrial rate. See rates.
See volts-per-meter.
The unit of electromotive force, or voltage, that if steadily applied to a circuit having a resistance of one ohm will produce a current of one ampere. See Ohm’s Law.
The driving force that causes a current to flow in an electric circuit. Voltage and volt are often used interchangeably.
The difference between the voltages at the transmitting and receiving ends of a feeder, main, or service line; with alternating current the voltage drop is not necessarily equal to the straightforward algebraic difference of the voltages at the two ends.
The change in secondary (output) voltage of a transformer as the load current is varied, usually expressed as a percentage of the rated voltage when the current is changed from no-load to full-load.
Usually an induction (transformer) device with the windings of the primary and regulated circuits adapted and arranged for the control of the voltage of the regulated circuit. Also see step-voltage regulator.
See relay.
The mathematical product of volts and amperes. Same as apparent power.
An instrument for measuring voltage or electrical potential difference, with a scale in volts or kilovolts.
A measure of electric field strength.