BPA Definitions - L

A     B     C     D     E     FGH     IJK     L     M     NO     PQ     R     S     TUV     WXYZ    

lag

The delay between two events. An electrical current whose phasing is behind the phasing of a voltage, for example, is said to lag.

LAN

See local area network.

larvae

The newly hatched, earliest stage of fish.

lattice

Descriptive of tower and substation structures designed with skew as well as horizontal and vertical members. Design generally used in the BPA system.

LCMM

See Least-Cost-Mix Linear Program Model.

leachate

A liquid that results from water collecting contaminants as it trickles through wastes, agricultural pesticides, or fertilizers and may result in hazardous substances entering surface water, groundwater, or soil.

leaching

The process by which soluble matter is dissolved in groundwater and carried downward and radially through the soil.

lead

1) The phase relationship (advance) between two circuits. An electrical current whose phasing is ahead of the phasing of a voltage, for example, is said to lead. 2) Refers to a conductor that connects a transformer winding to a bushing or to another winding.

leakage

An amount of water which flows around a dam without passing through the turbines, spillway gates, or navigation locks. Also see lockage.

leakage current

A small amount of current that may flow in a normally insulating medium and that is “lost” or “leaks off” through the insulating component.

Least-Cost-Mix Linear Program Model (LCMM)

A linear program computer model that estimates the amount of regional generation and conservation resources that should be acquired to yield a least-cost resource mix to meet a given firm load over a 20-year planning horizon.

least cost mix of resources

The most economical combination of generating and conservation resources that would serve a given amount of load for a given time period.

least-cost planning

The method of meeting future energy needs by acquiring the lowest cost resources first, taking into account all possible means of meeting energy needs and all resource costs including construction, operation, transmission, distribution, fuel, waste disposal, end-of-cycle, consumer, and environmental costs.

levelized costs

The expression of costs on an equal, per-unit basis, taking into account an appropriate interest rate. A home mortgage payment is an example of a levelized cost.

nominal levelized cost

Costs expressed on an equal, per-unit basis, taking into account an appropriate interest rate that includes the effects of inflation.

real levelized cost

The cost per unit of energy savings of a conservation measure over the life of the measure. Calculated by developing an annual cost for purchasing and operating the measure (minus the energy costs) which includes financing, discount, and inflation factors.

light load hours (LLH)

Times of low electricity usage. For BPA, light load hours are 10 p.m. to 6 a.m. Monday through Saturday and all day Sunday.

light water reactor

See nuclear reactor.

linear regression analysis

The derivation of a mathematical relationship between dependent and independent variables based on a random sample of observations.

line losses

See losses.

line miles

The number of miles of transmission line. Differs from circuit miles because individual circuits, such as the two circuits of a double-circuit line, are not counted separately but as total miles of line.

line post insulator

See insulator.

lis pendens

Literally means, “notice of suit pending.” The notice is usually recorded in the county records to give notice of pending litigation. At BPA, the term usually applies to land acquisition processes.

listed waste

Wastes listed as hazardous under the Resource Conservation and Recovery Act.

lithic scatter

A surface scattering of flaked stone material that is evidence of primitive tool-making activity.

litigation

Claims, suits, and complaints filed or pending against entities.

littoral zone

The shallow waters near the shore of a reservoir or lake.

live storage

Active storage. See storage.

LLH

See light load hours.

load

The amount of electric energy delivered or required at any specified point or points on a system. Load originates primarily at the energy-using equipment of consumers, such as heaters, air conditioners, lights, and motors. At BPA, load includes delivery to direct-service industries. (Note: load is slightly larger than metered energy because of normal transmission and distribution losses in delivery from generator to consumer. Because loads are used to determine resource requirements, forecasts of electricity use are converted to loads). Also see end-use load.

firm energy load

The sum of the hourly deliveries of firm load over a period of time such as one month.

firm load

The load that is served, on a guaranteed basis, 100 percent of the time, and that BPA or another supplier has a contractual obligation to serve.

firm peak load

The highest one-hour load on the entire power system each month

forecast load

An estimate or projection of the end-use consumption based on projected changes in future end-use, taking into account industrial loads, populations, business cycles, appliance saturation and efficiencies. May be forecasted by sector or consumer class. BPA forecasts direct-service industries load separately.

incremental load

1) Any increases in load relative to a specific baseload condition. 2) Electricity usage whose economic feasibility depends on lower-cost energy and that would not develop if energy at nonfirm rates were unavailable.

interruptible load

A load that, by contract, can be interrupted if the supplier needs the energy to meet its firm loads.

peak load

The maximum load in a stated period of time. It may be the maximum load at a given instant in the stated period or the maximum average load within a designated interval of the stated period of time.

load center

A point at which the load of a given area is assumed to be concentrated.

load curve

A curve showing the amount of power supplied over a specified period of time, illustrating the variations in load during the time period covered (day, week, month, 12-month period).

load deficit

The amount of forecasted load in excess of planned generating resources.

load diversity

See diversity.

load duration curve

A curve plotting load in order of magnitude for power, rather than hourly variations.

load factor

The ratio of average load to the peak load during a specified period of time; expressed in percent.

load factoring

The exchange of energy generated at one time for energy used at another time. The interval must be one week or less. If longer, the transaction is called storage.

load following

Generally refers to automatic changes in generation to follow changes in load on a second-by-second basis to maintain a continuous balance between loads and generation; only selected generators are controlled to follow load.

load forecast

See forecast.

load forecast range

At BPA, a series of five forecasts (low, medium-low, medium, medium-high, high) that describe potential future use in electricity use in the BPA service area.

load growth

Increase in demand for electricity.

load interruptor switch

A switch designed to interrupt currents not in excess of the continuous current rating of the switch. Does not have fault interrupting capability. Also called load interruptor.

load management

Methods or programs to reduce, reshape, or redistribute electrical loads to match available resources and comply with long-term objectives and constraints. Generally, attempts to shift load from peak use periods to low use periods. Also see demand-side management.

load profiles

Information on the shape, or pattern, of customers’ demands for electricity over time.

load/resource balance

The point at which the demand for electricity matches, or balances, the amount and type of resources available to serve that demand. Also called loads and resources balance.

load shape

The profile, or pattern, of a kilowatt demand of a load over time. Typical utility system profiles peak during the day and are reduced at night, with different types of businesses, industrial operations, and residential users showing markedly different profiles.

load shaping

The scheduling and operation of generating resources to meet changing load levels. On a hydro system, usually involves the adjustment of reservoir releases so that generation and loads are continuously in balance.

hourly/daily load shaping

Usually shaping from light load hours into heavy load hours.

seasonal load shaping

Moving available energy from one season, where it is not in such demand (spring, summer) into a higher demand season (fall, winter).

weekly/monthly load shaping

Shaping the availability of the total energy needed to serve load over a week or month to meet peak or heavy load hour requirements.

load shedding

The process of deliberately removing pre-selected loads from a power system, usually done automatically by relays, in order to maintain the integrity of the system under unusual conditions.

load tap-changer (LTC)

See tap-changer.

local area network (LAN)

A series of devices (such as personal computers, minicomputers, printers, workstations) that are connected together so they can communicate and share data and resources.

lockage

An amount of water that passes through the navigation locks and does not pass through the spillway gates or turbines of a dam. Also see leakage.

lockout

1) Prevention of a circuit breaker reclosure. 2) A general term that denotes keeping a circuit breaker open following the completion of a predetermined sequence of operations.

logger

A device, usually located in a dispatch center, that automatically prints out key information on the operation of power systems.

Long Term Intertie Access Policy (LTIAP)

The BPA policy that allocates both short- and long-term use of the Pacific Northwest-Pacific Southwest Intertie. Also see Intertie Access Policy (IAP).

long-term transmission contracts

Contracts covering a 20-year period between BPA and other entities for the use of the Federal Columbia River Transmission System.

loop

1) Generally, a network of transmission lines that form a closed path. 2) To tie a substation into an existing line by opening the line and looping it into and out of the substation, providing a circuit through the substation. Looping a line feeds all the power carried on the line into the substation (as opposed to a tap, which only brings in a portion of the line’s power). 3) In control system usage, a closed loop has feedback from the output that controls the input. An open loop has no feedback.

loopflow

See parallel flows.

losses

The general term applied to energy (kilowatthours) and power (kilowatts) lost when operating an electric system, occurring mainly as energy turns to waste heat in electrical conductors and apparatus.

energy loss

The difference between power supplied and power received, due to dissipation by the transmission line or other facility.

line loss

The electric energy lost (dissipated) in transmission and distribution lines. Varies with the current (amperes) of the line. If the current doubles, the losses will increase by a factor of four.

system loss

The difference between the system net energy (or power) input and output, resulting from losses and unaccounted energy between the sources of supply and the metering points of delivery on a system.

lost opportunity resources

Conservation and generating resources that may lose their cost effectiveness unless actions are taken to develop or to hold them for future use. For example, it is much more effective and less expensive to design energy efficiency in a building before it is built, than to retrofit energy-efficient measures later.

low density discount

A variable percentage discount on power that BPA grants to utilities with a small number of widely dispersed customers, in accordance with section 7 of the Pacific Northwest Electric Power Planning and Conservation Act, to promote the most widespread use of power in the region.

Lower Snake River Compensation Plan

A series of 13 fish hatcheries on the Lower Snake to mitigate the damage done to fish by the construction of Lower Monumental, Little Goose, Lower Granite, and Ice Harbor dams. Authorized by Congress in the mid-1970s, constructed by the U.S. Army Corps of Engineers, operated and maintained by the U.S. Fish and Wildlife Service. Expenses are repaid to the U.S. Treasury by BPA from power sales revenues, except one hatchery with shared funding.

low-head dam

See dam.

low-water year

A year in which less water than usual flows through the Federal hydro system, based on the 50-year average, commonly as a consequence of reduced rain and snow during the fall and winter months.

LTC

Load tap-changer. See tap-changer.

LTIAP

See Long-Term Intertie Access Policy.

LWR

Light water reactor. See nuclear reactor.

A     B     C     D     E     FGH     IJK     L     M     NO     PQ     R     S     TUV     WXYZ