Learning Center

scheduling: Operating a power system to balance generation and loads; managing the accounting, billing and information reporting for such operations.

scheduling utility: A utility that operates a generation control area within the Northwest, or any utility designated by BPA as a "computed requirements" customer.

seasonal exchange: A transaction that takes advantage of the seasonal diversity between Northwest and Southwest loads through transfers of firm power from north to south during the Southwest's summer load season and from south to north during the Northwest's winter load season.

sectors: The economy is commonly divided into four sectors for energy planning. These are residential, commercial (e.g., retail stores, offices and institutional buildings); industrial; and irrigation.

self-generation: A generation facility dedicated to serving a particular retail customer, usually located on the customer's premises. The facility may either be owned directly by the retail customer or owned by a third party with a contractual arrangement to provide electricity to meet some or all of the customer's load.

shaping: The scheduling and operation of generating resources to meet changing load levels. Load shaping on a hydro system usually involves the adjustment of water releases from reservoirs so that generation and load are continuously in balance.

share the shortage: An agreement among Northwest utilities, signed in late 1993, which sets forth a coordinated plan of action to respond to energy shortages. This agreement was not signed in 1998.

smolt: A juvenile salmon or steelhead migrating to the ocean and undergoing physiological changes to adapt from a freshwater to a saltwater environment.

solar generation: The use of radiation from the sun for heating or the generation of electricity.

spill: Release of water from a reservoir over a spillway rather than putting it through turbines to generate electricity.

spillway: Overflow structure of a dam.

spinning reserve: The unloaded (not in use) generating capacity of a system's firm resources that is available on five minutes' notice to take up load on a sustained basis.

steam generation plant: A thermal electric generating plant which creates steam to drive a turbine.

storage energy: The energy equivalent of water stored in a reservoir above normal bottom elevation.

storage reservoir: A reservoir which has space for retaining water from springtime snowmelts. Stored water is released as necessary for purposes such as power generation, fish passage and irrigation.

stranded investment or stranded asset: Generation facilities, owned by existing utility companies, that produce electricity at above-market marginal prices.

streamflow: The rate at which water passes a given point in a stream, usually expressed in cubic feet per second (cfs).

substation: An electric power station which serves as a control and transfer point on an electrical transmission system. Substations route and control electrical power flow, transform voltage levels, and serve as delivery points to individual customers.

surplus energy: Energy generated that is beyond the immediate needs of the producing system. This energy may be sold on an interruptible basis or as firm power.

tailwater: The water level directly below a dam, usually measured in feet above sea level.

tariff: A document, approved by the responsible regulatory agency, listing the terms and conditions, including a schedule of prices, under which utility services will be provided.

thermal generation: The production of electricity from plants that convert heat energy into electrical energy. The heat in thermal plants can be produced from a number of sources such as coal, oil, gas or nuclear fuel.

tiered rates: A rate design which divides customer use into different tiers, or blocks, with different prices charged for each.

time-of-day pricing: A rate design imposing higher charges during periods of the day when higher energy costs are incurred.

transition charge: A mechanism to assure fairness and stability for existing utilities as we shift to a new market structure. The net effect of transition charges will fall on customers who change suppliers during the transition phase. The purpose is to avoid cost-shifting, and to enable existing utilities to retire debt and compete fairly.

transition phase: Specific time periods for regulated activities as the new market structure evolves.

transfers to the general fund: Contributions in-lieu of taxes and franchise fees from city-owned utilities to their cities' General Fund.

transmission: The act or process of transporting electric energy in bulk from one point to another in the power system, rather than to individual customers.

transmission grid: An interconnected system of electric transmission lines and associated equipment for the transfer of electric energy in bulk between points of supply and points of demand.

turbine: The part of a generating unit which is spun by the force of water or steam to drive an electric generator. A turbine usually consists of a series of curved vanes or blades on a central spindle.