Page ContentElectricity produced at power plants is distributed on large interconnected networks of transmission lines, or grids. The grid in the western United States is mostly isolated from grids in the central and eastern U.S. by the Rocky Mountains. Most of the large-capacity, high-voltage power lines in the Pacific Northwest are owned and maintained by the Bonneville Power Administration. Nearly all the electricity produced by Energy Northwest is transmitted throughout the region on BPA’s lines. The energy, or “force,” that moves electricity along a power line is called electromotive force. It is more commonly called voltage. Increasing the voltage to 250,000 volts or more provides the force necessary to move the electricity efficiently from power plants to distant cities where it is needed. The high voltage lines deliver the power to residential substations where the voltage is lowered to the 120 volts commonly used in U.S. homes. It is then fed onto local distribution lines carrying the electricity to your home or work. Part of the cost of your electricity is the cost of transmitting electricity from power plants to your home. Here are a few electric terms and their common meanings: Ampere (amp) – The common measure of electric current. It is proportional to the quantity of electrons flowing through a conductor past a given point in one second. It is similar, or analogous to, cubic feet of water flowing per second. Circuit - The path that electricity follows. Conductor - Material that allows electric current to pass through it. Gold, copper and other metals are excellent conductors. Current - The rate of flow of electricity in a circuit, measured in amps. Generator – A machine that converts mechanical energy into electricity by rotating a magnet within a coil wire causing electrons to flow along the wire. Ground - The earth or any object that makes an electrical connection with the earth, which has an arbitrary zero potential energy level. Grounded - Anything touching an electrical current and ground at the same time is "grounded." Insulator - Material that strongly resists the flow of electricity through it. Glass, rubber and plastic are all good insulators. Substation - A collection of equipment, usually near populated areas, used to adjust the voltage of electricity before sending it to your home or office. Transformer - An electrical device that transforms the voltage of electricity, either up or down. Volt - A unit of electrical force or electric pressure. It is similar, or analogous, to measuring water pressure in pounds per square inch.