The structure of an electrical power or energy† system is very large and complicated. However, it can be represented basically by ve main components. The energy source may be coal, natural gas, or oil burned in a furnace to heat water and generate steam in a boiler; it may be water in a dam; it may be oil or gas burned in a combustion turbine; or it may be ™ssionable material, which in a nuclear reactor will heat water to produce steam. The generation system converts the energy source into electrical energy. The transmission system transports this bulk electrical energy from the generation system to principal load centers where it is distributed through (usually extra) highvoltage lines. The distribution system distributes such energy to consumers by using lower-voltage networks. Finally, the last component, that is, load, utilizes the energy by converting it to a required form for lights, motors, heaters, or other equipment, alone or in combination.