ABSTRACT
Power = voltage × current (4.1) Units of Measurement and Typical Values Voltage is measured in volts, and current in amps, arbitrary units of measurement for each, invented when the electric industry was in its infancy, and that are now standardized worldwide. High voltages in a power system are measured in terms of kV – thousands of volts, e.g., ten kV is 10,000 volts. Power is measured in watts. One watt equals one amp times one volt. The amount of power required, in watts, can be produced by any combination of voltage and current that gives the desired product. For example, one horsepower equals 746 watts. It can be produced by one amp being forced at 746 volts; two amps at 373 volts; 7.46 amps at 100 volts; or 746 amps at one volt. Large amounts of power are measured in kilowatts (1,000 watts) abbreviated kW, or megawatts (1,000,000 watts), abbreviated MW, or gigawatts, GW (1,000,000,000 watts). For no discernible reason, the “k” used in kilowatt’s abbreviation is not capitalized, whereas the M and G in megawatt and gigawatt are. Energy used is measured in terms of power times the duration of use. One kilowatt used for one hour is a kilowatt-hour, abbreviated as kWh, or kWhr.
