| Common Terms Used in the Utility Industry |
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| Power Plant
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| A facility, which converts fuel such as gas, coal, oil, nuclear or wind into an electrical energy (power). |
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Transmission Line
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| A transmission line is a bare, uninsulated high-voltage (46,001 volts to 750,000 volts) overhead line that carries power from power plants to substations or power distribution centers. Some transmission lines are underground cables. |
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Substation
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| A power distribution center that steps down transmission voltages (46,001 volts to 750,000 volts) to a primary distribution voltage (2,001 volts to 46,000 volts) with power transformers. Most circuits (distribution lines) radiate from this center toward customers. |
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Transformer
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| A device that steps voltage down from a higher voltage or up to a higher voltage depending on use (i.e. steps the voltage down from a primary distribution voltage of 7200 volts to 120/240 volts for residential use). |
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| Distribution Line |
| A distribution line is a medium- voltage (2,001 volts to 46,000 volts) overhead line that carries power from the substation to customer service areas. Some distribution lines are underground cables. |
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Service Line
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| (Service Drop)
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| A service line is a lower-voltage (up to 2000 volts) overhead conductor that carries power from the step-down transformer on the distribution line to a small-industrial, commercial or residential customer. This overhead conductor is the last connection from the utility to the meter on the customer’s premises. Service lines could be an underground cable. |
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Circuit
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| An overhead line on poles or underground cable that carries power from substation to customers. Circuit and distribution lines are terms used interchangeably. |
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| Meter
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| A device that plugs into a meter socket to measure the consumption of energy by the customer in kilowatt-hours.
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Watts
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| The basic unit for measuring energy or power in the utility industry. |
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Megawatt (MW)
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| An electrical quantity of energy that represents one million watts of power.
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| Kilowatt (KW)
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| An electrical quantity of energy that represents one thousand watts of power.
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| Insulator
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| An insulator is a device made of special material that supports and separates energized lines and equipment from non-energized parts to prevent unwanted current flow. Insulators support overhead lines or cables on utility poles. An insulator may also support energized conductors and equipment in cabinets and inside substations. |
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Fuse
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| An electrical device that interrupts the current flow to a circuit when it exceeds a predetermined value. A fuse is used to de-energize a circuit to minimize damage to lines and equipment. Fuses can interrupt current only one time and must be replaced in order to energize the circuit it protects. |
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Circuit Breaker
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| An electrical device which interrupts the current flow to a circuit when it exceeds a predetermined value. A circuit breaker is used to de-energize a circuit and can be set or programmed with various protection schemes to minimize damage to lines and equipment. Circuit breakers are designed to be re-closed after a current interruption. |
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Phase
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| Most power generation is three-phase and therefore needs three individual wires for each phase to convey it over distance to the end user. |
