Glossary of Electric Utility Industry Terms


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P

PCAT – An acronym for power-line accelerated testing. Transmission line conductors are operate conductors up to 300 degrees Celsius using high voltage and high current.

Peaker – A slang term used for a generator that produces power between 2 and 4 hours a day, during peak load periods. A more common term is peaking unit. (EUSO)

Peaking Unit – A generator that produces power between 2 and 4 hours a day, during peak load periods. (EUSO, System operator classes)

Pedestal – A free-standing structure in a residential area that serves as a connection point between a pad-mounted transformer and the houses, or that holds a watt-hour meter. (EUSO, CAEDS, EDS)

Penstock – The pipe or flume used to channel water to the turbine in a hydroelectric plant. (EUSO)

Phase – The term phase is used in two different ways. One way is to provide the number of voltage sine waves. Single phase implies one voltage sine wave and since voltage appears between points, single phase requires two conductors. Three phase implies three voltage sine waves. Three phase has three conductors with, for instance, one voltage appearing between conductors A and B, the second sine wave appearing between conductors B and C, and the third sine wave appearing between conductors A and C. The second way the term phase is used is to refer to a conductor. For instance, “connecting to A phase” refers to connecting to the conductor identified as phase A. (EUSO, CAEDS, EDS, IESO, System operator classes)

Phase Angle – Phase angle refers to the relationship of the sine waves from two different voltage sources. A phase angle of zero means the two sine waves change value exactly at the same time. They go positive at the same time, they reach a positive peak at the same time, and they drop to zero at the same time. A phase angle of 180 degrees means that the two voltages are exactly opposite to each other. When one voltage is at a peak positive, the other voltage is a peak negative. (EUSO, CAEDS, EDS, IESO, System operator classes)

Phase Angle Transformer – A term historically used for a phase-shifting transformer. A phase-angle or phase-shifting transformers use a difference in phase angle between the incoming sine wave and outgoing sine wave to direct power flow in a transmission system. These transformers can also be used to connect neighboring utilities together that are out of phase. (EUSO, System operator classes)

Phase Rotation – Phase rotation refers to the direction a 3-phase generator is rotating with respect to another generator, or with respect to a 3-phase load, such as a 3-phase motor or a 3-phase rectifier. Any two items that are to be connected, must have the same phase rotation. If two rotating devices are connected together without having the correct phase rotation, the larger device will attempt to instantaneously stop and change the direction of the smaller device. (EUSO, IESO, System operator classes)

Phase Shifting Transformer - A transformer that uses a difference in phase angle between the incoming sine wave and outgoing sine wave to direct power flow in a transmission system. These transformers can also be used to connect neighboring utilities together that are out of phase. (EUSO, System operator classes)

Phasing – Phasing refers to the procedure of determining the time relationship of the voltages from two different voltage sources. (This time relationship is phase angle. See above). When the voltages are in-phase, they go positive at the same time, they reach a positive peak at the same time, and they drop to zero at the same time. In order for two systems to be connected their timing must be relatively close. (EUSO, IESO, System operator classes)

PJM – A regional transmission organization (RTO) serving all or parts of 14 states consisting of Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and Washington, DC. It is the largest electric-energy wholesaler in the world. The letters P, J and M were taken from the states that were first served which were Pennsylvania, New Jersey and Maryland. It is the organization with the longest history of using economic dispatch for member-owned generating facilities. It was identified by the Federal Energy Regulatory Commission as a possible model for the development of RTO throughout the U.S. www.pjm.com (EUSO, System Operator classes)

Pot - A term used by some line crews for a pole-mounted transformer. Other terms include Bug, Can and Tub. (EUSO, CAEDS, EDS, IESO)

Pot Head – A connection from an overhead to an underground electrical system. (EUSO, CAEDS, EDS-photo, IESO-photo)

Potential – The force that causes electrons to flow. It is more often called voltage. (EUSO, CAEDS, EDS, IESO, System operator classes)

Potential Difference – The force that causes electrons to flow. It is usually called voltage. (EUSO)

Potential Transformer – A measuring device used to reduce a higher voltage down to a level at which is can be safely measured. (EUSO-photo, IESO-photo)

Power Factor – The ratio of the work-producing power to the total power in an electrical system. It is work-producing power divided by the total power. (EUSO, CAEDS, EDS, IESO, System operator classes)

Power Factor Charge – A charge implemented by electric utilities, on commercial and industrial customers, if the ratio of work producing power to the total power drops below a level set by the electric utility. A power factor charge is also called a reactive charge or a kVAr charge. (EUSO, CAEDS, EDS, IESO, System operator classes)

Power Factor Test A power-factor test measures the displacement of the current sine wave from the voltage sine wave in determining the quality of insulation. With a power factor test, the lower the reading, the better the quality of insulation. (EDS)

Power Leg - In a 3-phase delta-connected system, the phase that has a voltage between itself and ground that is 1.73 times higher than the voltages between the other two phases and ground. It is also called the bastard leg, high leg, wild leg and stinger. (CAEDS, EDS)

Power Line Carrier – A communication method that uses a utility’s transmission and/or distribution line(s) for communication. A high-frequency signal that contains the communication is impressed on the power line. It is also called carrier current. (EDS, System operator classes)

Power Quality – A customer-determined measure of the reliability aspect of the electrical energy the customer is receiving. Power quality is diminished by interruptions, voltage sags and voltage swells, noise, harmonics, flicker and surges. (CAEDS, EDS, IESO)

Primary – Any part of a utility distribution system that is rated more than 600 volts. Typically primary refers to the parts of the distribution system ranging from 2,400 volts to 38,000 volts. (CAEDS, EDS, IESO)

Prime Mover – The component in a generating plant that actually spins the generator. In steam plants, gas-turbine plants and in hydroelectric plants, the turbine is the prime mover. In a diesel plant, the prime mover is a diesel engine. (EUSO, IESO)

PT – An abbreviation for a potential transformer. See potential transformer. (EUSO-photo, IESO-photo)

PT Metering – A metering system in which the value of voltage is measured with a potential transformer. PT metering implies a larger commercial or industrial customer. Customers receiving any voltage above 600 volts will be PT metered. Customers receiving between 480 volts and 600 volts may or may not be PT metered. Customers receiving less than 480 volts usually are not PT metered and use direct readings of the voltage. (EUSO-photo, IESO-photo)

PUD – Public utility district.

Publicly Owned Utilities – Publicly owned utilities include municipal utilities, such as the Los Angeles Department of Water and Power, that are overseen by the city council or by a board appointed by the city council; Electric Membership Corporations (EMC); federal utilities such as the Tennessee Valley Authority, the Bonneville Power Administration, the Bureau of Reclamation (Grand Coulee Dam) and the Army Corps of Engineers (Bonneville Dam); state utilities such as Lower Colorado River Authority in Texas, Santee Cooper in South Carolina and the Salt River Project in Arizona; rural electric cooperatives (REC) that were formed in order to serve rural areas using federal loans; irrigation districts, such as those in central California; and public utility districts (PUD), such as those in Oregon and Washington, that typically serve a county or a portion of a county. (EUSO)


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