Delivery Systems

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State estimator

A state estimator is a software program that describes the current state of an electrical transmission or distribution system.

Steel pipe fabrication

Regardless of the technique used to create the pipe, all steel line pipe is coated to protect if from corrosion and other damage.

Sub-meter

Sub-meters are meters installed behind a master meter. Master and sub-metering is common in tenant occupancies like office buildings, shopping c …

Substation

A set of equipment on an electrical system that transforms voltage from high to low, or vice versa, and may perform other functions such as dire …

Surge impedance loading (SIL)

Surge impedance loading is a quantity used by system operators as a benchmark to determine whether a transmission line is acting as a capacitanc …

Switching

Switching is the process of rerouting the path that power takes through an electric transmission or distribution system by opening or closing sw …

Switchyard

A switchyard is the set of facilities outside a power plant in which voltage is transformed and electricity flow is directed onto transmission l …

Synchronization

In an AC electric power system, synchronization is the process of matching the frequency of a generator to all other synchronous generators on t …

Synthetic natural gas (Syngas)

Synthetic natural gas (SNG), also sometimes called syngas or substitute natural gas, is natural gas that is created from materials that contain …

System restoration

System restoration, sometimes simply called restoration, is the process of restoring service to customers after an outage or blackout.

Tennessee Valley Authority (TVA)

TVA is owned by the United States government. TVA provides wholesale electricity in seven southern states as well as services such as flood cont …

Therm

A therm is a natural gas unit equal to 100,000 Btu.

Three-part communication

Three-part communication is a process used in the gas and electric industries to limit errors due to lack of effective communication.

Three-phase power

Three-phase power refers to an electrical system that has three voltage or current curves.

Three-phase service

Three-phase service is typically provided to larger commercial and industrial customers. Any customer with a motor larger than 10 horsepower is …

Tidal hydropower plants

Tidal hydropower plants, also called tidal barrage plants, depend on dams across an estuary or tidal channel that trap incoming tidal flows and …

Transformer

A transformer is a device that changes the voltage of electricity.

Transmission management system (TMS)

A transmission management system, commonly called a TMS, is a suite of software tools used by system operators to monitor and manage the transmi …

Transmission outage

Transmission outages can be caused by a variety of reasons: weather events, lightning, fires, vandalism, terrorism, failure of substation or cir …

Transmission owner (TO)

In markets where the system operations function has been moved to an Independent System Operator (ISO), the term transmission owner, or TO, is u …