Grid Glossary

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ERCOT

The Electric Reliability Council of Texas serves as an independent system operator (ISO), managing the flow of electrical power over transmission infrastructure in the state of Texas.

Essential reliability services

A combination of automated and manual controls grid operators adjust to maintain grid reliability by ensuring a balance between supply (generation) and demand (load). They generally consist of three main aspects:

  • frequency response – short-term adjustments to maintain the grid’s oscillations at 60 hz)
  • balancing – related to frequency response but on longer time frames, to, for e.g., plan for energy resource outages due to maintenance, and 
  • voltage control – involves magnetic waves to allow for the movement of watts of energy
Federal Energy Regulatory Commission (FERC)

An independent agency that regulates the interstate transmission of natural gas, oil, and electricity. FERC also regulates natural gas and hydropower projects.

Federal Power Act

A United States law primarily regulating the interstate transmission and sale of electricity and the development of hydroelectric power. It was responsible for creating the body now known as FERC. It was created in 1920 and has been amended several times since. 

Firming requirements

Measures taken to ensure backup power, particularly of renewable energy, such as solar and wind generators. These requirements may require battery storage, ancillary services, or backup generation, such as an added gas plant to produce energy when a solar or wind plant does not.

Frequency

Electricity is supplied to homes and businesses in the United States in the form of alternating current, and frequency is the rate at which an alternating current changes direction, as measured in hertz (Hz). Across the power grid there is a consistent frequency which in the United States is 60 Hz. 

Frequency regulation or response

The ability of the grid to react to a change in

the frequency to bring it back to the normal operating frequency, which is 60 Hz in the United States

  • Inertial response refers to the injection of stored energy, such as battery energy, into the electricity grid to slow down a decline in frequency. 
  • Primary frequency response – The first line of defense against frequency fluctuations that could destabilize the grid. It takes the form of immediate, automatic adjustments in power output by generators and loads in response to frequency deviations in the electric grid.
  • Fast frequency response consists of the combined inertial response and primary frequency response. It injects energy in the seconds immediately following a disturbance to slow frequency decline and establishes the minimum frequency (called the nadir).
  • Secondary frequency response works on a slightly longer time frame than primary frequency response, on the order of 5-15 minutes. It maintains grid frequency and allows for scheduled energy transfers between balancing authorities, which include utilities, regional transmission operators, and other grid management entities.

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