Grid Glossary

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Loss of Load Expectation (LOLE)

Analysis is typically performed on a system to determine the amount of capacity that needs to be installed to meet the desired reliability target, commonly expressed as an expected value, or LOLE of 0.1 days/year.

Peak demand

The brief periods when electricity consumption is at its highest, often driven by factors like extreme weather or heat events. This is the highest amount of electricity demand for which a grid operator needs to plan.

Peaker Plant

A power plant that is designed to quickly ramp up and provide electricity during periods of high energy demand, such as during hot summer afternoons or cold winter evenings, to meet the increased needs of households and businesses. These plants generally only run during these peak events to supplement regular power generation. 

Performance incentive mechanisms

A regulatory tool that ties a portion of utilities’ earnings to the utilities’ performance on desired regulatory outcomes, offering utilities opportunities to create the programs and services needed to advance emerging priorities.

Photovoltaic

The conversion of light into electricity at the junction of two substances exposed to light. A photovoltaic system employs solar modules, each comprising a number of solar cells, which generate electrical power.

PJM

Pennsylvania-New Jersey-Maryland Interconnection- services 13 states in Midatlantic and Midwest region

Power

The rate of transfer of energy. It’s essentially how quickly energy is being used or converted from one form to another in an electrical circuit. Power is measured in watts (W), which represents one joule (J) of energy per second.

Power Factor

A measure of how efficiently electrical power is being used. It shows how much of the total power flowing in a circuit is actually doing useful work (active power) versus being ”wasted” as reactive power. A power factor closer to 1 means higher efficiency and fewer losses.

PUC

Sometimes also called a Public Service Commission (PSC), is a state-level governmental agency that regulates utilities like electricity, gas, and water. PUCs ensure that these essential services are provided fairly, reliably, and at reasonable prices, often by overseeing monopolies and protecting consumers.

Virtual Power Plant

A network of distributed energy resources—like rooftop solar panels, electric vehicle chargers, and smart water heaters—that work together to balance energy supply and demand on a large scale. They are usually run by local utility companies that oversee this balancing act.

Voltage

Often described as the “pressure” that pushes electric current through a circuit. It’s measured in volts (V) and is essentially the energy per unit charge. Think of it like water pressure: the higher the voltage, the greater the “push” on electrons, and the more current can flow.

Maintaining stable voltage on the grid  is critical to keeping the lights on and avoiding equipment damage. Voltage is not consistent across the grid, though it is locally constant, with higher voltages used for longer transmission lines and lower voltages used at the distribution level.

  • Voltage support – The ability of a power system to maintain stable voltage levels within a desired range, even during fluctuations or disturbances. It’s crucial for ensuring a reliable electricity supply and preventing equipment damage. Generally, it is achieved by a grid maintaining reactive power via generating units or other equipment absorbing or adding reactive power.

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