901 articles
Rotating inertia (power systems)
Rotating inertia in a power system is the kinetic energy stored in synchronized rotating machines, chiefly synchronous generators, which resists frequency changes when generation and load fall out of balance.
Rule 21 (California)
Rule 21 is a California Public Utilities Commission tariff setting interconnection requirements for generation and storage connecting to the state's investor-owned utilities' grids, first adopted in 1982.
RusHydro
RusHydro (РусГидро) is Russia's state-controlled energy holding and largest hydropower producer, founded in 2004 and operating plants, grids, and retail supply across more than 30 regions.
SA Power Networks
SA Power Networks, formerly ETSA Utilities and renamed in 2012, is the monopoly electricity distributor for South Australia, serving about 900,000 customers through more than 88,000 kilometers of powerlines.
Sabah Electricity
Sabah Electricity Sdn. Bhd. (SESB) is the licensed electricity utility for Sabah and Labuan in Malaysia, a subsidiary of Tenaga Nasional Berhad since privatization in 1998.
Sacramento Municipal Utility District
The Sacramento Municipal Utility District, known as SMUD, is a community-owned, not-for-profit electric utility serving most of Sacramento County and parts of Placer and Yolo counties.
Sag (power line)
Sag is the vertical drop of an overhead power line conductor between its two supports, deliberately built in to relieve tension but kept small enough to preserve ground and vegetation clearances.
SAIDI
SAIDI (System Average Interruption Duration Index) is an electric power reliability metric giving the average customer's total sustained outage minutes per year, defined in IEEE Standard 1366.
SAIFI
SAIFI (System Average Interruption Frequency Index) counts the sustained, non-momentary power interruptions the average electric customer experiences per year, calculated as total customer interruptions divided by total customers under IEEE 1366.
Sakhalinenergo
Sakhalinenergo (ПАО «Сахалинэнерго») is a Russian regional power company, the largest producer and guaranteeing supplier on Sakhalin Island, operating isolated plants including Yuzhno-Sakhalinsk TETs-1 as part of RusHydro Group since 2017.
Salt River Project
Salt River Project is a not-for-profit water and electric utility serving central Arizona since 1903, with more than 1.2 million electric customers in the Phoenix metropolitan area.
Samruk-Energo
Samruk-Energo is a state-owned, vertically integrated energy holding in Kazakhstan, wholly owned by the sovereign wealth fund Samruk-Kazyna and the country's largest electricity producer at 32.8% of national generation in 2025.
San Diego Gas & Electric
San Diego Gas & Electric (SDG&E) is a regulated utility providing electricity and natural gas to 3.7 million people in San Diego and southern Orange County, California.
Sarawak Energy
Sarawak Energy Berhad is Malaysia's vertically integrated power utility in Sarawak, Borneo, wholly owned by the state government and built around large hydropower plants like Bakun.
Sasan Mokhtari
Sasan Mokhtari is the founder, president, and CEO of Open Access Technology International (OATI), a Minneapolis energy software company he founded in 1995, elected to the National Academy of Engineering in 2019.
SaskPower
SaskPower, formally the Saskatchewan Power Corporation, is the Saskatchewan Crown corporation that supplies the province's electricity. Established in 1929, it is known for the Boundary Dam carbon capture project.
Schuko
Schuko, short for Schutzkontakt, is a German earthing plug and socket system, plug type F, introduced by Albert Büttner in 1925 and rated 16 A, 250 V.
Scottish and Southern Electricity Networks
Scottish and Southern Electricity Networks (SSEN) is the electricity network business of SSE plc, running transmission in northern Scotland and distribution in northern Scotland and central southern England.
Sea Link (interconnector)
Sea Link is a proposed 2 GW HVDC electricity transmission link between Suffolk and Kent in England, developed by National Grid to reinforce the grid between East Anglia and the South East.
Seattle City Light
Seattle City Light is the publicly owned, not-for-profit electric utility of the City of Seattle, created in 1910 and serving more than 503,000 customer premises with carbon-neutral electricity.
Sectionalizer
A sectionalizer is an automatic switching device on medium-voltage distribution feeders that isolates faulted line sections by counting the interruption operations of an upstream recloser or breaker.
Security-constrained unit commitment
Security-constrained unit commitment (SCUC) is the optimization problem of scheduling power generators, typically over 24 hours, at minimum cost while respecting transmission limits and credible outages.
Sembcorp Industries
Sembcorp Industries is a Singapore-headquartered energy and urban solutions company, formed in 1998 from a merger, operating 28.5GW of renewables and gas capacity across 11 countries.
Seminole Electric Cooperative
Seminol Electric Cooperative is a not-for-profit generation and transmission electric cooperative headquartered in Tampa, Florida, serving nine member cooperatives that reach about 2 million people.
Sensus
Sensus is a metering and communications company serving water, electric, gas, and heat utilities, best known for its smart meters and FlexNet radio network; Xylem acquired it in 2016.
Series arc fault detection
Series arc fault detection identifies sustained electric arcs in series with a conductor, most often in the DC circuits of photovoltaic systems, where they pose a fire hazard.
Service drop
A service drop is the overhead conductor assembly carrying electricity from a utility's distribution line, usually the last pole, to a building, where the customer's service entrance begins.
SF6 circuit breaker
An SF6 circuit breaker is a high-voltage switching device that interrupts electrical current in sulfur hexafluoride gas, which combines excellent arc quenching with extreme climate impact.
SGK-Novosibirsk
SGK-Novosibirsk (АО «СГК-Новосибирск») is a Russian heat and power company serving Novosibirsk, which supplies heat to 86% of the city's residents from five plants.
Shaanxi ENERGY Investment
Shaanxi ENERGY Investment (陕西能源) is a state-controlled coal-electricity integration enterprise in Shaanxi Province, China, mining coal and generating power, listed on the Shenzhen Stock Exchange since 2023.