Utility Industry Statistics

Quick Facts about Transformers

  • The first transformer was built in 1885.
  • Research on oil-based transformer fluid began in the late 1800s.
  • In 1892, General Electric became the first manufacturer to produce a transformer that utilized mineral oil.
  • Larger Transformers: According to the Federal Energy Regulatory Commission (FERC), there are approximately 132,000 power-class transformers in service in substation applications nationwide. Each of these transformers contains thousands of gallons of fluid.
  • Smaller Transformers: Millions of distribution-class transformers are installed on utility poles, underneath sidewalks, and on concrete pads near homes and businesses. The number of distribution transformers increases at a rate of close to one million a year. These transformers contain from a few dozen to several hundreds of gallons of fluid.
  • In the city of San Francisco, there are approximately 540 underground transformer vaults. In New York City, it’s estimated that there are more than 20,000 transformers.
  • It is estimated that billions of gallons of mineral oil are used in U.S. electric systems.
  • Many underground transformers were installed in the 1950s and 1960s as the United States quickly expanded its electrical infrastructure. These devices are approaching or have passed their recommended operational life.
  • Substation transformer failures are expected to increase 500 percent within the next 15 years.

Environmental Comparisons: Bio-based Fluid vs. Petroleum-based Mineral Oil

  • In 21 days, petroleum-based mineral oil biodegrades just 25 percent while vegetable-oil fluid biodegrades in excess of 99 percent per standard EPA method test.
  • The internal solid insulation material of a transformer filled with biodegradable bio-based fluid ages at a much slower rate—as much as eight times more slowly—than does the same material in a petroleum-based mineral oil-filled transformer. Slower aging means prolonged transformer life.

      • Transformer Safety Concerns

      • Industry data show one in five substation transformer failures results in a fire.
      • In Los Angeles, 97 transformer fires occurred in the first three months of 2006, averaging more than one per day.
      • In 2003, a West Coast utility paid $9 million in settlements to customers and city and state governments for a transformer fire that resulted in a four-hour power outage impacting more than 100,000 people.
      • In 2005, an underground transformer explosion in San Francisco caused an above-ground explosion, severely injuring at least one bystander.
      • In 1997, a Nashville transformer explosion resulted in injury to two bystanders, one fatality and a company settlement of $2 million.
      • Fighting transformer fires requires special fire-fighting equipment and hazardous material response procedures to capture the mineral oil contaminated runoff that occurs from fighting the fire.
      • In 2001, transformer fires in Los Angeles led to an average of one fire department dispatch per day. (Source: LAFD Weekly Bulletin March 27, 2002). In one such fire in 2007 in downtown Los Angeles, three men were seriously injured when a flash explosion occurred at a transformer they were installing at a construction site. Firefighters were transferred to a local hospital with severe burns.
      • In 2007, an explosion in a Greek Public Power company high voltage unit caused northern Greece’s network power supply system to fail, resulting in outages that spread to the neighboring countries of Macedonia and Thrace.
      • In 2007, damage to a reactor at a nuclear power plant near Hamburg, Germany was sustained when an oil-cooled transformer exploded approximately 50 meters from the reactor. Although there were no reported injuries, the shutdown of the reactor was responsible for numerous incidents that needed to be investigated by authorities.
      • 14,000 gallons of oil burned for two days after a transformer malfunction caused an explosion in Lakeland, Fl. Close to 2,600 residents and workers in the area were required to evacuate, while dozens of firefighters used liquid foam to keep the fire from spreading during the 2007 incident.
      • Fighting transformer fires requires special fire-fighting equipment and hazardous material-response procedures to capture the mineral oil contaminated runoff that results from fighting the fire. (Source: “A Transforming Disaster,” FireChief Magazine Online, http://firechief.com/mag/firefighting_transforming_disaster/, 2001).

      1 “Facilities Instructions, Standards, and Techniques Volume 3-32, Transformer Fire Protection,” US Department of the Interior, 2005 2 LAFD Weekly Bulletin March 27, 2002 3 “A Transforming Disaster,” FireChief Magazine Online, 2001 4 “An Analysis of Transformer Failures,” The Locomotive, William Bently, Hartford Steam Boiler