Hidden Substation

Anaheim Public Utilities meets rapid growth with innovative solutions.

Most municipalities don’t build a lot of substations, generally speaking, but you wouldn’t know it to see the project list at Anaheim Public Utilities. The city of Anaheim is experiencing rapid growth in densely populated urban areas, which means Anaheim Public Utilities is busy building multiple substations in highly creative and technologically innovative ways to provide reliable, economically feasible power in aesthetically pleasing ways, a trend also seen in “megacities” like neighboring Los Angeles.

Park Substation, the first underground gas insulated switchgear (GIS) substation in the U.S. The substation is hidden beneath Roosevelt Park in an east Anaheim residential neighborhood. Photo courtesy of Anaheim Public Utilities.
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To date, Anaheim Public Utilities has completed two substations and is currently building one more to serve current and future load growth. One is a substation built in a new building designed to blend into the neighboring historic structures and another is Park Substation, the first underground gas insulated switchgear substation in the United States.

Park Substation, a 112-MVA electric distribution substation with the capacity to serve 25,000 residential customers, was dedicated by Anaheim Public Utilities in October 2006. The substation is hidden beneath Roosevelt Park, a 2.5-acre property situated in an east Anaheim residential neighborhood. Anaheim utilized gas-insulated switchgear (GIS) from Siemens that saved about 70 percent of the space necessary to build an open air substation. This GIS technology allows Anaheim and other utilities to build substations closer to the customers who need the electricity, and in spaces that are considerably smaller than conventional designs, whether they are in customary or unique locations such as underground or inside buildings.

Valuing the community

The city of Anaheim owned a 2.5-acre site in east Anaheim, one of the nicest areas of the city. The original plan was to build a library on the site, but when the city presented the idea to the community, the homeowners objected to an increase in traffic and parking in their residential neighborhood. Anaheim Public Utilities came up with a “green solution”: build a substation underground with a park on top. Because the hillside property has a unique geographical feature–one side of the site is 25 feet to 30 feet above street level–the utility could easily access the substation through a wall built in the hillside, leaving the park landscape pristine. The GIS is insulated with SF6 gas, which allows the phase spacing of the electric components to be very close and protects the components from outside contamination.

The city of Anaheim held a significant number of community meetings to demonstrate the plan and answer questions regarding safety, construction concerns and the project timeline. In fact, Keith Tieszen, park substation project manager for the city of Anaheim, talked to the neighbors weekly to keep them informed on everything the utility was doing and the time frames for the various construction phases. The community actively participated in the development of the park. They didn’t want tennis courts, lights, parking or bathrooms, which fortuitously saved the city money. The city designed the basic plan for the park and worked jointly with the neighborhood association to design the monument that names the park.

The neighborhood benefits in many ways. The first and most obvious is the beautiful park to enjoy. People living there also profit from increased property value and home appreciation. There is no visible substation to obstruct the view and no vacant property to decrease the desirability of the neighborhood.

Park Substation, located underneath Roosevelt Park, at night. The underground substation is virtually maintenance free. Photo courtesy of Anaheim Public Utilities.
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While they may not realize it, people in the neighborhood also have greater access to reliable power because of the close proximity of the distribution substation–without unsightly equipment or safety issues, as neither humans nor vehicles can access the substation intentionally or accidentally. The inert gas used for insulation poses no safety risk and because it is underground with utility-only access, security at the distribution station is another benefit.

Financial considerations

Your first thought is probably, “Nice, but how much?” The total cost of Park Substation including the incoming and outgoing lines plus the substation was $19.5 million. Tieszen said that the city hadn’t built an open-air substation in close to 12 years, so although APU doesn’t build enough substations to really compare, he calculates the total cost at about 1.5 times the price of an open air installation.

For the additional upfront outlay, is there a cost savings long-term? The answer is a resounding “yes.” The underground substation is virtually maintenance-free because nothing is exposed to the atmosphere.
Approximately half of the major electrical components are enclosed in a gas medium. The balance of the plant equipment (e.g., transformer and capacitor banks and protection system) is conventional electrical equipment used in open air-insulated substations above ground.

In the long run, the underground model is more cost-effective than the conventional open-air substation. Cost benefits accrue over the life of the equipment because of greatly reduced inspection and maintenance requirements. Tieszen reports that most equipment suppliers estimate that the utility recoups the extra costs in eight to nine years. When the advantages are assessed, a gas-insulated substation is a cost-effective alternative to a conventional substation in an urban community.

Technology considerations

For Park Substation, Anaheim Public Utilities utilized Siemens’ gas-insulated switchgear (GIS), a proven technology used throughout the world. It offers many advantages over a conventional substation: less field construction work, resulting in shorter installation time; reduced maintenance; higher reliability and safety; and excellent ability to withstand seismic events such as those common in California. But in an urban community such as Anaheim, the primary advantage is its compactness, which allows a GIS to be placed closer to a load center.

The switchgear is enclosed in an inert, nontoxic insulating gas that allows the phase spacing of the electric components to be very close and protects the components from outside contamination. GIS compartments on the equipment are continuously monitored to ensure that any leaks are detected and eliminated. It has low noise emission and reduced fire and explosion potential, which make it particularly attractive for siting close to a residential neighborhood.


Looking back, after a year and a half of operations experience, the city of Anaheim and the residents of the neighborhood surrounding Park Substation are thoroughly pleased and satisfied with the substation underground–and beautiful Roosevelt Park above.


Holly Bounds is staff marketing communications specialist at Siemens Power Transmission & Distribution Inc. You may contact her at holly.bounds@siemens.com.

Keith Tieszen, project manager, system planning, City of Anaheim, Anaheim Public Utilities, provided input for this article.

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