The Adelanto Converter Station is the southern terminus of the Intermountain Power Project's Southern Transmission System (STS), which links southern California with central Utah.

The Southern Transmission System consists of two 490-mile, high voltage direct current (HVDC) transmission lines with a converter station at each end. The STS conveys electric power from the Intermountain Generating Station, near Delta, Utah, to southern California.

The Adelanto Converter Station is a 300 acre complex located on the southwest edge of the Mojave Desert in Adelanto, California. The $131 million converter station began commercial operation in July of 1986.

The $5.5 billion Intermountain Power Project (IPP) included Intermountain Generating Station, which consists of two, 750 megawatt, generators and two transmission systems. The project was conceived in the early 1970s to fulfill the projected power and load diversification needs of a group of Utah and California utilities.

By mid-1986, the project was providing power to 36 utilities in Utah, Nevada, and California. IPP participants include 23 municipal utilities, six rural cooperatives, and one investor owned utility in Utah and six municipal utilities in southern California.

When fully operational in 1987, IPP provided up to 1,461 megawatts of power to southern California, enough to serve the needs of more than 2 million residential customers.

IPP is owned by the Intermountain Power Agency (IPA), a political subdivision of the State of Utah. IPA appointed the largest municipal utility in the country, the Los Angeles Department of Water and Power, as project manager in charge of design, construction, and operation of the project.

In 1983, a joint powers agency, known as the Southern California Public Power Authority, agreed to finance construction of the IPP Southern Transmission System in return for the rights to the entire capacity of the system. The cities of Los Angeles, Anaheim, Riverside, Pasadena, Burbank, and Glendale form the STS participants in California.

Power from the Intermountain Generating Station is delivered to IPP participants in California over the STS. The Northern Transmission System (NTS) supplies power to the Utah and Nevada participants.

The IPP STS conveys power to the six participating California utilities over a +/- 500 kilovolt, HVDC transmission system stretching from the Delta, Utah generating station to the Adelanto Converter Station, in Adelanto, California. The IPP STS had a design capacity of 1,600 megawatts. The STS has since been re-rated to 1,920 megawatts.

The Intermountain Converter Station at the Utah plant site changes the AC power, generated at the Intermountain Generating Station, into DC power for transmission to the converter station at Adelanto. The Adelanto Converter Station then changes the DC power back to AC power for delivery to each southern California participant through the 500 kilovolt, AC network.

Power systems throughout the nation primarily operate on AC electricity. However, the DC method of transmission is the most economic process for moving large amounts of electric energy over long distances.

The IPP HVDC system is also capable of transmitting power in the reverse direction. This capability will allow participants in either state to purchase additional power to meet seasonal peak load periods and emergency power requirements.

The IPP NTS delivers power to Utah and Nevada over three AC transmission lines. The NTS consists of two 50-mile, 345 kilovolt AC transmission lines to the Mona Substation, near Mona, Utah; and a 144-mile, 230 kilovolt AC transmission line to the Gonder Substation near Ely, Nevada.

As a result of high oil and natural gas prices and reliance on unstable foreign governments for low sulfur fuel oil, utility companies throughout the country looked for other energy sources. The abundant coal supplies in central Utah offered project participants an efficient, reliable energy source to meet the needs of their customers.

IPP power will be used by most California project participants to displace their own oil and gas burning generation and meet anticipated load growth.

Construction of the Adelanto Converter Station also provided many benefits to the local community. The City of Adelanto has received nearly $5.3 million in offsite improvements to the community's water distribution system and roads. San Bernardino County received about $3.9 million in sales tax during construction, and will receive approximately $1.5 million annually in property taxes.

Construction of the Adelanto Converter Station began in May 1983. As project manager and operating agent, the Los Angeles Department of Water and Power oversaw the design and construction of the facility and operates the station. The primary contract for the major high voltage DC equipment, including the thyristor valves and the valve hall buildings, was awarded to ASEA, Inc. of Sweden. The buildings and equipment were erected by ASEA.

The design requirements for the IPP HVDC System include several technologically advanced features such as extensive overload capacity, a high degree of seismic-withstand capability, and extremely high availability and reliability.

The station thyristor valves, a key component in the power conversion process, are a primary example of the high efficiency, and reliability, which has been built in the system. The valves are installed in two groups. If one group has an outage, the other can operate at 150% of rated capacity. To provide maximum seismic protection to the 40-ton valves, each is suspended from a 70-foot ceiling.

The station's other major auxiliary equipment, the converter transformers, also incorporate a unique seismic-withstand capability in their design. The six converter transformers servicing the Adelanto station are the largest ASEA has ever built for the U.S. market. When the transformers are full of oil, they weigh approximately 467 tons each.

Thyristor converter valves are the heart of the two converter stations on the HVDC system. The thyristor valve is a solid-state rectifier/inverter. It converts AC power to DC power for transmission over the STS to the station at the other end, and then converts the DC power back to AC for transmission over the interconnected AC network.

The HVDC system includes 12 quadruple valves; six valves per station. A single valve consists of 144 water-cooled thyristors distributed into 12 modules. There are 48 modules per quadruple valve. Each quadruple valve is about 50 feet long.

In conjunction with the IPP Adelanto Converter Station, the Los Angeles Department of Water and Power financed and constructed the Adelanto Switching Station. This $45 million facility is owned and operated by the LADWP.

The switching station is an interface facility between the converter station and the surrounding AC transmission network. As installed, the switching station had four 500 kilovolt AC lines, two lines to nearby Victorville Switching Station, one each to LADWP's RS-E in the eastern San Fernando Valley and RS-Rinaldi in the northern San Fernando Valley. In the late 1990s the Mead-Adelanto Project brought a fifth 500 kilovolt transmission line was built connecting the Adelanto Switching Station to the newly constructed Marketplace Switching Station in Boulder City, Nevada.