As demand for electricity in the United States soared throughout the 20th century, two distinct AC power grids emerged. One connected utilities in the eastern part of the country, while a second grid developed in the West. The country’s Great Plains region in the Midwest formed a divide between the two power systems, however, which made it difficult for them to share electric power and back each other up during a power outage.
In the 1960s, utilities began looking for a way to connect the eastern and western U.S. grids. This led to the construction, beginning in 1986, of the Virginia Smith Converter Station in Sidney, Neb., which went into service two years later. The station was named after Congresswoman Virginia Smith, who served in the U.S. Congress from 1975 to 1991. She was the first woman to represent Nebraska in the House of Representatives.
The station was the first interconnection point linking the two grids to feature without separate static VAr compensators, which are sets of electrical devices that proide fast-acting reactive power on high-voltage electricity transmission networks.* It also had a high-voltage DV converter, which let both sides share power while maintaining separation so that disruptions on one grid did not affect the other. It is one of eight such converter stations linking grids around the United States that still operate today.
The station was honored in May with an IEEE Milestone. Administered by the IEEE History Center and supported by donors, the IEEE Milestone program recognizes outstanding technical developments around the world.
EAST MEETS WEST
Before the Virginia Smith station was built, converters required two separate reactive power-compensating devices to control the flow of voltage between the two grids. These were costly and often inadequate for responding to sudden changes in AC voltage and maintaining an even flow of power from one grid to the other; these inadequacies sometimes resulted in power outages.
The Virginia Smith station solved this problem by acting as a shock absorber: It converts each grid’s AC power (in which energy changes magnitude and direction) to DC (in which energy remains constant and flows in a single direction) and then converts it back to AC on the other side. It also prevents an overflow of power to one grid with high-voltage zinc oxide surge arresters and fast-closing breakers. This conversion method not only increases reliability but also helps keep problems in one grid from affecting the other. The station can transfer up to 200 megawatts of power at a time.
Siemens Power Transmission and Distribution, in Wendell, N.C., built the station for the Western Area Power Administration (WAPA), a utility that serves the Rocky Mountain and Great Plains regions.
A ceremony taking note of the new IEEE Milestone was held on 21 May. A plaque mounted on the wall of WAPA’s headquarters, in Lakewood, Colo., reads:
Built by Siemens, owned and operated by Western Area Power Administration (U.S. DOE), the 200-MW HVDC Virginia Smith Converter Station near Sidney, Nebraska, connected the eastern and western U.S. grids. Its core technology is an all-solid-state converter with integrated steady-state, dynamic, and transient voltage control up to its full rating. The station was an important advance in HVDC technology and cost-effectiveness.
*This article has been revised.