American Transmission Company's (Waukesha, Wisconsin, U.S.) annual 10-Year Assessment of the firm's electric transmission system, which was issued Tuesday, continues to point to the need for upgrades and additions to the existing transmission infrastructure to ensure system reliability.

"Continued study of the system reaffirms even more strongly the needs that were initially indicated for transmission construction and reinforcement," said Teresa Mogensen, director of transmission planning and service for ATC. "While we're not surprised by the findings, the studies are convincing evidence that the system is presently at its capacity."

Several trends throughout the ATC service area - which includes portions of Wisconsin, Upper Michigan and Illinois - indicate the system is operating with little or no margin for growth.

  • Limitations on transferring power into and through the ATC system.

  • Emerging voltage problems west of Milwaukee, in the Madison, Wisconsin, area, Door County, Wisconsin, and the western Upper Peninsula, and immediate voltage problems in the Rhinelander, Wisconsin, area.

  • Inability of the system to serve growth or accommodate new generation without transmission system reinforcement.

To address the needs raised in the 10-Year Assessment, ATC recommends an integrated approach to solving the transmission limitations within all areas of its system. Among the suggested solutions:

  • Implement the Arrowhead-Weston 345 kV line project from Wausau, Wisconsin, to Duluth, Minnesota.

  • Implement transmission reinforcements to address reliability concerns in the Rhinelander area and Upper Michigan.

  • Implement transmission reinforcements to improve transfer capability between Wisconsin and Upper Michigan.

  • Implement transmission reinforcement in and around the Madison area to address emerging reliability concerns.

  • Construct facilities to interconnect new generation.

  • Construct new transmission lines between the Milwaukee area and the Madison area to address reliability concerns west of Milwaukee and to facilitate power transfer within ATC's system.

  • Construct new transmission lines to neighboring states to improve Wisconsin's import capability.

The system investments proposed within the 10-Year Assessment, if built, carry a US$2.8 billion price tag over the next 10 years, which would lead to an approximate 7% increase in customer bills over that time period.