Although there have been reports since June that some turbines at Buffalo Ridge have not been dispatched due to transmission constraints, NSP says that transmission from the project has not limited the wind farm's output. The utility admits, however, that the Mid-Continent Area Power Pool (MAPP) does not have a robust transmission grid and that it will have to build more transmission lines to accommodate additional wind or other generation.
Most of the MAPP transmission was built for reliability and serve-sharing, not for spot generation, such as wind, says Charles Grunewald, senior engineer in NSP's transmission planning. MAPP consists of generating and transmission utilities throughout the Midwest, including North and South Dakota, Minnesota, Iowa and Nebraska.
"Since the mid-eighties, growth has been very low and there's been no transmission additions," says Grunewald. "The robustness has disappeared and now we only have an adequate system. If anywhere in MAPP's area there is any new generation, there will have to be significant transmission additions."
NSP has just completed an upgrade to the 115 kilovolt transmission line that delivers the 200 MW-plus of power generated at Buffalo Ridge into the power grid, adds Grunewald. That upgrade was to bring the line into compliance with the National Electrical Code and to shore up its stability. With the new amount of current on-line, NSP may have violated the code, so it had to modify it, mostly for line clearance reasons, he explains. In addition, the federal Western Area Power Authority recently completed work at a substation near Sioux Falls in South Dakota, also to accommodate generation from Buffalo Ridge.
Slow to upgrade
These are activities NSP should have taken before the turbines came on-line, according to Rory Artig, engineer at Minnesota's Department of Public Service (DPS). "As far as we know, the generation from the wind farm was available, but it's hard to know if there were any limitations," Artig says.
"DPS was definitely concerned and surprised to find that NSP had not completed all the elements when the turbines came on-line." As a result DPS Commissioner Steve Minn asked NSP President and CEO Jim Howard to finish its transmission work on the project. This was well beyond the June 30, 1999 cut-off for the federal wind energy tax credit, so there was a discrepancy in timing, Artig says.
Since then the DPS has met with NSP on several occasions to discuss what needed to get done to shore up transmission out of the wind farm, according to Chris Gilchrist, DPS spokesperson. Both parties agreed the work was to be completed by October 1, a deadline which has been met.
Process not problem
Grunewald says NSP had to do some additional planning and ordering of equipment before completing the line upgrade. "Things don't happen as fast in the transmission world as they do in the generation world. What some say was part of a problem, we see as part of a process," he comments.
The most recent addition to Buffalo Ridge consisted of 138 Zond Z-750 turbines with a total output of 103 MW. Last year, NSP contracted with Enron Wind Corp for 107 MW of wind generation at the site. Along with several smaller developments, NSP today buys over 250 MW of wind energy.
Bill Grant of the Isaak Walton League said his organisation is looking beyond the completion of the state mandate which requires NSP to buy 425 MW of wind, to a second mandate from the commission ordering NSP to buy another 400 MW. NSP has still to buy another 130 MW to fulfil the first mandate. "If we continue to build wind projects in Minnesota, something will have to be done about the transmission," says Grant.
NSP agrees. "With the next increment of wind, we'll have to build new transmission," says Donna Stephenson, NSP's director of transmission tariff management. "Phase 4 at Buffalo Ridge will very likely require new transmission. The existing system is tapped out." But this time, she says, the generation won't come without transmission additions.