The regional grid systems of North America—which interconnect to form a single network, but one that is managed by many entities—all operate in pretty much the same way. However, if a relay or circuit breaker on any grid fails or isn’t set correctly, that part of the network could trigger a cascading outage, warns transmission consultant Ben Richardson of Platts Research & Consulting (PR&C). Like this magazine, PR&C is part of Platts, a division of The McGraw-Hill Companies.

In short, Richardson says, the grid system “is a delicate, interdependent entity that can go down in any region, for any number of reasons and without warning.”

Today’s U.S. national grid is best characterized as a set of transmission networks that include those of big utilities and that are separated by relatively weak and often highly stressed interconnections. The exception is the Western grid, where the Pacific AC (alternating current) and DC (direct current) interties were designed to export huge amounts of hydropower from the Northwest’s Columbia River basin south to satisfy California’s summer air-conditioning load; in the winter, the flow reverses, bringing power north to heat Oregon and Washington homes.

Elsewhere, the typical regional grid has trouble moving power to load centers because it may have dozens of bottlenecks—transmission’s version of narrow roads. These constraints on transmission capacity have already led to blackouts, and their potential to cause an outage is growing. Why? Because traffic in megawatt-hours is on the rise.

Nowhere to go

Despite the traffic jams on grids, the generation industry recently has been on a construction binge, adding to the stress on transmission lines. The numbers speak for themselves: 9,900 MW of new capacity came on-line in North America in 1999, followed by 28,000 MW in 2000, 43,600 MW in 2001, 61,147 MW in 2002, and 43,670 MW through July 2003. Another 65,938 MW are currently under construction and slated to go on-line in years ahead. The spurt was fueled by supply shortfalls of the past decade and by the opening of the generation sector to competition in many states. But those shortfalls have since become surpluses in many regions, and the owners of the new capacity are seeking to export their commodity product elsewhere over strained lines.

At the same time, investment in U.S. transmission capacity has shriveled. The numbers are a little shocking. Between 1982 and 1994, transmission investment declined 1.4% annually, reports Dr. John N. O’Brien, president and CEO of Global Change Associates, a consulting firm. The decline nearly doubled between 1994 and 1999, when investment fell 2.2% annually. In all regions of the North American Electric Reliability Council, investment in new transmission dropped between 11% and 40% over the last several years, O’Brien says. According to PR&C, just during the last four years the investment in generation has outgrown transmission investment by more than 12 to 1 (see figure), making transmission the lonely stepchild of the industry.

The new generation capacity—think of it as additional stress on transmission—couldn’t have come on-line at a worse time, because grids’ ability to handle that stress continues to dlatts POWERmap group from data supplied by PR&C) shows the location of key grid chokepoints nationwide. The sheer number of constraints illustrates why it can sometimes be very difficult—even impossible—to move electricity from an area with surplus generation to one with a deficit. Usually, the difficulty manifests itself only as revenue losses for power marketers or utilities. But in the extreme, it also can result in a blackout, as was the case in the Midwest/Northeast in August, in California in 2000 and 2001, and in the Midwest in 1998.

In short, as the map illustrates, transmission constraints are everywhere. They weaken not only the bottom lines of power producers and retailers but the overall strength of the national grid as well. Eliminating constraints isn’t easy, because grids are like chains in that they are only as strong as their weakest link. Even in regions where higher-capacity, higher-voltage systems have been put in place, power flows often would be greater were they not constrained by thermal limits on lower-voltage lines. These constraints will likely limit the proliferation of distributed generation until local grids are reinforced. The map shows the existing system (230 kV and above); it is overlaid by bars indicating selected key constraints.

Big talk, no action

Before news coverage of the blackout of ’03 made Americans and Canadians aware of how little they know about where electricity comes from and how much they take it for granted, the causes of the sorry state of transmission in North America had already been identified.

One is that transmission capacity in all regions is limited because grids evolved primarily to meet the regional needs of electric utilities, not to accommodate large-scale wholesale power trading between regions. Another is that interregional capacity was built only to enable interstate utilities to import power from a plant in one of its service territories to customers in another. Such links also make possible modest levels of generation reserve sharing among utilities and regions.

Developers, regulators, and politicians also have known for years that much of the new generation capacity built since 1999 would be “trapped” by transmission constraints—but they approved those projects anyway. With another 66 GW waiting in the wings, the situation will only worsen. Unless states and provinces act to shore up their grids—as California is doing by adding a third leg to Path 15, its main north-south electricity superhighway—new generating capacity is likely to be bottled up in several regions, including New Hampshire, Maine, southeastern Massachusetts, Rhode Island, southern Louisiana, eastern Texas, Alabama, Washington, Alberta, and Arizona.

The only good news involving transmission is that the boom in power trading of the Enron years turned into a bust and didn’t substantially increase the stress on grids. The majority of traders’ transactions were financial rather than physical, so they hardly ever generated increased transmission traffic.
There is a lot of talk about transmission. But real action on transmission construction is scant. Conferences and reports abound. Projects of all sizes are being proposed. But, except for local reinforcements and new generation interconnections, only the most critical transmission construction proposals are moving forward. The vast majority of larger projects are stalled for lack of financial commitment.

That does not bode well for transmission reliability in North America. “We are due for another blackout any day,” predicts transmission consultant Robert Blohn. “The industry’s rule of thumb is that one major blackout every 10 years is acceptable. On August 14, we hadn’t had one for twice that long. Given the state of North American grids, I wonder why we don’t have blackouts more frequently.”