A Southern Illinois Power Cooperative's coal-fired plants supplies 272 megawatts of electricity to three Southern Illinois cooperatives. It will be up and running this summer, but because several generating plants owned by other utilities may be down, potential problems with the MAIN transmission grid could affect all Illinois cooperatives and other utilities.

If the weather this summer is unusually hot for an extended period of time, rolling power blackouts may be necessary in Illinois and Wisconsin. Utilities throughout the region are working hard to prevent possible blackouts, but also warning customers so they can prepare for the possibility.

The potential power supply shortage is the result of several regional problems. In May one-third of the region's nuclear power plants in both Illinois and Wisconsin were down. Several coal-fired generating plants also were out of commission. Although several plants are expected to be back on line before the summer's peak demand season, there still will be less generating capacity than is normally available.

It is anticipated that Commonwealth Edison will have 4,160 megawatts of nuclear capacity off line this summer out of a total capacity of approximately 22,000 megawatts. Three nuclear units, approximately 500 megawatts each, are off in Wisconsin, but two units are expected to be back on by mid-July. Illinois Power lost its 500 megawatt Wood River coal unit in a fire last Christmas and its Clinton nuclear plant also was closed. A portion of Wood River and the Clinton plant should be back on line before the worst hot summer weather hits. Fuel oil and natural gas-fired "peaking" generation units, which are more expensive to run than nuclear or coal-fired units, also are being readied for service.

Utilities also are concerned about a lack of transmission line capacity. Transmission lines are like the interstate highway system for electricity. With limited transmission line capacity, it can be difficult or impossible to import power from one area to another to resolve supply shortages. This is an especially severe and long-term problem for Wisconsin.

The Mid-American Interconnected Network (MAIN), a

22 ILLINOIS COUNTRY LIVING JULY 1997

"Utilities throughout the region are working hard to prevent possible blackouts, but also warning customers so they can prepare for the possibility."

regional power supply reliability council, warns that between 4,700 and 6,500 megawatts of power will be unavailable this summer. Soyland Power Cooperative and Southern Illinois Power Cooperative are members of MAIN. MAIN is a member of the North American Electric Reliability Council (NERC). NERC was formed in 1968 after the November 9, 1965, blackout that affected the Northeastern United States and parts of Canada.

NERC and the regional councils help U.S. utilities work together to maintain the most reliable power supply in the world. NERC officials do this by reviewing past lessons learned, monitoring for compliance with policies, standards, principles and guides, and assessing reliability of the bulk electric power systems.

Even though one utility, like Southern Illinois Power Cooperative, may have plenty of its own generating capacity, the problems within the MAIN region could affect all utilities. Even utilities in Iowa are concerned that the problems outside their region could spill over.

For example, last July 2 two million people in 15 Western states and parts of Canada were hit with a huge power outage. A similar outage on Aug. 10 left 4 million people in the dark. Power from the Northwest moving south to power air conditioners in California put an extremely heavy load on transmission lines. One transmission line under heavy load sagged into a tree and triggered the outage that dominoed, forcing power plants and transmission systems along the region's grid to shut down to protect themselves from damage and a longer outage. NERC found that bad planning and communication mistakes aggravated the situation.

Michehl Gent, president of NERC, believes that Illinois and Wisconsin are prepared to handle the summer's problems. But he warns, "Such shortages could require controlled interruption of electric service to customers in parts of the region."

Utilities throughout the MAIN region have taken precautionary measures. For example normal maintenance and testing of key components have been stepped up. Transmission right-of-way and lines have been double checked for potential problem areas. Communications systems and procedures have been tested with practice drills.

If a peak demand situation occurs there will be three levels of response. First a peak warning will be issued. Normal demand control procedures will go into effect. Peak demands can occur anytime between mid-June and mid-September, from noon to 8 p.m. Last year's peak was in early August for most utilities in the region. Utilities that have load control systems and agreements with consumers will begin cycling off water heaters and air conditioners with the cooperation of consumers who participate. Demand control practices vary for each utility. Local radio stations will make peak alert announcements and voluntary load reduction by consumers will also be urged.

The second level, in most cases, will be to require large commercial customers on interruptible rates to begin shutting down load. Voltage reductions also may be necessary at this stage.

"Even though one utility, like Southern Illinois Power Cooperative, may have plenty of its own generating capacity, the problems within the MAIN region could affect all utilities."

Finally, if normal load control methods do not work, rolling blackouts may be necessary for individual generating companies that do not have enough generation to serve their loads. Individual substation circuits will be turned off for approximately two hours. This situation will be avoided if possible, but the priority will be to keep the network intact and keep all generating units online. Once generating plants start tripping off line, a massive multi-state outage could result. Under the worst case scenario there will be little warning and entire substations circuits could be shut down.

Although many utility executives have debated whether or not to issue these warnings, most have agreed it is better to risk alarming the public unnecessarily than to leave consumers unprepared. Avoiding a disaster will take a lot of cooperation between utilities and consumers to keep demand from overwhelming the system.

JULY 1997 ILLINOIS COUNTRY LIVING 23