Starting in the 1990s, as electric power systems have been reorganized in the United States to allow for wholesale trading by producers and distributors of electricity, independent authorities called Independent System Operators (ISOs) have been established to manage grids. Today, several major blackouts later, it seems apparent that experience counts for something. The devastating California electricity crisis of 200001—which bankrupted huge utilities in a matter of weeks, cost the state’s governor his job, and led to the collapse of Enron—occurred when California’s new ISO was just getting on its feet. In 2003, at a time when a Midwest ISO was just setting up shop in Indiana and didn’t yet have its act together, a devastating outage started in its poorly regulated operating area and ended up blacking out almost the entire Northeast and Midwest of the United States, plus two Canadian provinces.
Tellingly, the 2003 blackout was largely contained by two ISOs that descended from power pools of long-standing and high repute. PJM (the PennsylvaniaNew JerseyMaryland Interconnection) lost only 4500 megawatts of the 61 200-MW generating capacity that was active at the time the blackout occurred. Managers and engineers at ISO New England, headquartered in Holyoke, Mass., breathed sighs of relief when the cascading outage stopped at the region’s New York state borders.
ISO New England’s activities are not confined to the control room. As a separate function, it maintains an online system in which electricity is traded on both a day-ahead and spot basis. Operationally, the ISO works intimately with five local control centers throughout the region, which open and close breakers at electrical substations in response to system requirements. The centers, besides acting on the ISO’s instructions, provide important redundancy. If the ISO itself were disabled, all management of the system reverts to them. At the same time, the centers, like the ISO, are doing state estimation and contingency evaluation in real time, cross-checking each other’s results.
The basic operating rule, explains Peter Brandien, ISO New England’s vice president for system operations, is to have enough generating reserves available at any given time so that, within 10 minutes, they could be called upon to compensate for the largest conceivable loss of generation.
Most days that’s easy, but how about a really hot day, when temperatures are rising and everybody’s turning on the air conditioning? ISO NE is always looking forward in time to estimate what conditions will be, says Brandien. If things are getting too tight, so that generating reserves could be inadequate, ”then we adopt procedures which initially will not be visible to the public. We start to communicate with generators, ensuring that they are making available all the power they can generate. We’ll ask the generators and utilities if they can begin to cut on their usage.
”If things continue to tighten, then we have to go out to the public and ask for demand customers to make cuts. [Demand customers are the large consumers that have contracted with the ISO to curtail their electricity consumption upon demand.] Then we’ll go to voluntary appeals for cuts, which we’ve found to be very effective in New England.
”If that’s still not enough, we ratchet up the level of appeals to state agencies, asking them to issue appeals of their own. The last resort is to impose rotating blackouts, but we have not had to do that here in New England, probably because of the extensive communications we maintain with all parties.”