Dearth of 'Reactive Power' Cited as Blackout Factor
By REBECCA SMITH
Staff Reporter of THE WALL STREET JOURNAL
An unreleased Energy Department chronology of the Aug. 14 blackout suggests that a dearth of energy called "reactive power" may have been an important factor in the huge electrical disturbance.
Reactive power, measured in VARs, or volt ampere reactive, is essential to maintaining stable power-system voltages for regular power, measured in megawatts. Reactive power can be produced by generating plants or by other pieces of electrical equipment, including capacitors. But there is less financial incentive to produce it for today's deregulated markets because generators get paid more money to produce megawatts.
Keeping sufficient reactive power on hand is a constant worry for electric-system operators. If voltage levels begin to deteriorate through the loss of power lines, for instance, capacitors become less capable of providing the reactive power needed to keep the system stable. What is more, reactive power can't travel far, unlike megawatts, which are the kind of electricity used to energize machinery and lightbulbs.
People who have seen the chronology, expected to be released as early as Friday, say it provides a detailed sequence of events, beginning at 12:05 p.m., and building toward the massive blackout that rippled across eight U.S. states and part of eastern Canada shortly after 4 p.m. The events include power-line failures and the sudden shutdown of power plants, first in the Midwest and then spreading east.
These people add, though, that the chronology doesn't explain the root causes of the disturbance. Nor does it identify at what point the Eastern Interconnection, the grid that is the backbone of the power system east of the Rocky Mountains, became destabilized.
The timeline also gives little indication of what grid operators at utilities and a pair of grid-oversight organizations knew about the condition of the system at different points in time. Such information might explain the apparent lack of action by those grid operators to restabilize the system. What the sequence does imply, though, is that voltage problems developed that day and that reactive power wasn't available in the quantities or places needed. To use a mechanical analogy, reactive power lifts a wheelbarrow and megawatts push a wheelbarrow forward. In this case, said people familiar with the chronology, the required reactive power wasn't there after a certain point in the sequence.
If that is the case, it would mirror events on Aug. 10, 1996, when the Western Interconnection, the grid west of the Rockies, collapsed. In that blackout, several power lines and power plants in Oregon went out of service, reducing voltages. Generators failed to provide reactive power in quantities expected and the instability spread to 11 Western states and parts of Canada and Mexico.
Write to Rebecca Smith at rebecca.smith@wsj.com
Updated September 12, 2003 12:48 a.m.
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