INDEPTH: POWER OUTAGE|
The blackout explained
CBC News Online | November 19, 2003
The massive power blackout on August 14, 2003, was caused by a series of failures that began with Ohio electricity provider FirstEnergy. This, according to a joint Canada-U.S. investigation into the outage that left 50 million people without power in Canada and the U.S. northeast.
On November 19, 2003, authorities released the findings of their three-month investigation in a 134-page interim report. They blame the outage on three main causes:
1. "Inadequate situational awareness" on the part of FirstEnergy and the Midwest Independent System Operator in realizing early enough there was a problem.
2. Inadequate tree trimming along key FirstEnergy transmission lines, allowing overloaded, sagging wires to short out on overgrown tree limbs.
3. A lack of real-time system monitoring on the part of MISO and an inability to determine the location or severity of problems. The report also cites a lack of co-ordination between MISO and adjacent operator PJM.
See below for a timeline of events leading to the blackout (all times EDT):
Midwest Independent System Operator's system monitoring tool is "rendered ineffective" after receiving "incorrect input data."
FirstEnergy's Eastlake 5 generation unit trips and shuts down automatically.
FirstEnergy's alarm and logging system fails and is not restored until after the blackout.
Some of FirstEnergy 345-kilovolt transmission lines begin tripping out after coming into contact with overgrown trees within right-of-way areas.
At this point, FirstEnergy and the Midwest Independent System Operator begin to realize there is a problem. The only possible way a blackout can be averted at this point is to drop at least 1,500 to 2,500 megawatts of load around Cleveland and Akron. No action is taken.
138-kilovolt lines start tripping out as a result of the loss of key 345-kilovolt transmission lines.
With the growing loss of transmission lines, FirstEnergy's Sammis-Star 345-kilovolt line goes down, wiping out the 345-kilovolt path between eastern and northern Ohio. Other parts of the grid are strained by the immediate increase in "unsustainable" demand.
With this critical link broken, electricity coming in from generators in Tennessee, Kentucky and Missouri, as well as northern Ohio, Michigan and Ontario, are automatically routed across alternative lines. These lines, already heavily loaded, began to trip and generators in Canada and the U.S. began to automatically take themselves offline to avoid damage.
By this point, more than 263 power plants (531 individual generating units) have tripped offline in Canada and the U.S., leaving 50 million people without power.