Smarter and FasterBy Mel Duvall | Posted 2003-11-01 Print
The Ohio utility's systems protected its 4.9 million customers during the Aug. 14 blackout. But did they knock out power to 50 million people in the process?
Smarter and Faster
Electromechanical relays perform just one function: Measuring the flow of power. The rotation of a metal disk may indicate how much electricity is passing through; and if the measurement gets too high, a "trip" may be set off, cutting the flow.
But that's all such a relay can do. It cannot watch other variables, such as demands for power coming from other networks; it cannot store information; and it cannot communicate with other devices.
Digital relays change the game completely, says Dolezilek. Sold by such vendors as Schweitzer, General Electric, Alstom SA, Cooper Industries, and Siemens AG, such relays have one or more microprocessors, memory chips, and the ability to communicate electronically.
These relays don't just monitor the flow of electricity, they analyze it and act on it. Information is stored, processed and forwarded to other relays as well as to central control systems, where either computers or humans can deal with it. AEP maintains such a control center in Columbus, which is fed information by its digital relays. Based on the input, computers monitor such factors as the level of power being pushed through the system, known as current; the speed at which it is being pushed, known as voltage; the "reactive power" that generates protective magnetic fields which help maintain that voltage as it passes through lines; whether breakers have been tripped; and whether any equipment in the network is in need of servicing.
Whereas an electromechanical relay can only measure or monitor one factor at a time, a digital relay can monitor a number of factors simultaneously.
The greatest advantage is instant communication within the grid, computer to computer and relay to relay. Relays can use built-in diagnostic capabilities to detect a problem and isolate it. They can reroute and restore power automatically without slower human intervention. The fastest digital relays make decisions in eight thousandths of a second. Investigators determined more than 100 power plants were shut down in about 15 seconds, at the height of the August blackout.
Even if all utilities used digital relays, the blackout still could have happened. Utilities have not set up their own Internet: Their relays are not interconnected and there is little sharing of data. While AEP's digital relays may have been smart enough to act against the swings in voltage on lines it shared with FirstEnergy, it could not pass that information on to Michigan.
The result was a sucker punch. "We got hit by the equivalent of a tsunami, and we didn't have a clue that it was coming," says Joseph Welch, president and chief executive of International Transmission Co. (ITC), the regional organization that oversees transmission lines in southeastern Michigan. "The results were devastating."
The blackout was a rude awakening for ITC. It had only taken over responsibility for the transmission grid in southeast Michigan in February of this year after purchasing the assets from DTE Energy. "On August 14, it was apparent that parties were choosing to operate the grid within their sphere of influence for their own purposes, without regards to rules procedures, or the impact of their actions on other users of the grid," Welch told the House energy committee in September, taking a slap at AEP.
CERA's Stauffer says Congress will have to address not just whether digital technology gets deployed by utilities and transmission companies, but how the deployments are coordinated so that information is ultimately shared nationwide in thousandths of a second. Otherwise, there will always be gulfs of information between stakeholders in the nation's power grid that can't be bridged at a moment of crisis.
"The right strategy is not isolation. There was a breakdown here where the information was available to some people and not to others," Stauffer says. "As a result, the people who could have done something [to prevent the blackout] didn't have it in time. Those that did used it to protect themselves."
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