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Brawn & Brains

September 15, 2003

By Peter W. Huber, Mark P. Mills

It now appears that the Aug. 14 blackout began—or at least gathered its destructive momentum—in an hour-long series of line failures and plant shutdowns in northern Ohio, near Cleveland. The final collapse took nine seconds to unfold—a long time, in the power business. This is excellent news—we know how to fix such problems, and relatively cheaply at that. The grid does need more expensive work, too. But first things first. To stop blackouts like this last one, add bits.

As instant pundits were too quick to point out last week, investment in grid assets has declined steadily in recent decades, while electricity demand has risen. Tangled regulatory reasons are to blame, and new investment in grid hardware is now urgently needed. But the grid was not, in fact, particularly stressed on Aug. 14. New power plants and transmission lines probably would not have averted this particular blackout.

Put aside the big plants that generate the power. The expensive parts of the grid itself are the wires—some 680,000 miles of transmission backbone and another 2.5 million miles of wires for local distribution. Because they're so long, and carry so much current, they store huge amounts of energy in the magnetic fields that surround them. When loads or supplies change quickly, this electrical inertia sends rogue power sloshing up and down the system, like waves in a bathtub that move water independently of the faucet and drain. Grid engineers call this "reactive" power—the wires appear to contain malignant generators of their own.

Engineers maintain and restore order, if they can, at "interties" and "substations." These switching points can flatten out or at least isolate the waves, by routing power in and out of different lines and through huge transformers and capacitors. High-power switches thus add order to the grid much as microscopic gates add logic to a Pentium.

The grid's "supervisory control and data acquisition" (Scada) networks move the bits that control the power. Sensors and dedicated communications links feed information about the state of the grid to regional transmission authorities and utility control centers, and the latter control the switches. With real-time access to Scada networks in Ohio, utilities across the Northeast could, in principle, have seen the problem coming, and activated protective switches before the giant wave swept east to overpower them.

But utility Scada networks have evolved piecemeal over the decades, and regulators have recently pushed the physical interconnection of power lines far out ahead of the interconnection of the data networks, and the deployment of software systems to provide automated monitoring and control. As currently engineered, the grid moves megawatts of power much farther and faster than it moves megabits of vital information.

This creates a relatively cheap opportunity for fairly quick improvement. Scada hardware and engineering services—provided by GE, Siemens, Schneider Electric, Rockwell Automation and dozens of smaller vendors—generate some $3 billion per year in global revenues—pocket change compared with what's spent on the physical networks that Scada networks control. "Advances in Scada, telecom and computing provide us now with significant opportunities for technology solutions to manage the grid more reliably," says Van Wardlaw, vice president of Electric Systems Operations at the Tennessee Valley Authority. "They offer us some unique solutions that were not even available to use five or ten years ago."

Control networks have their vulnerabilities, too, of course. Utility Scada systems have reportedly been probed by al Qaeda terrorists, and cyberattacks against these systems have certainly been multiplying rapidly. Scada systems "have generally been designed and installed with little attention to security" and are "highly vulnerable to cyberattack," concludes a recent report by Sandia National Labs, the federal entity in charge of promoting Scada security. "[S]ecurity implementations are, in many cases, nonexistent or based on false premises." But keeping the grid's control networks disconnected and comparatively stupid only increases the vulnerability of the physical assets, which are far harder to protect.

Scada networks need more and better instrumentation, too, and much more advanced software for automated control. At present, the grid has far too few sensors to monitor current, voltage and line temperature in real time, along with the status of capacitors, transformer oil, insulators, switch contacts and hundreds of other variables needed to provide effective advance warning of meltdowns. On-site power networks in many factories are monitored far more closely, and make much more sophisticated use of predictive failure algorithms.

Then, finally, the grid needs more and better strategically placed gates. Roughly speaking, each utility, at present, is expected to protect all its neighbors from faults on its own grid. But with real-time access to regional information, utilities could and would take steps to protect their own grids from problems unfolding elsewhere.

Almost all the grid's logic is currently provided by electromechanical switches. Ultrahigh-power silicon switches manufactured by companies like International Rectifier, Fairchild Semiconductor and Powerex (a GE-Mitsubishi joint venture) can now control power flows much faster, more precisely and more reliably. Cyberex (a Danaher business) and GE-Zenith Controls, for example, now build truck-size cabinets containing arrays of solid-state switches that can handle from several kilowatts to as much as 35 megawatts. These systems already play key roles in securing power supplies at military bases, airport control hubs and data and telecom centers. At ultrahigh-power levels—up to 100 megawatts—enormous custom-built arrays of solid-state switches are now being used to interconnect and isolate high-power transmission lines at about 50 grid-level interconnection points worldwide.

Meanwhile, the private sector has deployed 80 gigawatts of generating capacity—about 10% of the capacity that lights the grid—to back up (or substitute for) grid power. Another 3% to 5% of the public grid's capacity is backed up by arrays of batteries (and ancillary electronics) that cushion delicate equipment from electrical blips and supply power during blackouts ranging from minutes to hours. The bigger backup systems are controlled by local-area Scada networks of their own, as are all the electrically powered pumps and valves that control pipelines and industrial plants. New links between the private and public power-control networks would make it easier for private equipment to help relieve the pressure when the public grid gets dangerously overloaded.

With advanced control software, interconnected data networks and high-speed, high-power switches at key locations, the grid can become as smart as it is powerful. Power suppliers know where to put the software and the switches. Will they be given the economic incentive to do so?

Original Source:



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