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Service to the 9's? Power Quality in a Tech-Wreck World

Why it's just as important for the old economy.
Fortnightly Magazine - February 1 2001

and off, feedbacks can come back into the distribution system. If you're on a different substation, you're probably OK. But a facility like a steel arc furnace can create nearby 'transients' and voltage disturbances. And 'nearby' is a relative term. How big is the transient? As a utility you've always had to take precautions, like encouraging some customers to limit the number of times in a day that they start up a large motor."

What's different today, however, according to Gene Sitzlar, marketing manager for EPRI-PEAC, in Knoxville, Tennessee (subsidiary of EPRIsolutions, the for-profit arm of EPRI), is that the normal, everyday operation of the distribution grid now can create disturbances that were never a problem in the past, even though the power quality today is probably better than it ever was.

"We've always had flickering problems with arc furnaces," Sitzlar acknowledges. "But now so many motors are retrofitted with variable speed drives, or adjustable speed drives. They are much more sensitive than the older motors that they are controlling. These devices go in between the power supply and the motor and boost the frequency above 60 cycles- up into the thousands of cycles-to boost efficiency for motors."

"So in the 1990s, a lot of utilities formed their own power quality divisions, like the TVA, Duke Power, and Salt River Project. At the same time, we started working with the colleges and universities to build power quality training into the engineering curriculum."

But lately we've seen utilities that had a power quality division dissolve those divisions to try to become more efficient with restructuring, and outsource those services. The utilities have conducted training courses with their customers to help them identify and correct power quality problems.

As in the past, power quality problems and solutions today still are not entirely industry-specific.

Winnerling notes that much of EPRI's power quality business comes from the semi-conductor industry, but he adds that "continuous process industries" also play a big part, such as plastics molding and metals manufacturing, pulp and paper mills and newspaper presses, where even a momentary interruption in electric service can cause havoc.

"When they make plastic bags," says Winnerling, "they blow huge bubbles in the plastic, about 20-feet tall and hanging up in the air, like a tall standing sausage. After the bubble cools, they take it up on a large roller. Imagine if that process is interrupted. You end up with globs of hardened molten plastic.

"In a recent project here, we won an R&D award where we used flywheel energy storage in a textile mill that manufactured the plastic backing on wall-to-wall carpet, which involves another continuous process. We came in and demonstrated a flywheel with about 10 seconds of energy storage at about 250 kW, to avoid short-duration incidents."

In Tennessee, Sitzlar agrees that even the old economy needs power quality.

"Actually," he says, "we find that power quality problems cut across almost all industries. Semi-conductors, and the medical industry (whether hospitals or drug manufacturers)-they all use PLCs (programmable logic controllers). These PLCs are the brains of the manufacturing