Why it's just as important for the old economy.
Mention "power quality" and the mind conjures up visions of tech hotels stuffed with Internet servers running 24/7, retrofitted into inner city industrial warehouses-buildings sturdy enough to forgive the heavy installation of custom power supply equipment and racks of batteries. Or perhaps Silicon Valley.
"I've been in meetings with Intel where they say, just think of me as a black box and fix my power," says Ashok Sundaram, a product manager at EPRI in Palo Alto, California (also known as the Electric Power Research Institute). But for EPRI, the notion of power quality transcends any industry. It encompasses the entire electric grid.
"If you have a large customer like an Intel or a Motorola," Sundaram explains, "sometimes the processes are so large that there is no real way to install a solution on the customer side of the meter."
In that case, a network solution might seem more economical, with the electric utility making the required investment in the distribution grid, rather than on-site at the customer premises. But the problem really begins before that.
"A lot of homework has to be done," says Sundaram. "Not until you define the base level of power service can you even begin to talk about defining premium power, or start building premium parks. And the base level can vary by geographic area. California's base level of power quality is different than Florida, for instance, where they have all those thunderstorms. First, characterize what power quality you already have. Because setting a base level of power quality will set a base level for cost."
And so power quality today isn't just for the digital age. It's for pulp and paper and plastic bags, textile mills and light bulb filaments, aluminum rails and Coleman coolers-any ordinary manufacturer that employs a continuous process.
"We don't anticipate any black box solutions for power quality," adds Bill Winnerling, power quality expert at EPRI. "Issues continue to emerge. As we solve one problem, we see another. Sure, you can buy some remedies off-the-shelf. You can use a surge suppressor for your computer," he concedes.
"But not every industrial plant is going to be willing to pay for nine nines of reliability (assurance of service 99.9999999 percent of the time), which is what is required by some of these Internet servers and tech hotels." By contrast, electric utilities traditionally have assured reliability of service to four nines-only 99.99 percent of the time.
"The demands of the digital economy may force us to have an improved distribution system, but it's got to be done incrementally."
Helping Customers On Site
Power quality problems are nothing new. Ken Hall, manager of distribution (the utility distribution sector) at the Edison Electric Institute, notes that power grid disturbances long have been seen in rural areas, where a neighbor's water pump can upset the local grid, given the lack of load density.
"Sometimes the customer's worst enemy is the other customer down the road," he adds. "And 'nearby' is a relative term. When a large motor switches on 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 process. They are so responsive that they create problems, depending on how they've been programmed. They're used in petrochemicals, pulp and paper, textiles, and general manufacturing. And in the automotive industry for sure, with all the robotics they have.
"A PLC might require an adjustable drive to shut down if it senses a 50 percent voltage sag. But sometimes these controllers are too sensitive. They might come pre-programmed, or it could be the guy on the plant floor who reprograms the PLC and sets the tolerance too tight."
But even though manufacturers can buy power quality equipment off-the-shelf, including "ride-through" devices that allow a plant or process to work right through a voltage sag, Sitzlar believes there always will be a need for custom consulting services on power quality.
"Let me give you an example about really understanding the problem, as opposed to just applying a band aid."
"There was a company making tungsten filaments for light bulbs. They take huge bars of tungsten, run them through a press, and draw the filament out at the other end, as a small, hair-like wire that runs around a spool. But this plant had a problem. The wire was breaking, and they had to keep shutting everything down and restarting the process.
"They had several consulting companies come out to try to fix the problem. The first consultant proposed a SMES installation (Superconducting Magnetic Energy Storage) to support the entire manufacturing facility. It would address instantaneous problems-about a half-cycle of the input wave, to get you through the instant of the momentary disturbance. But that could have cost millions. "The local utility offered a different solution. They said, 'let's consider a parallel feeder as a backup to make the power more reliable.' That would increase reliability, but also could have cost a million dollars.
"So then the manufacturer asked for a third recommendation, and they called us in. And as we saw it, the problem wasn't the entire facility, but only the take-up spool. Every time there was a momentary sag on the line, the spool would pause for a microsecond, and then when the power was normal again, it would try to speed up and catch up, and it would overspin and snap the wire.
"So we recommended installing a small spring (a $5 fix) to serve as a shock absorber. The spring would take up any change in tension, rather than force all the tension on the filament itself."
Remaking the Grid
From a utility perspective, where is the economic tradeoff? At what point does it become cheaper for utilities to focus on distribution network solutions, rather than work out a remedy at the customer's facility? Winnerling acknowledges the much-touted idea of "the "premium park"-upgrading the grid in a neighborhood filled with high-tech offices.
"We have something called a 'UPS substation' (uninterruptible power supply). It comes equipped with a huge battery bank-literally hundreds of batteries-just to allow the utility to keep a few seconds of power on, at a high cost. But in some substations, in some neighborhoods, providing that premium power may be worth it for a high-tech industrial park or an Internet server office."
Nevertheless, as Winnerling adds, EPRI is looking for a way around that high cost, and for cleaner alternatives.
"We're trying to get away from lead-acid batteries-we're using ultracapacitors, for instance, and flywheels. We're also working with NIST (the National Institute of Standards and Technology) in testing high-tech equipment with voltage sag generators to see if we can make the machines less sensitive to power quality problems.
"In fact," notes Winnerling, "on a transmission level we've got a new program called CEIDS (Consortium for Electric Infrastructure to Support a Digital Society). It's a new initiative we're kicking off to enhance the performance of the entire transmission grid, all the way down to load, to focus on serving the digital economy.
"But the one thing we don't want to do is pay for a million-dollar fix on the network side to fix what is really a $100 problem. But when we have thousands of those $100 problems, then we can start doing something on the network side."
What about neighborhoods that run entirely on direct current, called "DC microgrids," designed to integrate electricity use with fuel cell technologies?
"We're doing research on using DC current inside individual buildings, such as in a high-tech area. In theory, all that Internet equipment doesn't need an AC power supply; it could run on DC. But any time you convert AC to DC you may create more power quality problems. And the equipment creates nonsinosoidal (distorted) wave currents (harmonics) in a backward direction back into the utility distribution network."
Then does distributed generation pose the same risk?
"One of the things we're doing now," says Sitzlar in Tennessee, "and which we haven't done in the past, is research work on distributed generation.
"We have created a power quality DG laboratory here-it's the only one in the country-to try to figure out how to integrate DG economically into the power system.
"We're testing in both directions. We're measuring the impact of the utility system power quality on the DG facilities, and then the impact of the output of the distributed resource on the power system. We'll be looking at things like running DG systems in parallel, and whether the distributed generation unit is synchronized with the grid."
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