Transformer

A Drill to Replace Crucial Transformers

The electric grid, which keeps beer cold, houses warm, and city traffic from turning to chaos, depends on about 2,100 high-voltage transformers spread throughout the country.

But engineers in the electric business and officials with the Department of Homeland Security have long been concerned that transformers are vulnerable to disruptions from extreme weather like hurricanes, as well as terrorist and computer attacks and even electrical disturbances from geomagnetic, or so-called solar, storms. One such storm, in 1989, blacked out the entire province of Quebec, and this week, a transformer fire of unknown origin blacked out parts of Boston.

And while replacing transformers is not technically difficult, it is a logistical and time-consuming nightmare that can take up to two years.

So this week the industry and the government have been carrying out an emergency drill unlike any that electrical engineers can remember, to explore how quickly the country could recover from a crippling blow to the power grid. Twelve trucks drove 800 miles from St. Louis to Houston to deliver three “recovery transformers.” When they arrived on Tuesday afternoon, workers began to install them as quickly as possible — reducing a task that normally takes weeks to several days.

“If you have to order a transformer from someplace, it’s two years to do it,” said Richard J. Lordan, a senior technical expert at the Electric Power Research Institute, a nonprofit consortium based in Palo Alto, Calif.

Transformers were seen as a potential problem to the grid as far back as 1990, said Sarah Mahmood, a program manager at the Department of Homeland Security, which paid for about half of the cost of the $17 million drill, with the rest picked up by the electrical industry. Transformers are about the size of a one-car garage and usually painted some drab industrial color, but without them, intersecting power lines would be like elevated highways with no interchanges.

For the test, the Electric Power Research Institute ordered three “recovery transformers” from a supplier, ABB in St. Louis. This week they were trucked to a substation owned by CenterPoint Energy near Houston. For security reasons, the company will not say precisely where.

Shipping the replacements was a problem. Ordinary transformers are often too big and heavy to travel by road, and they require special rail cars.  But because the transformers typically last 50 years, only a few dozen are shipped each year, so even the appropriate rail cars are in short supply. Ratcheting up the degree of difficulty, many of the places where a replacement transformer might have to go are no longer served by rail.

So the research institute tried a different approach, substituting three smaller, more mobile transformers for one conventional one, and specifying a size that would fit on a modified truck trailer. (A standard transformer costs roughly $5 to $7 million; buying and combining the three singles is slightly more expensive.)

Using a different transformer for each phase allowed shrinking the weight of the transformer from about 400,000 pounds for a single one to roughly 125,000 pounds for each of the three-phase units. In operation, the transformers are oil-filled, but in this case, the oil was shipped in tanker trucks in the convoy, to decrease weight.

With three transformers, three crews can work simultaneously to set them up, and setting up a small transformer is faster than setting up a big one.

In addition, installing a transformer usually requires pouring a concrete foundation, but one of these transformers was mounted on skids, eliminating that need..

Even with all these shortcuts, there were speed bumps. One is that utility executives think a stockpile is a good idea, but nobody is quite sure what to stockpile, or where.

The industry rule of thumb is that for every 13 transformers in the field, there are 10 designs. And the initial model that they will stockpile will only work as a replacement for about 500 of the 2,100 transformers in the system.

The next step will be a transformer unlike almost any in the field,that can be configured to work between more than two different voltages — say, operating not just between 138 kilovolts and 345 kilovolts, but also between 115 kilovolts and 345 kilovolts. That would cover a few hundred more.

In recent years, electric companies have been required to build entire duplicate control centers, at least 10 miles from the primary center, to reduce the possibility of a catastrophe that would knock down sections of the grid for months. After a flurry of fines and public embarrassments, the utilities have become better at maintaining their power lines. But this is the industry’s first major effort to solve the transformer problem.

A study for the Energy Department last year reinforced the need for speed, suggesting that hundreds of transformers could be lost to a “geomagnetic storm,” an eventuality that experts say could leave large parts of the North American continent blacked out for months.

Many engineers doubt that that could happen, but see a value in trying to compress the replacement schedule. CenterPoint was reluctant to provide a precise schedule but it is trying to do in a few days what often takes six to eight weeks.