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opinion | Lawrence Harmon

A world of wires

 Spacer cable consists of three small wires protected by a larger one, all separated by insulated spacers.
Spacer cable consists of three small wires protected by a larger one, all separated by insulated spacers.HENDRIX WIRE AND CABLE

Small municipal power and light companies in Massachusetts — called “munis’’ — often shine brightest on stormy nights when high winds and heavy snow send tree branches crashing down on overhead electrical wires. During the run of bad storms in recent years, customers of NStar, National Grid, and other investor-owned utilities sat in the dark while muni customers watched TV and made hot chocolate in the microwave.

The state’s 41 munis love to get under the skin of big power companies by emphasizing the local knowledge of their linemen and the ability of managers to concentrate on customers absent the gaze of outside shareholders. There’s something to it. But a better answer might be found simply by looking up.


What you want to see is spacer cable, a superior alternative to the uninsulated wire commonly strung along electrical distribution lines. Munis in Wellesley, Groton, Sterling, and others towns are busy phasing out bare wire in favor of spacer cable or have done so already.

“If a tree falls, it’s less likely to knock the power out,’’ said superintendent Donald Newell of the Wellesley Municipal Light Plant.

Spacer cable generally consists of a bundle of four wires, three of which are insulated and held up by the fourth — a high strength cable capable of deflecting falling objects, such as tree branches. The wires are separated by insulated spacers placed roughly 30 feet apart, which add greater mechanical strength. It’s tough stuff. There are even reports of power flowing uninterrupted after a pole collapsed, resulting in the mangling of spacer cable circuits.

James Bouford, a Maine-based electrical engineering consultant, summed up the advantages of spacer cable in a 2008 technical journal published by the Institute of Electrical and Electronics Engineers. Spacer cable, he wrote, “nearly eliminates tree-caused customer interruptions,’’ reduces dollars spent on tree trimming, and improves customer satisfaction.


So why aren’t NStar, National Grid, and other investor-owned utilities wrapping themselves in spacer cable, especially after last year’s massive outages and the companies’ miserable attempts to restore power?

One reason could be that the product costs about 25 percent more than bare-wire construction. Another could be that the state Department of Public Utilities, which oversees the investor-owned utilities, isn’t pushing the big companies to adopt spacer cable. In fact, the DPU doesn’t even keep track of what types of wires are used for the overhead distribution lines.

Choice of wire deserves a much closer look by the DPU as it launches its recently announced investigation of grid modernization technology and practices. State officials have been making a lot of noise of late about improving the reliability of the big utility companies. But the state’s energy seems focused mostly on green technologies and trendy stuff like smart appliances. Maybe it’s time to home in on the basics — such as wires.

Utility executives say they recognized the advantages of spacer cable long ago, especially in heavily wooded parts of their service areas. NStar utilizes spacer cable along 10 percent of its 7,800 miles of distribution lines, according to company spokeswoman Caroline Pretyman. National Grid vice president Cheri Warren estimates that spacer cable is used along 20-25 percent of its distribution lines.

Perhaps such percentages satisfy the needs of both customers and shareholders. The big utilities can certainly make the case that they performed well in the aftermath of Hurricane Sandy. But last year’s lengthy outages haven’t been forgotten by the public or by the state attorney general. And the roughly $26 million in combined fines hanging over the heads of NStar and National Grid could buy a lot of spacer cable.


Bouford said it would be unrealistic to expect investor-owned utilities to adopt spacer cable with the enthusiasm of smaller municipal power and light companies. The munis, he said, are often in a better position to absorb the higher costs of the materials because they are generally exempt from property taxes and can borrow money at lower rates. At investor-owned utilities, he said, those costs would fall directly on the ratepayers.

It’s a fair point. But where is the break-even point for utilities and their customers? Is 36 hours without power enough to warrant greater use of spacer cable? Two days? Four?

A lot more energy needs to go into finding the answer before the next round of super storms.

Lawrence Harmon can be reached at harmon@globe.com.