Porcelain is excellent for bathroom sinks, dolls and dishes. But when it comes to pin insulators, it is not nearly as effective or reliable.

This is the conclusion reached by many professionals working in the utilities industry. Specifically, Warren Hadley, a senior engineering technologist at Northeast Utilities, agrees with this assessment. Working for New England's largest utility system and serving more than two million electric and natural gas customers in Connecticut, Western Massachusetts and New Hampshire, Hadley has seen the superior performance of polyethylene insulators versus porcelain – firsthand.

"At Western Massachusetts Electric Company and Connecticut Light and Power, we use the Hendrix Vise Top insulators almost exclusively," said Hadley, who works in the company's standards department, specifying materials and construction standards for overhead construction. "There are a few instances where we're using porcelain insulators with bare wire, but even with bare wire we've started to use the molded Vise Top [polyethylene] insulators with aluminum inserts."

According to Hadley, the decision to move primarily to polyethylene insulators (supplied by Hendrix Wire & Cable, one of the premier providers of high-quality overhead and underground power distribution products), was made in the mid 1980's, based on research that Northeast Utilities conducted at that time.

"Back in 1984, we were having problems with tree wire burndown caused by lightning," Hadley said. "It was an issue at the time for most utilities, and there were a large number of manufacturers trying to solve the issue. Our engineering department conducted a research study and found that because of the material differences between the polycoating on the conductor and the porcelain insulators, we were getting tracking around the insulators."

"At the time it was more expensive to use a molded polyethylene Vise Top insulator," he added. "But we conducted further study and found that, by using aluminum inserts in the jaw for bare wire application and plastic inserts for covered conductor, it was possible to save substantial time during the installation. This helped us recover the additional cost of using the molded insulator products."

As a result, Northeast decided to go forward with the molded Vise Top insulators. By the late 80's, the company was using them for all covered-wire installations. According to Hadley, other manufacturers were developing a tie wire made out of polyethylene that they believed might help to solve the problem. At that time, it was a matter of trying a little bit of everything to see what worked best.

Hadley added that in the past, Northeast might have still employed porcelain insulators with radio free tops for a bare wire installation. But it has gotten to the point that the company linemen prefer the molded insulators because they don't have to go through the tedious process of wire tying; it's now just a matter of using the right Vise Top product for the type of conductor being used.

"You just screw it down and tighten the breakaway bolts," he said. "The Vise Top uses sheer bolts that are torque sensitive and it's done in minutes. So they use them now even for running bare wire. The porcelain versions are just used for certain repairs."

Obviously, putting up new wire is the optimal application for molded insulators. That's when it's most cost effective, because that's where the labor cost can be substantially reduced by virtue of being able to pull the conductor through the insulators using the Hendrix VTST-1 tool and then have them all in place. Retrofits can be time-consuming and expensive; still, Northeast has gone back to older circuits and replaced the insulators with polyinsulators because of the problem with the conductor covering breaking down.

Without question, the polyethylene Vise Top insulators – the kind that Northeast Utilities purchases from Hendrix on a large scale each year – offer superior performance as measured by virtually any criterion you can name.

Take vandalism, for example. Every year utilities report property destruction among the causes of service disruptions. The fragility of porcelain, as well as the fact that porcelain insulators can be easily shattered on impact, makes them attractive targets for stones, balls or projectiles. Conversely, the impact resistance of high density polyethylene (HPI) insulators makes them the natural choice in vandal deterrence. If hit by a ball or stone, there is no shattering.

Further evidence of HPI Insulators' near indestructibility can be gleaned from ballistics tests, showing that even with damage from rifle or shotgun fire these insulators are still able to operate. Using the HPI Insulator is analogous to putting up a fence around a pool or taking a ladder down around the house when not in use – it mitigates the "attractive nuisance" factor that is characteristic of porcelain.

Hendrix maintaines that porcelain insulators should not be used with a covered conductor. This is due to the inherent dielectric incompatibility between the two materials (polyethylene and porcelain).

HPI insulators also require less maintenance than porcelain insulators in the same environment. What's more, high density polyethylene is naturally hydrophobic, meaning that it is water repellent, i.e., water will bead up rather than penetrate and will leave dry spots between the water beads. This phenomenon is similar to a newly waxed car; the lack of stickiness, along with wind and rain, allows for a natural cleaning. This property, along with the HPI's superior track resistance and designed in increased leakage offers excellent resistance to polluted or salty environments.

The aforementioned features and benefits help to explain why polyethylene insulators give a utility company such as Northeast Utilities an advantage over a competitor using porcelain insulators. Hendrix Wire & Cable's HPI Insulators have proven to be an effective alternative solution for Northeast Utilities—and that's putting porcelain in its place, or in this case, polyethylene on the system!

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