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Polymer compounds suitable for electrical insulation can consist of 10 or more ingredients which can be broken down to three major categories. These include the base polymer, fillers which can make up nearly 50% of the total compound, and active additives. Compounding of an elastomer with fillers and additives to achieve the desired results for a given application is critical. The components are carefully selected to enhance field performance and ease of manufacture.

After defining the characteristics required of an ideal polymer (link to first blog) housing material, the next step is to develop an appropriate test protocol. Good polymer compounds (link to 2^nd blog) used for high voltage insulation should be tested for the ability to resist tracking, erosion, corona, and ultra-violet (UV) radiation exposure to ensure long term reliability. The section below provides a high-level overview of the key test procedures defined to achieve the previously mentioned characteristics. The testing regime, outlined in Table 1, allows various materials to be evaluated and led to the optimum material selection for electrical insulation applications.

It’s a commonly held belief that the single most important characteristic for insulating materials is hydrophobicity, the ability to shed water or cause water films to bead, breaking up the potential leakage current path. Because the polymer housing is the primary defense for system critical distribution equipment, there are several other important polymer characteristics worth taking into consideration.

Distribution lines can face harsh conditions. If standard products aren’t doing the job and you need more protection for your standoff brackets and guy strains, look no further. Here are four reasons to switch to silicone-coated fiberglass construction products:

Fiberglass Guy Strains may be installed anywhere along the guy wire to help protect against stray current that may be on the guy caused by lightning strikes or other sources. These fiberglass units serve as a replacement for porcelain insulators or johnny balls, and they extend the insulation length. They offer numerous advantages, including:

• variable lengths
• easy terminations
• resistance to fracture caused by brittleness

Distribution lines are likely targets for lightning strikes. Once the lightning touches the line, the surge divides and travels both directions. The lightning surge will then probably cause an insulator to flash over. Why?  

"In the old configuration, if we lost either feeder, 750-800 customers were without power until a trouble-crew drove out to open and close the switches to isolate the outage and restore power," shared the utility.

To install distribution arresters:

1. Follow the directions, recommended work practices and be safe.

2. Inspect the packaging and product, looking for signs of damage: packaging (left) and dented nameplate (right).