Utilities recognize that wooden poles are vulnerable to fire. However, replacing millions of wooden poles with metal or composite ones isn’t realistic from a cost and labor perspective. Reinforcing wooden poles with passive fire protection options is a promising alternative. To maintain the benefits of wood poles, utilities are choosing to deploy passive fire protection solutions in high risk fire areas, controlled burn zones, and active fire paths. This can reduce the duration and cost associated with power outages after a fire. There are two leading options for protecting wooden poles from wildfires: coatings and wraps. These products offer different benefits in terms of serviceability, ease of installation and removal, and breathability.
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 housing material, the next step is to develop an appropriate test protocol. Good polymer compounds 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.
There are three distribution arrester types commonly used to protect overhead distribution equipment from the damaging effects of overvoltage. IEEE C62.11 defines Normal Duty (ND) and Heavy Duty (HD) classes by their ability to withstand certain current impulse levels. The third, Heavy Duty Riser is a type, or variation, of the HD classification and utilizes a larger diameter Metal Oxide Varistor (MOV) disc.
When comparing different arrester designs, it is important to understand how the arrester was built to correctly evaluate the amount of protection it will provide. The IEEE C62.11 standard covers two types of Metal Oxide Varistor (MOV) distribution arresters that are available today, internally gapped and gapless. These arresters might look identical from the outside, but the different internal module design affects how the arrester protects voltage sensitive equipment.