Properly Maintained Wood Poles Exhibit Better Overload Capacity Than Alternative-Material Poles

Regulatory requirements driven by extreme weather event-related outages have caused utilities to refocus their efforts on reliability and grid resiliency. Utilities are exploring various methods of improving the resiliency of the grid through infrastructure hardening initiatives. Hardening can be done by designing redundancy and increased automation into the grid, increasing the frequency or scope of vegetation management, replacing open wire with covered wire, building to higher grade of construction and other well-established methods.

Some utilities have explored replacing wood poles with alternative-material poles such as steel or concrete as a tactic to increase the resiliency of their distribution systems. Pole replacement by itself, and especially with alternative-material poles, may be an expensive option which may not increase resiliency and may not positively impact the reliability of the grid during an extreme weather event. According to a technical bulletin prepared for the North American Wood Pole Council (NAWPC) by H. Martin Rollins P.E., a wood pole has a greater inherent overload capacity than an alternative material pole.

The National Electrical Safety Code (NESC) Rule 250 provides the minimum requirements in different geographical districts and climate zones for ice and wind loading. According to Rollins, “The NESC does not require the designs for structures less than 60 ft. in height to consider either the Rule 250C Extreme Wind Loads or the Rule 250D Extreme Ice and Concurrent Wind Loads.” One reason for the exclusion of poles under 60 ft. is because studies show many extreme weather event pole failures are caused by secondary damage such as flying debris and shifting ground conditions.

In an area subject to extreme weather conditions, properly maintained wood poles can continue to be the structure of choice for overall system reliability.

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