NESC Wind and Ice Load Effects on Wood Distribution Pole Design

The National Electrical Safety Code has three basic structural loading conditions that may apply to various components of an overhead line. These load cases are defined in Section 25 and are generally referred to as district loading (Rule 250B), extreme wind (Rule 250C), and extreme ice with concurrent wind (Rule 250D). Both the extreme wind and the extreme ice with concurrent wind paragraphs state that these loads apply when a structure or its supported facilities exceed 60 ft above the ground. For many years, there has been an industry-wide discussion regarding the application of the loading exclusion for short poles and the associated impact on overhead distribution design. This paper will evaluate a variety of three-phase distribution lines and examine the cost impacts of applying the extreme wind and extreme ice with concurrent wind load cases to the design of wood pole structures less than 60 ft tall.