SEI 2009 Electrical Transmission Substation Conference Technology for the Next Generation The Chaotic Confusion Surrounding 'Wood Equivalent' Non-Wood Poles

摘要

Unlike the statement in our American Declaration of Independence, which declares "all men are created equal", electrical transmission and distribution poles are not necessarily so. Yet as an industry, we continue to work very hard to "commoditize" poles of differing structural attributes and material behaviors and we continue to try to relate them as an "equivalent" to ANSI class wood poles. It is easy to understand why we want to do this as we want to keep things simple, foolproof, less work, and "standardized", etc., etc. etc. But with the industry's inconsistent application of basic structural principles, the practice can sometimes lead to much confusion - at times chaotic confusion.Since the development of the ANSI Standard Classification system for wood poles, a reasonable level of consistency and predictable behavior has been established for a highly variable product - natural wood poles. There is no doubt, that wood poles remain an integral and popular choice for supporting electrical power lines in the United States. But, for a variety of reasons utilities are increasingly specifying and installing non-wood poles of tubular steel, prestressed concrete and fiber reinforced polymer (FRP) materials in place of these wood poles for certain line design reasons. Those reasons are NOT the focus of discussion in this paper. Rather, this paper's discussion is intended to be focused on the potential structural differences that may be experienced when we take a single, quality and dimensional standard for one pole material (natural wood poles), and try to establish "equivalent" structural performance and behavior expectations across a variety of other structural materials. Understanding the performance and structural behavior characteristics of each of the materials is not that difficult. Our consistent specification and communication of desired structural characteristics across all materials is where the confusion seems to be. This paper will attempt to discuss such characteristics as: 1) nominal strength; 2) stiffness; and 3) durability and how they compare across common pole materials. As well, this paper also discusses how the current NESC and various RUS Bulletins deal with the various material strengths, reliability and behaviors.