Impact of Non-Wood Poles on Distribution Reliability

outline

This project investigated the impacts of non-wood pole (i.e. concrete, steel and fiberglass reinforced poles) structures on overall system reliability. The project was divided into three main tasks: lightning performance assessment, mechanical strength of non-wood poles, and impact on system reliability.

In Task 1, the lightning withstand strength of non-wood poles was analyzed in comparison with wood poles due to the fact that overhead distribution systems are extremely vulnerable to lightning strokes, as they cover a wide geographic region and are often the tallest objects within a given area. Critical flashover voltage (CFO) was adopted to measure the lightning strength of non-wood or wood pole structures. The CFO calculation tool (CFO CAST) developed in Program 10 (P10-10) was employed in Task 1 to compute CFO level for several commonly used distribution pole configurations (shown below) with wood, concrete, steel and fiber-reinforced composite materials.

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In Task 2, Physical Properties, various physical characteristics of the non-wood materials were investigated to explore their mechanical and physical properties. Strength-to-weight ratio, or specific strength, describes the ease of transportation; the higher the ratio, the “lighter” the material. Tensile and compressive strengths indicate the capability of a pole to withstand pulling force, i.e. conductor, wind and ice loading. Elasticity strength indicates how well a pole can return to its original shape after stress. Ductility strength reflects how well a pole can sustain deformation plastically without fracture, i.e., how likely is the material to fail under extreme loading.

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In Task 3, Impact on System Reliability, the impact of various aspects of non-wood poles on the reliability of distribution systems is discussed, particular, how the lightning performance and physical properties affect popular measures of reliability: SAIDI, SAIFI, CAIDI and MAIFI. An illustrative simulation shows how changes in overhead line failure rates and repair times, plausibly precipiated by a change in pole material, influence the system reliability.

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The outline for thw 55-page final report is shown below.

outline

This study was conducted in P12-5