Numerical Analysis of a Seamless Mild Steel Pole for Low and Medium-Tension Power Transmission Line in Borno State Nigeria

Abstract

This work presents a computational method of evaluating structural performance of a seamless mild steel pipe material under various load conditions for supporting low and medium-tension power transmission lines. The low and medium tension power transmission line seamless mild steel (LMTPTL-SMS) pole material was specifically analyzed for reliability and resilience considering the environmental and operational conditions of Borno State, Nigeria. Borno State’s power infrastructure is subjected to significant challenges, one of which is stochastic wind loads due to harsh environmental factors. This threat has led to poles failure resulting in vandalism and power outages. To ensure the reliability and resilience of the power network, a robust pole structural design is critical. In this work a 9.7536m seamless mild steel pole material ASME SA-106 Grade B was selected based on availability and cost for analysis. COMSOL Multi-physics 5.2 numerical code was used to develop and analyze the behavior of the pole material based on predefined loading conditions and on the assumptions of Euler-Bernoulli’s beam-column theory. Using the code’s solid mechanics interface displacement and stress distribution response on the pole when subjected to static, dynamic and aerodynamic loads simultaneously were computed and analyzed at an excitation frequency of 110 GHz. The result shows a frequency response of the transfer function in terms of electric field norm of 3.7 ???? 10−79????????−1 under the predefined loading conditions, which was greater than 8.5 ???? 10−78????????−1 the response
established by the manufacturers of the mild steel pipe material. The maximum stress recorded was 8.82????107 ????/???? which is less than the 8????108 ????/???? yield strength of the selected pole material. It was observed that the displacement is from 0???? at the root to maximum value of 0.11???? at the top. The maximum displacement recorded was 0.39m. This value is 22% less than the determined critical displacement of the pole material, which was 0.50m... Thus, the displacement was within the elastic limit of the pole material based on the defined geometry and boundary condition. Furthermore, the F-Test statistical tool used to validate these results with an experimental one carried out shows that there is no significant difference between the two results. Therefore, the analysis established that the selected pole material was reliable under the predefined simultaneously applied extreme loads, thus, the LMTPTL-SMS pole will be suitable for use in Borno State, Nigeria, thus objective of the work was achieved.