Experimental and numerical investigation of the influence of cables on utility pole modal property extraction

Pinto, Plinio Ferreira (2017) Experimental and numerical investigation of the influence of cables on utility pole modal property extraction. Masters thesis, Memorial University of Newfoundland.

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Abstract

This work is a preliminary study on the dynamic response of poles with and without the influence of electrical lines. It is part of a research collaboration between NL Hydro and Memorial University of Newfoundland to achieve a better method of diagnosing aging wooden poles through non-destructive techniques. Previous researchers in this collaboration have found a good correlation between modal testing and wooden pole decay when the poles were tested in the laboratory. However, this correlation weakens with results from field tests, possible due to foundation or attached cables. Therefore, the main objectives of this research are to create a dynamic model for a pole and cable, to design an experimental rig of a reduced scale pole and cable, to use the experimental rig to validate those models, and to gain insights on the influences of the cable on the pole response for future research. The pole model consists of a Euler-Bernoulli cantilever beam obtained through the separation of variables method. The cable was modeled by using a lumped segmentation technique that considers the system as a sum of several lumped elements containing mass, ideal springs and viscous dampers. Both models are implemented using the commercial software 20sim, which is a graphical solver for the bond graph formalism that simplifies the process of building, assembling and testing the models. These models are intended to be preliminary tools for future work with trustable simulations, thus will allow for the study of the interaction between systems, the scaling of long transmission lines and their effects on the results of modal testing, and the insertion of other electric components and attachments usually found holding the cables on the poles (i.e. isolators, cross arms, ground wire, guy wires, etc.). A reduced physical model for the pole and cable is designed to proceed with the validation of the developed models. Modal testing and time series measurements are performed over the apparatus and compared with the simulation results, showing good comparative results. In addition, the methods developed, physical and computational, can be used in the continuation of this work.

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