Optimal sensor placement for structural health monitoring of power transmission tower-line systems

This paper presents a numerical pre-test finite element modeling and optimal sensor placement study for power transmission structures. The number, geometry, repetition and importance of such structures require easier, quicker and cheaper monitoring methods. Vibration-based health monitoring methods determine the modal characteristics of the structure via a limited number of sensors. These characteristics are intrinsic properties, so that a variation in them may be induced by structural damage. Only a limited number of degrees-of-freedom can be measured for the system identification process. By developing a finite element model for the tower-line structure, these degrees-of-freedom can be identified. Prior to any modal analysis, a geometrically non-linear static analysis of the structure is required. Based on these results, two methods are employed to determine the optimal sensor number and locations. Both are formulated with the use of the modal properties of the structure model. The first scheme maximizes the independence of the target modal shape matrix in an iterative process, where those degrees-of-freedom that do not contribute to the independence of the target modes are eliminated. The second scheme is based on a mass-weighting of the previous one. Correlation results are developed between the tower and the tower-line structures in order to verify the influence of the lines in the modal characteristics. In order to simulate experimental measuring, modal properties are altered by adding Gaussian noise which determines the effect on the number and location of the sensors. It is concluded that employing the tower-line system is more accurate than considering only the tower structure; and the result of sensor placement is improved for structural health monitoring purposes.