Calculation of frequency-dependent parameters of power cables with digital images and partial subconductors

This thesis work presents the development of a general-purpose cable-parameter algorithm which uses digital images to discretize the cable geometry and the partial subconductor equivalent circuit method to estimate the cable parameters. The idea of the proposed geometry discretization technique is to draw the cable geometry, or scan its photograph, and to use this digital image (pixel map) to automatically identify the spatial coordinates of the square-shaped (pixel-shaped) partial subconductors into which the different conductors can be subdivided. Image resolution, penetration depth, edge detection, as well as area and geometric mean distance error reduction techniques are then used to reduce the dimensions of the problem and improve the accuracy of the results. The idea of the partial subconductors method is to transform the system of conductors into an equivalent network of subconductors. A set of coupled circuit equations represents the equivalent network, and "bundling techniques" are used to obtain the parameters of the cable system. These "bundling techniques" transform the equations of the subconductors into the equations of the conductors by row and column operations. Since the number of subconductors increases noticeably with the frequency, an algorithm to partition the impedance matrices is proposed. The proposed methodology adapts itself to the physical memory of the computer, thus allowing the program to partition the partial subconductor impedance matrices when their sizes exceed the available physical memory. Coaxial cables, buried cables, and sector-shaped cables are studied with the proposed technique, and the results are compared with those obtained from the analytic method, the finite element method, and Ametani's approximate method.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat