Iced conductor motion is induced by the aerodynamic instability. The aerodynamic characteristics of iced bundle conductors in turbulent flow are significantly different from that in uniform flow. The aerodynamic coefficients of iced 8-bundle conductors’ segment models under different turbulence intensities flow are measured by the wind tunnel experiment. Furthermore, the aerodynamic coefficients of each crescent- and sector-shape iced 8-bundle conductors under different turbulence intensities flow and ice thicknesses are obtained. The wind tunnel test results indicate there have obvious difference between aerodynamic characteristics of bundle conductors in turbulent flow and that in uniform flow. Then, key parameters, such as turbulence intensity, ice thickness and ice shape have significant influences on aerodynamic coefficients of each sub-conductors. Differences exist among aerodynamic coefficients of crescent-shape and sector-shape iced 8-bundle conductors. Finally, the galloping coefficients of iced 8-bundle conductors are discussed. The wind tunnel experiment results can offer useful reference resources for the comprehensive analysis of galloping of iced bundle conductors and their prevention techniques.

An improved mathematical model used to study the coupling characteristic of the multi-span transmission lines is developed. Based on the solution method for single-span cable, an expression for the dynamic stiffness of two-span transmission lines with an arbitrary inclination angle is formulated. The continuity of displacements and forces at a suspension point is used to derive the dynamic stiffness. Interactions between insulator strings and adjacent spans are accommodated. Considering the infinite dynamic stiffness corresponds to the natural frequencies of the transmission lines, the finite-element method (FEM) is employed to assess the validity of the dynamic stiffness. In the numerical investigation, attention is focused on the effect of the inclination angles, Irvine parameter, insulator string length and damping parameter. In addition, the modal function corresponding to the natural frequencies is derived. Then, the results of comprehensive parametric studies are presented and discussed. Special attention is paid to the effect of the Irvine parameter and damping parameter on the in-plane modal shapes. Finally, according to the theoretical model of two-span transmission lines, the generalized dynamic stiffness of transmission lines with an arbitrary number of spans and inclination angles is derived. The method can be used as the basis of the vibration analysis on a wide variety of multi-span transmission lines.

For the galloping of iced transmission lines, the influences of two simplified methods of dynamic tension on the galloping characteristics of transmission lines are investigated. Based on the variational principle for Hamiltonian, the partial differential equation of galloping of iced transmission lines is derived, then it is transformed into ordinary differential equation by Galerkin method. Two different simplified methods are used to convert the partial differential equation into ordinary differential equation. One is to average the dynamic tension over the span length, then Galerkin method is used. The other is that Galerkin method is used to convert the partial differential equation into ordinary differential equation directly. Firstly, the influences of two simplified methods on coefficients of ordinary differential galloping equation are studied. Second, the influences of the bending stiffness on the first-order frequency have been researched. In addition, the average method of two degrees of freedom (DOFs) is proposed and the galloping characteristics of iced transmission lines are studied by using multiscale method and average method, then the results are compared with that obtained by using numerical method. The parameters analysis shows that the two simplified methods of dynamic tension have significant influences on the coefficients of the two DOFs ordinary differential equation. By comparing the coefficients of galloping equation obtained by the two simplified methods of dynamic tension, it can find that with the increasing of tension and span length, the influences of bending stiffness on in-plane and out-of-plane natural frequency becomes smaller and smaller. The results of multiscale method and average method both show that the two simplified methods of dynamic tension have certain influences on the frequency, phase and amplitude of galloping of iced transmission lines. The conclusions obtained by this paper would promote the perfection of theoretical modeling about iced transmission lines, and could also give some references to practical engineering.

In view of the disadvantages of manual testing of bearing surface defects in the bearing production process, an automatic detection and identification method of bearing surface defects based on machine vision is proposed. Firstly, the source image is pre-processed by gamma correction algorithm, and the Canny algorithm is improved by adaptive selection of the Canny algorithm based on iterative threshold segmentation method and Ostu algorithm to improve the integrity and precision of the segmentation of bearing surface defects. The experimental results show that the method can be accurately detected of bearing surface defects, and the defect recognition rate has reached 93.33%.