Current measurement is a key part of the monitoring system for power transmission lines. Compared with the conventional current sensor, the distributed, self-powered and contactless current sensor has great advantages of safety and reliability. By integrating the current sensing function and the energy harvesting function of current transformer (CT), a time-multiplexed self-powered wireless sensor that can measure the power transmission line current is presented in this paper. Two operating modes of CT, including current sensing mode and energy harvesting mode, are analyzed in detail. Through the design of mode-switching circuit, harvesting circuit and measurement circuit are isolated using only one CT secondary coil, which eliminates the interference between energy harvesting and current measurement. Thus, the accurate measurement in the current sensing mode and the maximum energy collection in the energy harvesting mode are both realized, all of which simplify the online power transmission line monitoring. The designed time-multiplexed working mode allows the sensor to work at a lower transmission line current, at the expense of a lower working frequency. Finally, the proposed sensor is verified by experiments.

The effect of initial defect size on the mechanical behavior and failure mode of carbon fiber-reinforced polymer- confined concrete column was investigated through theoretical analysis, finite element software simulation and experiment validation. Qualitative theoretical analysis was firstly explored to study the effect of initial defect size on the mechanical behavior of confined concrete column from macro to micro perspective. Numerical simulations and experimental investigation were then carried out and compared to investigate the mechanical behavior of carbon fiber-reinforced polymer-confined concrete column with initial defects under axial compression and eccentric compression. The variation of defect criticality was investigated by varying the layer number of carbon fiber-reinforced polymer and cross-section size of concrete columns. The effect of initial defect size on the failure mode of carbon fiber-reinforced polymer-confined concrete column was finally demonstrated.