After a long-term operation, defects may occur in the composite insulators and threat the safe operation of the power transmission. To secure the power transmission system, it would be beneficial to detect the defects in their initial stage. In this paper, the terahertz technique combined with a deconvolution method was proposed, and a terahertz time-domain spectroscopy system was built. To validate the method proposed, three types of defects, namely single air gap defect, inclusion defect, and double-layer air gap defect were artificially prepared and tested. According to the test results, it was found that, compared with the traditional terahertz method, the air gap size that could lead to pulse overlapping was reduced from 1.22 mm to 0.57 mm. After the deconvolution process, air gap defect as small as 0.173 mm could be distinguished due to the shape characteristics of unipolar pulse. It was also found that when the defect was damp, the obtained waveform near the defect became smooth. The results of the present study demonstrate that terahertz time-domain spectroscopy (THz-TDS), combined with the deconvolution method, can have high potential in the detection of defects in composite insulators.

Misalignment of wireless power transfer (WPT) system’s transmitting and receiving ends can cause severe efficiency degradation and electromagnetic radiation. In this paper, a novel parallel transmission (TX) coil matrix structure was proposed to improve the performance of the WPT in the misalignment condition. The receiving (RX) coil’s position measurement method was innovated by investigating the magnetic field and the mutual inductance change caused by the relative position change between RX and TX coils. Both theory and experiments confirmed that the phase difference between signal coil and detector coil can be featured as the parameter to represent the magnetic field’s change. Based on this principle, a 4×4 TX coil matrix was made which verified the proposal and the sensitivity of the sensor. It was found that the position measurement result was sufficient to decide which TX coil to gate to facilitate the wireless charging in misalignment conditions. The structure and the size of the TX coil matrix could be further optimized to enhance the sensor’s reliability and sensitivity.

Composite insulator is prone to internal defects such as air gaps which seriously endanger the safety of power systems. To detect the internal defects in composite insulators, a terahertz (THz) imaging method based on edge detection algorithm was proposed in this article. First, air gap defect sample consisting of planar multilayers was imaged based on the envelope area of the THz reflection waveform. Then, Canny operator was applied to extract the edges of the defects. After that, the time interval of defect characteristic pulses was used to calculate the defect depth and then 3-D imaging of defects was, therefore, obtained. The experimental results showed that the imaging method based on envelope area was very effective in determining the edges of air gap defect and it had better performance compared with those using pulse amplitude or time interval as parameter for defect imaging. According to the results, the accuracy was quite satisfactory when the defect depth was above 0.339 mm. To verify the effectiveness of the proposed method, the developed THz imaging system was also applied to the rod of composite insulator. It was found that the relative error was smaller along the axial direction of the rod than the lateral direction.

Coupling attenuation and resonance loss due to imprecise transmitter/receiver alignment are critical challenges for reliable wireless drone charging. This paper introduces a novel, structurally simple hybrid coupler that effectively mitigates coupling fluctuations due to physical offsets without requiring additional control. The impact of magnetic core structure on the misalignment characteristics of the distributed-turn winding coil is investigated. The hybrid coupler structure that integrates a ferrite array with the distributed-turn winding coil is proposed. Besides, the design and optimization algorithm of the proposed coupler is further identified and outlined. The findings are substantiated through both simulation and experimental results, demonstrating the coupler’s efficacy. Notably, the coupler achieves a circular anti-offset region that covers 100% receiver coil radius, in which mutual inductance fluctuations are maintained below 2%. Compared with existing anti-misalignment couplers, the proposed coupler is at an advanced level in terms of anti-misalignment performance and coupling strength with simpler structure and requiring no additional control.