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SAR transmission tower detection is essential to transmission system monitoring and maintenance. Various methods have been proposed to detect transmission tower by using shallow feature. With the development of the deep learning based on convolutional neural network, this study proposed an improved SSD-based transmission tower detection method by introducing deep learning-based technique. First, SSD, a state-of-the-art object detection method, is analysed in detail. Then, the algorithm is modified to fit authors’ specific domain. According to the experiment results in real SAR images, it is showed that the modified method gains better detection performance. Finally, ablation experiments are also performed to confirm each modification step produces better result.

Full-scale discharge tests of transmission line–tower air gaps are costly and time-consuming, and they cannot exhaustively simulate all the gap configurations in practical engineering. In this paper, a machine learning model established by support vector machine is introduced to predict the switching impulse discharge voltages of the ultra-high-voltage (UHV) AC transmission line–tower air gaps. The three-dimensional finite element models of a UHV cup-type tower and a UHV compact transmission line were established for electric field calculation, and some features were extracted from the hypothetic discharge channel and the shortest path between the bundled conductor and the tower. These features under a given voltage were normalised and input to the SVM model, while the output is two binary values, respectively, representing gap withstanding or breakdown. Trained by experimental data of one type of the UHV transmission line–tower gaps, the SVM model is able to predict the discharge voltages of another gap type. The mean absolute percentage errors of the two engineering gap types, under different gap distances, are 8.31 and 4.86%, respectively, which are acceptable for engineering applications. The results provide a possible way to obtain the discharge voltages of complicated engineering gaps by mathematical calculations.

The modelling of tower grounding device is the key for calculation of lightning strike response and lightning withstand level. In order to solve this problem, this study proposes a method to calculate the lightning response of transmission line grounding device by combining the advantages of CDEGS and EMTP software. Firstly, the authors calculate the frequency domain response of the tower grounding model in CDEGS; then the result is fitted according to modified vector fitting method to obtain the rational approximation expression of the impedance function. Furtherly, the corresponding equivalent circuits of tower grounding device is established in EMTP to realise accurate simulation of grounding device lightning strike response. The results show that the equivalent circuit model is more accurate than non-linear resistance model. Then, the factors that influence the lightning response and lightning withstand level are analysed based on the above method according to an actual transmission line model, which can provide reference for the lightning protection and grounding design.

In order to study the fast calculation method of a surface electric field of the arbitrary-quantity bundled conductor and a ground nominal electric field of the HVDC transmission line on slope terrain. Based on the basic principles of the image method, this paper deduces the calculation formula of the surface maximum electric field of the arbitrary-quantity bundled conductor and the ground nominal electric field of the HVDC transmission line with single bipolar horizontal arrangement over the slope terrain by making the reasonable approximation and equivalence to the actual situation. Compared with the finite element method, the results got from the formula proposed in this paper verify that these formulas are accurate and valid. The effects of slope inclination, pole–pole spacing of the conductor on the electric field of the conductor surface and the ground nominal electric field of the HVDC transmission line are analyzed and obtained. The results of research indicate that the inclination of the slope and the pole–pole spacing of the conductor have a great influence on the conductor surface electric field and the ground nominal electric field. When the HVDC transmission line is erected on the slope terrain, the formula proposed in this paper can provide references for circuit design and electromagnetic environment analysis.

The transmission corridors can be effectively saved using 750 kV four-circuit transmission line on the same tower. In order to reduce the corona level, structure optimisation of fittings plays an important role in the transmission line design. In this study, the electric field distribution of 750 kV transmission line on six cross-arms tower was calculated based on finite element method, and the influences of pipe diameter, ring diameter and installation position of the grading ring were analysed. The results show that the increase of pipe diameter can reduce the electric field strength of grading ring while the increase of installation position and decrease of ring diameter are important to protect the end fitting of composite insulator. When using grading ring with the pipe diameter of 100 mm, the ring diameter of 700–900 mm and the installation position of 150–250 mm, the electric field strength can be controlled in a reasonable range. These results can provide references for the grading ring design of 750 kV four-circuit transmission line on the same tower.

Based on completely mastering ±800 kV transmission technologies, the first ±1100 kV direct current (DC) transmission demonstration project is being constructed in China. Combining theoretical analysis and a large number of experiments, the margin of switching overvoltage in converter stations, the configuration scheme and performance of lightning arresters, the shielding angles of ground lines under different geographical conditions, and the maximum air gap of lines have been determined. The switching impulse flashover characteristics of equipotential sphere and typical rod-plane air gaps are also provided. The external insulation is designed differently for light, medium, and heavy pollution areas. For the ±1100 kV project, if the 8 × 1250 mm^2 conductors are applied, the pole gap is 26 m and the height of the line is 25 m, all the electromagnetic parameters will meet the requirement of international electromagnetic standards. The key design points of ±1100 kV converter transformers, smoothing reactors, converter valves, and wall bushings are researched and the 75 mH smoothing reactors, ±1100 kV/5000 A converter valves, and ±1100 kV/5523 A wall bushings are successfully made. The optimised hierarchical connection modes and coordination control measure of the ±1100 kV project are studied and the results can provide sufficient technical support for the demonstration project.

Anticorrosion coatings are commonly applied to prevent rust-based corrosion in transmission towers. Unfortunately, anticorrosion coatings may drip onto the surface of composite insulators during the construction process, which is likely to do harm to operation characteristics of composite insulators. This Letter was conducted to determine the influence of anticorrosion coatings on composite insulator performance. The mechanical properties, hydrophobicity, hydrophobic transfer, and flashover voltage of high-temperature vulcanised (HTV) silicone rubber specimens with and without the coating were investigated in detail. Appropriate solutions for avoiding unwanted effects on insulator performance are proposed accordingly. The influence of coating on the pollution flashover voltage of the composite insulator was also determined by changing the type, area, and shape of coating attached to the insulator surface. Finite element software was also used to analyse the effects of coatings on the electric field distribution of the composite insulator. The coating slightly affects the mechanical properties of HTV silicone rubber, but significantly impacts its hydrophobicity and hydrophobicity transfer. The pollution flashover characteristics of test composite insulators covered with the anticorrosion coating are also worst than those without coating.