The detection and monitoring methods of power equipment are relatively complex. The analysis of a large amount of data obtained from detection and monitoring and the development of data recording methods make it possible to obtain higher-dimensional power data. If we adopt appropriate data analysis method to the data sets, we can better get the potential laws and value of power data. In this paper, we took various basic monitoring data and faults records of the 110kV main transformers into consideration, and the grid-equipment-environment data was fused. Based on the fused data, we used the decision tree and random forest algorithm to evaluate the main transformers’ defects and faults. The evaluation results of the two algorithms were obtained and compared, which proved the effectiveness of the fault evaluation algorithm and selected a more accurate fault evaluation algorithm. This paper provides new ideas for smart fault detection for power grid, and provides a reference for a more in-depth evaluation of power grid equipment.

Transient voltages in the power grid are the key for the fault analysis of a power grid, optimized insulation design, and the standardization of the high-voltage testing method. The traditional measuring equipment, based on electrical engineering, normally has a limited bandwidth and response speed, which are also featured by a huge size and heavy weight. In this paper, an integrated optical electric-field sensor based on the Pockels effect was developed and applied to measure the transient voltages on the high-voltage conductors in a non-contact measuring mode. The measuring system has a response speed faster than 6 ns and a wide bandwidth ranging from 5 Hz to 100 MHz. Moreover, the sensors have the dimensions of 18 mm by 18 mm by 48 mm and a light weight of dozens of grams. The measuring systems were employed to monitor the lightning transient voltages on a 220 kV overhead transmission line. The switching transient voltages were also measured by the measuring system during the commissioning of the 500 kV middle Tibet power grid. In 2017, 307 lightning transient voltages caused by induction stroke were recorded. The characteristics of these voltage waveforms are different from the standard lightning impulse voltage proposed by IEC standards. Three types of typical switching transient voltage in 500 kV AC power grid were measured, and the peak values of these overvoltages can reach 1.73 times rated voltage.

As the altitude increases, air density decreases to cause a decrease in the air insulation strength. Test results in low-altitude areas indicate the significant impact of front time $t$ (μs) on the characteristics of long-airgap discharge. Nevertheless, the impact of $t$ on the breakdown voltage at high altitudes has yet to be studied. In this paper, impulse discharge characteristic tests for rod-plane gap were conducted at altitudes of 2500 m and 4300 m, with $t \in [2,1000]$ . The rod-plane gap discharge characteristic curves are obtained, and the critical front time and 50% breakdown voltage in the two areas are determined. Subsequently, the influence of altitude on the discharge characteristics under critical wave and standard switching impulse wave is compared and analysed. Based on the experiments considering low altitude, 2500 m and 4300 m high-altitude areas, the applicability of the altitude correction method recommended by IEC 60 071 is analysed. Moreover, an improved altitude correction method is presented to adapt to wide waveform variations in high-altitude areas. These results provide fundamental data and support for the external insulation design approaches in power grids at high altitudes.

The transient analysis model of grounding systems is an important tool to analyze the lightning characteristics of grounding devices. When lightning enters the soil through the grounding device, there is a centralized discharge channel. The spatial structure of the discharge channel in the soil has a great effect on the accuracy of the transient analysis model of the soil impulse discharge. In this paper, based on the gray information analysis method, the volume of successive impulse discharge channels in the ground under various currents and soil conditions is calculated, and the changing law with time interval is analyzed. According to the experimental results, an analysis method of the model considering the discharge channel structure is proposed, and an example is analyzed. The results show that the time interval has an effect on the volume of the discharge channel. In a certain range, the volume of the channel increases with the time interval of successive impulse discharges. Taking the critical breakdown electric field strength as the judgment condition and the residual resistivity as the variable, the development process of the discharge channel can be simulated. The calculated results of the model are close to the experimental results.

This paper based on density functional theory (DFT) investigate the interaction of C5-PFK molecule with Cu (110) and (100) surfaces, in order to analyze the chemical compatibility of Cu metal in the environment of C5F10O (C5-PFK) insulation gas. The frontier molecular orbital theory implies that the C=O group in the C5-PFK molecule can interact strongly with the Cu surfaces. The results show that both Cu (110) and (100) surfaces have strong interactions with the C5-PFK molecule, showing chemisorption of the molecule, with Ead of -1.17 and -1.03 eV, respectively. Meanwhile, the C5-PFK molecule performs strong electron-accepting behavior in the interactions, which captures 0.262 and 0.204 e from the Cu (110) and (100) surface, respectively. Even though, the geometric and electronic properties of Cu surface are not largely impacted, as supported by the basically unchanged morphologies and DOS curves of Cu surfaces before and after gas adsorption. These findings manifest the favorable stability and compatibility of Cu metal in the C5-PFK environment. Our work uncovers the safe operation of C5-PFK immersed insulation devices with Cu-based generatrix and shell in a long running, which is of great significance to guarantee the safe operation of the power system.