Nanoparticles are found to have the capacity to improve the specific properties of polypropylene (PP) for recyclable cable insulation material. However, previous studies have focused on the modification effect at room temperature, and few studies, on the nano-modification effect under high temperature environments. This article aims to study the effects of nanoparticles on the electrical and dielectric properties of PP at different high temperatures. Both TiO₂ nanoparticles and PP/TiO₂ nanocomposite samples are prepared in the laboratory by the wet chemical method and surface modification. Then, the AC and DC breakdown strength, conductivity, permittivity, and dielectric loss of the PP/TiO₂ nanocomposite are measured at different temperatures. The results show that TiO₂ nanoparticles introduce a small amount of charge traps into PP to restrain the conductivity and improve the breakdown strength of PP. But due to the additional interfacial polarization between TiO₂ nanoparticles and the PP matrix, the permittivity and dielectric loss of the PP/TiO₂ nanocomposite are enhanced, especially at low frequency.

To reduce the impact of wildfires on the operation of power systems, a back-propagation neural network (BPNN) model is used to evaluate the wildfire risk distribution after feature selection. Data from 14 types of wildfire-related features, including anthropogenic, geographical, and meteorological factors, were collected from public data websites and local departments. The weight ranking was calculated using filtering and wrapper methods to form five feature subsets. These are used as the input sets of the BPNN model training, and network parameters are optimized by genetic algorithm (GA). Finally, the optimal feature subset is chosen to establish the optimal BPNN model. With the optimal model, the prediction results are graded to draw a wildfire risk distribution map. Situated in medium-, high-, and very-high-risk zones are 90.26% of new fire incidents, indicating the applicability of the proposed BPNN model.

The grounding current increases and the outer sheath heats up seriously, which will greatly reduce the operating heat capacity of the cable and affect the stable operation of the cable. Therefore, detecting the grounding current of the cable accessory is of great significance for monitoring the operation of the cable. In order to improve the operational monitoring level, the ground loop online monitoring system began to be gradually applied in the power system. In this paper, based on the operating environment of XLPE high-voltage cable, the structure design of the on-line monitoring system of grounding circulation is analysed. The examples of online monitoring system are given. The advantages and disadvantages of the monitoring system are discussed in combination with the operating experience.

The rod-rod air gap electric fields are perfectly symmetrical in all kinds of extremely inhomogeneous electric field while the maximum asymmetry exists in the rod-plane air gap electric field. Other types of uneven electric field air gap breakdown characteristics fit in between. The rod-plane air gap electric field is an important reference for the designing of insulation strength. In this paper, the impact tests of rod-plate air gap are carried out in the field environment of different altitudes. Discharge characteristic curves of switching and lightning impulse at different environmental factors were given. The increases of the 50% discharge voltage of the rod-plane air gap switching impulse and rod-plane air gap lightning impact are larger. The influence of altitude on rod-plane air gap lightning impact is tiny. Through the analysis of test results, the influence mechanism of environmental factors on the discharge characteristics is also discussed.

The impulsive discharge characteristics of the air gap is one of the main bases for the design of the external insulation of high-voltage electrical equipment; meanwhile, air gap discharge characteristics at different altitudes have been of concern for a long time. In this paper, the impact discharge tests of rod-rod gaps at different altitudes were carried out to study the influences of elements such as electrode shape, voltage polarity, altitude and temperature. It can be found that, with the increase of the gap distance, the 50% impulse voltage of the switching impulse tends to be saturated, and the discharge characteristic curve can be fitted by exponential function. The 50% impulse voltage of the lightning impact and the gap distance shows a good linear relationship which can be fitted by the linear function. This is no direct relationship with temperature and altitude. The saturation tendency of switching impulse's 50% discharge voltage decreased with the decrease of temperature. With the increase of the altitude and the decrease of the 50% impulse discharge voltage, the polar effect of the air gap between the rod-rod and the rod-plate decreases. The results are of great reference value for Insulation configuration of electrical equipment in high altitude.