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Gas-insulated transmission line (GIL)/gas-insulated switchgear (GIS) insulators usually withstand complex mechanical stress and strong electric field. This study investigates the insulation properties of epoxy resin subjected to mechanical stresses ranging from −10 to +10 MPa. The transition of mechanical stress from compression to tension leads to a decrease in the relative permittivity of epoxy resin, accompanied by an increase in conductivity, trap energy, and space charge accumulation. Due to the more pronounced impact of mechanical stress on conductivity than on relative permittivity, the dc electric field distribution of the epoxy insulator undergoes more noticeable changes under different mechanical loads, in comparison to those under ac or overvoltage conditions. Results of this study suggest to account for the impact of mechanical stress when designing an insulator.

In order to improve the technology for predicting flashover risks of ice-covered insulators, this article delves into the nonlinear characteristics of leakage current (LC) and the phase changes of arcing discharges. The dynamic relationship between them is analyzed quantitatively. The dc ice flashover experiment is conducted in the CIGELE artificial climate room. The dynamic characteristics of arcs during the dc ice flashover process were studied. The chaos of the LC time series is examined by estimating the maximum Lyapunov exponent ( ${L}_{\text {max}}$ ) using embedded space theory and the phase space reconstruction method. An analysis of the dynamic behavior of LC is conducted using recurrent plot (RP) technology, leading to the development of an index to quantify the regularity of the LC. A quantitative analysis of the cooperative relationship between the LC and arc length, as extracted through image processing, is performed, confirming the regular patterns of LC variation. The findings indicate that variations in the LC and arc length are effective in distinguishing between the three stages of ice flashover. ${L}_{\text {max}}$ exceeds zero at all stages, indicating the chaotic nature of the LC, which is most pronounced during the early phase of the second stage. RP technology provides a clear, dynamic visualization of icing insulator discharge behavior through graphic texture transformation. The nonlinear indexes, RR and DET, of LC, demonstrate an increase alongside the development of arc discharge, indicating a growth of the regular and deterministic components of the discharge. Additionally, there is a synchronous increase in the LC and arc length, with a clear correlation exhibited during the four arc extension periods (T1–T4). As the flashover approaches, the degree of fitting between them increases significantly.

This paper is a joint contribution from members of the IEEE DEIS Technical Committee for Diagnostics that highlights selected trends, challenges, and techniques in diagnostics and monitoring of high-voltage electrical insulation. Especially important are broad application areas including traditional generation, transmission and distribution, and renewable energy, along with emerging fields including new sectors in transportation electrification such as electromobility and electric aviation.

Surface charge accumulation is considered as a critical threat to the safe operation of epoxy insulators installed in gas-insulated switchgear (GIS). This article reports on the charge leakage phenomenon of the insulator with the occurrence of impact vibration under dc voltage. A full-sized disk insulator with a multiarc surface profile was employed as the test sample. A vibration system was established to output vibration to the insulator in two modes. In Mode I, the maximum acceleration was 338.9 m/ $\text{s}^{{2}}$ and the impact frequency was 1.1 Hz. In Mode II, the maximum acceleration decreased to 4.6 m/ $\text{s}^{{2}}$ but the impact frequency increased to 107.5 Hz. The charge densities on the insulator surface were measured before and after the vibrations. The results indicated that the vibration led to the obvious leakage of homo-charges during the dc stressing process, especially in the nonplanar region. The leakage of homo-charges under positive stressing was more remarkable than that under negative stressing. The reduction of homo-charge quantity was more serious in Mode I than in Mode II. It is suggested that the vibration-triggered charge leakage is mainly due to the charge detrapping caused by microdisplacement of molecular chain occurring in the insulator with the vibration and subsequent charge release to the gas phase under the normal electric field, by which the surface charge accumulation quantity is remarkably reduced.