Free conductive particles in a gas-insulated metal-enclosed system produce partial discharges during movement, resulting in insulator flashover and insulation failures. This study focuses on the partial discharge property of free conductive particles under DC and AC voltages. The relationship between the micro-discharge property and the intrinsic properties of the particles was obtained based on experimental tests. The results show that under DC conditions, the local discharge property varies linearly with particle size and density. The discharge probability of particles in SF6 is significantly reduced compared with that in air, while the discharge magnitude rapidly increases if the lift voltage exceeds a certain value. Under AC conditions, the partial discharge generated by the particle becomes less random, and the amplitude and phase angle of the discharge are not significantly related. As the size of the electrode decreases, the partial discharge current generated by the particles on the surface of the electrode with an uneven electric field increases significantly. This research provides a basis for the optimization of withstand voltage test method and its applications.

There are many defects in gas-insulated metal-enclosed switchgear (GIS) and gas-insulated transmission lines (GIL) that may cause accidents, such as floating potentials, metal particles, air gaps, and cracks in support insulators. Nevertheless, to-this-date, there is no effective method to recognize them to adjust their operation status. Accordingly, this study compared three typical defect models to explore the partial discharge process, and three typical experimental models were established to identify the characteristic parameters of acoustic and electrical information in the development of defects. The research study shows that that as the voltage increases, the partial discharge of free-metal-particle defects and air-gap defects obtained by the pulse-current method increase gradually. A sudden increase also occurred in the partial discharge of the floating potential defect. The discharge amount of free conductive particles obtained by an ultrahigh-frequency detection method was distributed symmetrically on both sides of the applied voltage peak, and the other two defects were on one side of the peak and yielded an obvious phase difference. The particle collision signal obtained by the ultrasonic method was obvious, but had no obvious phase relationship with the applied voltage. However, the obtained floating potential defect information had obvious phase differences, and the ultrasonic method was not sensitive to air-gap defects. The three typical defects can be identified by the combined method more accurately; this provides a theoretical basis and data support for GIS and GIS voltage tests, detection technologies, and online monitoring methods.

High-frequency overvoltage generated in railways results in explosions of Electric Multiple Units’ (EMUs) arrestors. To solve this problem, the leakage current characteristics and heat transfer process of high-gradient MOA plates under high-frequency overvoltage has been studied. The leakage current characteristics of arrestor plates under high-frequency voltage was obtained and the element distribution has been analyzed. Heat transfer distribution and the thermal properties of the Metal Oxide Arrestor (MOA) have been modelled. According to the results, for a given voltage, the higher the harmonic frequency, the greater the leakage current of the arrestor valve plate, and the greater the resistive component of the leakage current. The Zn and O elements in high-gradient MOA plates are more uniform. Under the same leakage current as conventional ones, the undertake voltage of a high-gradient MOA plate will increase by 10%. Longtime high-order harmonic action will still significantly improve the core rod temperature when MOA plates are coated. The temperature rise in the power supply section of EMUs during operation is roughly 35 °C. This result will provide a foundation and supporting data for the applicability of high-gradient valve plates in railroads and coating improvements for traditional arrestor plates.

Pollution usually accumulates on the surface of the insulator rapidly on high‐speed electric multiple units (EMUs) under operation condition, and the flashover can occur frequently, especially when the EMUs is running on a high‐altitude line. To solve the problem, this paper proposes the calculation method of insulator withstand voltage under the condition of non‐uniform fouling distribution of high‐speed airflow based on the characteristics of high altitude of Lanzhou‐Xin Line in China, and gives the design and test verification of insulator support insulator for 3500‐km altitude. The design and test verification of the supporting insulator of the rolling stock applicable to 3500 km altitude are presented. The result shows that the insulator should be reliable operation on 4430‐km high altitude area if the insulator structure height is 430 mm, the creep distance is 1250 mm. The anti‐pollution performance is fine in high‐speed wind if the radiuses of the large and small shed of the insulator are 196 and 145 mm, respectively, and the shed spacing is 45 mm. The 50‐Hz withstand voltage of the developed insulator is 131 kV and the light impulse voltage is 228 kV which is suitable for lines running on 3500 m. This research provides a theoretical basis and data to support the safety of high‐speed rolling stock in high‐altitude areas.