The temperature properties of real-type direct-current gas-insulated transmission lines (DC-GIL) with a basin-type spacer were investigated by the finite element method in this paper. A horizontally installed model was established and the temperature distribution was obtained with a 3D model. The specific heat capacity and thermal conductivity of the spacer were measured and applied in the simulation. The results show that the temperature of the convex surface was slightly higher than that of the concave surface. With an increase in the SF₆ pressure, the temperature of the spacer decreased, which can be attributed to the improvement of convection due to increases in the heat capacity per unit volume. With an increase in the ambient temperature, the temperature of the spacer increased linearly. The temperature difference between the inner and outer parts of the spacer increased with increases in the load current. Besides, an obvious increase in the surface electric field strength appeared under the influence of the thermal gradient compared to the results without the thermal gradient. Thus, special attention should be paid to the insulation properties of the spacer considering the influence of temperature distribution. This study evaluates both the thermal and insulation characteristics of the GIL along with the spacer under various conditions.

SF₆, which is currently widely used in gas-insulated power transmission equipment, is a greenhouse gas with a very strong greenhouse effect. Therefore, developing environmentally friendly gas insulation equipment to gradually reduce the use of SF₆ has become a hot research topic. As the most potential alternative gas, C₄F₇N is of great significance to study the electrical characteristics of the medium-voltage switching field to promote the green development of the power industry. Based on multi-physical field coupling to construct the 40.5 kV circuit breaker mode, this paper uses C₄F₇N/CO₂ mixed gas to compare and study the dynamic characteristics of a C₄F₇N/CO₂ mixed gas circuit breaker when breaking the short-circuit current and the dielectric recovery strength with no-load breaking, as well as to evaluate the electrical performance of C₄F₇N mixed gas in a 40.5 kV breaker with the gas breakdown criterion. The results show that mixing O₂ in a high current can improve the breaking performance of an environmental protection circuit breaker and increasing the C₄F₇N mass fraction can enhance the dielectric recovery strength of the environmentally friendly circuit breaker. Considering the overall performance of the gas, the 5%C₄F₇N/90% CO₂/5%O₂ mixed gas has some alternative potential.

Under DC voltage, charges accumulate on the surface of insulators inside gas-insulated switchgears (GIS) and gas-insulated transmission lines (GIL). Therefore, the influence of surface charge needs to be considered when evaluating the insulation characteristics and structural optimization. However, the traditional method of calculating surface charge by ion-flow model (IFM) occupies too much memory and takes a long calculation time, which limits the development of related study. Thus, this paper develops a fixed gas conductivity model (FGCM) based on the IFM. With the gas conductivity at 4×10⁻¹⁹ S/m and based on the basin-type insulator, the calculation results of the FGCM are compared with those of the IFM under various conditions. The results show that the calculation results of the FGCM are in good consistency with the IFM under various conditions such as changing the shape and conductivity of the insulator, changing the applied voltage, considering the temperature gradient and transient simulation. The memory usage of the FGCM is significantly lower than that of the IFM, and the calculation time is reduced by several orders of magnitude. This study can provide guidance for the design and optimization of DC-GIS/GIL insulators.

Grid-forming (GFM) energy storage can be utilized as a backup power source for the power grid to ensure the security of the power grid. GFM energy storage can also enhance the strength of the power grid and improve its stability. However, the GFM energy storage inherits the characteristics of the synchronous generator. Low-frequency oscillations may occur in GFM energy storage, which affect the stable operation of the power system. This paper proposed an additional damping control strategy for GFM energy storage to address the low-frequency oscillation. Firstly, this paper builds the state-space small-signal mathematical model of the GFM energy storage grid-connected system to analyze the participation factors of the low-frequency oscillation mode and clarify the key control parameters affecting the GFM energy storage grid-connected system the low-frequency oscillation. Then, this paper proposed an additional damping control strategy to increase the damping ratio of the low-frequency oscillation mode and improve the stability of the GFM energy storage grid-connected system. Finally, semi-physical experiments verified the effectiveness of the proposed additional damping control strategy.

The fast circuit breaker can achieve the rapid removal of short-circuit faults, which is of paramount significance for ensuring the safe and stable operation of the power system. This paper proposes a design scheme for the arc extinguishing chamber of the 550 kV fast circuit breaker, establishes a mathematical model of magneto-hydro-dynamics (MHD) arc, and calculates the trends of gas pressure, arc temperature, and nozzle airflow velocity inside the fast interruption arc extinguishing chamber under different arcing times. It compares and analyzes key interruption parameters such as airflow field characteristics, arc conductance, and post-arc current, researches the interruption performance of fast circuit breakers under different arcing times, and determines the prototype design scheme. It is found that the design scheme of the arc extinguishing chamber with the opening speed of 13.5 m s⁻¹, inflation pressure of 0.6 MPa, overtravel of 33 mm, cylinder radius of 80 mm, and nozzle throat length of 27 mm can compress the short arcing time to 6 ms, while maintaining good interruption performance for medium and long arcing, meeting the requirements of fast interruption. The prototype successfully passed the T100(s) interruption test, achieving a short arcing time of 6.2 ms, as well as corresponding medium and long arcing interruptions, verifying the effectiveness of the simulation calculations. The 550 kV fast circuit breaker successfully reduced the total interruption time to within 25 ms, and the research results successfully guided the development of the fast circuit breaker prototype.

Benefiting from their good mechanical and electrical properties, epoxy resin materials are widely utilized in the field of high-voltage electrical insulation devices. However, with the increase in voltage levels of equipment, the epoxy resin materials used for insulating pull rods in high-voltage electrical equipment are facing increasingly severe challenges. This study enhanced the mechanical and insulating properties of epoxy resin materials by molecular structure regulation, composite incorporation and formula optimization. The tensile strength, bending strength and impact strength of the epoxy resin materials with molecular structure regulation increased by 20.6%, 8.5% and 42.1%. The breakdown strength successfully increased from 27.6 kV/mm to 29.9 kV/mm. After combining with the modified Al₂O₃ nanofillers, the breakdown strength, surface resistivity and volumetric resistivity of the composite further improved to 35.8 kV/mm, 2.7 × 10¹⁶ Ω and 5.8 × 10¹⁷ Ω·cm. The insulating pull rod prepared by this method achieved a flashover voltage of 18.5 kV, meeting the requirements for both insulating and mechanical performance of a prototype of 200 kV high-voltage direct current floor tank-type high-speed mechanical switch. This study can provide important support for the optimization of epoxy resin material formulation design and the development of epoxy-resin-insulating pull rods.