The rapid growth of energy demand in China has led to a significant increase in the construction of UHVDC projects and natural gas pipelines. However, it is crucial to address the major technical challenge posed by the impact of UHVDC grounding current on natural gas pipelines, as thousands of amperes of ground current can result in high potential on these pipelines, leading to corrosion and potential damage to pipeline equipment, as well as posing risks to personal safety. Overcoming this major technical issue requires collaborative efforts from both the electric power and petroleum energy industries. The paper presents a simulation model of long-distance pipelines affected by ground current, incorporating pipeline protection measures based on the method of moments. By utilizing both the simulation model and experimental data from real long-distance pipelines, this study investigates the impact of pipeline protection measures. Consequently, comprehensive pipeline measures with superior effectiveness are identified and implemented to mitigate the influence of DC ground current in practical long-distance pipelines. Furthermore, validation of the simulation model using actual pipeline measurement data enhances its applicability in UHVDC projects and natural gas pipeline planning and operation.

The HVDC project is the backbone of new energy power transmission in the new power system and the key technology to realize the “double carbon” goal. When the HVDC system uses the earth as the loop path, DC current from the grounding electrode will be injected into the earth, possibly damaging their protective devices, thereby posing a risk to personal safety. The research work on the coupling effect between the HVDC grounding electrode and natural gas pipelines considering complex soil structure model has not been effectively carried out. In the paper, A calculation method of DC current distribution in the complex soil structure model considering the vertical partition and horizontal stratification of soil resistivity is proposed. A simulation model of the influence of the DC ground current on long-distance pipelines under complex geological conditions is established based on the method of moments. The calculation results of the simulation model, which incorporates a complex soil structure, show excellent agreement with the actual test results. The effect of pipeline measures to reduce the impact of the DC current was studied by the simulation model in depth. This provides a theoretical basis for the design and implementation of the protection measures of the pipeline.

In this paper, a 2-D time domain method is proposed to simulate Trichel pulses in the negative corona discharge on a line-to-plane geometry. Three ionic species in the ionization layer, including electrons, positive ions, and negative ions, are taken into consideration. The FEM is used to solve the Poisson's equation, while the finite volume method is used to solve the charge transport equations. Trichel pulses on a line-to-plane geometry are analyzed and compared with the measured results of a designed experiment in the laboratory. Good agreement is obtained between the calculated results and the measured ones, verifying the validity of the proposed scheme.

For the connection of remote energy sources, HVDC offers higher efficiency and flexibility compared to conventional HVAC. As the acceptance for overhead lines in Europe is often low, the detailed understanding of its environmental effects, such as audible noise is of crucial importance. Still, only few experimental studies have investigated HVDC corona. Recent publications have demonstrated, that existing prediction models for DC audible noise show strong deviations when extrapolated for higher surface gradients. While audible noise is considered negligible in rain, research has shown that the discharge amplitudes increase significantly during transitions from dry to wet weather and vice-versa.

In this paper, a 3-D iterative approach is presented to calculate the nonlinear ion-flow field around two cross-over HVdc transmission lines. The electric-field resulting from space charges is calculated by an integral method. An analytical formula to calculate the space charges along the electric-field lines determined by the electric field is derived based on a 3-D method of characteristics. The electric-field distribution and the space-charge distribution are calculated iteratively until a convergence is reached. Since both the electric field and the space charges are mainly calculated by analytical approaches, the approach greatly reduces the computing scale and can be used for 3-D calculation. The approach was validated by the experiment on a reduced-scale model. The ion-flow field at the crossing of two ±800-kV transmission lines was calculated with the method and discussed.

The movement of metal particles in the electric field of the DC gas-insulated transmission line (GIL) may cause local electric field distortion on the surface of the spacer, which seriously affects the operation stability of the GIL. In this paper, based on a ±320 kV GIL platform, the movement characteristics of metal particles (aluminum blocks, aluminum wires, aluminum balls) inside the GIL are studied. The suppression effect of particle activity for particle trapping and surface coating are experimentally studied in DC electric field. The relationship between particle trap porosity and particle suppression effect are discussed and verified with experiments. The research results show that under negative voltage, the minimum take-off voltage of metal particles in ±320 kV GIL is −190 kV, which is far lower than the steady-state operating voltage of GIL. Once the spherical and blocky particles take off, they will continue to reciprocate rapidly between the conductors. When the block particles are close to the spacer, they might be attracted and adsorbed on the surface of the spacer. Metal wires after taking off tend to show ‘firefly’ movement near the high-voltage conductor. The coating has a significant effect on increasing the take-off electric field of metal particles. It is verified that the traditional AC GIL particle trap is not effective in inhibiting particles in DC voltage. The suppression of the DC GIL particle is positively related to the porosity of the particle trap to a certain extent. The conclusions of this paper can be reference for the development of future stable and reliable DC gas-insulated equipment.