Corrosion of tower foot in ultra-high voltage transmission lines is a critical issue for ensuring the safe operation of power grids. Recently, severe corrosion of tower foot has been observed on several UHV transmission lines in southern China, highlighting the emergence of this new problem both domestically and internationally. However, its underlying mechanism remains unclear and requires further investigation. This paper first surveyed the corrosion of on-site tower foot, and obtained comprehensive photographic documentation. The corrosion products at the tower foot were retrieved, and their surface morphology and material composition were analyzed by SEM, EDS, XRD, and XPS. The mechanism and cause of tower foot corrosion were inferred to be the soil corrosion resulting from the deposition of soil and dirty substances on the tower foot. Subsequently, our newly developed soil corrosion monitoring sensor was employed for on-site measurement of soil corrosion rate. It was observed that temperature and moisture exerted significant influence on soil corrosion, with its rate surpassing that of atmospheric corrosion. Therefore, the measurement results of soil corrosion also provided a reasonable explanation for the more severe corrosion observed at the tower foot compared to that at the other part of the tower, thereby offering empirical evidence for understanding the mechanism of soil corrosion at the tower foot. Ultimately, based on this understanding, an effective method for protecting against soil corrosion at the foot of the tower was proposed.

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 external insulation of the equipment in the valve hall of UHV DC converter station must be able to withstand AC-DC combined voltage influences. Investigating the surface discharge characteristics of external insulation under AC-DC combined voltage is currently a significant research topic. The investigation into the surface streamer characteristics under AC-DC combined voltage is instrumental in elucidating the mechanism of surface flashover. The streamer characteristics of different phases in a single cycle under AC-DC combined voltage were determined by conducting surface streamer discharge tests. The relationship between surface streamer characteristics and different phases under AC-DC combined voltage was summarized. By comparing the test results of surface streamer discharge under DC voltage, this study analyzed the effect mechanism of AC-DC combined voltage on surface streamer characteristics. The directional motion of space charge under AC-DC combined voltage was identified as the primary determinant of surface streamer characteristics.

Surface discharge was a common accident in power systems, significantly impacting the safe and stable operation of the power grid. The insulation structure of power equipment was intricate, and surface discharge characteristics were influenced not only by the insulation material but also by electrode geometry. In the paper, characteristics of streamer discharge along the insulation surface with embedded electrode were investigated under negative DC voltage. The streamer propagation field, velocity, and luminous intensity, were measured by photomultiplier tubes and ICCD camera. Unexpectedly, the disparity in the characteristics of streamer discharge along the insulation surface, with and without an embedded electrode, was substantial. Furthermore, the investigation also revealed that the length of the embedded electrode has a significant influence on the characteristics of surface streamer discharge. Through analysis, it had been determined that the presence of the embedded electrode did not significantly impact the electric field along the insulation surface. However, it had an influence on the charge distribution on the insulation surface, consequently affecting the characteristics of surface steamer discharge. The findings from this research would provide valuable technical support for enhancing external insulation design and operation strategies in DC bushings and other related equipment.

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.