A coupled electrothermal damage theory model for pipelines is proposed to assess the failure behavior of buried pipelines under lightning strikes. This article considers local thermal nonequilibrium (LTNE) conditions in the soil-water porous medium and the nonlinear characteristics of lightning functions. The calculation results show that the proposed theoretical model has better applicability and accuracy compared with previous models. Parametric analysis shows that under lightning conditions of Im = 20 kA and T1/T2 = 1.2/50 mu s, the maximum local temperature of the soil around the pipeline can reach 2160 K, leading to pipeline breakdown. Metal pipelines are shown to be more effective in conducting charges, which alters the electric field distribution in the soil and impacts the formation of plasma channels. The half-peak value of the lightning waveform has a significant impact on pipeline breakdown, and its increase will increase the risk of pipeline breakdown gradually. When considering LTNE conditions, the change in the pipeline surface temperature becomes more pronounced. Under 8/30 and 8/40 mu s lightning waveforms, the pipeline surface temperature is approximately 150 and 550 K higher, respectively, compared with the thermal equilibrium conditions. The thermal conductivity and porosity of backfill soil can also affect the thermal damage of lightning-struck pipelines. With clay filling, the highest pipeline surface temperature can reach 2590 K, while with fine sand and coarse sand, it is 1980 and 1510 K, respectively. The pipeline lightning disaster model proposed in this article has engineering significance for the investigation of pipeline lightning failure and disaster prevention mechanisms.

This paper presents a comprehensive assessment of the accuracy of high-frequency (HF) earth meters in measuring the tower-footing ground resistance of transmission line structures, combining simulation and experimental results. The findings demonstrate that HF earth meters reliably estimate the harmonic grounding impedance (R25kHz) at their operating frequency, typically 25 kHz, for a wide range of soil resistivities and typical span lengths. For the analyzed tower geometries, the simulations indicate that accurate measurements are obtained for adjacent span lengths of approximately 300 m and 400 m, corresponding to configurations with one and two shield wires, respectively. Acceptable errors below 10% are observed for span lengths exceeding 200 m and 300 m under the same conditions. While the measured R25kHz does not directly represent the resistance at the industrial frequency, it provides a meaningful measure of the grounding system's impedance, enabling condition monitoring and the evaluation of seasonal or event-related impacts, such as damage after outages. Furthermore, the industrial frequency resistance can be estimated through an inversion process using an electromagnetic model and knowing the geometry of the grounding electrodes. Overall, the results suggest that HF earth meters, when correctly applied with the fall-of-potential method, offer a reliable means to assess the grounding response of high-voltage transmission line structures in most practical scenarios.

In this investigation, the electromagnetic effects of lightning on uncoated and PVC-coated high-steel metal buried pipes are numerically modelled and analyzed at varying earth surface depths of 1-2 m and varying PVC coating material thicknesses of 0.001-0.002 m. A typical lightning-injected current waveform was taken into consideration, and the corresponding return stroke current along the channel at different heights was thoroughly studied initially when it struck the earth's surface to validate the model. The study found that the density of induced current and field strength below the earth's surface is significantly impacted by the depth, with shallower depths having greater influence. The field strength and density of the induced current decrease with increasing depth. As seen, the insulation of PVC-coated metal buried pipe facilitates a higher density of induced current on the upper surface of the PVC coating, particularly for the finite earth surface conductivity (0.01 Sm-1). For finite earth surface conductivity (0.01 Sm-1) and a PVC-coated thickness of 0.0015 m at a fixed 0.105 m PVC coating diameter, the density of induced current at the mid- of the PVC top surface reaches about 6696.37 Am-2. Additionally, the density of induced current at the mid- of the pipe top surface was found to be about 14 Am-2, significantly lower than 5047.09 Am-2 for the uncoated metal buried pipe at the same depth. PVC-coated metal buried pipe has significantly lower induced currents than uncoated metal buried pipe at shallower depths. The proposed structure and reported analysis of PVC coating thickness may be beneficial in developing the mechanism of failure and designing a prevention plan for high-steel metal buried pipes from burns or physical damage.

Two types of grounding systems are recommended for use in the international standard IEC 62305-3, Part 3: Physical damage to structures and life hazard. One of these is a radial-based grounding system (type-A), which is used in soil resistivities of up to 3000 Omega m and is considered in this paper. It is a well-known fact that during lightning strikes, only a part of the grounding wire contributes to dissipating the lightning current into the surrounding soil. This effective part of the grounding system depends on several features, such as soil resistivity, burial depth, and rise time of the dissipated lightning current. The effect of all of these features on the effective length of the type-A grounding system is explored in this paper. A suitable supervised machine learning regression model is developed, which will enable readers to accurately approximate the effective length of the type-A grounding system for realistic values of input features. The trained model in the paper yielded an R2 value of 0.99998 on the test set. In addition, two simple mathematical formulas are also provided, which produce similar but less accurate results (R2 values of 0.989883 and 0.998557, respectively).

The electrical network, essential to our society, frequently encounters disruptions from lightning strikes, resulting in material damage and power blackouts. Swift diversion of lightning currents to the ground is imperative to safeguard the grid. This study proposes a proportionality coefficient (K) to effectively distribute lightning current between grounding and network flow. The optimality of this coefficient depends on the tower grounding system resistances; lower resistances facilitate optimal distribution, enabling more current to flow to the ground. In the examination of the Djiri-Ngo power line in the Republic of Congo, grounding systems were optimised based on soil types. Three electrodes were used for clayey sand, while fifteen were employed for siliceous sand. Optimal coefficients were determined to be 0.86 for clayey sand and 0.81 for siliceous sand. These coefficients denote that 86% and 81% of the lightning current were directed to the ground, in contrast to non -optimal resistances (69% and 29% with a single grounding electrode). The experiments highlight the importance of adapting grounding systems to soil characteristics, rather than adhering to a uniform approach. Efficient diversion of lightning current to the ground is paramount for grid protection.

Lightning strikes can cause equipment damage and power outages, so the distribution system's reliability in withstanding lightning strikes is crucial. This research paper presents a model that aims to optimise the configuration of a lightning protection system (LPS) in the power distribution system and minimise the System Average Interruption Frequency Index (SAIFI), a measure of reliability, and the associated cost investment. The proposed lightning electromagnetic transient model considers LPS factors such as feeder shielding, grounding design, and soil types, which affect critical current, flashover rates, SAIFI, and cost. A metaheuristic algorithm, PSOGSA, is used to obtain the optimal solution. The paper's main contribution is exploring grounding schemes and soil resistivity's impact on SAIFI. Using 4 grounding rods arranged in a straight line under the soil with 10 Omega m resistivity reduces grounding resistance and decreases SAIFI from 3.783 int./yr (no LPS) to 0.146 int./yr. Unshielded LPS has no significant effect on critical current for soil resistivity. Four test cases with different cost investments are considered, and numerical simulations are conducted. Shielded LPSs are more sensitive to grounding topologies and soil resistivities, wherein higher investment, with 10 Omega m soil resistivity, SAIFI decreases the most by 73.34%. In contrast, SAIFIs for 1 klm and 10 klm soil resistivities show minor decreases compared to SAIFIs with no LPS. The study emphasises the importance of considering soil resistivity and investment cost when selecting the optimal LPS configuration for distribution systems, as well as the significance of LPS selection in reducing interruptions to customers.

The induced voltage generated by lightning electromagnetic (EM) field often damages photovoltaic (PV) panels. To address this issue, a novel solar-cell string wiring is proposed. By the crossover connection of solar-cell strings, the induced voltages are offset by each other. The lightning EM transient of PV array installed on flat ground is computed by using the method of moments. Compared with the conventional wiring, the proposed wiring can not only reduce the induced voltages of most PV panels but also the voltage between the outputs of PV array. The proposed wiring is highly recommended to be used in the PV array on the soil with great resistivity. Moreover, the effect of the proposed solar-cell string wiring on rooftop PV array is assessed. The results indicate that the rooftop PV array with the proposed wiring has a minimum induced voltage. This novel solar-cell string wiring does not require additional protection devices and is easy to implement.

To study the damage mechanism of soil when struck by lightning, this paper proposes an electro-thermal coupled numerical model of soil for solving the problem. The double exponential function is used to represent the naturally occurring lightning waveforms. The novel numerical computational model indicates the electrical disasters and damage mechanism of soil under lightning action. The calculation results show that under the action of lightning, the soil produces electrical penetration and causes thermal damage. In addition, a machine learning strategy has been devised to evaluate changes in soil damage conditions, and a formula for soil damage tensor related to the basic electrical parameters of soil is provided. The innovative numerical modeling reveals the mechanism of soil failure and electrical penetration during lightning strikes and and provides theoretical support for mine mitigation.

Over the past twenty years, there have been numerous instances of damage to the outer sheath of cables, the cause of which remains unknown. Surprisingly, some of these cables were not even in use at the time of the incidents. Most of the damages occurred in areas with a high frequency of lightning strikes. To address this issue, a research study is currently underway to examine the impact of direct lightning strikes on medium voltage cables and develop protective measures. As part of the study that is ongoing, we are developing a simulation model that takes into account factors such as soil ionization, lightning parameters, and moisture to mimic realistic lightning strikes on the ground. The main aim is to utilize the acquired knowledge to aid in selecting suitable cable design for future projects.

Forest fires lead to permafrost degradation and localized drought, and regional droughts increase the probability of forest fires, leading to a positive feedback loop between climate change and fires. However, the relationship between fire occurrence and climatic factors change is unclear for boreal forests, which represent the largest land-based biome and stock of carbon. Here, we analyzed the relationship between lightning fire occurrence and meteorological and topographic factors based on the fire frequency, burned area, and meteorological data from the primeval forest region of the northern Daxing'an Mountains in China. We found that lightning fires occurred most frequently at an altitude of 600 to 700 m. From 1999 to 2019, the frequency of lightning fires showed an overall upward trend, whereas the affected area had no obvious change. It can be attributed to fire suppression efforts and greatly increased investment in fire prevention in China. Snow cover had a strong regulatory effect on the start and end dates of lightning fires for seasonal cycle. The frequency of lightning fires was positively correlated with the average temperature, maximum temperature, and surface evaporation and negatively correlated with precipitation and surface soil moisture (0-10 cm). The result will be useful in the spatially assessment of fire risk, the planning and coordination of regional efforts to identify areas at greatest risk, and in designing long-term lightning fires management strategies.