In the realm of electrical infrastructure, power grounding systems play a crucial role in maintaining both safety and reliability. These systems provide a pathway for electrical fault currents to flow into the earth, thus preventing potential hazards such as electrical shocks, fires, and equipment damage. For critical electrical subsystems, like substations, having a proper power grounding system in place is essential.
One key aspect of designing effective power grounding systems is the investigation of soil resistivity. This parameter is crucial as it helps in determining the most suitable sites for grounding systems. Sites with lower soil resistivity are preferred due to their cost-effectiveness and efficiency in ensuring optimal performance and safety. Accurately determining soil resistivity is essential, as inaccurate values can lead to faulty grounding systems.
In Thailand, the Electricity Generating Authority has established a threshold of less than 80 Ohm-meters for soil resistivity in substations. However, in practice, soil resistivity often fails to meet these requirements, highlighting the need for more robust assessment methods. Various studies have explored the relationship between soil resistivity and different geotechnical properties like water content, unit weight, salt content, clay content, and particle sizes. While these studies have provided valuable insights, there is still a need for a comprehensive predictive model that integrates these relationships.
A recent study led by Professor Shinya Inazumi from Shibaura Institute of Technology addressed this challenge by conducting a thorough investigation into the behavior of soil resistivity and its relationship with geotechnical parameters. The researchers developed a predictive model based on their findings, aiming to accurately predict soil resistivity under field conditions. This model has significant implications for designing grounding systems in regions with diverse soil types, such as Thailand.
The researchers analyzed 30 soil samples from various locations within a power grid substation in Thailand. They found a clear relationship between soil resistivity and water content, with resistivity increasing as water content decreased. While the correlation between resistivity and plasticity index or dry density was less significant, a combination of water content, plasticity index, and dry density proved to be a reliable predictor of soil resistivity.
Despite the promising results of the predictive model, the researchers acknowledged its limitations. The model was only able to predict soil resistivity for cohesive soils with fine particles due to the limited variety of soil samples used. However, this limitation can be addressed in future research by including a broader and more diverse set of soil samples.
The study’s findings offer a method for optimizing substation grounding designs, which is crucial for protecting equipment and personnel from electrical faults. By reducing the need for extensive soil testing and modifications, costs can be minimized while maintaining regulatory compliance. Additionally, the predictive models developed in the study could have broader applications in environmental monitoring.
Proper soil resistivity assessment is essential for the construction of ground systems in electrical substations. By developing robust predictive models that consider various geotechnical parameters, engineers can ensure the cost-effective and efficient design of grounding systems. This not only enhances the safety and reliability of power supply but also contributes to stable economic growth. The study’s breakthrough in soil resistivity assessment marks a significant step towards achieving these goals.