P35.006 Lightning Performance and Grounding

Develop a Lightning Attraction Model Utilizing LiDAR Data: Lightning performance calculations are usually done on a line considered in an open terrain, which leads to conservative results for shielding failures. Typically, there are trees and objects on the sides of transmission lines, which help to reduce the shielding failure flashover rate. The TFlash module, within TLW-Gen2, allows to handle trees considered as boxes on the sides of the line model. Nevertheless, adding a precise description of the sides of a line when studying a poorly performing line is time consuming. EPRI is developing a method to use LiDAR data to evaluate the effects of trees and objects on the shielding failure rate. In 2026, EPRI intends to apply this method to a specific transmission line to identify limitations and potential improvements of the approach and publish their findings in the report Using LiDAR Data to Estimate the Shielding Failure Performance of Existing Lines.

Evaluate Electromagnetic Survey Methods to Estimate the Soil Resistivity: Unanticipated grounding electrode improvements are both costly and time consuming when constructing a new transmission line. A good estimation of the soil resistivity along the line during the planning phase of the project is necessary to correctly select a ground electrode design. Advances in electromagnetic surveying could speed up the process dramatically compared to Wenner surveys more typically used by utilities. In 2026, this task intends to continue the benchmark started in 2025, but focusing on identifying the limits of the different methods on several known simulated soil configurations. EPRI intends on publishing their findings in an updated report, Electromagnetic Survey Techniques to Estimate the Soil Resistivity.

Evaluate the Use of Ground-Penetrating Radar to Assess Existing Buried Electrodes: Ground-penetrating radar (GPR) is a noninvasive method in geophysics. It is classically used to detect the presence of pipes or cables buried in the ground to prepare road works and identify potential risks before digging. EPRI intends to evaluate if GPR could be used to identify the type of grounding electrode design buried in the soil without digging and used to locate counterpoises and check their electrical continuity. In 2026, EPRI intends to share their understanding of the technology and results from a preliminary field demonstration in a report, Using Ground-Penetrating Radar to Assess Existing Buried Electrodes.

Test Lightning Impulse Performance of Polymer Brace Post Insulators: In 2026, EPRI intends to continue testing the lightning performance of brace post insulators to develop a formula to estimate their lightning impulse strength including a unique flashover path. The results of these tests are intended to be published in the Lightning Impulse Tests on Brace Post Insulator Configurations report.

Update the Lightning and Grounding Reference Book (The Gray Book): The Gray Book was developed to be a single resource that consolidates fundamental learnings from decades of research in the area of lightning performance and grounding. To facilitate understanding of content contained in The Gray Book, calculators have been developed and are housed on The Transmission Resource Center. In 2026, The Gray Book will be available on The Transmission Resource Center and the chapter on surge arresters will be updated.

Update the Transmission Line Workstation—Generation 2 (TLW-Gen2): Lightning Performance and Power Frequency Grounding Modules: In 2026, these modules will be updated to incorporate the latest research results and correct any software and usability issues.

Provide Tools and Resources on the Transmission Resource Center: The following calculators, tools, result summaries, and references are planned to be available on the Lightning Performance and Grounding Transmission Resource Center: