P35.006 Lightning Performance and Grounding of Transmission Lines

Quality of Grounding Measurements: Grounding measurement methods traditionally yields a single deterministic value, offering limited insight into the uncertainty or confidence level associated with the measurement. Measurements close to the utility’s target raises questions about the necessity of returning to the field to take extra readings. EPRI is developing a method that enhances the traditional Fall-of-Potential method by embedding it within a probabilistic framework that quantifies uncertainty in the measurement. In 2027, EPRI intends to use this new method on several case studies and to publish the results in the Enhancing Lightning Performance Assessment Through Uncertainty Quantification in Grounding Resistance Measurements Using the Fall of Potential Method report.

Lightning Arc Damage to OPGW: In recent years utilities are increasingly utilizing Optical Fiber Ground Wires (OPGW) whereby the ground wire is utilized to carry a communication link. Severe damage to the OPGW could result in failure of the communication link. EPRI performed multiple lightning arc tests in the recent years to study the impact of several parameters of the tests, using the fibers as distributed sensors in some cases. In 2027, EPRI intends to review the test setup, the acceptance criteria and method to specify the class used in standardized tests to propose updates or improvements and publish this in the Lightning Arc Test for OPGW – Improvements and Class Selection report.

Test Lightning Impulse Performance of Polymer Brace Post Insulators: The lightning impulse strength of insulators provided on drawings by manufacturers is questionable. EPRI performed extensive lighting impulse testing on polymer insulators installed in I-string configurations to identify a simplified formula to estimate the critical flashover voltage to be used in lightning performance studies from their dry-arc distance. As opposed to I-strings, brace post insulators are not highlighting a unique flashover path which would make the estimation of the lightning impulse strength easier. In 2027, EPRI intends to continue testing the lightning performance of brace post insulators to help develop a formula to estimate their lightning impulse strength. 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 2027, the chapter on surge arresters is intended to be updated.

Update the Transmission Line Workstation—Generation 2 (TLW-Gen2): Lightning Performance and Power Frequency Grounding Modules: In 2027, these modules intend to 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: