P35.012: Porcelain and Glass Overhead Transmission Line Insulators

Evaluate the Performance of Rubber-Coated Insulators: Rubber coated glass insulators are relatively new with limited global experience. This task aims to collect information from utilities about the performance of rubber coated glass insulators used in their service territories. The information can help utilities develop informed guidance to reduce installation and handling damage, understand the useful lifespan of the rubber coatings, and evaluate if coating degradation introduces performance concerns at end of life.

Study Glass Insulator Failure: As the use of glass insulators continues to increase, utilities are likely to experience a higher number of shattering incidents. Understanding the underlying cause helps the utility implement appropriate corrective actions. Because shattering typically destroys the insulator itself, post‑failure assessment relies heavily on examination of the remaining stub. EPRI is developing and refining methods to interpret fracture patterns in the residual glass to identify the cause of the shattering. Building on existing data and experience, this task aims to improve the accuracy and consistency of failure cause determination, enabling utilities to select more effective and targeted mitigation strategies.

Using Steep Front Impulse Flashover Test to Assess Insulator Quality: Steep impulse testing is useful for assessing the quality of porcelain and glass insulators. As manufacturing location or technology changes over time there can be changes in insulator quality. Testing samples of new batches allows utilities to monitor these changes and identify potential quality‑related risks. In recent years, utilities have increasingly adopted glass insulators and EPRI intends to expand steep impulse testing of newly manufactured glass insulators to document performance characteristics and track quality trends over time.

Update the Insulator Calculation Engine (ICE): With the emergence of rubber-coated glass insulators, controlling corona to reduce rubber degradation becomes crucial. This tool helps calculate electric field stress along an insulator string to determine the need for grading devices. EPRI continually updates this tool based on user feedback to ensure ease of use and relevance.

Update the Insulator Reference Book (The Violet Book): This comprehensive guide provides state-of-the-art information on insulator selection, inspection, and maintenance to help utilities better specify, install, and manage transmission line insulators. Revisions to the book intend to include mechanical considerations when selecting insulator for different configurations.

Provide Tools and Resources on The Transmission Resource Center: The following calculators, tools, result summaries, and references are planned to be available on the Glass and Porcelain Insulator Transmission Resource Center: