P35.018: Line Switches
Objective
Transmission line switches are critical assets for the resilience of the transmission system, given that they minimize outage impacts by remotely isolating faulted line sections following outage events or serving as mechanisms for control of load flow. Therefore, line switches are important systems designed to enhance the resilience of the grid. Conversely, line switches may introduce additional issues and jeopardize the installation if not properly designed, installed, or maintained. Moreover, the many options of configurations and manufacturers pose an additional challenge with respect to asset management because different switches can have different installation and maintenance requirements.
This project aims to support utilities in reducing maintenance costs and maximizing the reliability of line switches through engineering tools and information for design, testing, installation, inspection, assessment, and troubleshooting.
Research Value
Research related to the selection, installation, and maintenance of line switches aims to:
- Enhance safety for utility workers and the public through safe switching operation
- Improve the reliability of electric service through effective specification, design, installation, and operation of line switches
- Lower “early failure” because of optimized commissioning protocols of new line switches
- Improve reliability and reduction in maintenance costs by increasing the effectiveness of inspection and condition assessments
- Reduce capital and operational expenditures through enhanced understanding of performance, component aging, and deterioration mechanisms of line switches
Planned 2025 Research
This project aims to support utilities in reducing maintenance costs and maximizing the reliability of line switches through a variety of tasks:
Quick Break Whip Device Testing: This task intends to develop guidelines and determine, through laboratory testing, the performance and current handling of quick break whip arc interrupting devices. Because there is currently no test methodology for evaluating quick break whips, this research is intended to advance the knowledge and understanding of laboratory evaluation of these devices. In 2025, EPRI intends to focus on the electrical and mechanical endurance of different whip manufacturers.
Inspection and Maintenance Considerations for Line Switches: This task investigates the use and application of existing, new, and emerging technologies for inspecting, assessing, and monitoring the health conditions of line switches. The information obtained is intended to be compiled into a comprehensive guide to form the basis for understanding components, inspection, and monitoring techniques. Technologies such as unmanned aerial systems, testers, and sensors are intended to be explored. In 2025, EPRI intends to work on additional detailed inspection procedures for specific components and include new line switch models in electronic form for the inspection of line switches.
Transmission Line Switch Vintage Guide: This task aims to develop a comprehensive technical resource intended to provide guidance and strategies on procedures to assess the condition of transmission line switches in service by model and vintage. For that, underlying failure and degradation modes and mechanisms have been identified and catalogued by component to help estimate life expectancy and required maintenance actions. In addition, this task assists utilities in the performance of root cause and failure analyses. In 2025, EPRI aims to include results of additional forensic investigations and compile case studies provided by utilities.
Catalog of Component Degradation Modes: This task seeks to catalog degradation modes of line switch components from different manufacturers. The information will be gathered through findings from forensic investigations and utility reports and organized in the Transmission Resource Center (TRC) website.
Practical Installation Guide of Line Switches: This task intends to provide the technical basis and guidelines to support field engineers and technical staff with information regarding component specification, design, installation, and commissioning protocols of new equipment, as learned through best practices. In 2025, EPRI intends to include technical information about line switches with permanent bypass capabilities and initiate design templates for different switch manufacturers.
Motorized Switches Evaluation: This task seeks to gain a better understanding of the functionality of and inspection techniques required for motorized switches compared to manually operated switches. Possible topics include the additional components needed for motorization such as batteries, supervisory control and data acquisition (SCADA) systems, and alternatives of power supply. Findings from this task are anticipated to be shared through the Inspection and Maintenance Guide and the Line Switch Vintage Guide technical updates.
Anticipated Deliverables
| Deliverable | Type | Date |
|---|---|---|
| Quick Break Whip Testing: Electrical and Mechanical Endurance | Technical Update | December 2025 |
| Inspection and Maintenance Guide | Technical Update | December 2025 |
| Transmission Line Switch Vintage Guide | Technical Update | December 2025 |
Past EPRI Work on Topic
| Product ID | Title | Description | Published Date |
|---|---|---|---|
| 3002027140 | Quick Break Whip Device Testing: Laboratory Testing and Preliminary Analysis | This report explains the duty and relates the role of arc behavior and its interaction with the source and load-side capacitances to current interruption using whip-type auxiliary interrupting devices. In 2023, preliminary results and findings from a pilot test performed on a 115-kV vertical break disconnect switch equipped with a standard quick break whip were presented and discussed. | November 2023 |
| 3002027141 | Practical Maintenance Guide for Installation of a Transmission Line Switch: Vacuum Interrupters and Utility Experience | This practical maintenance guide seeks to provide solid information about line switch components and configurations and practical guidance on the siting, installation, and commissioning of new line switches. | November 2023 |
| 3002027142 | Vintage Guide: Development of the Outline | This is the first report of a series that aims to establish a comprehensive reference guide for utilities on the diagnosis of root cause and failure analyses of high-voltage switches installed in overhead transmission lines, establishing relationships with aspects such as specification, design, and installation and maintenance protocols by reporting the experience and findings of utility, consulting, and equipment engineers. | November 2023 |