P35.019: HVDC Lines
Objective
As new high-voltage direct current (HVDC) lines are being planned and built and existing lines refurbished, it is important to understand the performance of the line as well as the line components. Although there is experience operating HVDC lines built more than 30 years ago, knowledge gaps remain in line component selection, application, and long-term performance. Information collected from experience and research will assist the power industry in specifying, evaluating, and applying components on HVDC lines and in improving the performance of existing HVDC lines.
HVDC lines have different electric effects characteristics when compared to ac transmission lines. For example, corona from HVDC lines causes audible noise, electromagnetic interference, ozone production, and spark discharges that are similar to those of the high-voltage alternating current (HVAC) lines; however, the space charge from DC lines is unique to DC. These differences require special attention during the design and operation of the line. The objective of this project is to provide knowledge, information, and tools to assist in the design, inspection, and maintenance of HVDC lines.
This project intends to address the following knowledge gaps:
- Component performance and benchmarking of new line designs and refurbishments
- Component specifications for new construction or refurbishments
- Knowledge on safe live-work methods and procedures
- Electrical effects in the vicinity of HVDC lines
Research Value
This project could have the following benefits:
- Improve reliability by selecting appropriate components and improving system performance
- Reduce cost by providing guidance to optimize the design and operation of HVDC lines for electrical effects
- Provide members with the scientific basis for assessing the electrical effect to assist during the permitting phase of HVDC lines
Approach
This project intends to provide tools, guidelines, and methodologies that address component performance and the electrical effects of overhead HVDC lines. Components for new lines need to be evaluated beforehand to confirm compatibility and performance levels. Components on existing lines need to be tested to assess their integrity to prevent failures. In 2026, the following tasks are anticipated:
Update HVDC Electrical Effects Module in TLWorkstation: Based on the results and data obtained from the reduced-scale, full-scale, and operational line measurements, the existing algorithms used in the EPRI TLWorkstation software tool intend to be updated and the user interface improved.
Update HVDC Transmission Line Reference Information: This task intends to update the Overhead Line specific HVDC reference document which was previously published by EPRI in the early 1990s. This document details the design characteristics of existing lines, and describes the testing conducted and results obtained in determining the corona and electric field characteristics of HVDC transmission lines.
Update HVDC Line Design Guide: This task, updated each year, collects relevant information on HVDC line designs from various completed HVDC research tasks. Topics will include design aspects pertinent to HVDC and will identify areas of design that are similar between dc and ac. The guide is updated each year with new information.
Perform Live-Line Tool Testing: This task intends to test live-line tools under HVDC conditions. The plan is to investigate the effects of space charge and corona to determine their impact on the flashover performance and voltage distribution along the length of the tool. Work might also be done to determine the accuracy of voltage detection devices under HVDC conditions.
Evaluate Insulator Dimensioning for Contaminated Environments: Contamination is the main driver for insulation coordination of HVDC lines. Contamination performance of DC is vastly different from AC. This task intends to determine the latest state of the science in HVDC insulator dimensioning for contaminated environments. Testing and long-term aging of insulator materials may also be carried out.
Update HVDC Reference Book (The Olive Book): An electronic version of the updated HVDC reference book will be made available to project funders. This reference book, updated each year, contains information on overhead lines and converter stations.
Perform Hardware and Insulator Corona Tests: When specifying corona requirements for HVDC insulator hardware assemblies, many utilities use the equivalent peak ac voltage for testing. Currently, no HVDC hardware corona test specifications exist. This task intends to develop test specifications based on laboratory testing and develop guidelines to assist in specifying corona tests for HVDC hardware. In 2026, the intent is to review numerical simulations and to update the testing protocols.
Provide Tools and Resources on the Transmission Resource Center: The following calculators, tools, result summaries, and references are planned to be available on the HVDC Lines Transmission Resource Center:
| Resource Title | Resource Type |
|---|---|
| HVDC Voltage Detector Testing | Results Summary |
| HVDC Line Performance | Reference |
| HVDC Corrosion ResearchQuestions and Objectives | Reference |
Anticipated Deliverables
| Deliverable | Type |
|---|---|
| HVDC Reference Book (TheOlive Book) | Reference Book |
| TLW Gen 2 – HVDC Electrical EffectsModule | Software |
| HVDC Corona TestingEvaluation | Technical Update |
| HVDC Transmission Line DesignGuide | Technical Update |
Past EPRI Work on Topic
| Product ID | Title | Description | Published Date |
|---|---|---|---|
| 3002029614 | HVDC Anomalous Flashovers: AStudy of the Anomalous Flashovers on Manitoba Hydro's HVDC System | This technical updateinvestigates the phenomenon of anomalous flashovers on Manitoba Hydro’s HVDCsystem, focusing primarily on their characteristics, underlying causes, andthe significant challenges they pose. The report details historical and morerecent research efforts that have provided valuable data on flashover events. | December 2024 |
| 3002027146 | High-Voltage Direct CurrentOverhead Line Design Guide: AC to DC Line Conversion | This version of the guideincluded information on AC to DC line conversion. Including the factors thatgo into determining whether an AC line is suitable for DC conversion. | December 2023 |
| 3002024472 | HVDC Voltage Detector Testing | Three different HVDC voltagedetectors were evaluated as part of this study. | December 2022 |