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 improving the performance of existing HVDC lines.
HVDC lines have different electric effects characteristics compared to alternating current (ac) transmission lines. For example, corona from HVDC lines causes audible noise, electromagnetic interference, ozone production, and spark discharges similar to those of the HVAC lines; however, the space charge from direct current (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 costs by providing guidance to optimize the design and operation of HVDC lines for electrical effects
- Provide members with the scientific basis for assessing electrical effects to assist during the permitting phase of HVDC lines
Planned 2025 Research
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 must be evaluated beforehand to confirm compatibility and performance levels. Components on existing lines must be tested to assess their integrity to prevent failures.
Tasks undertaken could include the following:
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.
Anomalous HVDC Flashovers: Unknown flashover events have occurred on several HVDC lines around the world. This task is intended to document the various cases of unknown flashovers and analyze the data to determine trends that could identify possible causes of these events.
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 flashover performance and voltage distribution along the length of the tool. Work might also be performed to determine the accuracy of voltage detection devices under HVDC conditions.
Insulator Dimensioning for Contaminated Environments: Contamination is the main driver for insulation coordination of HVDC lines. Contamination performance of dc is vastly different from that of 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 performed.
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.
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 are intended to be updated and the user interface improved.
HVDC Transmission Line Reference Guide: This task intends to update the Overhead Line HVDC reference book, 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.
Anticipated Deliverables
| Deliverable | Type | Date |
|---|---|---|
| HVDC Reference Book (The Olive Book) | Reference Book | December 2025 |
| TLW Gen 2: HVDC Electrical Effects Module | Software | December 2025 |
| HVDC Overhead Lines Reference Book | Technical Update | December 2025 |
| HVDC Transmission Line Design Guide | Technical Update | December 2025 |
Past EPRI Work on Topic
| Product ID | Title | Description | Published Date |
|---|---|---|---|
| 3002027146 | High-Voltage Direct Current Overhead Line Design Guide: AC to DC Line Conversion | This version of the guide includes information on AC to DC line conversion, including the factors that go into determining whether an AC line is suitable for DC conversion. | December 2023 |
| 3002024472 | HVDC Voltage Detector Testing | Three different HVDC voltage detectors were evaluated as part of this study. | December 2022 |
| 3002021589 | HVDC Hardware Corona Testing | Tests were performed to develop corona testing specifications for HVDC lines. | December 2021 |