Efficient and Effective

Improved Statistical Ratings for Distribution Overhead Lines

Project Data

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End date:





The project will develop a software tool that will enable GB DNOs to further optimise regional or line specific OHL ratings. The project is led by Western Power Distribution and UK Power Networks is a contributing licensee.

What is the project about?

Distribution overhead line ratings are based on CEGB research work and further assumptions described in ENA ACE 104 and ENA ER P27
published nearly 30 years ago. These ratings are now considered out of date. In the meantime, changing demands on networks are increasing the
pressure to maximise overhead line capacity. In addition, existing ratings take no account of regional differences in climate, nor of any
changes in climate that may have occurred over the last 30 years.

Distribution Network Operators (DNOs), therefore, need a cost-effective, up-to-date and robust methodology (supported with the necessary
tools) for calculating and optimising overhead line ratings at both the regional and line specific level, both for today and the future.

How we’re doing it

Under this project, an OHL test rig will be operated continuously at a set current for 24 months, with conductor temperatures and weather
conditions recorded at specified time intervals. At the end of the first 12 month period, an in depth analysis of the data collected will be

When the data collection activity has been completed, following intensive data analysis the OHRAT and OHTEMP tools (which calculate line
ratings and temperatures respectively) will be updated.
Using the data collected and analysed by the project, a more sophisticated overhead line assessment software tool will be developed.
By using predicted weather datasets, assessments could even be made about future line ratings, taking climate change into account.
In parallel with the data analysis and software tool development, the test rig will continue to gather data, with a second 12 months’ data
being used to provide further confidence in the statistical relationships established with the first 12 months’ data.

What makes it innovative

This project will develop a specific novel operational practise directly related to the operation of distribution OHLs.
For new lines, improvements in ratings could allow smaller conductors and lighter, shorter, structures to be used, providing savings in
construction costs.

For existing lines, improvements in ratings can allow reinforcement projects to be delayed; load growth and/or new connection applications
might be accommodated with increased ratings where previously the line would require reinforcement.

As the activities are being undertaken as a collaborative project, any unnecessary duplication will be avoided.

What we’re learning

This project will lead to an improvement in the understanding of overhead line conductor ratings by updating ENA ACE 104/ENA ER P27,
the OHRAT and OHTEMP tools.

This project will also enable the development of new tools for deployment throughout all GB DNOs in the form of a tailored weather
package to be produced by the Met Office and a software tool that will enable overhead line designers and operators to better manage
overhead line loading within statutory limits and design new overhead lines that are more cost-efficient.

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