Oct 2013
Electricity Transmission
Enhanced AC and DC safety voltage limits assessment
Oct 2013
Oct 2015
National Grid Electricity Transmission
Jude Robinson: box.eto.innovationteam@nationalgrid.com
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Network Innovation Allowance
ET - Network improvements and system operability
Electricity Transmission Networks
Currently, we do not specify what the ground surface needs to be when construction of a new substation is being undertaken. This work would give us an appropriate basis to be able to publish a policy document that could state what materials are and aren’t appropriate for use in substations where HVDC systems are in use. It would give us a good understanding of the types of problems we are looking for when specifying ground surfaces, and also allow the tool to be used in exercises when deciding what surface to use. Because surfaces would have a standard set of measurements associated to them, which judging would be based on, it would be fairly simple to incorporate new materials into the tool for consideration when they arise. We would simply test the new material electrically, and then input the parameters into the software.

There are three main objectives that this project is aiming to deliver, with one stretching objective. These are (in no particular order) to produce a standard for ground surfaces in terms of earthing of an AC/DC system. Secondly, to quantify the existing electrical performance of commonly used substation materials. Lastly, to develop a piece of software that calculates and quantify these safety voltage limits.

The stretch target for this project is to make the standard internationally acceptable throughout the electrical community.


The research being done in this project will aim to quantify the electrical resistance of ground surfaces currently installed on the network, and then provide a calculating tool that can produce safety criteria under AC & DC conditions, a variety of site use scenarios and a realistic range of surfacing materials.

The project will be successful if, at the end of the project, we have the tool for quantifying the electrical resistance of the ground surface, a dataset of common materials, and a recommendation for changes that are needed to the National Grid policy document.