Author Archives: Laurence Howe

In order to meet the needs of moving to carbon zero over the coming years, it will be necessary to increase the power transmission capacity of the National Grid by a factor of at least two. Currently, the perceived view is that a large number of additional grid links will be needed to facilitate the increased capacity. That would require extensive planning applications and would further delay any project planning and design development. It is thought that this could involve a delay of up to fifteen years. However, there is a simpler solution that would not require any additional power lines. Of course, there would be additional work to be done on the infrastructure, but it should not involve any additional planning permissions.

Outline Solution

Additional power can be transmitted via the existing grid. Now power is the product of voltage and current, so increasing either or both would increase the capacity of the grid. However, there are problems with both potential solutions.

Increasing the voltage would be the most problematical because the distance between adjacent phases may need to be increased and the distance between the transmission lines and the pylon may also need to be increased. This is because, particularly during damp conditions or periods of high humidity, leakage between phases or between the transmission lines and the pylons may be an issue. That may involve the complete redesign and replacement of all pylons. It would also involve replacing the transformers and upgrading the voltage rating of the infrastructure within the grid substations.

Increasing the current would require increasing the diameter of the transmission lines. Such an increase may cause the physical load capacity of the pylons to be exceeded, requiring additional strengthening of the pylons and insulators.

It is clear that increasing the current would require significantly less work than increasing the voltage. Therefore, increasing the current is the preferred solution.

Practical Considerations

Doubling the diameter of the transmission lines would enable the grid to carry four times its present capacity. However, there would need to be a significant increase in the capacity of the grid substations and local transformer stations. Increased capacity between the grid and local transmission networks would also be required. The loadbearing ability of all existing pylon designs would need to be assessed to ascertain whether or not any strengthening work or insulator replacement would be necessary.

Another consideration is the connection of the onshore converter stations to the grid. It will be necessary to construct links between the converter stations and the existing grid. It is assumed here that the planning of these connections has been incorporated into the converter station project plans. However, some reconfiguration of the converter stations may also be required in order to feed increased current to each grid link.