From the National grid:
To help increase the capacity of the country’s electricity transmission system and to support new power generation we need to build a new 400,000 volt (400 kV) substation at Sellindge.
As well as building a new substation, we are also carrying out refurbishment work on the overhead line that runs from Sellindge to Dungeness. This includes replacing the existing wires and the fixtures and fittings on the pylons. We will also be carrying out some upgrade work on some of the pylons.
For more info, download their leaflet here.