Overview
Our project to increase the capacity of our two lines between Tokaanu and Whakamaru involves:
- Undertaking the work needed to allow the lines to operate at a higher temperature - what we call a 'thermal upgrade' (Stage 1)
- Doubling the number of wires on the line to provide more capacity (Stage 2)
Stage 1: Operating the lines at a higher temperature - 'thermal upgrade'
When we run our transmission lines hotter they can carry more electricity but the wires will sag more (steel expands when heated), bringing them closer to ground. In some cases, the wires will be too close to the ground and we will need to do work on the towers to make them taller, adjusting how the wires are held at the tower, or earthworks on the land underneath. Alongside this, we may also need to strengthen the towers by reinforcing them with extra steel, or strengthening their fourndations with concrete (or more concrete). You can read about the types of work we have to do to these lines to increase their height.
Stage 2: Doubling the number of wires - 'duplexing'
By adding more wires to the existing lines, we can get a big increase in capacity - moving up to 150% more electricity. Doing this does add more load to the towers, so just like the work to run the lines hotter, we need to do some further work to strengthen the towers (more steel) and foundations (concrete or more concrete). You can read about the types of work we have to do to these lines for this work.