Nuts and Bolts
South Island Work
The clearance review works on the overhead HVDC line between Benmore and Fighting Bay involve a number of different techniques to effectively raise the conductor. This will establish increased electrical clearances between the conductor and the ground or lower voltage lines beneath.
There are a number of different means of raising the conductor. On this line this includes:
- converting the existing insulator sets to shorter composite insulators
- other insulator configuration changes
- raised or replacement towers
- earthworks under the conductors
- vegetation trimming
- realigning low voltage lines
- combinations of the above options
All proposed works will be discussed with the relevant land owner before being finalised.
North Island Work
The work to replace the conductor on sections of the overhead HVDC line between Oteranga Bay and Haywards in the North Island is known as reconductoring. The sections of line requiring this work are:
- The first 5 kms from the Oteranga Bay cable station towards Makara
- A 10 km section from close to Makara township to the back of Johnsonville (but not including Churton Park)
- The final 10 km section into Haywards substation.
Running blocks are installed on each tower and then the existing conductor is connected to the new conductor. At designated wiring sites (every few kilometres), heavy tensioning equipment is positioned to pull the conductor through the running blocks. Once the conductor is tensioned correctly, the running blocks are removed and the conductor is clamped into position. All insulators and associated hardware would be replaced.
Because of the importance of the HVDC line to New Zealand's power supply, the programmed work may involve the installation of temporary towers.