Replacing familiar eyesores with the ‘supermodels' of the power world — tall, slender, tubular poles — has improved not only the appearance, but the strength, safety and capacity of the local line.
Marlborough's old steel lattice towers have brought power to the area since 1927, all the way from the Waihopai hydro station down into the Wairau Valley. Few people would consider the towers objects of great beauty, however they play a vital role in growing the local economy.
These trusty workhorses have served the area well for more than 80 years, but they are starting to show their age. Some of the footings have begun to corrode and increased conductor loadings test the line's capacity.
When Marlborough Lines embarked on the mammoth task of replacing the towers and rebuilding the line, we saw it as a perfect opportunity for improvement. We have so far replaced 10km of lattice towers with the supermodels of the power world – tall, slender, steel tubular poles that not only look good in the landscape, but ensure better performance.
The line through Blenheim and Renwick runs past wineries and lifestyle blocks, and some residents had hoped it could be replaced with underground cabling. Unfortunately, the cost to do this is prohibitive, but we have made sure the new octagonal poles – worth around $5,300 each – are both safer and more attractive. The new poles are 14 metres high, around two metres taller than the original towers, improving safety for those working under them with tall equipment such as ladders and cherry pickers. Their pale silvery colour (as opposed to dark metal) and height, helps them to blend into the surroundings more. Because they are stronger, around one-third fewer poles are required overall so they can be placed further apart. The strength of the new poles supports heavier conductors that have more than twice the capacity of the old line.
As part of the construction of the new line, all associated 400V reticulation has been placed underground, as has 11kV reticulation where it is near intersections. The Company has worked with landowners to increase the distance of the poles from the road, enhancing driver safety. Where possible, the line was relocated to overhang private property.
Rebuilding the line is not a simple task. It has to be constructed along the old route where the Company already has obtained easements; increasing both costs and complexity. Minimising disruption to customers is a top priority. The first stage of the project took eight months to complete, partly due to our desire to stagger the work; reducing the impact of power outages. Supply to a number of important customers had to be maintained throughout the first construction phase using alternative sources, including the Company's portable 1MVA diesel generator on two occasions. Temporary switches were installed to reduce the area affected during each shut-down.
The completed cost of the new style towers for stage one was in excess of $2.5m. The project has generated a positive response from those living and working nearby and the new poles will serve the region for at least the next 80 years.