Science Centres: Energy

More power down the line

NIWA staff recently spent about 20 days in the backblocks providing meteorological measurements for line surveys commissioned by Transpower. The aim is to get maximum use out of the existing lines and to increase the reliability of the power supply.

Transpower wants to know how much extra power it can put down the lines before the lines sag so much (as a result of heating up) that they get too close to roads, buildings, trees, and the like. The temperature and sag of the lines are influenced by the ambient air temperature, heating by the flow of electric current, heating by the sun, and cooling by the wind.

The surveys are a major undertaking. This year, the main contractor was a UK company, Network Mapping, and previously we've worked with a Russian firm, Opten. A helicopter equipped with an aerial laser survey unit pinpoints the position of the lines and other features to within millimetres, supported by baseline GPS stations set up by Connell Wagner.

NIWA’s part is to supply the vital weather information. We establish up to 20 temporary weather stations each day to take ground-level measurements along the helicopter’s route, and we use a 'helikite' to measure the temperature and wind up to an altitude of about 60 metres. We supplement this with data at 10-minute intervals from permanent electronic weather stations in our National Climate Network. The work is an example of how careful application of meteorological data collection and modelling can contribute to key national infrastructure.