Woodville substation $2.6 million project completed

From left: Transpower project manager Garry Lamb, Brendan Olsen, Transpower Lower North Island regional service manager, Broadspectrum Project supervisor Adam Burns in front of the Last Disconnecting Circuit Breaker.

Transpower, the owner and operator of New Zealand's high voltage transmission network, completed a $2.6 million project at the Woodville substation last week.

The project included major equipment replacement for the 95-year-old facility that provides power to Woodville and areas north and is also a critical node for the wider Tararua District with connections through to Dannevirke, Waipawa and Mangamaire.

Since 2007 it has also been the connection point for around 90MW of wind generation. It was an opportunity to bring Woodville up to today's standards of maintainability.

That meant replacing older equipment for new modern equivalents. Fifty-five-year-old circuit breakers that use bulk oil as an insulator were replaced with gas-insulated options that provide more features and take up less room. Around 29,000 litres of oil were removed from site for recycling as a result – helping Transpower's drive to reduce its own environmental footprint.

"With less componentry comes less need for maintenance and accordingly the maintenance interval can now shift from a 4 year to 8-year service," said Brendan Olsen, Transpower Lower North Island regional service manager.

"While space has been saved, new space has been added to provide for easier maintenance too. Many older substations like Woodville were originally built without too much thought of the distances needed between equipment – provided you could get a ladder and spanner in – was the mantra then. "Today, use of mobile equipment like elevated work platforms provide a much safer environment for Transpower's crews. Accordingly, by extending the footprint of the facility, better access for elevated work platforms allows easier and safer maintenance.

"As well as circuit breakers, the project also saw the replacement of equipment that has not lasted as it should. Some models of 'Arteche' current transformers (that measure and regulate current on the main transformers) have proven to fail in mid-life (10 years). Transpower has a programme in place to replace these, including Woodville.

"Owing to their potential to fail without warning, the crews designed and installed a protective barrier to allow work to be undertaken safely during their removal while keeping power on to the local lines company Scanpower and the local community.

"I was pleased to get the work completed on time and to budget particularly with some of the work happening during restrictions because of Covid.

"The crews worked exceptionally well to get this project completed given all that has been happening nationally – and importantly for the people of Woodville and the wider region, they now have a much more reliable and resilient substation that will continue to provide service for many decades to come."

■ Four 110 kV bulk oil circuit breakers (largely 1965 models), and eight air disconnectors removed and replaced with four integrated gas filled disconnector circuit breakers

■ Two Arteche current transformers were replaced with newer ABB/Nissin models.

■ Switchyard extension with 2 replaced circuit breakers and old empty bulk oil circuit breaker waiting for the metal recycler.

■ Testing on the final Circuit Breaker on the Woodville – Dannevirke – Waipawa Circuit 1 prior to commissioning.

■ Temporary wall in place to allow faulty current transformers to be replaced safely.