• Two year, $750,000 project to help prevent weather-related power outages on 110kV line from Tuai.
• Specialist linesmen have installed 200 interphase spacers along 91.5 kilometres of line.
• These are designed to prevent ‘galloping’ and clashing caused by wind and snow.
“Our job is to keep the lights on for the region,” is how general manager Brent Stewart sums up Eastland Network’s responsibility.
The company’s vital role covers everything from ongoing infrastructure maintenance to emergency repairs during storms; from the power poles in every street through to the high voltage transmission lines that connect our region to the national grid.
Eastland Network recently completed the first stage of a two year, $750,000 project to help protect the region’s power supply from the effects of severe weather.
This has involved installing interphase spacers along 91.5 kilometres of 110kV transmission line, on the highest spans (above 450 metres) and the longest spans (longer than 650 metres).
“The Gisborne-Tuai line has a history of trippings during snowstorms ever since it was commissioned in 1958,” says Mr Stewart.
“With some exposed spans, snow build-up can fall off one line onto the one below, causing it to flick up and clash. Extremely high winds can also cause lines to gallop and clash. These issues have resulted in power cuts to the region in the past.”
Previous modifications have significantly reduced the issue, and the interphase spacers are expected to offer further protection.
They have been tested for durability, reliability and effectiveness on several Transpower transmission lines, including in Wellington, and the concept has been adopted around the world.
Eastland Network ordered and installed 200 of the latest generation interphase spacers, which come from international suppliers.
“The project was logistically complex, and involved multiple sites across a large number of farms,” explains Eastland Network transmission assets manager Richard Leckie.
“The work was carried out over two weeks by teams of specialist linesmen from Broadspectrum, using a helicopter flown to the region specifically for this job.
“The conditions had to be perfect, with no wind or rain.”
Each morning, switching staff went to the substation in Valley Road. Following detailed safety protocols, they would turn off the power to the transmission line the crew would be working on that day. (The power to the region continued uninterrupted through the other line.)
The interphase spacers were assembled on site, then a crew of two linesmen were helicoptered into position. The helicopter hovered above the line for about 20 minutes at a time, while the team wrapped a protective layer around the line, then attached two interphase spacers.
They returned to collect two more, and repeated this process throughout the day. The interphase spacers were attached at staggered intervals, to keep the lines apart.
Each afternoon, once the crew had finished, staff returned to the substation and turned the power back on.
“We’ve completed all but one of the most exposed areas, from the Ruakituri River to Gentle Annie,” says Mr Leckie. “We have a further 112 interphase spacers to install in the second stage of the project, which will be happening when resources and weather allow.”
On Thursday, Transpower announced it will begin a $5.5 million programme of improvements at several substations and on the major transmission line into the Hawke’s Bay region. They noted that, since September 2000, four extreme weather events have resulted in significant power interruptions to the Hawke’s Bay and Gisborne districts.
“We welcome the investment Transpower is making,” says Mr Stewart. “It complements our own project and will further improve the reliability of the region’s power supply during severe weather.”