News

Major transmission infrastructure project pending
By Iain MacIntyre

Transpower New Zealand is expecting later this year to embark on a $683 million project to establish a new electricity transmission line between Whakamaru and Auckland.

The development, which is currently awaiting Board of Enquiry approval, would be the largest transmission infrastructure project undertaken in the country since Pole 2 of the high-voltage direct current was replaced in 1991.

A major component of the three-legged project entails establishing a 185-kilometre double-circuit overhead transmission line from a new substation near the existing Whakamaru facility to a new transition station at Brownhill Road (near the South Auckland urban boundary).

Initially geared to handle 220kV, the line would ultimately be capable of 400kV operation at about 2700 MVA per circuit. It would be supported by 426 steel lattice towers ranging in height from 25 to 70 metres, set at spans ranging from 54 to 837 metres, that would traverse 297 properties.

A second element of the project involves the laying of two underground cables from the new transition station at Brownhill, which would be of 220kV operation and have a continuous (uncooled) rating of about 660 MVA per circuit.

The first 9.5-kilometre section of cables would connect to the Pakuranga substation, rather than Otahuhu, which would allow diversity of supply with the second section of cables connecting to the Otahuhu substation at a later date, as dictated by demand.

A final significant component of the project entails developing necessary substation and transition station facilities, including a 220kV Air Insulated Switchgear (AIS) switching station near the existing Whakamaru substation. A transition station at Brownhill Road would also be extended to a 220kV Gas Insulated Switchgear (GIS) switching station when the Otahuhu cables were installed, and the existing Pakuranga Substation would be upgraded from 110kV to a 220kV AIS.

Other associated works would include converting the existing 110kV Otahuhu-Pakuranga line to 220kV operation, dismantling the existing 147-kilometre-long and 460-tower 110kV Arapuni-Pakuranga transmission line, and planning the works – including the acquisition of designations, consents and easements to allow for an eventual upgrade to 400kV operation.

Transpower communications manager, Adele Fitzpatrick says this, and other North Island Grid Upgrade projects, will help provide security of electricity supply to the upper North Island.

“[It] is vitally important to meet the growing demand for electricity,” says Ms Fitzpatrick.
“There are currently six transmission lines running north to Auckland. The last of these were built in the 1960s. In the intervening 40 years, the population of the upper North Island has more than doubled, electricity use has more than trebled and the population is forecast to continue to grow.

“By building a transmission line which is 400kV-capable (although will only be operated at 220kV initially) provides greater transmission capacity to meet any increases in demand going into the future, while only requiring one new line to be built, rather than two. This is of benefit both economically, as well as being less disruptive to those communities affected by Transpower works.”

Although still awaiting the Board of Enquiry decision under the Resource Management Act – which has been delayed to the first half of this year – Ms Fitzpatrick says Transpower has nonetheless moved to award the overhead powerline component of the contract.

Understood to be valued at about $230 million, this contract was let to a joint venture of British engineering, construction, services and investment group, Balfour Beatty and Australasian engineering and property services company, United Group.

“We’ve gone ahead and formed the alliance regardless, because the project is so important to us and we need to get started on it. If we have to stop then we’ll just have to cover that loss.

“Transpower undertook an extensive and robust selection process with a number of parties for the overhead transmission line work, to ensure the best possible partnership could be formed.

“[This joint venture] was selected for their international and local experience, as well as meeting our normal selection criteria. United Group is also currently a preferred supplier of maintenance and construction services to Transpower.”

Although the electricity transmission line, which is expected to be commissioned by late 2011, will be the first large addition to the electricity network since 1991, Ms Fitzpatrick says the work involved “is not unfamiliar”.

“Building and upgrading lines and substations is a core part of our business it’s just on a much larger scale.

“The 220kV underground cable, which runs from Brownhill Road transition station to Pakuranga substation, is a unique component of the project as no underground circuits of that capacity currently exist in New Zealand.”

Aware of the potential impact of its projects and works, Ms Fitzpatrick adds that Transpower is committed to balancing the needs of both communities and the National Grid.
“Transpower has recently developed new and comprehensive consultation processes that give communities and individuals more time to participate in the selection process of what is built to help meet the electricity needs of New Zealand.

“This approach was recently trialled in the Wairakei area, as part of the Wairakei Ring Facilitating Renewables Project, before any decisions had been made as to what solution was most economic or appropriate, so that the views of interested parties could be considered in our early decision making.

“Transpower has also established a CommunityCare Fund to assist communities impacted by Transpower assets and projects, by providing funding for projects that benefit the community as a whole.

“The CommunityCare Fund has assisted 37 community organisations with more than $1 million in funding so far. This includes a number of projects in communities which are likely to be affected by the North Island Grid Upgrade.”

Having maintained a long period of “very low investment”, Transpower has now moved to a concentrated period of high reinvestment in the Transmission Grid, says Ms Fitzpatrick.
“Major upgrade projects that are important to the security of the overall power system are now in various stages of development or construction, with a total projected investment of $3.5 billion over the next ten years. The new transmission line from Whakamaru to Auckland is just one of these projects.”

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