Media release
25 May 2007

Transpower welcomes Notice of Intention to approve its Otahuhu substation diversity project

Transpower has welcomed the Electricity Commission’s Notice of Intention to approve an investment plan that will modernise the Otahuhu substation and provide greater security and diversity of electricity supply to Auckland.

The Electricity Commission today advised Transpower of its Notice of Intention to approve its proposal. The proposal includes building a new physically separate, enclosed, high reliability 220 kV switchyard on the Otahuhu site.

Chief Executive Dr Ralph Craven said Transpower has responded to concerns about Auckland’s heavy reliance on the existing substation equipment at Otahuhu.

“This is a significant investment that addresses historical issues. For many decades Otahuhu substation has been the key link in the network, where electricity comes into Auckland from the south and is then distributed throughout Auckland and Northland. However, the Otahuhu facility is ageing and is in need of some additional equipment.”

“The current design of the substation evolved between the 1930s and the 1960s. Currently there are 110 kV and 220 kV outdoor switchyards located side by side and the switchyards are at risk for high impact, low probability events. By providing a separate, new technology switchyard, it will significantly reduce this risk and improve reliability of supplies into Auckland,” Dr Craven said.

The power outage of 12 June 2006 occurred when an earthwire fell across one of the busbars. This is an example of a high impact, low probability event.

Dr Craven said that this project is an important step in a long-term strategy to provide much improved diversity of supply into and across Auckland. “It is also consistent with the objectives of the Government Policy Statement on Electricity. This policy supports investments that provide resilience against the effects of high impact, low probability events and that provide diversity to larger load centres.”

Transpower had planned to upgrade the Otahuhu substation by 2011 as part of the proposal to build a new transmission line from Whakamaru to south Auckland. That line is now proposed to terminate at Pakuranga substation, further improving diversity of electricity supply into Auckland. The Otahuhu substation development proposal was submitted separately for approval to the Electricity Commission. Transpower intends to commission the new facilities at Otahuhu by the end of 2009.

For more information:
Rebecca Wilson, Communications Manager; 04 498 2695; 021 578 608

Questions and Answers on the Otahuhu Diversity Project

What is the justification for this project?
Transpower considers this project to be an urgent reliability upgrade to reduce the possibility of high impact, low probability events disrupting power supplies to the Auckland area. The existing substation configuration is not up to current international best practice for a major load centre.

How much will the upgrade at Otahuhu substation cost?
The estimated capital cost is $83m in 2006 dollars, including contingencies ($75m excluding contingencies). This represents the maximum cost that Transpower will be seeking to recover. Transpower will only recover the actual costs if they are lower than $83 million.

What does the project include?
 New indoor 220 kV gas insulated switchgear (GIS), physically separate from the existing outdoor switchyards
 Underground cable for all transmission line entry and exit points
 Reconnect half of the existing 220 kV circuits to the new switchyard
 Underground cable connections between the new and existing switchyards

What is Gas Insulated Switchgear (GIS)?
GIS technology has been preferred over air insulated switchgear (AIS), which is currently used at Otahuhu. GIS has a higher capital cost but has a number of advantages:
 GIS is much smaller than AIS and greater physical separation can be achieved from the existing equipment
 GIS is housed indoors, in a building similar in size or possibly smaller than the existing warehouses on the Otahuhu site
 As the GIS is fully enclosed it is a controlled environment that is more protected from outside influences
 Using GIS will leave room for future upgrades at the Otahuhu site.

How does this project fit into a strategic long-term plan for Auckland’s electricity supply?
There are two important projects that will impact on the medium-term (5-6 years) development at Otahuhu substation:
 A new high capacity transmission line into Auckland from the south
 Enhanced supply across Auckland
At Otahuhu substation these developments will require new connections for additional incoming and outgoing circuits, new transformers and voltage support equipment. In the longer-term, Transpower intends to replace the existing outdoor switchyard with modern new equipment.

What approvals are needed?
The Electricity Commission has issued its Notice of Intention to approve the project. Transpower owns the land at Otahuhu substation but some consents may be required from the Manukau City Council, with whom initial discussions have been held.

How long will it take?
Transpower intends to commission the new facilities at Otahuhu by 2009.

Ends

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