NZ Engineering Excellence Awards win for first seismically base isolated convertor station

New Zealand Engineering Excellence Awards

05 December 2014 - At an awards ceremony held in Auckland on Friday, 28 November, the Pole 3 HVDC upgrade project was named winner of the Energy and Resources category at the NZ Engineering Excellence Awards.

Transpower’s Pole 3 HVDC Upgrade required the construction of new convertor stations at the Benmore and Haywards electrical substations. The HVDC link is a vital piece of New Zealand’s infrastructure and required a capacity and technology upgrade to meet growth and reliability needs.

Aurecon, working as part of a Design and Construct (D&C) team with client Siemens, completed the $450M upgrade of Transpower’s critical DC power link between the North and South Islands of New Zealand. The previous aged system has operated at a reduced capacity and this upgrade project nearly doubled the transfer capacity to 1200 MW. At the commencement of the project in 2009, The Minister of Infrastructure, Gerry Brownlee described the project “as the most important piece of infrastructure to be built in New Zealand in the next 10 years”.

The project required the construction of two new converter stations and associated switchyards at Haywards near Wellington and Benmore in the South Island. Located in hilly terrain only 200m from the main Wellington Fault Line and partly on a previously filled gully that could mobilise under seismic shaking, the Haywards site posed particular seismic and geotechnical design challenges.

Transpower required the Converter Stations housing the sensitive valves, transformers and controls to continue in operation after a 500 year return period earthquake and be capable of being rapidly returned to service after a massive 2 500 year event (to illustrate, it is thought the 2011 Japanese earthquake represented a 1:1000 year event).

In order to achieve this, and provide seismic diversity from the old Pole 2 link, the converter stations are base-isolated – a world first to protect the sensitive equipment through base isolation. Use of a base isolation system in this application created a number of very complex building and plant interaction issues that required unique solutions.

The seismic performance of the plant and building have required intensive modelling and analysis to a level of detail rarely achieved in seismic engineering in NZ to develop a range of innovative solutions to achieve the best outcomes for the owner Transpower. For example in the base isolation design of the building and equipment it is critical that the addition of the base isolation does not improve the building structural performance at the expense of the plant performance.

John Szmalko, Aurecon’s Expertise Leader, Power Transmission and Distribution says: “This is a fantastic win. Probably only those in the Power Transmission and Distribution space really appreciate the significance of this project. The HVDC convertor stations are leading edge technology and in simple terms are a switching power convertor, like your PC power supply, but capable of 1000's of MWs. There are typically only a handful in construction around the globe. This award recognises Aurecon’s exceptional input into the world first ‘base isolated’ HVDC convertor hall that integrally houses this equipment and protects it from earthquake damage.”

Commissioning of the Pole 3 project commenced in March 2013; the station has now been running successfully in test or market operation for one year.

It also won gold at the recent ACENZ awards in August of this year.

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