HVDC Fully Operational

Media release
30 April 2009
HVDC Fully Operational

Pole 2 of the inter-island High Voltage Direct Current (HVDC) link was operational from 1am this morning.

Transpower CEO, Dr Patrick Strange is pleased with the speed and quality of the repairs. “Our people worked around the clock to locate the fault, repair and test”, he says.

“An HVDC transformer is different to a supply transformer and special in nature. It’s a very large and complex piece of equipment and our guys did a great job.”

The outage was caused by a complex circuit fault located within a secondary component of the convertor transformer, rather than the transformer itself.

Extensive tests and checks of the transformer showed the damage was isolated to the circuitry, which was replaced.

“The HVDC is critical to the country’s infrastructure so we had to thoroughly test it to ensure it would run well after the repairs.”

“While the wet weather didn’t help our repair work, we’re always pleased to see rain in the Waitaki.

“The major inflows the southern hydro lakes have experienced this week indicate we’re a long way away from dry winter issues.”

Transpower operated Pole 1 of the HVDC for 24 hours during this time at a capacity of 130-200 MW. Pole 1 was taken out of service in late 2007 but can be operated for limited periods when necessary.

“Pole 1 operated without fault, thanks to the extensive maintenance that it’s been subject to over the last six months.”

The inter-island High Voltage Direct Current (HVDC) link includes two pairs of converter stations (Pole 1 and Pole 2), which convert the power from AC to DC at Benmore and back to AC at Haywards – or the reverse for the increasingly common southward flow.

The first pole, Pole 1, was commissioned in 1965. Pole 2, on which the outage occurred, was added to the system in 1991.

ENDS

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