KEY POINTS:
Transpower's chief executive, Patrick Strange, yesterday briefed Auckland City Councillors on interim measures to restore the security of the electricity supply while the Penrose substation is without one of its three transformers.
The faulty machine has been inspected by an expert from Germany in the course of investigations
into why it failed on February 3 when 74,000 homes and businesses were without power for up to 2 hours.
Dr Strange said it was believed the fault originated in the machine's tap changer, a moving part which changes voltage. "So we have taken action on the other transformers' tap changers to prevent that happening again."
The faulty machine could take weeks to fix, he said, leaving supply exposed though with a "low probability" of further outages.
"We need measures in between to limit any impact if something goes wrong."
Transpower was working on options with network company Vector.
A new machine had been ordered but it could take two years to be commissioned. If the failed one could not be repaired, or work was taking too long, spare transformers could be moved in, though their weight - up to 120 tonnes - made transport difficult.
Dr Strange was questioned about the nation's aged transformers and their failure rate compared with those in the Australian network.
"We lose one about every nine months and we have 400 of them ... this is very low and is the international norm, despite our transformers being older. The average age is 10 years older than our Australian equivalent though our performance and reliability is similar."
Dr Strange said a programme to replace older transformers was under way.
Councillors also asked what Transpower was doing in the longer term to strengthen supplies in to Auckland. Dr Strange listed more than $1.5 billion of grid projects either completed, under way or proposed from Taupo north.
Later, city development committee chairman Aaron Bhatnagar said the briefing was comprehensive and a list of 18 questions were answered.
Councillors appreciated that the outages earlier this month had the potential to be catastrophic for the region.
$50M BOOST
Transpower has brought forward $50 million of maintenance work on the national grid, with another $50 million in the pipeline as the Government looks to save jobs and stimulate the economy.
Energy Minister Gerry Brownlee said the grid operator had brought forward work planned for the next 10 years after talks with the Government.
He said a further $50 million of accelerated infrastructure work on the grid involving conductor upgrading was also planned pending regulatory approval.
Mr Brownlee said contracts to work on the upgrade would be offered as soon as April. "Not only is it important work for maintaining the transmission network, but it has relatively high labour and New Zealand material costs."
- NZPA