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Transpower says technology will allow consumers to "ride out" failures in New Zealand's power grid to which it is especially vulnerable.

New Zealand's long backbone grid with few alternative routes is less resilient than the high-meshed networks of Europe and North America so "we must be able to apply uniquely New Zealand solutions," Transpower says in a report, Transmission Tomorrow, which looks ahead to 2040.

No grid can guarantee 100 per cent continuity of service but investment to eliminate every possible outage is uneconomic, the report says.

"It is often more cost-effective for the customer to bear the cost of very infrequent outages or take other measures to compensate for the grid's temporary unavailability."

While consumers would demand increasing reliability from electricity-powered services, this did not mean a matching increase in grid reliability.

Local storage from electric cars or batteries to maintain some services may well become more economic.

"In the next 10-20 years we believe that technology will emerge to allow many consumers to ride through relatively short interruptions, using local storage and the ability to turn off non-essential load [such as refrigeration]."

Grid failures are costly. A 31-hour blackout in northeastern United States in 2003 affecting 50 million people was said to have cost US$9 billion ($11.6 billion). The cost of Auckland's six-hour outage in 2006 after equipment failure was estimated at $70 million.

In the 2009-10 year there were 44 separate outages which caused 22 minutes of unavailability on the grid.

Among measure to make the grid more resilient, Transpower maintains key spares such as towers and transformers to use to patch up the system.

In the past two years it has spent $30 million on spare transformers to ensure a failed transformer can be replaced within a month.

The state-owned enterprise has also built new substations to increase diversity on its network and is studying risks at critical sites - Penrose in Auckland and Central Park in Wellington - to eliminate high-impact failures such as a fire in one transformer spreading to others.

Transpower chief executive Patrick Strange said investing in long-term strategies and technology was crucial both to defer the need for some new equipment and to create better options when it is required.