Grid failure for Delta down to corrosion on Indonesian transformer
Corrison in a near-new high-voltage power transformer bought by Delta from Indonesia has been linked to a failure that caused a power surge across Dunedin.
Delta chief executive Grady Cameron confirmed corrosion had been found inside one of two new high-voltage transformers – each costing $500,000 – installed at the city’s ”crucial” Halfway Bush substation in December.
Both transformers were bought from Indonesian supplier Pauwels and were still under warranty, but the second was yet to be checked for any similar fault, he said.
Delta – a Dunedin City Council-owned company – is contracted to maintain the electricity lines network owned by Aurora Energy Ltd, another council-owned company.
The corrosion had been discovered within the past two weeks and had prompted Delta staff to deactivate the transformer and connect a mobile substation as backup over the weekend, Mr Cameron said.
It was while connecting the mobile equipment that a failure occurred about 8pm on Sunday, causing a loud bang at the substation and flickering lights across the city.
Mr Cameron said the power surge had caused only minor damage to the mobile substation’s connection and there was no risk of a power outage or damage to consumers’ electronic equipment.
However, the discovery of the corrosion was ”unusual” and repairs could take up to three months, he said.
Staff from Pauwels were due to travel from Indonesia to Dunedin this week to inspect the damaged equipment and the second transformer, before repairs – at Pauwels’ expense – were agreed, Mr Cameron said.
”The transformer’s still under warranty with the supplier, and we’re obviously working with the supplier of the transformer to establish the cause of the corrosion and what … required repairs will be necessary.
”Until the inspections are completed we are unable to establish what the nature of the repairs required will be, and obviously therefore the … cost involved.”
The lines network included 37 substations, each with ”one or two” transformers, across Dunedin and Otago, Mr Cameron said.
All the transformers were bought overseas, as no New Zealand supplier made them.
Pauwels was a ”very large” company and its work was usually up to an ”extremely high” standard, but the two companies’ supply agreement would be reviewed as a result of the fault.
”We constantly review suppliers and we will certainly be having some conversations with them as part of this.
”These are big, expensive pieces of kit … for one to be in service for such a short period of time and to have corrosion in it … it is pretty unusual.”