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Power poles are just the tip of the iceberg as Dunedin’s creaking electricity network shows signs of neglect across the board. Chris Morris reports.
Richard Healey says it is a miracle the lights have stayed on in Dunedin as parts of the city’s ageing electricity network threaten to implode.
But the poles were just one symptom of wider neglect that has left Aurora’s network at risk of multiple failures, Mr Healey believed.
And nowhere was that threat more critical than within the ageing web of high-voltage 33kV underground electricity cables, dating back to the 1950s and 1960s, still powering Dunedin.
The cables were old and neglected, but their exact condition was a mystery, and the consequences of a failure could be dire, he warned.
The results were evident in Auckland in 1998, when four old high-voltage cables failed one after another, cutting power to large parts of the CBD for weeks.The same event was "getting more likely by the day" for Dunedin, Mr Healey told ODT Insight.
"I’m amazed they’ve made it this far," he said.
It was a claim reinforced by Aurora, which identified the cables as "perhaps the most significant risk of a catastrophic asset failure" facing the city in its 10-year asset management plan.
The risk was also pinpointed by consultant Strata Energy Ltd, in a report on Aurora’s network for the Commerce Commission, in 2013.
Strata warned the condition of Dunedin’s 33kV cables was "largely unknown and, given their age, failures may increase significantly with little notice".
Delta — which manages Aurora’s network — had since replaced one 33kV cable and planned to replace others, but not for another six years.
In the meantime, its back-up plan for any failure involved re-routing power through smaller 11kV and 6.6kV lines.
But Mr Healey said there was a problem with that plan — the back-up equipment was also poorly maintained and could also fail.
"The problem is now we have a whole lot of medium-voltage switchgear which is inoperable or poorly maintained, and with an enhanced probability of failure when you actually need it," he said.
The commission also highlighted "concerns" with the back-up plan in 2014, when Aurora was warned for failing to meet quality standards.
It said Aurora’s reliance on the 6.6kV network as a back-up "could lead to major power outages" in Dunedin.
One of the city’s oil-insulated 33kV cables — running from the central city to South Dunedin — had been leaking since 2009, allowing up to 7000 litres of oil to escape over the years, he said.
The ongoing leak was noted in Aurora’s asset management plan, but Delta staff had so far been unable to find the hole.
Mr Healey said a gas-insulated 33kV cable at the city’s Smith St substation — near the Town Hall — had also failed.
It remained out of action because spare parts had been discarded by Delta and were not manufactured any more, he said.
Mr Healey said the state of the 33kV cables was not known, and predicting the end of their useful life was "really, really difficult".
What was known was that other cities had "vigorously" replaced their cables, and Dunedin appeared to be "out of whack with the rest of the world".
But the city’s ageing 33kV lines were not the only problem facing the network, nor the most dangerous, he said.
He described a network littered with equipment either broken or operating well beyond manufacturers’ specifications.
The biggest risk to workers — other than faulty poles and overhead wires — was high-voltage switchgear that has "not been maintained for 50 years", he said.
A fault could generate an "extremely large" arc flash and ignite oil inside the equipment, generating a "fireball", he said.
An incident in Western Australia involving "exactly the same switchgear we use here" had already claimed two lives, he said.
The public was also at risk from lesser-known hazards, including "several hundred" cast iron "potheads" suspended from power poles, he said.
The small terminals linked overhead lines to power cables or other equipment, but were "extremely prone" to failure as they aged.
"When they fail they explode just like a bomb.
"Bits of cast iron fly everywhere from a spot seven metres in the air, and it’s filled with bitumen, so the bitumen melts and also gets thrown out from that blast," Mr Healey said.
Delta staff had been told not to touch the potheads, which were now 50 years old, but the company planned to replace just 10 each year, he said.
He was already aware of one near-miss in Dunedin, involving a pothead that exploded as a woman walked past in the street.
"It shredded her down jacket and covered it in bitumen, but fortunately she wasn’t badly injured."
As well as faulty equipment, vegetation growing into power lines was "out of control" despite an extra $8 million spent trying to tackle the problem in the past three years, he said.
The company expected to spend millions more replacing equipment, including dozens of substations and thousands of pole-mounted transformers, for which "end of life may be imminent", its 10-year asset plan showed.
Aurora would also, from next year, begin to "critically evaluate" the need to begin replacing more than 1000km of low-voltage power lines, although there were ‘‘no current plans’’ to do the work itself.
Mr Healey said the bill for that would be massive, as Dunedin’s inner-city power lines approached the end of their estimated 70-year life.
"In 10 years, we’re looking at re-reticulating the entire CBD of Dunedin. What do you think that’s going to cost?
"Hundreds of millions ain’t gonna touch it."
Aurora has unveiled a $417million, 10-year capital programme to renew parts of its network, including an accelerated $30million plan to replace dangerous power poles.
Despite that, Delta chief executive Grady Cameron would not answer questions about the state of the network, the risks it posed to safety, or the likely total cost of renewal, this week.
Instead, Aurora board chairman Dr Ian Parton, in an email, would say only the issues were being addressed "at an operational level" and it was not appropriate to discuss them with media.
"If further investment is needed, we will consider it as necessary when required and base our decision on the best information available."
However, Delta spokesman Gary Johnson, answering questions earlier in the week, had stressed the "significant progress" renewing Aurora’s network since 2013.
The back-up plan for Dunedin’s 33kV cables was "in line with industry practice", and "conservative" network management meant it remained one of the most reliable in the country, despite being one of the oldest.
Aurora was also ahead of the curve when comparing its average of 130 minutes without power per consumer to last year’s industry average (368 minutes), he said.
However, some other indicators remained in the red, such as service failure events which increased from 11 in 2003 to 60 last year, and the amount Aurora paid to electricity retailers as a result rose from $63,000 to $205,000 in the same period.
The number of faults per 100km of overhead lines, at 20.25, was also nearly double Aurora’s target of 10.5.
And, despite repeated assurances from Dr Parton and Mr Cameron that the network was safe, inadequate investment in lines renewal was heightening "concerns about potential safety risks", Aurora’s 10-year plan said.
The number of contractor injuries recorded, at 93.87 in 2015, was also above the target of 55.2 for the year.
And, since April 1, 2015, there had been 68 incidents recorded involving "either a high or extreme risk" to public safety.
"Not surprisingly failed poles and conductor down events account for 80% of the total," it said.
Mr Healey said the network’s problems were the inevitable consequences of inadequate investment.
"It’s not aged — it’s decayed. It’s not deferred maintenance — it’s neglect.
"Honest to God, this place is shot. It is a miracle that we haven’t killed someone else," he said.