Basslink has refuted an analysis of its subsea cable outage of 2015-16 released by Hydro Tasmania that said the subsea cable was pushed beyond its design limits.
Malcolm Eccles, Basslink CEO, said the report merely puts forward one idea and does not provide any "conclusive and definitive proof".
"Hydro Tasmania's experts did no actual testing on the Basslink cable or any similar HVDC [high-voltage direct current] cables. They used a theoretical model based on certain assumptions to come to a set of conclusions," Eccles said. "These assumptions make the experts' conclusions speculative and not based on actual facts."
The report from engineering consultancy DNV GL said the cable had exceeded its temperature design limits, and that the overheating and subsequent cooling of the cable degraded it.
"Basslink has operated and maintained the Basslink facilities in accordance with the instructions from the manufacturers, Siemens and Prysmian, and in accordance with good electricity industry practice," Basslink said on Friday.
The company said the cable has control systems to prevent overheating, and even though it does not accept the findings of the analysis, has agreed to run the cable at a continuous 500MW rating.
"The experts believe the cable can safely and reliably operate above 500MW in future, if [Basslink] adopts a new control system and extends the cable's 'rest period' between polarity reversals (between export/import and vice versa) from two minutes to five minutes," Hydro Tasmania said on Wednesday.
Eccles said that neither Basslink, nor cable manufacturers Siemens and Prysmian were consulted during the creation of the Hydro Tasmania report.
"Basslink stands by the independent investigation that was undertaken by CCI, who described the exact cause of the subsea cable fault as 'cause unknown'," the company said.
The Basslink Interconnector was down between December 2015 and June 2016, with the fault discovered 90.5km from the Tasmanian coastline, and removed and capped three months after going down.
Basslink operated its subsea cable in a way that exceeded its temperature limitations, with the overheating and cooling of the cable resulting in the outage last year, according to independent experts.
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