TAU media liaison officer, Trevor Pitt says, Sunday’s prolonged outage was due to a complication of issues that stemmed from a single generator engine fault.
He says the engine fault was related to its cooling system and was isolated to that engine.
“However, in the transfer of load to other engines as a result of this generator shutting down, the electrical issues compounded into a total power outage for the island.
“While one generator should have been able to handle the total load shift for a short time to allow a back-up to come online, it did not. Consequently, the main engine shut down and the island went ‘black’.”
TAU is now investigating why.
Pitt says: “There are a number of possibilities including an intermittent fault involving the automation system and the proportional sharing of the load between solar photo-voltaic generators and diesel generators.”
“Three quarters of the island’s PV systems cannot be monitored by TAU so that aspect is a complex one to investigate.”
He adds the complication was compounded from the position of a “black start” – starting up the generators from a total blackout state.
“Restart problems were encountered when Te Aponga Uira technicians discovered the engines kept shutting down. The automated generators run together under a programmed communications system.”
He says the delay was thus prolonged until TAU could over-ride the pre-programmed engines and revert to manual re-starts. Power was restored area by area, around Rarotonga, which took three to four hours to complete.
Pitt adds that if people have future concerns about appliances that are in use when a power cut strikes, switching off and/or disconnecting them is the best option.
Having surge-protected appliances and electronics is also helpful, he says.
The outage follows an hour-long power problem that affected parts of the island earlier this month. That fault is thought to have been caused by earth movement.
“The problem affected the Avatiu area through to the Ruaau meeting house in Arorangi.”