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ASPA gives detailed update on causes of last week’s power outage

ASPA director Young, an engineer, briefed Samoa News

Pago Pago, AMERICAN SAMOA — Responding to Samoa News queries, American Samoa Power Authority executive director Wallon Young has followed up on information about the lighting strike that caused an island-wide power outage on Tutuila this past Saturday.

Young explained in response to Samoa News questions, that lightning struck at least two distribution feeders at 1.34 pm on Saturday afternoon near the Futiga road intersection where three distribution feeders converge.

“Although uncommon, lightning occasionally strikes power lines, causing a surge in electrical pressure and significant voltage spikes on power lines that extend into the power plant,” Young said.

He explained that Saturday’s lightning strike damaged, “beyond repair” a high voltage Air Break Switch on Feeder-6. Four gen-sets at Tafuna plant needed minor repairs before power could be fully restored to the West side.

Although the 34.5KV Tie Line between the Tafuna and Satala power plants did not suffer any damage, but the line was tested before it was returned to service at 11:30pm on Saturday night.

Additionally, the Satala Plant feeders were restored within 12 minutes of the outage, beginning with Feeder-8 at 1.42pm, F3 at 1.44pm, F-1 and F4 at 1.45pm. The StarKist feeder was re-energized after the all-clear notice was given by StarKist engineers.

According to the executive director, delays in restoring feeders at Tafuna plant were due to repairs to Caterpillar gen-sets T1, T2 and T6 and the reprogramming of GE generator no.2 after the lightning strike.

The inability of remaining Caterpillar gen-sets T-5, T6 and T10 to withstand magnetizing inrush currents during feeder energizing also delayed restoration efforts Tafuna Feeders-5, 7 and 9 were first re-energized at 1:49pm, but operators were unable to keep them on because the Tafuna plant 13.2KV Bus voltage kept rising past 14KV. 

“This voltage rise caused over-voltage protection devices to shut down the plant two more times,” he said.

Reactive power settings on GE gen-set #2 were reprogrammed to stabilize the Tafuna plant bus voltage at 13.2KV and repairs to Caterpillar gen-sets T1, T2 and T6 completed, before full restoration could be completed. Tafuna Feeder-5 was finally restored at 3:40pm, Feeder-9 at 3:47pm, Feeder-6 at 4:37 pm, Feeder-7 at 4:50pm and Feeder-10 at 5:05pm.

Young said ASPA has ordered two new 3.5MW GE gen-sets to replace the six 3516 Caterpillar sets at Tafuna plant. The new GE’s are 33% more fuel-efficient and will mitigate the tripping issues associated with feeder faults and magnetizing inrush currents.

Furthermore, ASPA will also install additional lightning arrestors on primary lines around the Futiga road intersection, which it now lists as a lightning prone area.

“ASPA sincerely apologizes for the outage and thanks the public for its patience,” he concluded.

ASPA also posted the update on the power outage on its Facebook page.