Two electricity generators went down last week, forcing Tonga Power Ltd. to carry out emergency load shedding or rolling power cuts on Tongatapu to avoid power blackouts.

The generators came back on line by Saturday evening, 18 February.

All seven generators are now fully operational, stated Tonga Power Ltd (TPL) in an update today 20 February.

On Friday TPL announced that due to the unexpected failure of two out of its seven gensets, would conduct emergency electricity load shedding operations on Tongatapu.

TPL required all seven gensets to be operational to meet the customer electricity demand, but due to the failure of the two gensets, the company had to implement load shedding measures to balance the supply of electricity with customer demand.

The company's battery energy storage systems could not collect sufficient renewable energy due to the cloudy and rainy weather.

Update

TPL's Strategic & Business Development Manager, Andrew Kautoke, told Matangi Tonga today, that all seven gensets have been fully operational since Saturday evening, 18 February.

"TPL has the parts and expertise to fix it, but due to the scale of the works required that’s why it took a week to complete."

He said their generation capacity when all gensets are running is at 13.6MW, which can meet the total electricity average customer demand, which is 10 to 11 Mw per day during the hot weather months it has peaked to 12MW.

"So, with two of our gensets being down last week the only electricity generation capacity TPL could generate is 8.5MW out of its total generation capacity of 13.6MW.

“With a total average daily electricity demand from our customers of 10 to 11MW, which in hot days peak to 12 MW, this means that the demand for electricity from customers is over, compared to our existing electricity generation capacity which is only 8.5MW. Meaning TPL will have to shed an electricity load of 3.5MW or more to prevent an entire blackout to the island.

“This is why we conducted the electricity load shedding to certain areas depending on the how much the electricity customer demand exceeds our generation capacity."

“At the same time, TPL prioritized the hospital, telecommunication, and utility services to ensure the least disruption to our essential services power supply.

“We try our best to keep the power outages fair to different parts of Tonga, which included all districts [Vahe Hihifo, Hahake etc).The power outages are usually in the evening hours as this is the time there is the most electricity usage from customers.”

Technical problem

Meanwhile, the technical issue with the generators was an unexpected fault to these two machines, whereby some of the genset functions for the machines unexpectedly did not perform the functions it was supposed to.

Andrew said water is very important for their power generators to operate, when the engine gets too hot the section of the machine that manages water inflow ensures that the water takes the heat from the engine and brings it to a cooler, where it gets cooled down again and starts the process all over again.

The incident occurred when instead of the water going through the normal pathway it leaked through a device called a charged air cooler which then resulted in excess water finding its way to the lube oil used for generating electricity, which caused the engine to shut down.

The team then worked on installing another component called an aftercooler to the machines and testing to ensures that its back performing the functions it meant to perform.

The team completed these tests on Saturday and now the machines are back in operation, he said.

"TPL has the parts and expertise to fix it, but due to the scale of the works required that’s why it took a week to complete."

He said TPL had discussed this with the team on increasing the monitoring and maintenance of the machines and parts to ensure all important components of the machine performs as expected.