Corrosive ash residue from the Hunga-Tonga Hunga-Ha'apai eruption is destroying Tongatapu's new High Voltage network, in what Tonga Power Ltd. said yesterday is an unprecedented crisis that will cost around $20 million pa'anga to fix.

Recent power outages around the Nuku'alofa area were caused by damage to the High Voltage Aerial Bundled Cabling (HV ABC) from solidified abrasive ash substances.

"The problem is a first of its kind", said project manager Andrew Kautoke at a press conference on 13 October at Matatoa to explain the crisis. The low voltage cable is also damaged, adding to the problem with the HV ABC.

Tonga Power is facing multiple complaints from the public of damaged appliances, such as washing machines, refrigerators, and office computers, due to the major power outages that started on 16 September last year, and were repeated again on 11 January and twice in the last month September-October, mainly in Area 1 of the grid.

New spiral cabling

Before the HTHH eruption in January 2022, Tonga Power had installed new spiral cabling under the Nuku’alofa Network Upgrade Project (NNUP), upgrading the electricity network in five areas of Nuku'alofa, with NZD$9.3 million NZD funding from the Asian Development Bank and NZD$11 Million from the New Zealand government.

The installation of the stronger cabling, capable of withstanding high winds from cyclones, had effectively reduced network fault incidents and successfully decreased line losses from 17.45 to 10%, Tonga Power stated.

The new cabling is wrapped together in a spiral configuration around a metal support cable.

But despite these engineering advancements, this cable became an unexpected ash magnet during the powerful HTHH eruption that blanketed Tongatapu in ashfall.

Tonga Power's engineering manager Paini Lie, said that the ash sticking to the cable can cause a reaction when mixed with water and heat from the sun, and it causes corrosion to the cable.

Short circuits

The solidified abrasive ash substances remain an ongoing challenge for the Tonga Power teams.

“This residue has exacerbated friction between the cabling, mixed with cable heat from electricity flow, sunlight heat and corrosive nature of the solidified abrasive ash substances, which results in short circuits across parts of our High Voltage network,” Tonga Power said.

High winds and hot days associated with the recent El Nino, have compounded the issue.

“In response, our team is executing emergency scans and surveys, utilizing specialized equipment to pinpoint potential breaks in the network with ABC cabling.”

Remedial actions involve replacement of new cables and meticulous cable cleaning. With help from the Fire Department, Tonga Power said they had started cleaning up the cables in most areas in Nuku'alofa using water blasting over wide areas, “but it won't ultimately be a problem-solving, as the ash can still cause the same problem,” said ACEO Finau Moa,

"The cost for repairing and renewing of the line damages would be about $20 million...".

He also said "the possibility that the people will not pay for this cost is for us to ask from the donors again."

Tonga Power expects that there will be more power outages on Tongatapu.

“We ask for your understanding whilst we address these issues as quickly and safely as possible,” they said.