More Extreme Weather Ahead – Threatens Transformers and Power Supply

Transformer Failures

– Lightning causes damage and total failures on transformers. Each year we see between six and twelve such transformer failures. That’s why, just like Møre Trafo as manufacturer, we put strong focus on this issue, says Leif Johann Wenaas, Head of Planning, at Nordvest Nett AS in Ørskog.

Nightmare

He makes no secret that it is a real nightmare when the storm rages and you have to send people out into the field to find faults and map out whether a transformer has failed or not. Nordvest Nett has overall responsibility for planning, construction, operation, and maintenance of the power grid in Haram, Skodje, Ørskog in Ålesund municipality, Stordal in Fjord municipality, and Vestnes municipality.

Winter Lightning and Thunder

When it comes to lightning and thunder, there are big differences between geographic areas. Southern and Eastern Norway see large amounts of lightning in the summer half of the year and have many operational disturbances linked to warm summer weather. The coastal areas are more exposed to extreme weather and, in thunderstorm-heavy years, experience many lightning strikes, often in connection with winter storms.

NVE Report

According to the NVE report, every lightning strike in Norway carries a probability of nearly two percent of causing a transformer failure, which adds up to an annual destruction of 0.6 percent of all transformers in the country. The calculations are based on statistical data collected by NVE, Statnett and Sintef. The largest share of both operational disturbances and energy not supplied (ILE) caused by thunderstorms is in the medium-voltage distribution grid.

Challenging

– For us, lightning and transformer failures are mainly linked to the winter season, and that naturally makes fieldwork extra challenging. When transformers fail, it feels safe to have a transformer manufacturer nearby and be part of an emergency preparedness agreement with Møre Trafo. That cooperation works very well, says Wenaas.

Stock Agreement

Under the agreement between Nordvestkjøp and Møre Trafo, Møre Trafo maintains emergency readiness and a dedicated stock reserved for the companies in the agreement: Mørenett, Stranda Energi, Sykkylven Energi, Nordvest Nett, Istad Nett and Sandøy Energi.

“At the same time, we keep a small stock of smaller transformers ourselves. It’s all about fixing faults and restoring the power supply as quickly as possible. This is what we’re measured on,” says Wenaas, who estimates they have somewhere between 600 and 800 transformers in their grid.

The Lightning Challenge

Sales Manager Ivar Lifjeld at Møre Trafo says that a lot has happened, and keeps happening, to make the power grid safer. That also includes making transformers more resilient against storms and lightning.

“Overhead lines are replaced with more cable. There is better protection and impulse earthing at the transformers. The transformers are better equipped to handle overvoltages through design and higher material quality, among other things,” says Lifjeld.