“Last winter was by far the worst winter our grid has faced since statistics began. In a normal winter, we dislodge frost from about a hundred spans, but last winter we treated about a thousand spans for frost. Frost appeared in areas where it had never been detected before. Conversely, in the year before that, there was hardly any frost build-up. This shows that forecasting has become more difficult,” says Jarmo Lahtoniemi, Expert at Fingrid.

The frost removal work is conducted on live lines so no service outages occur. Fingrid has developed a new method for dislodging frost in collaboration with Helikopterikeskus Oy Helsinki.

“The frost conditions are analysed by helicopter in any case, so it was a natural progression for us to attach a fully-insulated frost removal tool to the helicopter and scrub the frost from the lines during the reconnaissance flight. This is a more cost-efficient way of removing frost, and it is also much faster than the old method. This work was previously done by snowmobile patrols. A technician would throw a rope over the earth wire and scrub the frost away,” Lahtoniemi says.

According to the standby agreement, the helicopter service is available to Fingrid within one day of the need arising. The Finnish Meteorological Institute produces a frost forecast, which helps to predict the need.

“We have designed stronger structures for areas known to suffer from particularly bad frosts. These structures are designed to handle twice as much ice as a standard structure.”