The sturdy concrete foundation has set, and the next transmission line tower will soon be erected by crane. Elsewhere, lines are already being installed on towers using a puller and tension machine. The line is strung on pulleys and earthed with earthing rollers at the puller and tension end and earthed pulleys along the span.
The structures carry a 400 + 110 kilovolt transmission line to reinforce the Lake Line. The connection from Vaala to Joroinen is 291 km long.
“The Lake Line will reinforce transmission connections from north to south. It will also enable more wind and solar power to be built in Eastern Finland,” says Tommi Olsson, Project Manager at Fingrid.
The large Lake Line project is divided into four sections. Eltel Networks is working on one section stretching approximately 70 km from Kajaani to Iisalmi.
Verification rather than assumption
The new transmission line under construction mainly runs alongside the existing Lake Line. For this reason, those on the worksite must pay special attention to the induced voltage in the new structures by the existing transmission lines.
Induced voltage can be life-threatening.
“We have prepared worksite earthing plans, which Fingrid has approved. The line under construction has additional earthing at least every two kilometres. Furthermore, the linesmen connect their personal earthing when going onto the line. This double safety check prevents an electrical accident, even if one of the additional earthing connections detaches or breaks,” says Jukka-Pekka Kivistö, HSE Supervisor at Eltel Networks.
Cranes and other work machinery operating near the live line are also earthed.
Induced voltage is a familiar phenomenon, and additional earthing is routine.
“Induced voltage is a familiar phenomenon, and additional earthing is routine. However, this is an important matter, so we do not simply assume everyone knows about it. Instead, we provide an orientation on every worksite as if it were a new topic: repetition is the mother of all learning,” adds Niko Ollikainen, Project Manager at Eltel Networks.
Safe doing every type of work
Naturally, all the general ground rules of occupational safety also apply to the Lake Line. For example, every employee completes a worksite orientation and Fingrid’s general online courses on occupational safety.
“Occupational safety plans have been prepared for various work phases on the site. In addition, any risks are assessed as part of the day-to-day work,” says Mika Laulumaa, Site Manager at Eltel Networks.
He mentions one practical example:
“When we work at heights, we use safety harnesses and follow the Always Attached rule: when a linesman moves along a tower, they do not remove the hook attached to the structure until they have attached a second safety hook.”
The pros and cons of winter
The section of the Lake Line in Eltel Networks’ worksite has rather varied terrain. For example, it includes dry sand cloth, rocks, and boulder deposits, as well as marshland that can only be accessed when the ground freezes in the winter.
“Winter opens up new access routes and allows us to do work that we cannot do in the summer. However, very low temperatures also restrict us: they prevent us from working with machinery, for example. We also need to be prepared for slippery conditions in the winter—for example, by gritting surfaces or wearing studded boots,” says Laulumaa.
There are two substations on Eltel Networks’ worksite.
“Where our worksite meets the substation site, it is important to coordinate work with the substation contractor. Everyone needs to know who is doing what and when,” says Ollikainen.
There is also a railway on the worksite:
“We cross the railway using Fingrid’s scaffolding, which prevents the wire or line from making contact with the railway’s overhead line,” notes Ollikainen.
