Network safety

Ensuring the safety of the electricity network is an integral part of our business. We build and maintain our electricity network so that it does not pose a risk to our customers or the environment.

The electricity produced by the power plants is transmitted to the grid where the voltage is 110, 220 or 400 kilovolts. At the substation, the voltage is converted to match the distribution network. In the medium-voltage network, the voltage is most commonly 20 kilovolts. At the distribution substation, the voltage is further converted to 400 volts for distribution to homes on the low-voltage network. Homes are connected to the low-voltage network by a connection cable that brings the power to the main distribution board. This in turn distributes the electricity to the property's own power grid for life and comfort.

Get to know the electricity network

This page contains information about the common structures of an electricity network so that you can recognise them and know how to act in a safe way in their vicinity. Please remember that in no circumstances should you touch electric wires.

High-voltage open wire 110–400 kV

110, 220 and 400 kV wires are high-voltage wires. The national main grid uses 110–400 kV wires. In addition, 110 kV wires are also used for regional power transmission. High-voltage wires transfer electricity over long distances from power plants to closer to consumption centres.

110–400 kV open wires use different pylon structures. The pylons used outside urban areas are of the guyed, bipedal, gate-shaped type. The pylons used in urban areas are free-standing lattice masts. You can tell high-voltage wires by the length of the insulator chain and the number of insulator plates.

Wire voltage	Length of insulator chain	Number of insulator plates	Vertical distance to ground/road
110 kV	approx. 1 m	6–8	6 m/7 m
220 kV	approx. 2 m	10–12	6.5 m/7.5 m
400 kV	approx. 4 m	18–21	8 m/9 m

Substation

An essential part of the electricity network, substations convert the voltage level used for power transmission into a lower voltage. Usually, the voltage is converted from 110 kV to 20 kV. Substations include network protection and automation systems, which ensure the safety of the electricity network and uninterrupted electricity distribution. With the construction of a smart electricity network, the level of automation will also increase in other parts of the distribution network. Substations are located inside enclosures, where access is prevented for safety reasons.

Medium voltage underground cable 20 kV

The medium-voltage cable transmits electricity from substations to transformer stations. Most of our network is underground cable. Underground, the electricity network is safe from wind, storms, thunder and snow loads. A weatherproof grid is also environmentally friendly and safer than overhead lines. The underground electricity network cannot be seen and its location must be found out from the cable location service. The underground cable is located about 70 cm below the surface.

Medium-voltage overhead line 20 kV

Open wires are used in distribution networks for local power transmission between substations and distribution transformers. The construction of an open wire comprises a metal phase conductor attached to insulators on a beam. Another type of wire that is used is PAS, which is an open wire covered by a thin layer of plastic. The conductors are located closer to each other than in an uncovered open wire. The distance of the wire is at least 5 m from the ground and 6 m from the road. Outside urban areas, you can see 20 kV overhead lines near roads, usually on wooden pylons. The image shows a 20 kV open wire.

Kiosk-style transformers

In a kiosk-style transformer the 20 kilovolt voltage is converted to 400 volts for distribution to customers. Kiosk-style transformers protect the transformers from extreme weather, small animals and birds. Kiosk-style transformers are also environmentally friendly because they include reservoirs for potential oil leaks.

Pole-mounted transformer

In a pole-mounted transformer station, the transformer is built on one or two poles. The transformer converts 20 kilovolts of voltage into 400 volts suitable for customers. Pole-mounted transformers are found particularly in sparsely populated areas on the overhead network. In conjunction with laying the underground cables of the Elenia Säävarma electricity network, we will dismantle the pole-mounted transformers with the overhead line network and replace them with kiosk-style transformers.

Link box

Part of the low-voltage electricity network, link boxes are most commonly used in underground cable networks. They are a common sight in urban and residential areas, where they distribute electricity to end users. Link boxes are installed in easily accessible places to enable unobstructed access for repairs or maintenance.

Low-voltage underground cable 0.4 kV

A low-voltage cable brings electricity to your home. The connection cable bringing electricity to properties is usually an underground 0.4 kV electricity cable. The location of the cable is about 70 cm below the ground.

Low-voltage AMKA wire 0.4 kV

Low-voltage wires are used in the vicinity of settlements and in the lighting networks near roads and running paths. AMKA refers to a bundle assembled aerial cable, where the phase conductors insulated with black plastic are wrapped around a metal wire acting as a support cable. You can tell an AMKA cable by its twisted structure, which separates it from a straight telephone line. The height of the wire is at least 4 m from the ground and 5.5 m from the road.

Are you planning work in the vicinity of an electricity network?

Make sure your work does not pose a risk to the power grid or to people.