All live wires and electrical equipment are surrounded by electrical and magnetic fields, collectively termed electromagnetic fields. Magnetic fields occur when power flows through wires or electrical devices. The magnitude of the magnetic field depends on the current through the wire or the installation, the distance to the installation and the combined effect of multiple power sources. Magnetic fields are measured in microtesla (μT).
In Norway, the power supply is based on alternating current at a frequency of 50 Hz, and the magnetic fields change direction at this frequency. However, this is so low that no radiation is emitted. Therefore, this is referred to as ELF – a field that varies with extremely low frequency.
Traffic along high-voltage installations
Our substations and switching stations are fenced in, and access is controlled by the operations manager at the installation. Our power line installations are open for general traffic with the following exceptions:
- It is not permitted to climb pylons without permission.
- After heavy snowfall or when power lines are weighed down by ice, we mark off areas that are no longer open to the general public.
We also follow Norwegian regulations relating to marking of aviation obstacles and Norwegian regulations relating to reporting and registration of aviation obstacles. For example, we mark our overhead lines with power line markers to alert low-altitude aircraft of the obstacle.
Noise from high-voltage installations
Power lines produce corona noise, which makes a crackling sound. Corona are discharges from the surface of the live parts. The noise from the discharges is particularly noticeable in humid weather. Experience shows that noise from power lines is usually the loudest when the power lines are new because of irregularities and grease residues on the power line surface. The noise will decrease over time.
Substations will emit coronary noise from switching stations, transformers and other components. Transformer noise can be heard mainly as a deep humming that comes from 50 Hz alternating voltage. There will also be cracking sounds when connections are made in the switching systems. In addition, some of our substations will generate noise from cooling fans.
During the construction of power lines and substations, there will be noise from transport and construction activities. We take into account areas that are particularly vulnerable to audible noise, and provide information to neighbours well in advance about construction and noise, coupling power liners, blasting work and helicopter use.
If you see or hear irregularities concerning safety and security at Statnett's facilities, please call: +47 71 68 90 20.