The nuisances that neighbours to power lines may experience in practice are seldom caused by magnetic fields. More often than not the electric fields are the culprit.

Electric charging
The electrical fields emanating from 400 kV power lines may cause objects underneath the line to become electrically charged. This could, for example, be houses with sheet-metal roofing, deactivated electric fences, metal ladders, metal bathtubs used as drinking troughs for animals, etc. When you touch the objects, you could get a small electric shock like the one we know from static electricity. It is not hazardous to your health, but it may be irritating. The problems often manifest themselves in dry weather and in particular if the objects are poorly earthed. The problems can therefore often be remedied by earthing the objects with, for example, a copper wire.

If a fluorescent lamp is placed close to the ignition coil in a car or a high-voltage line, it can be charged so that it starts to light, and sometimes you can also experience a faint tingling sensation on your arms when you are standing under one of the largest high-voltage lines. Both phenomena are caused by the electric field.

Noise
Under normal weather conditions overhead lines rarely make any noise. In damp weather noise often emanates from the largest 400 kV power lines. The noise is caused by small spark discharges on the surface of the power lines. This phenomenon is called corona. As is the case with electric fields, the corona effect depends on power line voltage. When the power line is not disconnected, the voltage is almost constant, and changes in the corona therefore depend on the weather and, in particular, air humidity. Magnetic fields, on the other hand, depend on the electric current, not the voltage, and the noise is therefore not an indication that the magnetic fields are stronger at the times when they generate an audible noise.

Computer screens
In some instances, relatively strong magnetic fields can distort the image on computer screens. Not only fields emanating from wires can distort the screen image. Fields emanating from equipment in the vicinity of the screen can also distort the image. Some modern desk lamps, for example, incorporate a transformer in the base. If the lamp stands right next to the screen, the image may flicker. Only older screens with cathode ray tubes are affected by the fields, not modern flat screens.

Pacemakers
The electric field around the very large high-voltage transmission lines could potentially interfere with certain older types of pacemakers. The pacemaker will in such case switch to a different frequency. It will, however, return to the original frequency when the person wearing it leaves the field. It is uncomfortable but not life-threatening. Modern programmable pacemakers can often be adjusted to avoid such effects. Magnetic fields created by high-voltage lines are too weak to interfere with pacemakers. If you have a pacemaker, you should to be on the safe side talk to your doctor if you often walk around under high-voltage lines.