Comparative measurements of magnetic field from low voltage switchgears

Utilities in Sweden have a number of old transformer stations, placed in normal buildings in the centre of the town. A utility started an investigation to find low voltage switchgear of low magnetic emitting type, to replace the old installations. The ABB Kabeldon busbar system has a c-c distance of 85 mm between the busbars. The system is used in both cable distribution cabinets manufactured by ABB Kabeldon and in switchgear, manufactured by different companies. Current in busbars with this small separation generates a relatively low magnetic field. An “improved” design of a standard switchgear, equipped with ABB Kabeldon busbar system, resulted in a magnetic field, 3 m above the ground of approx. 0.2 μT for a 1200 A balanced current and 0.45 μT for a 400 A unbalanced current. This 3 m level is approximately the floor level above the switchgear. The small modifications made on a “standard” switchgear, resulted in a low magnetic emitting switchgear at a low extra cost