Photovoltaic system for use on roof of building for producing electric current form sunlight, has strings including up and down lines that are sealingly guided over at each other in region of monitoring units so that fields are compensated

摘要

The system has strings (2a, 2b) including up lines (4a, 4b) and down lines (5a, 5b), which are sealingly guided over at each other in a region of monitoring units (6) so that magnetic fields in a region of a magnet field sensor e.g. reed contact, are mutually compensated when current of a same quantity flows through the up lines or the down lines. The magnet field sensor is arranged in a middle between the up lines or the down lines, and detects a resultant difference-magnetic field, which is obtained by overlapping the magnetic fields. An independent claim is also included for a monitoring unit.