Abstract: The invention proposes: a distributor measuring box (2) designed to be installed on a photovoltaic solar module (40), having a housing with a support section (3) embodied to be supported on the solar module, an encompassing side wall, and a cover, and string line feedthroughs (4a) and/or string line connectors (4b), and having a string current measuring module (1) that includes a measuring component (30, 30a, 30b, 30c) and an evaluation unit (20) for measuring the string current in the distributor measuring box (2); a photovoltaic solar module having a plurality of solar cells, in which a distributor measuring box (2) is mounted to the back of the solar module (40) oriented away from the sun; and a photovoltaic system having a plurality of photovoltaic solar modules (40), having a plurality of string lines (10, 10a, 12), having a generator junction box, and having at least one inverter for supplying the electrical power produced by the photovoltaic generator.