Interconnecting solar generators and solar modules is prone to essentially the same problems as interconnecting solar cells. Modules are basically super solar cells with higher voltages and stronger currents. However, owing to the higher voltages and stronger currents exhibited by solar generators, more robust preventive measures are needed in view of the far higher outputs entailed by a malfunction. Thus the modules used should be rated for total system voltage at a minimum, i. e. total available direct current in PV installation go-live mode.
A large solar generator should be subdivided into groups that can be switched individually in the event of a failure and that can also be maintained separately without the need to shut down the entire generator. To this end, one should make sure that all solar generator fuses, circuit breakers and switches are expressly rated for DC operation at the relevant voltage (> 1.2 ■ Voca – STC) and current (VOCA is the system open-circuit voltage). Even under low voltages (above 24 V), shutting down direct current is far more difficult than alternating current owing to the absence of a zero crossing in direct current. In most cases, AC materials can only be used for DC systems at very low voltages (e. g. in lieu of 230 V AC, for 24-48 V DC only). Owing to possible cloud enhancements (see Section 2.3), cables, diodes, bypass diodes and fuses need to be sized in such a way as to ensure that at maximum temperature 1.25 (or, better, 1.4) times the short-circuit current ISC-STC of the relevant string can be conducted for an unlimited period [4.10]. Moreover, cooling elements should be integrated into the system diodes if necessary.