In wiring solar modules of the same type in series with a view to ramping up system voltage, it is necessary to bypass each module using a bypass diode, if such devices are not already integrated into the system. For most high-voltage modules, two to six diodes should be used for each module (see Section 184.108.40.206) and the vendor’s data and recommendations in this regard must be followed to the letter.
Series connection of multiple (nMS) solar modules is referred to as a string (see Figure 4.28). In cases where a series (nSP) of such strings is parallel connected, as a rule an element that safeguards against reverse current and overload in the string cables, such as an additional diode (string diode, reverse current diode, blocking diode (red) and/or a fuse or circuit breaker (green)), should be wired in series in each string. For test purposes, the strings should be arranged on either side of the other solar
string diode, blocking diode
Fuse, circuit breaker
generators, i. e. at least one fuse, disconnect terminal or a special PV plug (blue) should be installed on either side. Such special disconnect-enabled plugs are also frequently used to interconnect modules, appreciably reduce string wiring work and allow a string to be divided into various segments where VOC < 120 V (low voltage). This is useful fortroubleshooting in the event of a failure. Wherever possible, protection class II modules should be used for high-voltage systems.