maximum value can simply be the module reverse current IR-Mod specified by the vendor, the wiring rating permitting. Only DC fuses or circuit breakers that are specified by the vendor for direct current should be used, and they should be rated for around 1.2 times maximum system open-circuit voltage Voca stc for the solar generator at STC power output. String fuses should be rated for the entire range, which means that gPV or possibly gR fuses should be used; under no circumstances should aR fuses be used. To avoid failure induced by heat build-up or cloud enhancements, sufficient clearance should be allowed between individual fuses and between fuses and string diodes, to prevent false trips. Fuses should never be used for direct current, as this could provoke arcing. Although electric cut-outs rather than fuses are a better solution in that they allow individual strings to be disconnected while under load, these devices are rarely used owing to their high cost. Circuit breakers should be used to protect the circuits between arrays and the solar generator in larger installations.