Solar PV rooftop systems: Selecting Connectors for your rooftop system
TheDC wiring of a conventional PV installation uses a relatively large number of terminals. In such cases,incorrect wiring can disable an entire string or even cause arcing and a fire. Hence only quality terminals should be used, and wherever possible ones that integrate elements that prevent wires from coming loose. Terminals without springs should be checked periodically for loose connections and should be tightened if necessary (copper is subject to creep under stress). The cables and wires should be mechanically fastened down via suitable fittings or the like so that in the event of a wire coming loose it will not touch another terminal or the housing.
Modules that integrate plugs for plug-in connectors or short wires with such connectors on them allow PV modules to be wired to strings in a safe and non-confusable manner. PV plug-in connectors are available from numerous vendors.
In as much as the ends of cables with PV plug-in connectors are not hazardous when plugged in, including when live, disconnect terminals are often unnecessary for systems that integrate quality PV plug-in connectors. If necessary, a string can simply be unplugged from the PV generator. Like disconnect terminals, PV plug-in connectors should only be touched with the system powered down and should never be used for switching purposes.
Source: Book on PV system design and practice