DEHN SCI protection and disconnection technology is used in DPS (surge protective devices) for photovoltaic systems. The system is exclusive to DEHN, German manufacturer of protective devices for electrical installations.
In Brazil, DEHN is represented by Proauto Electric. The SCI (Short Circuit Interruption) is a protection mechanism composed of contact with low melting temperature solder, spring-driven rotary latch and electric arc extinguishing fuse.
Many commercially available surge protectors present a risk of melting and fire when they reach the end of their useful life. The low impedance presented by the varistor element (when its useful life ends) produces the passage of an electrical current that can put the electrical installation in a short circuit.
To avoid this, manufacturers insert rudimentary disconnection systems that are based only on opening the contact when the current is perceived. The danger lies in the fact that opening contacts in direct current installations with high voltages inevitably produces electric arcs, with the electric current passing through the air.
The electric arc produces high temperatures and is a known cause of fires in electrical installations in general, especially photovoltaic ones. Opening the contact in the SCI system occurs in four steps:
The first stage corresponds to the natural state of the DPS, operating normally within its useful life. In the second stage we can observe the switching at the end of the DPS's useful life, a process that normally triggers an extremely powerful electric arc in photovoltaic systems, which is often responsible for generating fires and physical destruction.
Also read: Fire in PV systems: the dangers of electric arc
The third stage of the process is the effective application of the SCI system, in which an electromechanical spring system acts to cut and extinguish the arc, inhibiting the arc from passing through the original contacts and directing the current to a parallel auxiliary circuit with fuse.
The fourth and final step consists of breaking the fuse, within which the electric arc is extinguished, and activating the device's burnout indication, remotely or physically requesting the replacement of the equipment. For more information about DEHN and its technology click here.
Material produced by the editorial team Canal Solar with information from Osvaldo Quibao and Robson Bezerra – Technical Sales Department at Proauto Electric.
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