According to statistics, more than 60% of PV power plant fires are due to DC arcs. DC arc is a gas discharge phenomenon, which can be understood as a high-intensity instantaneous current generated in the case of insulation. According to literature reports: when the electric switch disconnects the current or the contact is poor, if the circuit voltage is not less than 20 volts and the current is not less than 80~100mA, a DC arc will be generated between the contacts of the electrical appliance. Unlike the AC arc, the DC arc does not have a zero-crossing point, which means that if a DC arc occurs, the triggering part will maintain stable combustion for a long time without going out.
In a photovoltaic power station, if the cable joint is not tightened, it will lead to poor contact; the reliability of the connector or direct switch; the long-term aging of the insulating layer, and the damage of the insulating layer due to external force will cause DC arcs. As the operating time of the plant increases, so does the probability of DC arcing. The high temperature generated by the DC arc can easily exceed 3000 ℃, which can directly lead to fire. Based on domestic and foreign cases and data, DC arcs have become the number one killer of power station fires