A DC circuit is a direct-current electrical path, common in photovoltaic and battery-backed systems. Unlike AC power, DC flows in one direction and can remain energized whenever sunlight, stored charge, or connected batteries are present. In solar installations, DC circuits run through panels, strings, combiner boxes, disconnects, and inverters before the energy is converted for site use.
For cyber security and industrial safety, DC circuits matter because they are part of the physical attack surface of critical infrastructure. A technician, intruder, or faulty control sequence that assumes a system is “off” may still encounter live conductors, creating arc-flash and shock risk. Defenders reduce that risk by isolating DC sources, verifying absence of voltage, using lockout/tagout, and segmenting monitoring systems from field equipment. In real-world attacks or failures, the danger is often not malware itself but unsafe access to energized hardware, miswired disconnects, or remote commands that leave hidden power on the line.