A DC arc fault is a sudden high-power discharge between conductors. In a PV system it can occur in series along neighboring conductors in a string, or in parallel between parallel strings. A series arc forms when a conductor or connection opens while current is flowing. The spark ionizes the air into plasma, and if the current is high enough the plasma keeps the current flowing across the gap as a visible arc. Once a series arc starts, it can last for seconds, minutes or longer. Typical causes are a loose module connector, a loose combiner box terminal, or a solder joint that separates inside a module. Other common causes are damaged or badly mated PV connectors, pinched or abraded conductors, and damage to modules. A parallel arc fault is different: it comes from an insulation failure between two conductors. The NEC 690.11 arc fault requirement covers only series arcs. DC arcs are severely damaging and usually cause destructive fires. Field experience puts arc faults and ground faults as the two most common causes of PV array fires. Arcs are transient, which makes them hard to detect. Inverter arc fault detection looks for the electrical noise of a series arc and shuts down the inverter, and string-level arc fault circuit interrupters add further protection.
explainsSeparates arcs that form along one conductor path (series) from arcs between conductors or between parallel strings (parallel).
sec=2.9 h=6199cd73a1f7sec=6 h=f9609f5bf2cfsec=h4 h=675522b8fd06c2 drafted · lead Electrical fire
DC arcs usually cause destructive fires. Arc faults and ground faults are reported as the two most common causes of PV array fires.
sec=2.9 h=6199cd73a1f7sec=6 h=f9609f5bf2cfsec=h10 h=709d473ec789related_toc3 drafted · lead DC arc flash
sec=2.9 h=6199cd73a1f7review note: support check: partial - u1 describes DC arc faults, but no passage mentions DC arc flash as a hazard or relates it to them.
c4 drafted · lead DC arc-fault protection
The inverter arc fault function detects and interrupts DC series arcs.
tbl=6.r7 h=0a2c4c8b596asec=h15 h=d574c58e979cc5 drafted · lead Arc fault circuit interrupter
Arc fault circuit interrupters installed on individual strings protect against arc faults.
sec=2.9 h=6199cd73a1f7c6 drafted · lead Arc fault detection board
sec=h10 h=709d473ec789sec=h15 h=d574c58e979cc7 drafted · lead Waveform spectrum analysis
Arcs are found by spectrum analysis of current and voltage waveforms, or by detecting the electrical noise that comes with a series arc.
sec=2.9 h=6199cd73a1f7sec=h15 h=d574c58e979cc8 drafted · lead UL 1699B proposed
sec=h15 h=d574c58e979creview note: support check: partial - u21 says the inverter's arc fault detection complies with UL 1699B and relates it to series arcs, but the link is via a specific product.
c9 verified · fact Poor connector contact
Loose, separated, damaged or badly mated connections are a common cause of series arcs.
sec=h13 h=48f3c580120esec=6 h=f9609f5bf2cfsec=h5 h=a958fac316ceverified by: review-workflowverified on: 2026-10-24
c10 drafted · lead DC connector
sec=h13 h=48f3c580120esec=6 h=f9609f5bf2cfc11 drafted · lead Solder bond defect
Separated, cracked or corroded solder joints in modules can start a series arc.
sec=6 h=f9609f5bf2cfsec=h5 h=a958fac316cec12 drafted · lead Loss of electrical insulation
Parallel arc faults come from an insulation failure between two conductors.
sec=h3 h=05678f48e57a