Page "Arc-fault circuit interrupter" Paragraph 14

AFCIs do not detect low line voltage.

Low line voltage can cause electro-mechanical relays to repeatedly turn off ( relay opens ) and on ( relay closes again ).

If current is flowing through the load contacts it will cause arcing across the contacts when they open.

The arcing can oxidize, pit and melt the contacts.

This process can increase the contact resistance, superheat the relay and lead to fires.

Power fault circuit interrupters are designed to prevent fires from low voltage across loads.