FIELD: electrical engineering. SUBSTANCE: optrons consisting of two-electrode ion device 13, 17 and light-sensitive device 14, 18 are used as leakage current pickup. Ion devices of optrons are connected to power supply network via resistive dividers. Midpoint of dividers is linked to frame of protected installation 1. Light-sensitive devices 14, 18 control keys 24, 25. Relay 10 disconnecting installation from network in case of protection operation is coupled to output of one of keys. Relay operates with emergence of preconditions of injury with electric current; decrease of insulation resistance or shorting of circuit: installation frame to ground through humans body. EFFECT: avoidance of false operations and provision for operation with optional connection to zero or phase of power supply network. 1 dwg
