The invention relates to a method and a device for impedance monitoring for a single- or multi-phase, ungrounded power supply
system (2), comprising the method steps: measuring a complex impedance (Z1, Z2, Z3) to earth (PE) simultaneously for each active conductor (L1, L2, L3) by means of a measuring device (12); calculating a complex touch current (I1, I2, I3) for each active conductor (L1, L2, L3) by means of a computing unit (14) as the quotient of a conductor-to-earth
voltage (UL1_E, UL2_E, UL3_E) of the respective conductor (L1, L2, L3) and the parallel combination of the complex impedances (Z1, Z2, Z3), wherein a total body impedance (Zk) is added to the complex impedance (Z1, Z2, Z3) of the active conductor (L1, L2, L3) that is touched by a person;
Check in the computing unit (14) whether the respective complex touch current (I1, I2, I3) exceeds an adjustable body
current threshold;Generating a
switching signal (20) in the
processing unit (14) when the body
current threshold is exceeded; controlling a switching element (22) with the
switching signal (20) to switch off or disconnect the power source (4). The impedance monitoring device comprises a measuring device (12), a
processing unit (14) and a switching element (22) for implementing the method according to the invention.