Abstract: A method and device for insulation monitoring and insulation fault location in an unearthed power supply network operate without a testing current generator by using an insulation monitoring device to generate a permanent measuring voltage between a mains conductor and earth and to feed a measuring current into the network. Measuring currents are detected using at least one current transformer arranged at each mains outgoing circuit, and total measuring current and proportional measuring currents in the mains outgoing circuits are determined and evaluated such that the measuring current used for insulation monitoring of the overall network is also used for insulation fault location in individual circuits. From a time variation of each circuit measuring current and the measuring voltage, an ohmic insulation resistance and a capacitive reactance (and/or impedance) are determined and analyzed for each mains outgoing circuit.

Abstract: The present invention relates to a method for insulation monitoring with an insulation monitoring device and insulation fault location without a testing current generator for unearthed electrical power supply networks, comprising A) providing a permanent measuring voltage between the mains conductor (60) and earth (80) and feeding in a measuring current by means of an insulation monitoring device (61), B) determining the measuring currents by means of at least one current transformer (64) arranged at each mains outgoing circuit (79), characterised in that the method further comprises C) determining the total measuring current and the proportional measuring currents in the mains outgoing circuits (79) by means of an insulation monitoring device (61), D) evaluating the measuring currents detected, wherein E) the measuring current of the insulation monitoring of the entire network is also used for insulation fault location in the individual circuits of the network, and F) the ohmic insulation resistance (69