Device for recognizing a fault condition in two-voltages or plural-voltages supply networks

A device (1) for detection of faults in two or more voltage levels motor vehicle power supply networks, where the networks are galvanically isolated in separate power networks (2, 3). Monitoring modules (15-18) and or a monitoring unit (8) are used to monitor the isolation of the two partial networks. The number of monitoring modules is determined by the number of supply voltages in the network. Once a monitoring device detects that an isolation resistance measurement exceeds a preset reference value then one or more power partial networks are switched off and or at least the corresponding control device is switched off.