The Siemens Insulation monitoring relays are used for monitoring the insulation resistance between ungrounded 1- or 3-phase AC supplies and a protective conductor. They measure insulation resistances between system cables and system ground. If the value falls below the threshold value, the output relays are switched to fault status. With these devices, which are suitable for both AC and DC networks, a pulsed test signal is fed into the network to be monitored and the isolation resistance is determined.

Wide control supply voltage range
Frequency range 15 to 400 Hz
Monitoring of broken conductors