The high reliability of IT systems is ensured by continuous insulation monitoring. Insulation monitoring detects developing insulation faults and immediately reports that the value has fallen below the minimum. This prevents an interruption in operation due to a second, more serious insulation fault. ABB developed a completely new range of insulation monitoring devices for AC, DC or AC/DC IT systems up to 690 V AC or 1000 V DC. Most standard applications can be served with just 4 devices. In addition, a version for solar applications with increased leakage capacity has been added.