Overvoltage Protection Modules

Increasing Availability via Improved and Preventive Maintenance

According to the IEC 60204-1 standard, measures must be taken to reduce the probability of malfunctions due to insulation faults/ground faults in a control circuit. A common option is connecting 0 V to the ground potential in the control circuit, in combination with an upstream fuse. With the new ground resistance signaling module (789-665), WAGO offers the possibility of detecting not only the grounding of the 0V potential, but also the full and automatic undershooting of a non-adjustable, unbalanced insulation resistance between +24 V or 0 V of the supply voltage and ground. An integrated potential-free contact can be used to signal the Iso OK status to a controller, for example, a PLC. Additionally, on-module LEDs clearly indicate the insulation fault to the operator. Compared to mechanical ground conductor disconnect terminal blocks, maintenance is considerably simplified. Early detection of imminent ground faults enables improved preventive maintenance, ensuring increased system uptime.

The module can be used in single-phase grounded and ungrounded control circuits, but it does not meet the requirements for insulation monitoring devices according to IEC 61557-8. A slide switch allows the user to select the grounded/ungrounded control circuit operating mode. With the new ground resistance signaling module, it is possible to upgrade from the former manual testing of a ground fault to a permanent test of the insulation resistance.