Earth-fault detector 789-665

WAGO's module signals a value falling below a non-adjustable, asymmetric isolation resistance between +24 V or 0 V of the supply voltage and ground with a potential-free (Iso OK) contact and status LED. The Iso OK contact can be evaluated via a PLC. This status is maintained until the next measurement interval. Operation with Grounded Control Circuit (Functional Potential Equalization) ■ The module establishes an internal connection between the 0 V (X2.2) and ground (X2.1) connections via a semiconductor switch. ■ At 10 s intervals, this connection between 0 V and ground is interrupted for 0.5 s, and the isolation resistance between +24 V (X1.3) or 0 V (X2.2) of the supply voltage and earth (X2.1) is determined. ■ The grounding connection on the module does not meet the requirements of a protective earth terminal (PE). It serves as a functional ground. The measurement method does not involve the module establishing any permanent connection between 0 V and ground. Operation with Ungrounded Control Circuit In this operating mode, the semiconductor switch to establish a connection between 0 V (X2.2) and ground (X2.1) is deactivated. At 1 s intervals, the isolation resistance offset is determined for 0.5 s. The module does not meet the requirements of an isolation monitoring device per EN 61557-8. “Iso OK” Contact The potential-free contact serves the purpose of supporting evaluation (e.g., via a PLC) of looming isolation faults. This contact must not be used to switch safety-related products that could cause the circuit to switch off.