Ground Fault Alarm (Signal Output)

What does ALARM 2 mean?

This alarm signal from the ground fault monitor (option +Q954) is intended for general alarm indication purposes, rather than directly tripping the drive. The contact is normally closed when no ground fault is present and has a higher load capacity of 250 V AC, 8 A. It is crucial to understand that the monitor's internal self-testing might briefly activate this signal, requiring careful interpretation by any receiving alarm or monitoring system.

• Developing insulation degradation in motor windings or cables, leading to increased leakage current that exceeds the alarm threshold but not the trip threshold.
• Accumulation of moisture or conductive dust on motor terminals, connection blocks, or within the motor itself, creating an intermittent or high-resistance ground path.
• External electromagnetic interference (EMI) affecting the ground fault monitor (+Q954) sensing circuit, causing a false alarm signal without an actual ground fault.
• Parameter P3-11 (Ground Fault Alarm Level) is set too low, making the system overly sensitive to normal operational leakage currents.
• Fluctuations in supply voltage or load conditions causing temporary increases in capacitive leakage current through aging insulation.

Click steps to track your progress.

1. 1

   Inspect the wiring connections for the ground fault monitor's alarm output at terminals X1:3 and X1:4 for integrity and absence of loose strands or corrosion.

2. 2

   Monitor the ground leakage current using a clamp-on ground leakage current meter around the main power cable's ground conductor (PE) during drive operation under varying loads.

3. 3

   Perform an insulation resistance test (megger test) on motor windings and cables (U, V, W to PE) to identify any areas with insulation degradation (readings between 1 MOhm and 5 MOhm may indicate early warning).

4. 4

   Verify the drive parameter P3-11 (Ground Fault Alarm Level) is configured correctly according to system specifications and the expected capacitive leakage in the IT system.

5. 5

   Check for potential sources of EMI (e.g., contactors, switching power supplies) near the ground fault monitor or its current transformer (CT) that might induce false alarm signals.

6. 6

   If intermittent, consider trending insulation resistance over time using an insulation monitoring device to detect gradual degradation that may not be apparent during a single spot test.