Applicable Systems
Okken
Symptoms
The Vigirex ground-fault relay trips and the main incomer opens. The relay display shows the residual current value and the faulted feeder indication. The system is de-energized.
Possible Causes
- Single-phase insulation failure in a motor or cable feeder
- Moisture ingress into the Okken room or cable trenches
- Incorrect shield grounding causing circulating ground currents
- Capacitive charging current from long cables exceeding the relay threshold
Troubleshooting Steps
- Step 1: Isolate each feeder sequentially and measure insulation resistance
The faulted feeder shows <1 MOhm; healthy feeders read >10 MOhm - Step 2: Inspect the room HVAC, humidity levels, and cable trench drainage
Humidity <60% RH; no standing water in trenches or cable trays - Step 3: Verify cable shield grounding is single-point at the switchboard end
No circulating currents measured in the PE conductor with a clamp meter - Step 4: If using long cables (>500m), verify the capacitive charging current is below the Vigirex setting
Charging current <30% of the ground-fault pick-up setting
How to Reset
Reset the Vigirex relay by pressing the reset pushbutton after isolating and clearing the fault. Acknowledge the event log. Reclose the incomer only after verifying zero residual current.
Common Replacement Parts
- RH197: Schneider Vigirex RH197 residual current relay (Compatible with Toroidal CTs for 30mA to 30A sensitivity)
Frequently Asked Questions
- Q: What sensitivity should I set for motor feeders?
Typical settings are 0.5A to 5A with a 0.1-0.3s delay. High-sensitivity (30mA) is for personnel protection, not equipment.
- Q: Can I operate with a ground fault if it is below the trip threshold?
No. Any ground fault indicates insulation degradation and should be investigated promptly to prevent escalation.
Source: Schneider Electric Okken Switchboard User Manual, DOCADOC-001
Category: Electrical