Applicable Systems
Freedom Series
Symptoms
The PGR-3100 ground-fault relay trips the main incomer and the ground-fault indicator illuminates. The fault log records the magnitude and feeder number. The system is de-energized.
Possible Causes
- Insulation failure in a motor winding to ground
- Water ingress into a conduit or cable tray in the MCC room
- Damaged cable insulation due to abrasion against sharp edges
- Incorrectly grounded shield causing circulating ground currents
Troubleshooting Steps
- Step 1: Isolate each feeder sequentially and measure insulation resistance to ground
The faulted feeder shows <1 MOhm; healthy feeders read >10 MOhm - Step 2: Inspect conduit seals, cable tray drains, and room humidity
No standing water; humidity <60% RH; all seals intact - Step 3: Check cable routing for abrasion points against tray edges or threaded rods
Cables are properly supported with protective grommets where needed - Step 4: Verify cable shield grounding is single-point at the MCC end per manufacturer guidance
No circulating currents in the ground conductor measured with clamp meter
How to Reset
Reset the PGR-3100 by pressing the reset button after isolating and clearing the ground fault. Acknowledge the event log. Reclose the incomer only after verifying zero ground current.
Common Replacement Parts
- PGR-3100-120: Eaton PGR-3100 ground-fault protection system (Includes current transformer, relay, and test resistor module)
Frequently Asked Questions
- Q: How sensitive is the PGR-3100?
Sensitivity is adjustable from 0.5A to 25A with time delays from 0.0s to 2.0s. Typical motor feeder setting is 5-10A with 0.1s delay.
- Q: Can I operate with a persistent ground fault?
No. A ground fault is a precursor to a phase-to-phase fault and must be cleared immediately.
Source: Eaton PGR-3100 Application Guide, SA02601001E
Category: Electrical