Stator Rewind With IEEE Testing & Partial Discharge Mapping Case Study
When a critical 22,000 HP stator arrived for rewind, the customer didn't just need it fixed — they needed a fully documented, test-verified repair package built for long-term condition monitoring. Continental executed a complete rewind with a customer-directed acceptance program including IEEE-standard electrical testing, Tip-Up baselining, and partial discharge (PD) slot mapping using an IRIS system.
Asset: GE Stator | 22,000 HP | 13,800V | 679A | 1,800 RPM | Frame 923L3
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Overview
Industry: Pulp & Paper
The Challenge
This wasn't a standard rewind. The customer defined a high bar for both workmanship and documentation:
- Full rewind data capture for traceability
- IEEE-standard tests as factory acceptance criteria
- Tip-Up baseline measurement (IEEE 286) for ongoing maintenance trending
- VLF Hi-Pot per IEEE 95
- Baseline partial discharge collection and PD map by slot using an IRIS system and TVA wand
- Structured coil QC program, including spare coils and destructive evaluation
Passing the tests wasn't enough. results needed to be reproducible and usable as a future baseline.
Our Work:
1. Incoming Inspection & Documentation: Detailed visual inspection, full rewind data capture (dimensions, winding details, connection data), and initial core testing to confirm the correct repair path before any work began.
2. Teardown & Core Preparation Removed rings, burned out the existing insulation system, cleaned slots, lightly blasted the core and frame, inspected weld areas, and performed follow-up core testing to confirm lamination integrity before rewinding.
3. Coil Quality Control The customer specified a strict coil verification program. Three spare coils were ordered — the worst-performing coil was destructively evaluated to validate the coil run, and the best-performing coils were designated as line coils. All coils were surge-tested to IEEE 522 before installation.
4. Rewind & Assembly Coils, fillers, and RTDs were installed and inspected. Coils were lashed to outer surge rings with felt blocking at both ends for vibration control. Stator wedges were installed, series joints and pole jumpers formed and brazed, and windings Hi-Pot tested throughout assembly — not just at the end.
5. Resin Treatment & Final Finishing Stator prepared and completed with spray resin treatment, main leads installed per customer instruction, RTD leads connected and terminated, updated auxiliary nameplate supplied, exterior painted, and unit prepared for shipping.
Findings and Observations
Factory Acceptance Testing (FAT)
The customer-directed FAT package included:
- IEEE 286 Tip-Up Test — baseline for the customer's ongoing condition monitoring program
- IEEE 95 VLF Hi-Pot — high-voltage insulation verification
- Blackout Test — per facility requirements
- Partial Discharge Mapping — baseline PD collection by slot using IRIS system and TVA wand
These results are designed to be trended year-over-year — giving the customer a documented starting point for condition-based maintenance decisions.
Final Electrical Verification
At completion, Continental recorded:
- Impedance balance test
- Insulation Resistance and Polarization Index (PI)
- Winding resistance
- Three-phase impedance and balance verification
Results
- Complete rewind built on a validated core — no shortcuts in the foundation
- Coil quality confirmed through IEEE 522 surge testing and destructive QC evaluation
- FAT package delivered with Tip-Up baseline and PD slot map — ready for immediate trending
- Fully documented, traceable repair record supporting commissioning confidence and long-term reliability planning
Need a rewind partner who can meet strict acceptance requirements?
Continental delivers fully documented repair packages — IEEE surge testing, VLF Hi-Pot, Tip-Up baselining, and partial discharge mapping — built for FAT and long-term condition monitoring.