Emergency stator rewinding and rotor refurbishment for a 500 MW thermal power plant generator, completed 50% faster than the original outage window with zero safety incidents.
Review the project background, diagnosis, intervention steps, standards, and results summarized below.
Project Background
A base-load 500 MW thermal power plant experienced insulation failure on a main generator during a planned outage. The defect was more severe than initially identified, threatening to extend the outage beyond the grid-committed window and risking penalties and lost generation revenue.
Assessment & Diagnosis
On-site visual inspection and partial discharge indications highlighted severe insulation ageing on several stator slots.
Offline tests (IR, PI, tan-delta, winding resistance) confirmed insulation degradation beyond acceptable limits.
Bore-scope inspection identified localised hotspot damage and partial core lamination distress.
Root cause analysis linked the failure to thermal cycling, historical overloads and aged insulation system.
Execution & Intervention
Developed an accelerated outage programme in coordination with plant operations and grid commitments.
Executed complete stator rewinding with upgraded Class F/H insulation system and improved slot support.
Refurbished rotor including rotor winding checks, balancing, and refurbishment of critical components.
Performed core flux testing, EL-CID test and corrective work on affected core laminations.
Implemented enhanced cooling and ventilation improvements as part of the rewind design.
Quality & Standards
All work executed under ISO 9001:2015 Quality Management System.
Testing and acceptance criteria aligned with IEEE 43, IEEE 56 and IEC 60034.
Site safety procedures aligned with ISO 45001 and plant-specific HSE requirements.
Final testing performed under NABL-accredited laboratory supervision for key measurements.
Measurable Results
Project completed approximately 50% faster than the originally forecasted extended outage duration.
Zero safety incidents recorded throughout the project, including confined-space and high-voltage activities.
Stator insulation test values improved significantly post-rewind, with tan-delta reduced from approximately 0.015 to around 0.004 and PI improving from ~1.5 to ~3.5.
Generator efficiency improved by approximately 15% compared to pre-failure baseline, with operating vibration maintained within OEM limits (< 20 µm on critical bearings).
Plant returned to grid within the committed window, avoiding penalties and unserved energy costs.
Talk to RKELC about how we can apply the same engineering approach to your rotating equipment.