What Faults Occur in an On-Load Tap-Changer (OLTC)?
Quick answer — Common OLTC faults are contact wear or burning, diverter-switch and resistor failures (often from a broken transition path), mechanism and motor-drive faults, and oil contamination or gas (acetylene) from arcing. OLTC faults are a leading cause of transformer-related trips, and are detected by acetylene in the OLTC oil, contact resistance, temperature and operation monitoring.
What are common on-load tap-changer faults?
Contact and diverter faults
The tap contacts and the diverter (especially the resistor/arc path) wear and arc under load. This is seen as acetylene in the OLTC oil and as increased contact resistance.
Mechanical and drive faults
The drive, the mechanism and the coupling can seize, slip or fail to complete a tap change, causing a mis-position.
Detection and prevention
Monitor the OLTC oil (DGA for acetylene), the contact resistance and the drive/temperature; follow the maintenance cycle and change the contacts and oil as specified.
References & standards
- IEC 60214 (tap-changers)
- IEC 60076-1
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
Related components
Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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