Winding failures Terminal board failures
Turn-to-turn failures Loose connections
Surges Leads (open)
Moisture Links
External faults Moisture
Overheating Insuffi cient insulation
Open winding Tracking
Deterioration Short circuits
Improper blocking of turns
Grounds
Phase-to-phase faults
Mechanical failures
Tap changer failures Core failures
Mechanical Core insulation failures
Electrical Ground strap broken
Contacts Shorted laminations
Leads Loose clamps, bolts, and wedges