Trouble Shooting On Transformer
Transformer failures may occur in either the electric, magnetic or dielectric circuits.
Symptom | Cause |
Electric Circuit | |
Overheating | Continuous overload Wrong external connections Poor ventilation High surrounding air temperature(Rating is based on 30°C average temperature over 24 hour period with peaks not to exceed 40°C) |
Reduced or Zero Voltage | Shorted turns Loose internal connections Faulty Tap changer. |
Excess Secondary Voltage | Input voltage high Faulty tap changer. |
Coil Distortion | Coils short circuited. |
Insulation Failure | Continuous overloads Mechanical damage in Handling Lightning surge |
Breakers or Fuses Opening | Short Circuit Overload Inrush current Internal or External. |
Excessive Bushing Heating | Improper bolted connection. |
High Voltage to Ground | Usually a static charge condition (using rectifier or VTVM meter) |
Magnetic Circuit | |
Vibration and Noise | Low Frequency High input voltage Core clamps Loosened in shipment or handling |
Overheating | High input voltage. |
High Exciting Current | Low Frequency High input voltage Shorted turns |
High Core Loss Low frequency | High input voltage. |
Insulation Failure | Very high core temperature due to high input voltage or low frequency. |
Dielectric Circuit | |
Pressure Relief Device Operation | Insulation failure. |
Burned Insulation Lightning surge Broken bushings, taps or arrestors | Switching or line disturbance |
Overheating | Inadequate ventilation |
Breakers or Fuse open | Insulation failure |
Bushing Flashover | Environmental contaminants Abnormal voltage surge. |
Mechanical | |
Cracked Bushing | Overstress due to cable load Mechanical handling |
Loss of Pressure | Check gaskets, cracked bushing, welds |