What typically causes transformers to fail?

A transformer can fail for a variety of reasons, but the most common causes include lightning strikes, overloading, wear and corrosion, power surges and moisture. Regardless of the cause, the result can be remarkable. Transformers contain mineral oil keeping the transformer cool.

What is fault current in transformer?

Short circuit fault current I(fault) in kilo amps is equal to 100 times of transformer’s rating S(kVA) in kVA divided by the multiplication of root 3, transformer’s secondary voltage V(V) in Volts and percentage impedance in percentage. I(fault) = S(kVA) x 100 / (1.732 x V(V) x \%Z). The \%Z will lie between 4 to 10\%.

Why do Transformers stop working?

Usually, a transformer fails only after another part in the electrical circuit shorts to ground or draws an unusually high amperage. In these cases, replacing the transformer without first finding and correcting the fault will only cause the transformer to fail again.

How do you know when a transformer is failing?

Symptoms of power quality issues include vibration, excessive buzzing or humming and overheating. Technicians should occasionally check the power of transformers that supply nonlinear loads, such as variable frequency drives (VFDs) or switching power supplies.

What are Interturn faults?

An interturn fault can accelerate the aging of the insulation system or may lead to the complete breakdown of the transformer. Internal faults are generally turn-to-turn or turn-to-ground short circuits in the transformer winding.

What are incipient faults in transformer?

Incipient faults are low magnitude and fast decaying transients, lasting only for a few microseconds during impulse tests of transformers. They are very difficult to detect, even for experts, and may cause severe problems leading to faults and consequent outage.

Can a transformer be repaired?

Low and medium voltage coils which have been damaged can be repaired, refurbished or replaced. This would typically be done for larger, often medium voltage transformers which have sustained damage to the outer, primary winding.