Transformers are electrical devices that are meant for stepping the voltage of your electrical supply up or down. To minimize the losses of transmission, utility companies usually transmit electricity at much higher voltages across the overhead or on buried wires.
Finally, transformer will step down this incoming voltage to make suitable supply for household use. If transformer fails, then it can nosedive enormously at times. This can result in fire or explosion and so you will need to repair transformer.
Electrical transformer has 2 coiled wire sets around a single ferromagnetic core, which is a basic element of this device. The side which is connected to high-voltage line will have more coils as compared to the one coupled with residential line.
If power flows through denser coil, then it creates magnetic field that transfers electrical current to other side of transformer at much lower voltage. Insulation will protect the wires and also coolant like mineral oil will help to keep the entire assembly from getting overheated.
Causes of failure
For variety of reasons transformer explosions can take place. Most common reason is lightning strike due to storm forcing the transformer to overload. Various damages to equipment or wires elsewhere in electrical grid may also cause much of electricity to flow in the transformer that can cause it to explode.
There are protection circuits in the transformers, which are designed to shut the system off in case there is a spike in the voltage. Nevertheless, all these safety devices may take about 60 milliseconds to respond, which may not be quick enough to prevent transformer from blowing.
Besides, corrosion and wear over a period of time may weaken wire insulation, or many other components and increases the possibility of failure.
The result can always be spectacular whether the failure occurred due to corrode insulation or when lightning strike. Worn wiring or overcharging may create heat and spark, which is enough for igniting the mineral [keeps transformer cool].
As the mineral oil starts burning, it will create massive overpressure inside sealed transformer that eventually causes the vessel to get ruptured with loud bang, shower of flames and sparks.
Since the materials are involved, color of the flash can be bluish-green. It will be seen during night from much longer distance.
Aftermath and repair
As the transformer blows, it will interrupt electricity service to residences or businesses, which are connected to it.
The destroyed hardware must be replaced by electric service crews, after shutting down the electrical line for preventing damage or injury.
Based on the extent of damage, service crews may need to shut off all other electrical service temporarily, so as to prevent stress on the power grid while changing the destroyed transformer.