Power Transformer Blast/Explosion incidents: Reasons & Precautionary measures to avoid such incidents

It is evident from the picture, that how dangerous these incidents are.

So, let’s see, what happens inside a transformer so that it literally blows up. Any enclosed body like a transformer, needs a huge amount of pressure inside the tank, to explode.  Some recurrent, and evident reasons, for transformer blasts, are 

1. Temperature rise, or deterioration of transformer oil: The temperature of oil rises due to cooling system failure, or transformer overloading. And oil deterioration happens due to incipient internal fault, or oil contamination.

2. Severe internal faults: Severe internal faults occur such as winding earth fault, core fault, etc.

Due to all such mentioned cases, the pressure inside the transformer increases. Incipient faults and oil contamination lead to gas formation in oil, which over the period, increases pressure. Severe faults create huge pressure in a very short period of time. This pressure is so huge that, it explodes the transformer. 

There are multiple prevention and protection layers, which can avert transformer blast.

The temperature rise of oil is monitored by O-T-I, called as Oil Temperature Indicator. Also, an effective and functional cooling system prevents temperature rise. Buchholz relay gives an alarm, and subsequently trips transformer, in case of gas accumulation due to incipient fault. Also, D-G-A, which means Dissolved Gas Analysis, of transformer oil, is done periodically, to identify any gas formation or degradation of oil.

Severe internal, or external faults, are identified and isolated by relays.

Even if all these systems fail, there is a P-R-D installed on the transformer tank, called a Pressure Relief Device. As the name says, this device provides a passageway, for oil to release the pressure, developed inside the transformer. Hence, with these monitoring and protection systems, it becomes very easy, to identify in advance and prevent transformer blast incidents.

Now, Let’s see, how to prevent transformer blast incidents.

1. Any incipient fault affects transformer oil. Oil starts deteriorating and produces gases. These gases trigger the Buchholz relay or can be identified during the D-G-A test of oil. If any gases are identified, indicating a fault, then immediately transformer internal inspection should be done, such as windings, leads and core should be checked for any insulation damage, or any other fault.

2. Protection relays, and circuit breakers, should be checked periodically, so that protection relays and circuit breakers function efficiently during a fault, and isolate faulty portions effectively. This effective fault isolation avoids excessive stresses on the power transformer, preventing it from a possible explosion.

3. Overloading of the transformer should be avoided, overloading leads to overheating, which consequently starts oil deterioration. It should be standard practice to note down O-T-I and W-T-I readings, that is the transformer oil temperature and winding temperature readings periodically.

4. The cooling system of the power transformer should be functional and effective. Even if all the preventive measures fail, and P-R-D called a pressure relief device, is in functional condition, then it gives a passageway to pressure, preventing transformer explosion.

5. Also, it is equally important, to keep a track of transformer bushings’ healthiness.

If all the discussed and necessary precautions are taken, then transformer blasts also called transformer explosion incidents, can be avoided.