What Happens When a Transformer Explodes?

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When a transformer blows, the noise, heat, and fumes that are released may be a bit of a frightening experience. In some cases, you may even be able to see a fireball or a charged ball as it leaves the transformer and starts traveling down the power lines. Although this is not a nice sight and your safety may be put in danger, by knowing whom to contact when this happens, you can preserve your safety and the safety of your family members. 

In reality, power transformer blows are very rare. As most power transformers are made to withstand power surges and other damaging factors, they are safe pieces of electrical equipment. This is why you can see so many of them around your neighborhood, but will very rarely hear of transformer explosions. 

In fact, the US power transformers only have around a 0.1% chance of explosion per service year. This amounts to just 2% for a service period of over 20 years. Still, however negligible this chance may be, consider how many transformers there are in the US. This is a serious overall threat and the utility company has to work hard to maintain the transformers and keep them operating in a safe way. 

What is a Power Transformer?

A power transformer is a piece of electrical equipment that helps power your home. The electricity traveling through the power lines is of a very high voltage. Although this is the best voltage for the electrical grid, it is still too much electricity for a single home. If this current was sent to your home, it would be an equivalent of a lightning strike to your home – including all the wiring and expensive appliances that can be seen there. 

Power transformers protect your home by reducing the voltage of the current traveling through the power lines. In fact, the transformer box is also there to absorb a lot of power surges and to protect the electrical system in your home by switching energy from a higher voltage to a lower voltage. However, faulty mechanisms and some factors outside of our control can still cause damage. 

When this happens, transformer explosions ensue. This does not mean that any lightning strike or every power surge will result in a transformer explosion. Rather, it means that the transformer can receive a bit of damage. Over years, this damage may accumulate, resulting in a loud boom and a power outage in your home or the local area. 

Causes of Transformer Explosions

However frightful an electrical transformer failure and explosion may be, it is necessary to understand what actually happens and how to protect yourself. When you understand the basic principles behind how a power transformer works, you will be able to take measures and ensure your safety. Before discussing what causes transformer explosions, we should take a look at how an electrical transformer works. 

First things first, an electrical transformer reduces the voltage of the electricity that should be sent to your home. As power lines carry electricity of a very high voltage, reducing the voltage is necessary to ensure the safety of devices in your home. The transformer does this job by means of coils coiled around each other. As electricity passes through one coil, it evokes the electrons in the other one by means of forces known as electromotive forces. 

The entire machinery is submerged in an insulating material, known as mineral oil. This petroleum-based mineral oil can help the transformer cool down by absorbing excess heat from it, effectively transferring energy in the form of heat and capturing it. When the power surge is too high, such as in lightning strikes, the incoming electrical line may carry enough electricity to start boiling the mineral oil (or the insulation fluid), effectively evaporating it or heating it past the fire point and increasing the pressure in the transformer. 

When this happens, a transformer explosion may occur. If there were several lightning strikes in your area before, this may happen as well. Here are some causes of transformer explosions: 

  • Lighting, 
  • Extreme weather, leading to an increase in power demand, 
  • Failing trees, as they can damage power lines, 
  • Electrical failure, as it may cause other damage to the transformer, not just an explosion, 
  • Mechanical failures, as transformers are mechanical devices, 
  • Outdated transformers, as they have a limited lifespan, and 
  • Any foreign objects entering the transformer, such as critters, too much dust, rodents, branches, and/or leaves. 


Lightning is the most common cause of transformer failure. Power companies have to deal with several exploded transformers every time there is a lightning storm. The reason behind it is that the sudden surge of power may heat the insulating liquid past the fire point and cause fire, insulation evaporation, or setting it on fire. As it usually goes, these are not only problems that lightning may cause, as the insulator vapor contains methane, a highly flammable has that you may see ignite from the high temperature in the transformer. 

Extreme Weather

Extreme weather can also damage transformers in your area. In extreme weather conditions, the power grid has to work extra hard. The damage occurs when the realistic capacity of the network is exceeded or the grid is nearing that state. In reality, cold weather boosts energy use, but the cold air keeps the insulation in place. In hot weather, especially in high humidity, the mineral oil is already melted and heated, resulting in poor insulation properties and possible hazards. 

Falling Trees

Falling trees can also damage the transformer. As the tree falls, it may hit the powerline, causing over-voltage and damaging the insulating oil inside. Additionally, a tree can also hit the transformer itself, causing mechanical damage that can, in turn, cause a short circuit, overheating, and explosion. 

Electrical Failure

Electrical failure within the transformer itself can also cause damage, as safety devices themselves in the transformer can be damaged. There are several factors that can cause electrical damage to the transformer: 

  • Poor wiring, 
  • Poor insulation, 
  • Static electrification, 
  • Power surges, and
  • Over-voltage. 

Mechanical Failure

Mechanical failure can also cause a transformer to fail and explode. In this case, the transformer may suffer from: 

Needless to say, any mechanical damage to the external casing of the transformer can cause damage to the internal components. 

Outdated Transformers

We can often hear that the grid needs modernizing. The thing is that the grid is being modernized every single day, but considering its scope, not all of them can be up to date. The reason behind failed transformers can often be the sheer age of the transformers. As most of them are designed to last 20-30 years, periodically replacing them is necessary to ensure a good and reliable power supply. 

Critters & Foreign Objects

Critters and other foreign objects can fall in or creep into the transformer. When this happens, the risk of short-circuiting the internal wiring and causing electrical damage ensues. The same happens if rodents get in, as well as when thick dust deposits fill out the inside space in a transformer. 

Things You Should Do When a Transformer Explodes

Downed power lines and other factors can damage the transformer in your neighborhood. If this happens, you should know that a damaged transformer is a very dangerous thing. The voltage levels that get discharged, if a line is down, can kill a person in a matter of seconds, so staying away is the most important thing to preserve your safety. Seeking professional help by calling your local utility company. 

Do Not Approach

Approaching a power transformer that is damaged, exploded, or otherwise dysfunctional can be fatal. The discharge coming out of it can kill a person and stories of sightings of ball-lightnings being emitted by the transformers circle the Web. In any case, stay far away, possibly in the house or another object. If you have to leave the property, stay as far away from the transformer and any lines which may be touching the ground, as they do not automatically disrupt the current. 

Seek a Professional

Seeking a professional is the next thing to do. Immediately contact your utility company and let them know what has happened. Give them your address, and any other details they may ask you. Never try to attempt fixing or moving fallen parts on your own. The one voltage you want to avoid is ANY VOLTAGE. 


Why does Fault Occur in Transformer?

There are many reasons faults may occur in a transformer. The transformer may be damaged by lightning, extreme weather, fallen trees, electrical failure, traffic accidents, mechanical failure, any objects or insects ending up in it, or simply due to its age. Never attempt to fix any issues on your transformer. 

How Much Does it Cost to Replace a Transformer?

Repairing or replacing a transformer is not cheap. In fact, an average transformer costs $3,000 to $7,000 to replace. This is why regular maintenance and reporting any issues you may see is essential for the equipment and its functioning. Never try to replace/repair any transformer parts. 

Do you Lose Power When a Transformer Blows?

Yes, when a transformer blows, you lose power. In fact, the transformer is one piece that is necessary for you to have a power supply in the first place. Connecting your home to the power line itself is dangerous and will damage all electrical equipment in your home. 

Can a Transformer Shock You?

Yes, a malfunctioning transformer can shock you. This is the reason why you should never touch it, try to repair it, or otherwise meddle with it. You should always contact your local utility company if any issues arise, even if branches around the transformer need to be cut. 


Transformers are complex pieces of machinery that deliver power straight to your home. Although safe and reliable, designed to last anywhere between 20-30 years, your power transformer may still get damaged and shock you. If you notice an interruption to your service or to the transformer itself, contact the utility company immediately and stay away from it. 

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