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Power transformers are critical—and expensive—parts of the power grid. These devices convert electricity to higher (or lower) voltages so it can be used appropriately. Transformers are generally classified by the cooling systems that allow them to dissipate heat as they run. Some use oil as an insulator and coolant, while others use gas or even dry powders. But all types require transformer fire protection. We’re addressing frequently asked questions and breaking down transformer fire protection standards in this blog.

Can a Bad Transformer Cause a Fire?

Transformers catch fire due to mechanical failure and electrical issues, so yes, a poorly-maintained transformer can cause a fire. Lightning strikes and other bad weather can also start transformer fires. Between 2 and 4% of transformers can be expected to cause a fire during their service life. While this is a low risk, it is not zero risk–and the impacts of a transformer fire can be significant. This is why regular transformer maintenance is essential: to keep the machinery in good working order and make any risks known in advance.

What Happens If a Transformer Catches Fire?

If a transformer catches fire, the portion of the power grid that relies on that transformer is going to go dark. In these circumstances, there are four main areas of concern: human impact, economic impact, impact on public confidence, and impact on government capability. These four areas are outlined in a transformer risk assessment strategy document from the US Department of Energy.

  • Human impact: The effects on life and physical well-being, both from the fire itself and from the results of power outages.
  • Economic impact: The direct and indirect costs of both the fire and the power outages, including lost utilities revenue, cost to repair the grid, food spoilage, lost business, and more.
  • Impact on public confidence: The shift in goodwill that occurs due to both the fire and power outages, including indirect effects on the perception of both public and private institutions.
  • Impact on government capability: The impact on the ability to ensure public safety and health, maintain order and security, and deliver other essential services.

When a transformer catches fire, there are risks in all of these areas. As a result, the International Council on Large Electrical Systems (CIGRE) developed an international guide for transformer fire safety practices. This technical brochure includes information such as guidance on the probability of transformer fires occurring, the physics behind electrical arcing risk, a summary of transformer fire protection methodologies, and more.

What are the NFPA Requirements For Transformers?

The National Fire Protection Association (NFPA) transformer fire protection requirements include specific guidance about fire protection systems and lightning protection systems. They also have separate firewall guidance for power plants and high-voltage converter stations in particular.

  • NFPA 15 is the standard governing design, installation, and testing of water spray systems for fire protection, including necessary sprinkler systems for transformers that use oil.
  • NFPA 780 is the standard governing lightning protection system installation and specifications.
  • NFPA 850 is the recommended practice for fire protection at electric plants and high-voltage power stations.

Much of this guidance is specific to oil-type transformers. Dry-type transformer fire protection is unique because dry-type transformers are almost always used indoors but also handle lower voltages. Generally, under NFPA 15, when only dry-type electrical  equipment is used, a dedicated sprinkler system for just the transformer may not be required but still may be preferred.

What Happens When a Transformer Is On Fire? Plan Your Response Before The Event

Though the transformer(s) at your factory, hospital, school, or other location might never catch fire, the potential consequences are a lot to bear. Installing a transformer fire protection system allows you to operate with peace of mind and protect the surrounding area if a fire does occur. There are a few different types of systems that can be used:

Learn How to Protect a Transformer From Fire

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