Heat Waves and Transformer Failures

During a heat wave, you may see articles or news reports referencing the role that transformers have in outages that occur when the weather is hot. When the mercury climbs, the level of electrical load on the transformer (the amount of power that can be delivered or carried) increases as people crank up their air conditioners and fans. When the power-handling capacity of a transformer is exceeded for an extended period of time at hot ambient temperatures, it greatly increases the risk of the transformer’s failing. Most transformer failures result in a fuse operation and a limited power outage without severe consequences.

Sometimes, however, transformers rupture and can even explode. If the transformer is filled with petroleum-based mineral oil, it will also likely catch fire and burning oil can leak from the tank. There have been reports of leaking, burning oil flowing beneath nearby vehicles and causing them to catch fire. Even transformers installed in underground vaults, often right underneath city streets, have caught fire, their flames rising above the cooling grates on sidewalks.

Bio-based Fluid Can Take the Heat

When a heat wave hits, bio-based transformer fluid is of particular benefit. Here’s why.

• First, transformers filled with bio-based fluid can handle up to 10-20 percent more electrical load than equivalent units filled with mineral oil.
• Second, a transformer filled with bio-based fluid has its insulating paper age more slowly, so the transformer’s life can be double or more.
• In the event a transformer does fail and rupture, bio-based fluid-filled transformers are much less likely to catch fire than petroleum-based mineral oil-filled transformers. This is due to the fact that bio-based fluid has a much higher fire point. In fact, among the 50,000-plus transformers in service using bio-based fluid, no fires have been reported.
• Lastly, any leak or spill that may result from a petroleum-based mineral-oil filled transformer rupture or fire exposes the environment to a fluid with a poor environmental profile, limited biodegradability, and materials that may contain a confirmed carcinogen.* Bio-based fluid, on the other hand, is non-toxic and meets the EPA’s Ultimate Biodegradability classification.

*While today’s mineral transformer oils are highly refined, there are hundreds of millions of gallons in existing older transformers that contain significant quantities of polynuclear aromatics. According to U.S. Environmental Protection Agency (EPA) Environmental Technology Verification (ETV) Report EPA 600/R-02/042, the primary component of this mineral oil-based transformer fluid was a hydrotreated light naphthenic petroleum distillate, ranging from 30 to 100 percent. Due to this content, such oil “was identified in Chemical Abstract Service (CAS) No. 6472-53-6 as an International Agency for Research on Cancer (IARC) confirmed carcinogen based on experimental data for animals.”