Invented in the 1880’s, the job of adjusting to useable levels the thousands of volts generated by power utilities has always fallen to electrical transformers. They’re amazingly simple devices—but nonetheless require end-of-life hazardous waste management.

What is an electrical transformer?

In sum, an electrical transformer consists of one wire coil encased closely to a second. When the first or “primary” coil is fed alternating current, another alternating current is induced in the nearby “secondary” one. But that’s only half of it.

Consider: the voltages of the two AC currents will match the sizes of the two coils in exact proportion to one other. For example: If the primary coil is half the size of the secondary, the voltage appearing in the secondary will be twice larger. This is called a “step-up transformer.”

Conversely, if the primary coil is twice larger than the secondary, then the voltage appearing in the secondary will be half as much. This is called a “step-down transformer.”

How are electrical transformers used?

Utilities use massive step-up transformers to increase voltage (aka tension) in order to push electricity more efficiently through long-distance transmission lines—hence the term “high tension wires.”

They use step-down transformers, for example, to reduce voltage to the relatively safe and familiar 120/220 VAC we have in our homes. One type is those things you see atop utility poles in front of houses; they look like big tin cans with wires popping out the top.

Thus, there are literally millions of transformers in use across America and rest of the world. Problem is, each will eventually wear out and require hazardous waste disposal.

Why do electrical transformers require hazardous waste removal?

As the laws of physics would dictate, the enormous amounts of current applied to the primary coil and induced in the secondary together generate considerable amounts of heat: enough to turn both coils into useless blobs of molten copper.

To prevent this, the transformer encasement is filled with oil, so that both coils are effectively bathed in it. Oil is basically nonconductive, so it won’t short-circuit the coils, while its very high boiling point allows it to absorb a great deal of heat, thus preventing the copper from melting.

What kind of oil is used in electrical transformers?

Oddly enough, although they’ve been around for over 130 years, finding the best kind of oil to cool electrical transformers is still the Holy Grail among engineers.

At first, polychlorinated biphenyls (PCBs) were employed, since they’re nonflammable and highly nonconductive. Sadly, they’re also extremely toxic; they’re not biodegradable; and they’re absorbed faster than they can be metabolized (or excreted) by animals and humans. Incinerating PCBs generates such poisons as chlorinated dioxins and dibenzofurans, which are even more toxic to humans, animals, and the environment than the PCBs themselves.

Given that rouges’ gallery of drawbacks, production of PCBs was banned in the United States in 1979.Thereby, PCBs haven’t been used in electrical transformers for 40 years, more-or-less. This is good in the obvious sense, but it also means that there’s a lot of legacy equipment in existence that’s nearing end-of-life (or languishing in junk piles) that needs to be disposed, and so doing will require careful hazardous waste removing.

What’s the alternative to using PCBs in electrical transformers?

Mineral oil is the most common alternative, but its insulating properties are rapidly degraded by any amount of moisture. It’s also highly flammable. If a transformer were to leak mineral oil, it could easily start a fire.

Because of its flammability, fire codes often prohibit transformers that are cooled with mineral oil from inside buildings or structures. And although mineral oil is relatively more benign than PCBs, it’s nonetheless an environmental contaminant that requires careful hazardous material removal.

Another consideration: mineral oil is fully miscible with PCBs. This means it will form a homogenous mixture with them in any proportion; and years ago the same drums, pumps, and hoses used to deliver mineral oils were used for PCBs.

Thus, PCB contamination can still be an issue for transformers that are ostensibly PCB-free. For instance, concentrations of PCBs greater than 5 parts per-million are classified as hazardous waste in California.


PCBs haven’t been specified inside electrical transformers for nearly 40 years. This is good in the long run. But it also means that there is a great deal of legacy equipment that’s nearing end-of-life that will require hazardous waste management, as PCB contamination is particularly onerous, and the regulations surrounding its disposal are commensurately strict.

It’s also worth noting that mineral oil—the most common replacement for PCBs—might be contaminated with PCBs and thus require a more rigorous level of hazardous waste management than is common for less-toxic waste oils.

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