Transformers produce substantial heat that can quickly become problematic without adequate cooling.
Unmanaged heat builds up, decreasing efficiency, accelerating wear, and potentially leading to failure.
There are three approaches to cooling the power transformers. Let’s look at them individually and assess their pros and cons.
Oil has long reigned as the transformer cooling medium of choice because of its high heat capacity and electrical insulating properties.
Most oil-cooled transformers use natural or forced circulation, cycling hot oil from the top of the transformer through external radiators or heat exchangers before returning it to absorb more heat.
Oil cooling is valued for its simplicity and durability.
With few or no moving parts, maintenance is straightforward.
Oil also insulates against short circuits and other electrical faults.
However, oil has flammability and environmental risks requiring containment. It also degrades over time, losing cooling and insulating performance, necessitating monitoring and changeouts.
Where oil poses impractical risks, air cooling is a viable, lower-hazard transformer cooling option.
Air-cooled or dry-type transformers use ambient air, relying on natural currents or fans to dissipate heat from hot coils.
Air cooling avoids oil-related fire and spill risks, permitting safer indoor installation or deployment in sensitive environments. Without oil maintenance, air cooling is more straightforward to sustain.
However, air cooling capacity falls far short of oil’s potential. Air’s lower heat capacity constrains performance, mandating bulkier and costlier air-cooled transformer designs for given ratings.
Air cooling also exposes transformers to dust, moisture, and other environmental contaminants that can hurt airflow and heat transfer.
Water cooling delivers excellent performance for extreme-duty or space-constrained applications where heat loads overwhelm air cooling.
Water-cooled transformers circulate deionized water through channels directly contacting hot windings. External heat exchangers then cool and return this water to the transformer.
Water cooling leverages water’s fourfold advantage in heat capacity over air, enabling very compact transformer designs ideal for offshore wind farms or urban substations.
However, closed-loop water cooling entails added complexity. Careful monitoring and maintenance can help combat corrosion, deposits, and leaks.
Keeping the water deionized also demands continual testing and treatment for purity and nonconductivity.
Ultimately, there is no universally superior cooling solution. The ideal approach depends on the application, weighing power, environments, space, and maintenance.
Oil cooling remains prevalent for larger utility and industrial transformers where reliability and efficiency are paramount. Air cooling suits smaller, indoor applications, prioritizing safety and simplicity. Water cooling tackles extreme loads and tight spaces where performance overrides complexity.
Careful cooling selection, design, installation, and upkeep remain essential for longevity, regardless of approach.
