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Preventing a Transformer Fireworks Display

Infrared inspections of oil filled transformers can help to increase reliability and extend transformer life. Detecting hotspots on the bushings of these transformers may also help to prevent a catastrophic explosion.

Hot spots on transformer bushings are usually due to a loose or deteriorated electrical connection. Frequently, the source of a hot bushing connection is external to the transformer and can be corrected by repairing the defective connection. However, loose connections which originate within the transformer case can represent an extremely dangerous condition.

Loose electrical connections within an oil-filled transformer can lead to a condition known as arcing. When arcing occurs in oil, the molecular structure of the transformer oil breaks down forming several combustible gases. The most significant gases produced are acetylene, hydrogen, methane, ethane, and ethylene.

The amount of gas produced will depend upon the temperature of the arc and length of time; however, even small amounts of gas can lead to a potentially explosive condition. In a sealed, oil-filled transformer these gases can build to a potentially explosive level within a very short time. In short, combustible gases combined with an arcing condition within a transformer are a recipe for potential disaster.

When inspecting oil filled transformers, any inexplicable temperature rise on bushings should be investigated and corrected immediately. Performing a dissolved gas analysis of the transformer oil is recommended if the cause of the problem is suspected to originate within the transformer.

Infrared inspections of electrical distribution systems is a topic covered in all Infraspection Institute Level I training courses.  For course locations and dates or information on our Distance Learning courses, visit infraspection.com or call us at 609-239-4788.