Arc flash labels for transformers

[Isaiah]

The question came up today if power transformers 15kV to 480V require arc flash labels on both primary and secondary air terminal chambers - comments?


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[jim dungar]

Different voltages so different PPE.
Different incident energy so different PPE

 

[D. Castor]

Labeling is required for equipment likely to be serviced or examined while energized. A-F labels on transformers is common but not always done. If the two enclosures are physically separated, I'd put two labels. The alternative might be one label based on the higher of the two calculated incident energies.

 

[jim dungar]

.... based on the higher of the two calculated incident energies.

This is hard to justify. I would base a single label on the highest voltage and the source incident energy.

In a typical transformer, especially <150kVA, the HV and LV terminals are actually in between each other. You cannot have a fault involving one set of terminations without it propagating to the source side conductors. Of course this is not true for larger transformers and those with dedicated termination compartments.