What Is the Dielectric Strength of a Transformer?
Quick answer — Dielectric strength is the maximum electric field the insulation can withstand before a breakdown. For the oil and the paper it depends on the cleanliness, moisture, temperature and the thickness. It is what the insulation system relies on, and it is verified by the breakdown-voltage (oil), power-factor and applied/impulse tests. Keeping the oil and paper dry, clean and moisture-free preserves the dielectric strength.
What is the dielectric strength of a transformer?
What it is
The highest electric stress the insulation can take before it breaks down; a high dielectric strength means the insulation can withstand a high voltage.
What it depends on
Moisture, particles, contamination, temperature, pressure and the thickness/geometry all reduce or set the strength. A dry, clean oil is much stronger than a wet one.
Why it matters
The dielectric strength of the oil and the paper sets the insulation margin and the BIL; a loss of it leads to a partial discharge and a failure.
References & standards
- IEC 60156 (oil BDV)
- IEC 60076-1
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
Related components
Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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