What Is a Lightning Impulse Test?
Quick answer — A lightning impulse test applies a standard 1.2/50 microsecond voltage surge to the transformer winding to prove the insulation can withstand a lightning (or switching) surge. It is a type test, with both full-wave and chopped-wave forms, and the insulation must not flash over or show a breakdown. It verifies the insulation coordination and the BIL.
What is a lightning impulse test on a transformer?
The standard wave
A 1.2/50 us lightning impulse (rise time 1.2 us, time to half-value 50 us) is the standard. The full-wave and chopped-wave (a wave cut by a gap flashover) are both applied.
What it verifies
It proves the insulation (especially between turns and windings, and at the BIL) can survive a lightning surge without a flashover or insulation breakdown.
Why it matters
It confirms the insulation coordination with the arresters and the system overvoltage, so the transformer does not fail on a surge in service.
References & standards
- IEC 60076-3 (dielectric tests)
- IEEE C57.12.90
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
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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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