Impulse Voltage Distribution in Transformer Windings Why Your HV Winding's First Few Discs Carry the Heaviest Burden When a lightning strike or switching surge hits a power transformer, something remarkable — and potentially destructive — happens inside the winding. The voltage does not spread itself evenly across all the discs as it does under normal power frequency operation. Instead, it crowds violently toward the line terminal end, forcing the first few discs to absorb a