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T/F: flashover voltage vs puncture voltage

Short answer

FALSE. Insulators are designed to flash over before puncture because puncture causes permanent damage, whereas flashover is self-clearing. Puncture strength is kept well above flashover voltage, with a safety factor of about 1.3–1.5 for suspension discs.

State whether the following statement is TRUE or FALSE. Justify your answer with a brief explanation: The insulators are designed so that it will punctured before it gets flashover.

FALSE. Insulators are designed so that they flash over before they puncture.

  • Flashover: an arc through the air over the insulator surface. The insulator is not damaged (perhaps slight glazing burn) and service resumes after the breaker recloses.
  • Puncture: breakdown through the porcelain/glass body. The disc is permanently damaged and must be replaced.
  • Therefore the puncture strength is kept well above the flashover voltage. The ratio
Safety factor=Puncture strengthFlashover voltage\text{Safety factor} = \frac{\text{Puncture strength}}{\text{Flashover voltage}}

is about 10 for pin insulators and 1.3–1.5 or more for suspension discs (impulse).

✓ Answer checked by Claude Opus 5.5 (high effort)

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