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T/F: lightning overvoltage in distribution system

Short answer

TRUE. Distribution lines have low BIL and no shield wire, so even induced surges cause flashover. Transmission lines have higher BIL, shield wires, and low tower footing resistance; lightning is dominant only up to about 220 kV, while switching surges govern at higher voltages.

State whether the following statement is TRUE or FALSE and justify your answer with brief explanation: Lightning over voltage is more dominating in distribution system than in transmission system.

TRUE.

  • Distribution lines (11 kV, 33 kV) have low insulation levels (BIL about 75–200 kV). Even an induced surge from a nearby lightning stroke (100–300 kV) is enough to flash them over; direct strokes always do.
  • They usually have no overhead shield wire, short and low poles, and run through open areas where many strokes occur.
  • Transmission lines have high BIL (550–1550 kV), shield (earth) wires and low tower footing resistance, so most strokes are intercepted and induced surges are harmless.
  • In EHV lines (400 kV and above) the insulation is governed mainly by switching surges, not lightning.

Hence lightning is the dominant over-voltage for distribution systems, while switching surges become dominant as transmission voltage increases.

✓ Answer checked by Claude Opus 5.5 (high effort)

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