Modelling Lightning Results with an Equal Frequency

Lightning strikes and their present waveforms come in numerous types and aren’t fully predictable. Lightning strikes can both be upward or downward initiated and both destructive or constructive polarity. Downward flashes happen in flat territory and to decrease buildings. Upward flashes are extra outstanding for uncovered or increased buildings. The chance of direct strike to a construction will increase with construction peak.

All impulse present parameters of upward flashes are lower than these of downward flashes and a better lengthy stroke cost of upward flashes isn’t confirmed. Subsequently, the lightning present parameters of upward flashes are thought of to be coated by the utmost values for downward flashes.

About 85 to 95 % of the flashes to buildings having heights lower than about 100 metres on flat or rolling terrain are destructive downward. The opposite 5 to fifteen % are both destructive upward or constructive. Thus, from {an electrical} transmission or substation viewpoint, aside from mountainous terrain or very excessive river crossing towers, the destructive downward flash is of main concern. Solely 2 to 10 % of whole flashes are constructive polarity [ref. 1].

A lightning strike consists of a number of totally different strokes (usually mixed):

  • impulses (quick strokes) with length lower than 2 ms.
  • lengthy strokes with length longer than 2 ms.

Strokes have a polarity (constructive or destructive) and a place (order) through the flash. A polarity ratio of 10 % constructive and 90 % destructive strokes is at all times assumed within the absence of native info.


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