lightning protection

Lightning Protection Calculation

Calculation for Evaluating Need for Protection - by BS6651 1. Collection Area, Ac (sqm) 1.1. Rectangle Building Length（m ）

Width （m）

Height （m）

Collection Area Ac (sqm）

10

10

12

1032.4

Radius （m）

Height （m）

Collection Area Ac （sqm）

10

30

5026.6

2

Formula: Ac=LW+2LH+2WH+лH

1.2. Tower

Formula: Ac=л(H+R)2

1.3. Sloping Roof (Here pitch ≧45°,if pitch <45°,adopt 1.1) Collection Length（m Height Area Ac 2 ） （m） （sqm） Formula: Ac=лH +2LH 20 30 4027.4 2. Flash density, Ng (per/sqkm) Thunderstor m days per year Td 20 Note: adopt for north Africa

Flash density, Ng (per/sqkm)

From Curve of Table 6

1.10

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Lightning Protection Calculation

3. Risk of being struck, p 4. Overall risk factor 1 2 Risk of being struck, A p Use of structure (Table 8)

1.1E-03

0.3

1.1E-03

3

4

Formula: p=Ac×Ng×10

5

Weighting factors B C D Type of Contents or Degree of construction consequential isolation (Table 9) effects (Table 11) (Table 10) 0.4

0.3

1.0

6

E Type of country (Table 12)

0.3

Note: Risk less than 1×10-5 do not generally require protection; risk between 1×10-5 and 1×10-4 protection is recommended; risk greater than 1×10-4 require protection.

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7 8 Overall Overall risk multiplying factor (product factor of columns 1 (product of and 7) columns 2 to 6)

0.011

1.23E-05

9 Recommendations

protection recommended

Weighting factors

Flash density

Weighting factors

Flash density

Curve of Flash

density and Thunder day per year

Note: This curve is made from Table 6 of BS 6651