Calculate Lightning Protection for Building / Structure


Example: Calculate Whether Lightning Protection is required or not for following Building. Calculate No of Down Conductor for Lightning Protection

Area of Building / Structure:

  • Length of Building (L) = 60 Meter.
  • Width of Building ( W ) = 28 Meter.
  • Height of Building (H) = 23 Meter.

Lightning Stock Flushing Density

  • Number of Thunderstorm (N)= 80.00 Days/Year
  • Lightning Flash Density   (Ng)=69 km2/Year
  • Application of Structure (A)= Houses & Buildings
  • Type of Constructions (B)= Steel framed encased without Metal Roof
  • Contests or Consequential Effects (C)= Domestic / Office Buildings
  • Degree of Isolation (D)= Structure in a large area having greater height
  • Type of Country (E)= Flat country at any level
  • Maximum Acceptable Overall Risk Factor =0.00000001
Reference Table As per IS:2309
Thunder Storm Days / Year Lightning Flash Density (Flashes to Ground /km2/year)
5 0.2
10 0.5
20 1.1
30 1.9
40 2.8
50 3.7
60 4.7
80 6.9
100 9.2
Application of Structure Factor
Houses & Buildings 0.3
Houses & Buildings with outside aerial 0.7
Factories / workshop/ Laboratories 1
Office blocks / Hotel 1.2
Block of Flats / Residences Building 1.2
Churches/ Hall / Theaters / Museums, Exhibitions 1.3
Departmental stores / Post Offices 1.3
Stations / Airports / Stadium 1.3
Schools / Hospitals / Children’s Home 1.7
Others 1.2
Type of Constructions Factor
Steel framed encased without Metal Roof 0.2
Reinforced concrete without Metal Roof 0.4
Steel framed encased with Metal Roof 0.8
Reinforced concrete with Metal Roof 1
Brick / Plain concrete or masonry without Metal Roof 1.4
Timber framed or clad without Metal Roof 1.7
Brick / Plain concrete or masonry with Metal Roof 2
Timber framed or clad with Metal Roof
Contests or Consequential Effects Factor
Domestic / Office Buildings 0.3
Factories / Workshop 0.3
Industrial & Agricultural Buildings 0.8
Power stations / Gas works 1
Telephone exchange / Radio Station 1
Industrial key plants, Ancient monuments 1.3
Historic Buildings / Museums / Art Galleries 1.3
Schools / hospitals / Children Homes 1.7
Degree of Isolation
Factor
Structure in a large area having greater height 0.4
Structure located in a area of the same height 1
Structure completely Isolated 2

Calculation:

Collection Area (Ac)=(L x W) + 2 (L x H) + 2(W x H) +(3.14 x H2)

  • Collection Area (Ac) = (60×28)+2x(60×23)+2x(28×23)+(3.14x23x23)
  • Collection Area (Ac) =7389 Meter2

Probable No of Strikes to Building / Structure (P)= Ac x Ng x 10-6 No’s / Year

  • Probable No of Strikes to Building / Structure (P)= 7389x69x106 No’s / Year
  • Probable No of Strikes to Building / Structure (P)= 05098 No’s / Year

Overall Multiplying Factor (M) =A x B x C x D x E

  • Application of Structure (A)= Houses & Buildings as per Table Multiplying Factor = 0.3
  • Type of Constructions (B)= Steel framed encased without Metal Roof as per Table Multiplying Factor =0.2
  • Contests or Consequential Effects (C)= Domestic / Office Buildings as per Table Multiplying Factor =0.3
  • Degree of Isolation (D)= Structure in a large area having greater height as per Table Multiplying Factor =0.4
  • Type of Country (E)= Flat country at any level so as per Table Multiplying Factor =0.3
  • Overall Multiplying Factor (M) =0.3×0.2×0.3×0.4×0.3
  • Overall Multiplying Factor (M) =0.00216

Overall Risk Factor Calculated (xc)= M x P

  • Overall Risk Factor Calculated (xc)= 0.00216 x0.05098
  • Overall Risk Factor Calculated (xc)= 000110127

 Base Area of Structure (Ab) = (LxW)

  • Base Area of Structure (Ab)=60×28
  • Base Area of Structure (Ab)=1680 Meter2

Perimeter of Structure (P) =2x (L+W)

  • Perimeter of Structure (P)=2x(60+28)
  • Perimeter of Structure (P)=176 Meter

Lightning Protection Required or Not

  • If Calculated Overall Risk Factor Calculated > Maximum Acceptable Overall Risk Factor than only Lighting Protection Required
  • Here Calculated Overall Risk Factor is 0.000110127 > Max Acceptable Overall Risk Factor is 00000001
  • Lightning Protection is Required

 No of Down Conductor

  • Down Conductors As per Base Area of Structure (s) =1+(Ab-100)/300
  • Down Conductors As per Base Area of Structure (s) =1+(1680-100)/300
  • Down Conductors As per Base Area of Structure (s) =6 No’s
  • Down Conductors As per Perimeter of Structure (t)= P/30
  • Down Conductors As per Perimeter of Structure (t)= 176/30
  • Down Conductors As per Perimeter of Structure (t)= 6 No’s
  • Minimum No of Down Conductor is 6 No’s

 Results:

  • Lightning Protection is Required
  • Down Conductors As per Base Area of Structure (s) =6 No’s
  • Down Conductors As per Perimeter of Structure (t)= 6 No’s
  • Minimum No of Down Conductor is 6 No’s
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Approximate Fuel Consumption for Diesel Generator Set

Generator Size (Kva) @0.8 PF 1/4 Load (Liter/Hr) 1/2 Load (Liter/Hr) 3/4 Load (Liter/Hr) Full Load (Liter/Hr)
25 2.27 3.41 4.92 6.06
38 4.92 6.82 9.09 10.98
50 6.06 8.71 12.12 15.15
75 6.82 10.98 14.39 18.18
94 9.09 12.88 17.42 23.11
125 9.85 15.53 21.97 28.03
156 11.74 18.94 26.89 34.47
169 12.50 20.45 28.79 37.12
188 13.64 22.35 31.82 41.29
219 15.53 25.76 36.74 48.11
250 17.80 29.17 41.67 54.55
288 20.08 33.33 47.35 62.88
313 21.59 35.98 51.52 68.18
375 25.76 42.80 60.98 81.44
438 29.92 49.62 70.83 95.08
500 33.71 56.44 80.68 108.33
625 41.67 70.08 100.00 135.23
750 50.00 83.33 119.32 162.12
938 61.74 103.79 148.86 202.27
1250 81.82 137.88 197.35 269.32
1563 101.89 171.59 246.21 336.36
1875 121.97 205.68 294.70 403.41
2188 142.05 239.39 343.56 470.45
2500 162.12 273.48 392.05 537.50
2813 182.20 307.20 440.91 604.55

Approximate Current (Amp) Rating of Diesel Generator Set @ 0.8 PF

KVA kW 220V 240V 400V 440V 450V 480V 600V 2400V 3300V
8 6.3 16.5 15.2 9.1 8.3 8.1 7.6 6.1    
9.4 7.5 24.7 22.6 13.6 12.3 12 11.3 9.1    
12.5 10 33 30.1 18.2 16.6 16.2 15.1 12    
18.7 15 49.5 45 27.3 24.9 24.4 22.5 18    
25 20 66 60.2 36.4 33.2 30.1 24 6 4.4 3.5
31.3 25 82.5 75.5 45.5 41.5 40.5 37.8 30 7.5 5.5
37.5 30 99 90.3 54.6 49.8 48.7 45.2 36 9.1 6.6
50 40 132 120 73 66.5 65 60 48 12.1 8.8
62.5 50 165 152 91 83 81 76 61 15.1 10.9
75 60 198 181 109 99.6 97.5 91 72 18.1 13.1
93.8 75 247 226 136 123 120 113 90 22.6 16.4
100 80 264 240 146 133 130 120 96 21.1 17.6
125 100 330 301 182 166 162 150 120 30 21.8
156 125 413 375 228 208 204 188 150 38 27.3
187 150 495 450 273 249 244 225 180 45 33
219 175 577 527 318 289 283 264 211 53 38
250 200 660 601 364 332 324 301 241 60 44
312 250 825 751 455 415 405 376 300 75 55
375 300 990 903 546 498 487 451 361 90 66
438 350 1155 1053 637 581 568 527 422 105 77
500 400 1320 1203 730 665 650 602 481 120 88
625 500 1650 1504 910 830 810 752 602 150 109
750 600 1980 1803 1090 996 975 902 721 180 131
875 700 2310 2104 1274 1162 1136 1052 842 210 153
1000 800 2640 2405 1460 1330 1300 1203 962 241 176
1125 900 2970 2709 1640 1495 1460 1354 1082 271 197
1250 1000 3300 3009 1820 1660 1620 1504 1202 301 218
1563 1250 4130 3765 2280 2080 2040 1885 1503 376 273
1875 1500 4950 4520 2730 2490 2440 2260 1805 452 327
2188 1750   5280 3180 2890 2830 2640 2106 528 380
2500 2000   6020 3640 3320 3240 3015 2405 602 436
2812 2250   6780 4095 3735 3645 3400 2710 678 491
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