lightning protection calculation

Lightning Protection Calculation - Building 911 10/15/2012

ANNUAL THREAT OF OCCURANCE, FROM NFPA 780 2011 APPENDIX L6.6.1 = USER INPUT REQUIRED

DIRECT STRIKES TO STRUCTURE (SECTION L.6.6.1.1)

Nd = 0.0037

Ng = 1.0

C1 = 0.25

Ae = 14702.42

STRUCTURE COLLECTIVE AREA CALCULATION (SECTION L.4)

Length (L) 200 ftWidth (W) 100 ftHeight (H) 45 ft

Figure H.4.2(a) Results 5319.2 m2

Figure H.4.2(b) Results 14702.4 m2

Figure L.4.1(a) Calculation of the equivalent collective area for a rectangular structure.

Figure L.4.1(b) Calculation of the equivalent collective area for a structure where a prominent

part encompasses all portions of the lower part of the structure.

lighting ground flash density in flashes/km2/year (See Figure L.2)

equivalent collection area of structure (m2) (choose from below)

environmental coefficient (see Table L.4.2)

yearly average flash density in the region where structure is located

Detailed Risk Assessment 1 of 14


STRIKES NEAR STRUCTURE (SECTION L.6.6.1.2)

NM = 0.0573

Am = 243815.4

STRIKES TO AN ADJACENT BUILDING (SECTION L.6.6.1.4)

ADJ. BLDG. COLLECTIVE AREA CALCULATION

Nda = 0.0059 Length (L) 300 ft

Width (W) 200 ftHeight (H) 45 ft

Ng = 1.0

Figure H.4.1.2(a) Results 5319.2 m2

C1 = 0.25 Figure H.4.1.2(b) Results 23435.3 m2

Ct = 1.0

Ae = 23435.3


environmental coefficient of adj. bldg. (see Table L.4.2)

equivalent collection area of adj. bldg. (m2) (choose from below)

annual threat of occurrence due to strikes near structure (min of 0)

correction factor for presence of an HV/LV transformer located b/t strike point and structure (0.2 if one present, otherwise 1.0)

collection area of flashes near structure (m2)

annual threat of occurrence due to strikes near structure



STRIKES TO AN INCOMING SERVICE (SECTION L.6.6.1.3)

NL = 0.02236

Ng = 1.0

C1 = 1.0

Ct = 1.0

SERVICE COLLECTIVE AREA CALCULATION

Hc 0 mlc 1000 m

Al = 22360.7 Ha 0 mHb 0 m

r 500 Wm

Al 0.0 m2 22360.7 m2

Ai 1000000.0 m2 559017.0 m2

collection area of flashes striking the service (m2) (see Table 6.7.1)

Aerial Buried


environmental coefficient of incoming service (see Table L.4.2)


annual threat of occurrence due to strikes near structure



STRIKES NEAR AN INCOMING SERVICE (SECTION L.6.6.1.5)

NI = 0.2795

Ng = 1.0

Ce = 0.5

Ct = 1.0

Ai = 559017.0

environmental coefficient of incoming service (see Table L.6.7.2)


collection area of flashes striking near service (m2) (see Table 6.7.1)


annual threat of occurrence due to flashes near a service



ANNUAL PROBABILITIES OF DAMAGE, FROM NFPA 780 2011 APPENDIX L6.6.2

PROBABILITY OF INJURY DUE TO DIRECT STRIKE (SECTION L.6.6.2.1)

PA = 0.000001

PROBABILITY OF PHYSICAL DAMAGE DUE TO DIRECT STRIKE (SECTION L.6.6.2.2)

PB = 0.001

PROBABILITY OF INTERNAL SYSTEM FAILURE AS FUNCTION OF SPD PROTECTION (SECTION L.6.6.2.3)

Sec. L.6.6.2.3PC = 1 probability of failure of internal systems

as function of SPD protection (see Table L.6.7.5)

probability of injury due to direct strike to a structure (see Table L.6.7.3)

probability of physical damage due to direct strike to a structure (see Table L.6.7.4)



PROBABILITY OF INTERNAL SYSTEM FAILURE DUE TO STRIKES NEAR STRUCTURE (SECTION L.6.6.2.4)

PM = 1

KS = 0.0648 protective measures factor

KS1 = 1.8 structural shielding efficiency factor

KS2 = 1.8 internal shielding efficiency factor

probably of failure of internal systems due to strikes near structure (see Table L6.7.6). Without coordinated surge protective devices -- PM = 1.0

In those structures where it is ensured that steel reinforcing bars are interconnected and terminated by approved grounding electrodes, w is the spacing between the reinforcing bars.

If the equipment is located closer to the applicable boundary than the distance, w , the values of K S 1 and K S 2 should be doubled. In those cases where multiple internal boundaries exist, the resulting value of K S2 is the product of each individual value of K S2 .

For continuous metal shields with a thickness of 0.1 to 0.5 mm, K S1 and K S2 should be assigned the value of 10-4 to 10-5 (scaled linearly). Where not otherwise known, the value of K S1 and K S2 can be evaluated by the following relationship as long as the equipment is located a distance, w from the boundary shield:

w = distance measured in meters and given by a mesh grid spacing, the spacing between down conductors, or the spacing between structural steel columns.



KS3 = 0.02

U W = lowest withstand voltage of the hardware in the system under consideration

KS4 = 1 system voltage factor

PROBABILITY OF INJURY FROM STRIKE TO INCOMING SERVICE (SECTION L.6.6.2.5)

PU = 0.8

Therefore, Table L.6.7.8 gives value of 1.5 based on P U = 1

PV = 0.8

Where SPDs are not provided, the value of P V is equal to the value of P U . Where SPDs are provided, the value of P V to be used in the equation for the risk of physical damage due to a strike to a service is the lower value between P C and P U .

internal wiring characteristic factor (see Table L.6.7.7)

Where SPDs are provided for equipotential bonding, the value of P U to be used in the equation for the risk of injury to humans due to flashes to a service is the lower value between P C and P U . For unshielded services, a value of P U = 1 is used. Where physical restrictions, warning notices, etc., are used, the value of P U can be further reduced by multiplying it by P A .

probability as a function of the resistance of cable shield and impulse withstand voltage of equipment (see Table L6.7.8)

PROBABILITY OF PHYSICAL DAMAGE FROM STRIKE TO INCOMING SERVICE (SECTION

L.6.6.2.6)

probability of physical damage from strike to incoming service



PROBABILITY OF INTERNAL SYSTEM FAILURE DUE TO STRIKE TO INCOMING SERVICE (SECTION L.6.6.2.7)

PW = 0.8

PZ = 0.1

Where SPDs are installed, the value of P W is the lower value of P C or P U . Where SPDs are not installed, the value of P W to be used in the equation for the risk of failure of internal systems due to a strike to a service is equivalent to the value of P U .

probability of physical damage from strike to incoming service

Where SPDs are not installed, the probability of failure of internal systems due to a flash near the connected service (P Z ) can be taken from Table L.6.7.9. Where SPDs are installed, the value of PZ can be taken to be the lower value of PC or PZ.

probability of internal system failure due to strike near an incoming service

PROBABILITY OF INTERNAL SYSTEM FAILURE DUE TO STRIKE NEAR AN

INCOMING SERVICE (SECTION L.6.6.2.8)



LOSS FACTORS, FROM NFPA 780 2011 APPENDIX L6.6.3

LOSS OF LIFE TO HUMANS (SECTION L.6.6.3)

LA = 0.1142 estimated, mean, value

np = 260 number of possible endangered persons (victims)

nt = 260 expected total number of persons (in the structure)

tp = 1000

INJURY TO HUMANS (SECTION L.6.6.3.1)

LA = 1.00E-07 value for loss of human life

LU = 1.00E-07 value of loss of living being

ra = 0.01

Lt = 0.00001 mean value of loss of life (see Table L.6.7.10)

time in hours per year for which the persons are present in a dangerous place, outside of the structure (Lt) or inside the structure (Lt, Lf, Lo)

Typical mean values of Lt, Lf , and Lo, for use when the determination of np, nt, and tp

is uncertain or difficult, are given in Table L.6.7.10.

reduction factor for type of surface soil or floor (see Table L.6.7.11)



PHYSICAL DAMAGE (SECTION L.6.6.3.2)

LB = 0.00004 value of loss due to direct strike to the structure

LV = 0.00004 value of loss due to strike to incoming service

rp = 0.2

rf = 0.01

hZ = 2

Lf = 0.01

Lf, calculated = 0.1142 Calculated value based on number of people at risk.

LB, calculated = 0.00046

LV, calculated = 0.00046

value of loss due to direct strike to the structure, based on number of people at risk

value of loss due to strike to incoming service, based on number of people at risk

mean value of physical damage loss (see Table L.6.7.10)

reduction factor for risk of fire to structure (see Table L.6.7.13)

factor for the kinds of hazard in the structure (see Table L.6.7.14)

reduction factor for provisions take to reduce consequences of fire (see Table L.6.7.12)



FAILURE OF INTERNAL SYSTEMS (SECTION L.6.6.3.3)

LC = 0.001 value of loss due to direct strike to the structure

LM = 0.001 value of loss due to a strike near the structure

LW = 0.001

LZ = 0.001

LO = 0.001 mean value of loss of internal system (see Table L.6.7.10)

value of loss due to a strike to a service connected to the structure

value of loss due to a strike near a service connected to the structure



RISK COMPONENTS (SECTION L.6.4)

SUMMARY OF NUMBER OF STRIKES (SECTION L.6.6.1)

Nd = 0.0037NM = 0.0573Nda = 0.0059NL = 0.0224NI = 0.2795

SUMMARY OF PROBABILITY OF DAMAGE (SECTION L.6.6.2)

PA = 0.000001PB = 0.001PC = 1PM = 1PU = 0.8PV = 0.8PW = 0.8PZ = 0.1

SUMMARY OF LOSS FACTORS (SECTION L.6.6.3)

DifferenceLA = 0.0000 0.0000 0%LB = 0.00004 0.00046 91%LC = 0.001 0.001 0%LM = 0.001 0.001 0%LU = 0.0000 0.0000 0%LV = 0.00004 0.00046 91%LW = 0.001 0.001 0%LZ = 0.001 0.001 0%

Alternate, based on number of

people at risk



SUMMARY OF RISK COMPONENTS (SEE TABLE L.6.6)Difference

RA = 3.68E-16 3.68E-16 0%RB = 1.47E-10 1.68E-09 91%RC = 3.68E-06 3.68E-06 0%RM = 5.73E-05 5.73E-05 0%RU = 2.26E-09 2.26E-09 0%RV = 9.03E-07 1.03E-05 91%RW = 2.26E-05 2.26E-05 0%RZ = 2.57E-05 2.57E-05 0%



TOTAL RISK COMPONENTS (SECTION L.6.5)

R 1 = R A + R B + R C * + R M * , + R U + R V + R W * + R Z *

Alternate

R1 = 9.05429E-07 1.03124E-05

R1* = 0.00011015 0.000119557 *

R 2 = R B + R C + R M + R V + R W + R Z

R2 = 0.000110147 0.000119554

R 3 = R B + R V

R3 = 9.03171E-07 1.03102E-05

R 4 = R A ** + R B + R C + R M + R U ** + R V + RW + R Z

R4 = 0.000110147 0.000119554

R4** = 0.00011015 0.000119557 ** applicable only for structures where animals might be injured.

TOTAL OVERALL RISK (SECTION L.6.2 & L.6.5)

R = R 1 + R 2 + R 3 + R 4

R = 0.000222103 0.000259731 R NR NRR* = 0.000331348 0.000368976 R NR NRR** = 0.000222106 0.000259734 R NR NR

Lightning Protection

IS NOT required for Loss of Historical SignificanceIS NOT required for Loss of ServiceIS required for Loss of Life

applicable only for structures with risk of explosion, for structures with life-critical electrical equipment (such as hospitals), or other structures where the failure of internal systems immediately endangers human life.

0.001

RT - Loss of Historical Significance

RT - Loss of Life or Injury RT - Loss of Service

0.000001 0.001


lightning protection calculation

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