In Article " Design Process for Lightning Protection Systems ", I indicated the (3) phases of the Design Process for Lightning Protection Systems as follows:
Design Process For Lightning Protection Systems
The design process of lightning protection systems is commonly broken into discrete phases, allowing the lightning protection designer to present an integrated design package. These phases can be listed as follows:
A Quality assurance is required in each phase in above.

Introduction To Design Calculations Of Lightning Protection Systems
It is very important before explaining the design calculations of lightning protection systems to highlight some important topics or expressions that will be used in these calculations. These topics can be listed as follows:

Design Calculations of Lightning Protection Systems – Continued
Third: Detailed Design Phase

The lightning protection design process involves a number of design steps as in Fig.1.
Fig.1: The Lightning Protection Design Process 
Step#1: Characteristics of the Structure to Be Protected

Step#2: Risk Assessment Study

Methods Of Calculations
For Risk Assessment Study
The risk assessment study can be done by (4) different
methods as follows:
1 Manual Method (equations and tables method),which will be
explained as per:
2Software Method,
3 Excel Sheets Method,
4Online Calculators Method.

First: Manual Method (Equations
And Tables Method) as per IEC 62305

Procedure For Performing The Risk Assessment Study By Manual Method
Procedure for performing the risk assessment
study includes three parts as follows:

 Step#21: Identify the structure to be protected,
 Step#22: Identify the types of loss relevant to the structure to be protected Rn,
 Step#23: For each loss to be considered, identify the tolerable level of risk RT,
 Step#24 First Part: Identification of the Risk Components Rx.
Also, in Article " Design Calculations of Lightning Protection Systems – Part Four ", I explained Step#24 Second Part: Calculations of the Risk Components Rx and I indicated that:
Each of the risk
components Rx is obtained using further calculations, subcalculations and
reference tables based on the general equation:
R_{X} = N_{X} x P_{X} x L_{X}
Where
N_{X} = number of dangerous
events per year,
P_{X} = probability of
damage to structure,
L_{X} = amount of consequent loss.
X = A, B, ...
So, The task
of the risk assessment therefore involves the determination of the three
parameters N_{X}, P_{X} and L_{X}.

In this Article, I explained how to calculate the first Parameter NX: number of dangerous events per year.
And in Article " Design Calculations of Lightning Protection Systems – Part Five ", I explained how to calculate the second Parameter: PX = probability of damage to structure.
Today, I will explain how to calculate the Third Parameter: LX = Amount of Consequent Loss.
Step#24 Second Part: Calculations of the Risk Components Rx

Calculations of Third
Parameter: L_{X} = Amount of Consequent Loss

Amount of Consequent Loss L_{X}
The loss L_{X} refers to the mean relative
amount of a particular type of damage for one dangerous event caused by a
lightning flash, considering both its extent and effects. The loss value L_{X} varies with the type of loss
considered (see Fig.3):
For more information, please review Article " Design Calculations of Lightning Protection Systems – Part One ", paragraph “Types of Loss”.
Notes:

1 Loss of Human Life (L1)
The loss value LX for each zone can be determined
according to Table1, considering that:
Table1: Type of loss L1: Loss values for each zone
Where:
Table2: Type of loss L1: Typical mean values of LT, LF and LO
Notes:
When the damage to a structure
due to lightning involves surrounding structures or the environment (e.g.
chemical or radioactive emissions), additional loss (LE) should be taken into account
to evaluate the total loss (LFT):
LFT = LF + LE
Where:
LE = LFE x te / 8760
Note:
Table3: Reduction factor rt as a function of the type
of surface of soil or floor
Table4: Reduction factor rp as a function of
provisions taken to reduce the consequences of fire
Notes:
Table5: Reduction factor rf as a function of risk of
fire or explosion of structure
Notes:
Table6: Factor hz increasing the relative
amount of loss in presence of a special hazard

2 Unacceptable Loss of Service to The Public (L2)
The loss value LX for each zone can be determined
according to Table7, considering that:
Table7: Type of loss L2: Loss values for each zone
Where:
Table8: Type of loss L2: Typical mean values of LF and LO

3 Loss Of Irreplaceable Cultural Heritage (L3)
The loss value LX for each zone can be determined
according to Table C.9, considering that:
Table9: Type of loss L3: Loss values for each zone
Where:
Table10: Type of loss L3: Typical mean value of LF

After the
calculation of the three parameters N_{X}, P_{X} and L_{X} and For evaluation of risk components
RX related to lightning flashes to
the structure and based on the general equation:
R_{X} = N_{X} x P_{X} x L_{X}
The following relationships for each Risk
Component are illustrated in the following Table11 with their
corresponding source and type of damage:
Table11: Risk Component Equations
Note: In many cases NDJ may be neglected.

Step#25: Calculate Rn = Σ Rx = R1 + R2 +R3

Each risk, R, is the sum of its risk
components. When calculating a risk, the risk components may be grouped
according to the source of damage and the type of damage. So, the risks R1,
R2 and R3 will be calculated from the following equations:
R1: Risk of loss of human life:
R1 = RA1 + RB1 + RC11) + RM11) + RU1 + RV1 + RW11) + RZ11)
1) Only for structures with risk
of explosion and for hospitals with lifesaving electrical equipment or other
structures when failure of internal systems immediately endangers human life.
R2: Risk of loss of service to the
public:
R2 = RB2 + RC2 + RM2 + RV2 + RW2 + RZ2
R3: Risk of loss of cultural
heritage:
R3 = RB3 + RV3
The risk components corresponding
to Risk of each type of loss are also indicated in below Table12:
Table12: Risk Components Corresponding to Risk of Each Type of Loss

Step#26: Comparing the calculated actual risk Rn of
each loss to a tolerable level of risk (R_{T})

Comparing the
calculated actual risk Rn of each loss to a tolerable level of risk (R_{T}),
then we have (2) cases:
Case#1:
If the calculated
risk Rn is equal or less than the respective tolerable risk R_{T }i.e.
Rn ≤ R_{T }, then Structure is adequately protected for this type of loss and
no lightning
protection is required for this type of loss,
Case#2:
If the calculated
risk Rn is higher than the tolerable risk RT i.e. Rn > RT, then Install lightning
protection measures in order to reduce Rn.

Step#27: go back to step#24 and make a series of trial
and error calculations until the risk Rn is reduced below that of RT (Rn ≤
RT).
Note:

End of
Manual Method (equations and tables method) for Risk Assessment Study as per IEC 623052

In the next Article, I will explain Manual Method (Equations and Tables Method) for Risk Assessment Study but as per NFPA780. Please, keep following.
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