In Article " Design Process for Lightning Protection Systems ", I indicated that the Design Process for 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:
- Planning phase,
- Consultation phase,
- Detailed Design phase.
Also, in Article " Design Calculations of Lightning Protection Systems – Part One ", I explained an Introduction to design calculations of lightning protection systems.
Today, I will Continue explaining Design Calculations of Lightning Protection Systems.
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: Lightning Protection Design Process
Step#1: Characteristics of the Structure to Be Protected
A- The Characteristics of the Structure
When Lightning strikes affecting a structure, the Characteristics of the structure will determine the damage level to the structure itself and to its occupants and contents, including failure of internal systems. The damages and failures may also extend to the surroundings of the structure and even involve the local environment. The Characteristics of the structure include:
1- The Design Of The Building:
2- The Environment Around The Building:
3- The Material In The Building:
4- The Number Of Lightning Strikes To Earth In The Area Of The Building:
5- The Value Of The Building And Its Contents:
6- Sensitive Electronics In The Building:
7- Loss Of Revenue In The Event Of Breakdown:
8- Escape Facilities And The Number Of Persons In The Building:
9- Fire Protection In The Building:
10- The Historic And Cultural Value Of The Building:
11- The Social Function Of The Building:
12- Cable Laying Up To The Building:
13- Conductivity Of The Ground In The Area Of The Building:
14- The Risk To The Surroundings:
B- Effects Of Lightning On A Structure
Table-1 reports the effects of lightning on various types of structures as follows:
Table-1: Effects of lightning on typical structures
Step#2: Risk Assessment Study
A- What are the benefits from performing risk assessments study?
The benefits from performing the risk assessment study are to:
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:
3- Excel Sheets Method,
4-Online Calculators Method.
First: Manual Method (Equations And Tables Method) as per IEC 62305-2
Procedure For Performing The Risk Assessment Study By Manual Method
Procedure for performing the risk assessment study includes three parts as follows:
Part#2: Determination of Required Protection Measure
Repeat from step#2-1 to step#2-6.
Step#2-7 in above procedure: ignored.
Step#2-8: if the lightning protection measure is needed, then we have (3) cases:
Case#1: check if the risk components RA+RB +RU+RV> RT. if yes, Install an adequate type of LPS. Otherwise, install adequate type of LPMS. Then go back to step#2-4 to calculate new values of risk components and make a series of trial and error calculations until the risk Rn is reduced below that of RT (Rn ≤ RT). Otherwise go to case#2.
Case#2: If the structure under study had LPS installed but the Risks still need to be reduced, you will need to install LPMS. Then go back to step#2-4 to calculate new values of risk components and make a series of trial and error calculations until the risk Rn is reduced below that of RT (Rn ≤ RT). Otherwise go to case#3.
Case#3: If the structure under study had both LPS and LPMS installed but the Risks still need to be reduced, you will need to install other protection measures. Then go back to step#2-4 to calculate new values of risk components and make a series of trial and error calculations until the risk Rn is reduced below that of RT (Rn ≤ RT).
The other protection measures that can reduce and influence the values of the risk components are shown in Table-2:
Table-2: Factors influencing the Risk Components
The following flow diagram in Fig.3 shows this procedure for Determination of Required Protection measure.
Part#3: evaluating the cost-effectiveness of protection measures
In the next Article, I will continue explaining Step#2: Risk Assessment Study. Please, keep following.