In Article " Design Calculations of Lightning Protection Systems – Part Two ", I indicated the lightning protection design process involves a number of design steps as in below Fig.1.
Fig.1: The Lightning Protection Design Process |
Step#1: Characteristics of the Structure to Be Protected
Explained in Article " Design Calculations of Lightning Protection Systems – Part Two "
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Step#2: Risk Assessment Study
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Also, In above Article, I indicated that the risk assessment study can be done by (4) different methods as follows:
Methods Of Calculations For Risk Assessment Study
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Articles
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First: Manual Method (Equations And Tables Method) as per IEC 62305-2
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First: Manual Method (Equations And Tables Method) as per NFPA 780
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Third: Excel Sheets Method For Performing The Risk Assessment Study
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Fourth: Online Calculators Method Used for Need for Lightning Protection calculations
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Step#3: Selection Of External LPS Type and Material
Explained in Article " Design Calculations of Lightning Protection Systems – Part Fifteen "
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Step#4: Sizing of Air Termination System Components
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In Article " Design Calculations of Lightning Protection Systems – Part Sixteen ", I explained the following points:
- Types and forms of Strike Termination Subsystem,
- Sizing of Air Terminals Based on IEC 62305-3 and Based on BS EN 62305-3,
- Sizing of Natural Air Terminals,
- Positioning / Placement of Air Termination System Components.
- The Class of LPS/LPL influences on the (3) Positioning Methods.
Method for Positioning of
Air Terminals
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Article
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The Rolling Sphere Method (RSM)
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The Protective Angle Method (PAM)
The Mesh Method
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Also, I explained the Recommendations for the Best Positioning of Air Terminals in Article " Design Calculations of Lightning Protection Systems – Part Nineteen ".
Today, I will explain Other Steps of the Lightning Protection Design Process.
Today, I will explain Other Steps of the Lightning Protection Design Process.
For more information, please review the following Articles:
Step#5: Design of Down-Conductor System
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This Step was
explained before in the following Articles:
Article " Conventional Lightning Protection System Components – Part Two ", which includes the
following points:
1- Function
of Conductor Subsystems,
2- Effects
of Lightning Strikes on Conductor Subsystems,
3- Conductor Subsystem Material
Requirements:
3.1Comparison
between Copper and Aluminum as a Lightning Conductor Material
3.2 Use of
Dissimilar Metals in the Same Lightning Conductor Subsystem
3.3
Lightning Conductor Geometry
Article " Conventional Lightning Protection System Components – Part Three ", which includes the
following points:
1- The Correct Choice Of Lightning Protection Components
(LPC)
2- Types of the Conductors in Conductor Subsystems:
2.A
Down-Conductors for a Non-Isolated Lightning Protection System
2.A.1
Temperature Rise Criteria:
Case#1: If
the wall is made of flame-resistant material or material with a normal level
of flammability
Case#2: If
the wall is made of highly flammable material
Case#2-A:
The temperature rise of the down-conductor systems is not hazardous
Case#2-B: The temperature rise of the down-conductor
systems presents a hazard
2.A.2 Requirements of Down
Conductor Installation in Non-Isolated Lighting Protection System
2.B Down
conductors of an isolated external lightning protection system
3-
Installation Requirements For Down Conductors:
3.1 General Consideration For Down Conductors Installation
3.2 Down Conductor
Routing:
3.2.A Structures with
overhangs
3.2.B
Routing Down Conductors within Walls, Or the Wall Cavity
3.2.C
Large Flat Structures
3.2.D
Courtyards
3.3 Fixing Of Down
Conductors
3.4 Measuring Points (Test
Joints)
Article " Conventional Lightning Protection System Components – Part Four ", which includes the following
points:
1- Natural Components
Used as Down Conductors
1.1 Metal Installations
1.2 Facade Elements,
Mounting Channels and the Metal Substructures of Facades
1.3 Metal downpipes
1.4 Rebar in
Reinforced Concrete
1.5 Rebar in Precast
Concrete
1.6 Rebar in
Prestressed Concrete
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Determination Of The Number Of Down Conductors
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Second: According to NFPA 780-2011
1- General Rule:
2- Special Rules:
2.1 For flat or
gently sloping roofs:
2.2 For irregularly
shaped structures:
Example#1:
For a pitched roof
structure shown in Fig.3 with spacing between shown points as follows:
Find the Minimum
required number of down conductors?
Solution:
Total perimeter = 40 m (130 ft) + 26 m (85 ft) + 26 m (85 ft)
+ 26 m (85 ft) + 26 m (85 ft) = 144 m (470 ft)
Since, the average distance
between down conductors does not exceed 30 m (100 ft).
Required down conductors = 144
m / 30 m = 4.8 = 5 down conductors
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Third: According to Rules
of Thumb
Table#2
Example#2:
If the total perimeter of
intermediate school = 625 mt, Find the Minimum required number
of down conductors
by the rules of thumb method if the intermediate school height < 30 m?
Solution:
Since intermediate school height
< 30 m , then use One down conductor for each 30m of
building perimeter.
the No. of down conductor =
625 / 30 = 20.83333 = 21 down conductors
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Practical Recommendations For Determining Number Of
Down Conductors
1- Number of down
conductors for isolated LPS:
2- Number of down
conductors for non-isolated LPS:
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Step#6: Design of Earth Termination System
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This Step was
explained before in Article " Conventional Lightning Protection System Components – Part Five ", which includes the
following points:
1- Grounding
Electrode Subsystem (Earth Termination System)
2- Functions
of Grounding
Electrode Subsystem:
3- Grounding System – General Overview
4- Resistance value for Grounding Electrode
Subsystem
5- Grounding
Electrode Subsystem Types
5.A Type A arrangement
5.A.1 Type A Arrangement
Criteria
5.A.2 Calculating the
minimum total length of electrode at each down-conductor for Type A arrangement
5.A.3 Type A Arrangement For Sites
With Extreme Weather Conditions
5.B Type B
arrangement,
5.B.1 Type B Arrangement
Criteria
5.B.2 Calculating the
minimum length of the ring earth electrode for Type B arrangement
5.C Comparison of
Type A and Type B arrangements
5.D Type C
arrangement: Foundation earth electrodes.
5.D.1 Type C Arrangement
Criteria
6- Earth Termination
System Testing
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Step#7: Design of Internal LPS System
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This Step was
explained before in the following Articles:
Article " Conventional Lightning Protection System Components – Part Six ", which includes the following points:
1- The Internal Lightning Protection System
2- Function of Internal
Lightning Protection System
3- How Internal Lightning
Protection System prevent hazardous sparking inside the building or
structure?
4- Components Of The Internal Lightning Protection System
5- The Internal Lightning Protection System subsystems
5.A
Equipotential Bonding Subsystem,
5.A.1 General Notes For Equipotential Bonding
5.A.2 Parts Of Equipotential
Bonding Subsystem
5.A.2.a Main
equipotential bonding,
5.A.2.b
Supplementary equipotential bonding.
5.A.2.c The
Difference Between Main And Supplementary Equipotential Bonding
5.A.2.d Considerations
For Different Cases Of Main Equipotential Bonding In Any Installation
5.A.2.d.1 Lightning
Equipotential Bonding For External LPS
And External Conductive Parts
5.A.2.d.1.2 Lightning
Equipotential Bonding Of External Services
5.A.2.d.1.3 Lightning
Equipotential Bonding For Internal Systems
5.A.2.d.1.4 Lightning
Equipotential Bonding Of Roof Top Fixtures
Article " Conventional Lightning Protection System Components – Part Seven ", which includes the following points:
1- Components Of Equipotential Bonding
Subsystem
1.1 Equipotential bonding
conductors
1.1.A Sizing Of
Equipotential Bonding Conductors
1.2 Equipotential bonding
bars,
1.3 Connection Components .
2- Separation (Isolation) Distance Requirements
2.1 Why a separation distance
between the external LPS and the structural metal parts is needed?
2.2 Calculation of Separation distance
(S)
3- Test And Inspection Of
The Equipotential Bonding Subsystem
4-
Surge Protection Subsystem.
4.1 General Overview of Surge Protection Subsystem
4.2 What Is A Surge
Protective Device?
4.3 Importance of
Surge Protective Devices SPDs
4.4
Working Principle for Surge Protective Devices SPDs
4.5 Selection and
Installation Of Surge Protective Devices SPDs
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Step#8: LPS Design Drawings and Specifications
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First: LPS Design Drawings
Complete design drawings
shall be submitted to the engineer for approval and
showing at least the
following:
You can download Example of Lightning Protection System Design Drawings by click on the link.
Second: LPS Design Specifications
A general format of a common LPS
Design Specifications will include the following parts as a minimum:
PART 1 – GENERAL
1.1. Objective: To provide safety for
the building and occupants by eliminating
damage to the entire structure
caused by lightning, surges and other related
occurrences.
1.2. Standards: list the specifications and
standards used in design.
1.3. System Design: The
design of this system is to be in strict accordance
with this section of the
standards and specifications. If any departure from
the contract drawings or
submittal drawings covered below are deemed
necessary by the Contractor,
details of such departures and reasons therefore
shall be submitted as soon
as practical to the architect and engineer for approval.
1.4. Submittals: Complete
design drawings, product catalogs and calculations
shall be submitted to the
engineer for approval.
1.5. Quality Assurance: The
LPS shall conform to the requirements and standards
for LPS(s) in accordance
with section of the standards and specifications.
PART 2 – PRODUCTS
2.1 Standard: The system
furnished under this specification shall be the standard
product of a
manufacturer regularly engaged in the production of lightning
protection
equipment and shall be the manufacturer’s latest approved design.
2.2 Equipment: Provide and
install a complete LPS in compliance with
the specifications and standards of
the most current editions listed in section
of the standards and
specifications.
2.3 Materials: All lightning
protection materials and components shall comply in
weight, size and
composition with the specifications and standards of the most
current
editions listed in section of the standards and specifications.
PART 3 – EXECUTION
3.1 Installation: An
experienced installation company shall directly supervise
the installation to
accomplish its completion. All equipment shall be installed
in a neat,
workmanlike manner.
The system shall consist of a complete network of
conductor cables at the roof
and include air terminals, connectors, splicers,
appropriate bonding, down lead
cables and proper ground terminals.
3.2 Coordination: The
lightning protection contractor will work with other
trade contractors to
ensure a correct, neat and inconspicuous as practical
installation. It shall
be the responsibility of the lightning protection contractor
to assure a
proper common bond to the appropriate grounded utilities; such as
the
electric service ground, incoming water and gas pipe, etc.
3.3 Inspection and Certification: Upon
completion of the installation, the contractor shall furnish the Master Label
Certification issued by a certified inspector for this system. If the
existing structure does have a LPS, the contractor shall advise the Owner of
any additional work required on
the existing system to achieve compliance
with regulations requirements.
You can download an Example
of A General Format for Lightning Protection
System Specification by click on
the link.
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Can I get password for Need for Lightning - IEC62305-2 Locked
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ReplyDeleteUnderstanding the design calculations of lightning protection systems (LPS) is essential for engineers and architects. Part Twenty of this series delves into critical calculations ensuring effective protection against lightning strikes. It's a must-read for professionals aiming to implement robust LPS solutions, ensuring safety and compliance in construction projects.
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