In Article " Introduction to Lightning System Design- Part One ", I listed all terms, abbreviations and Symbols used in lightning field.
Also, in Article " Introduction to Lightning System Design- Part Two ", I answered the following questions:
- What is Lightning?
- What are the types of Lightning flashes?
- What is the shape of The Lightning Waveform?
- How Lightning strikes can affect the electrical and/or electronic systems of a building?
- What are the main effects of Lightning?
And in Article " Types Of Lightning Protection Systems LPS ", I list the main types of Lightning Protection Systems as follows:
Types of Lightning Protection Systems LPS
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Types of Lightning Protection Systems LPS
Lightning protection
systems for buildings and installations may be divided into three principal
types as follows:
1- LPS for Protection
for buildings and installations against direct strike
by lightning, which includes:
A- Conventional lightning
protection system, which includes:
B- Non-Conventional
lightning protection system, which includes:
a- Active Attraction
LPS, which includes:
b- Active Prevention/Elimination
LPS, which includes:
2- LPS for Protection
against overvoltage on incoming conductors and conductor systems,
3- LPS for Protection
against the electromagnetic pulse of the lightning.
Notes on different Types
of Lightning Protection Systems LPS
Each system’s design
requires the following:
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And in Article " Conventional Lightning Protection System Components – Part One ", I indicated the Conventional Lightning Protection System parts and components as follows:
Conventional Lightning Protection System LPS Components
The Conventional Lightning Protection System consists of
two main parts:
1- The External Lightning Protection System, which includes:
2- The Internal Lightning Protection System, which includes:
Another important components of the Lightning Protection System is the Connection Components which include but not limited to:
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Components of External
Lightning Protection System
External Lightning
protection systems have (3) distinct subsystems. They are:
1- Strike Termination
Subsystem, which has (2) types:
And has also (4) forms as
follows:
A- Vertical Air Terminals,
B- Horizontal air
termination network, which include two sub-forms:
C- Combination of Vertical
Air Terminals and Horizontal air termination network,
D- Natural Air Terminals.
2- Conductor Subsystem,
3- Grounding Electrode
Subsystem.
These
individual Subsystems of an external LPS should be connected together using
appropriate lightning protection components (LPC). This will ensure that in
the event of a lightning current discharge to the structure, the correct
design and choice of components will minimize any potential damage.
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Conductor Subsystem
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1- Function of Conductor Subsystems
The function
of conductor subsystems is to conduct the intercepted lightning current to
the earth-termination system without intolerable temperature rises, for
example, to damage the structure.
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2- Effects of Lightning Strikes on Conductor
Subsystems
As we indicated before in Article " Introduction to Lightning System Design- Part Two " that the waveform represents
the lightning strike can be analyzed as follows:
In
general, it is essential to minimize resistance and inductive reactance in
the conductor subsystem of a lightning protection system.
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3- Conductor Subsystem Material Requirements
Note:
The
standards do not prescribe any relative performance advantages between these
choices; all are adequate to conduct the lightning current. But, when
considering service life, aesthetics, galvanic compatibility with building
materials and ease of installation, there is generally a preferred clear
choice of material for a given structure.
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3.1 Comparison between Copper and Aluminum
as a Lightning Conductor Material
Therefore,
most lightning protection systems are entirely copper or utilize an upper
aluminum portion connecting to a copper earth termination system. As aluminum
and copper are not compatible, a bimetallic joint should be used to
interconnect these two materials.
Note:
As
aluminum and copper are not compatible, a bimetallic joint should be used to
interconnect these two materials.
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3.2 Use of Dissimilar Metals in the Same
Lightning Conductor Subsystem
For example:
A bare
copper conductor should not be directly connected to steel, as the
electrochemical potential difference is 0.53 V (≥ 0.5 V). However, if the
copper is tin plated then the difference becomes that of tin (0.24 V), which
is acceptable.
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3.3 Lightning Conductor Geometry
There are
many choices of conductor geometry as follows:
The
following table indicates a comparison between above choices of conductor
geometry as follows:
Note:
PVC covering
limits the effectiveness when conductors are used as air terminations; it is
common to see air-termination networks that are basically insulated. This
does severely compromise the performance of the air-termination. The IEC
standards do not specifically address PVC covered conductors. However, in the
interest of improved performance, it is strongly recommend not using PVC
covered conductors as air terminations.
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In the next Article, I will explain the following points:
- Types of Lightning Conductors,
- Using Natural Structure Components As Down Conductors,
- Installation Requirements For Down Conductors.
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