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:
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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And I explained the Strike Termination Subsystem in this Article.
Also, in Article " Conventional Lightning Protection System Components – Part Two ", I began explaining the Conductor Subsystem through the following points:
- Function of Conductor Subsystems,
- Effects of Lightning Strikes on Conductor Subsystems,
- Conductor Subsystem Material Requirements.
Today, I will continue explaining the Conductor Subsystem through the following points:
- Types of Lightning Conductors,
- Installation Requirements For Down Conductors.
Conductor Subsystem -Continued
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2- Types of the Conductors in
Conductor Subsystems
The Conductor Subsystem is consisting of two types of conductors as
follows:
Note:
It is possible that the same conductor type may be used for:
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2.1 The
Air-Termination Conductors (The Main
Conductors)
The Air-Termination Conductors is the electrically conductive
connection between the air-termination system and the down conductors.
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2.2 Down Conductors (The Extension Conductors)
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2.2.A Down-Conductors for a Non-Isolated
Lightning Protection System
In non-isolated
lightning protection system, the down-conductors are primarily mounted
directly onto the structure (with no distance).
But, sometimes
a separation distance is required between the down conductors and the
structure. This is governed by the criteria of temperature rise in the event
of lightning striking the lightning protection system.
Temperature
Rise Criteria:
The
temperature rise criterion is based on the level of flammability for the
structure walls; we have two cases as follows:
Case#1: If
the wall is made of flame-resistant material or material with a normal level
of flammability
In this
case, the down-conductor systems may be installed directly on or in the wall.
For example,
Wood with a bulk density greater than 400 kg/m2 and a thickness greater than
2 mm is considered to have a normal level of flammability. Hence the
down-conductor system can be mounted on wooden poles.
Case#2: If
the wall is made of highly flammable material
In this
case, we have two sub-cases according to considering the temperature rise
(when lightning currents flow) is a hazard or not, this is can be known from
table as follows:
the below Table states
the maximum temperature rise ΔT in K of the various conductors for each class
of lightning protection system. These values mean that, generally, it is even
permissible to install down conductors underneath heat insulation because
these temperature rises present no fire risk to the insulation materials.
This ensures that the fire retardation measure is also provided.
So, the two
sub-cases for case#2: If the wall is made of highly flammable material, are:
Case#2-A:
The temperature rise of the down-conductor systems is not hazardous
In this
case, the down conductors can be installed directly on the surface of the
wall.
Case#2-B: The temperature rise of the down-conductor
systems presents a hazard
In this
case, the down conductors must be mounted (by using Standoff brackets for
example)(see fig.1) to ensure that the separation distance between the down-conductor
and the wall is greater than 0.1 m. The mounting elements may touch the wall.
Notes:
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2.2.A.1 Requirements of Down
Conductor Installation In Non-Isolated Lighting Protection System
The following
requirements for Down Conductor Installation in Non-Isolated
Lighting Protection System must be considered:
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2.2.B Down conductors of an isolated external
lightning protection system
The
general requirements for down-conductors in an isolated LPS are:
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3- Installation Requirements For Down
Conductors
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3.1 General Consideration
For Down Conductors Installation
To avoid
damage caused during the lightning current discharge to the earth-termination
system such as side flash which depends on inductance value of the down
conductors. The following requirements must be considered:
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3.2 Down Conductor Routing
The criterion for the
best routing of down conductors is as follows:
We have many cases
where special solutions must be provided for correct routing of down
conductors as follows:
1- Structures with
overhangs
h>2.5+ s
Where:
h = Height of the
overhang (in meters),
s = Required
separation distance calculated in accordance with Section 6.3 of BS EN
62305-3.
2-
Routing Down Conductors within Walls, Or the Wall Cavity
Care is
required in routing conductors within walls, or the wall cavity:
3- Large
Flat Structures
4-
Courtyards
Structures
with enclosed courtyards having a perimeter greater than 30 m (see fig) must have down-conductor
systems installed with the distances (see fig.11).
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3.3 Fixing Of Down Conductors
Fixing
centers for the air termination and down conductors are shown in below Table:
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3.4 Measuring Points (Test Joints)
Each down conductor will be
provided with a test joint designed and situated to:
Notes:
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In the next Article, I will explain How to use Natural Structure Components as down Conductors. Please, keep following.
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