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
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.
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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:
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And I explained the Strike Termination Subsystem in this Article.
Also, I explained the Conductor Subsystem in the following Articles:
And in Article " Conventional Lightning Protection System Components – Part Five ", I explained the Grounding Electrode Subsystem.
Also, in Article " Conventional Lightning Protection System Components – Part Six ", I began explaining the second part of Lightning Protection System; The Internal Lightning Protection System.
Today, I will continue explaining the Equipotential Bonding Subsystem and General Overview of Surge Protection Subsystem.
The Correct Choice Of Lightning Protection Components (LPC)
1- Within Europe:
Various standards series have been issued by (2) National Committees which are:
The CENELEC has released the EN 50164 series of standards. The EN 50164 series are component standards to which the manufacturers and suppliers of lightning protection components should test their products to verify design and quality. The EN 50164 series currently comprises of:
Notes:
For example:
IEC 62305-1 (IEC version) is parallel to EN 62305-1 (CENELEC adopted copy of the above)
And both are parallel to BS EN 62305-1 (British National Standard adoption ofthe above)
2- Within USA:
Various standards series have been issued such as:
Note:
For heavy fault conditions, Conductor Size should be calculated in accordance with IEEE Std 80.
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Equipotential Bonding Subsystem - Continued
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Components Of Equipotential Bonding Subsystem
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1- Components Of Equipotential Bonding Subsystem
Generally, Equipotential
bonding subsystem include the following components:
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1.1 Equipotential Bonding
Conductors
Sizing Of Equipotential
Bonding Conductors:
The cross section of
equipotential bonding conductors depends on the cross section of the main
protective conductor as per below Table#1. The main protective conductor is the
one coming from the source of current or from the service entrance box or the
main distribution board.
Notes On Table#1:
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1.2 Equipotential Bonding Bars
Equipotential bonding bars
are a central component of equipotential bonding which must clamp all the
connecting conductors and cross sections occurring in practice to have high
contact stability; it must be able to carry current safely and have
sufficient corrosion resistance.
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1.3 Connection Components
Connection
Components include but not limited to:
The most
important component among them is the clamps.
Pipe clamps:
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2- Separation (Isolation) Distance Requirements
2.1 Why a separation distance
between the external LPS and the structural metal parts is needed?
Note:
Separation distance requirements
also apply to internal electrical and electronic circuits, thus it is
especially important to consider them with respect to the existing and future
use of the building.
2.2 Calculation of Separation distance
(S)
This separation distance
can be calculated from the following formula:
Where:
S is separation distance,
ki Relates to the appropriate Class of LPS
(see Table#2),
kc Is a partitioning coefficient of the
lightning current flowing in the down conductors (see Table#3),
km Is a partitioning coefficient relating
to the separation medium (see Table#4),
l Is the length in meters
along the air termination or down conductor, from the point where the
separation distance is to be considered, to the nearest equipotential bonding
point.
Notes:
Table #2: Values of coefficient ki (BS EN 62305-3 Table 10)
Table#3: Values of
coefficient kc (BS
EN 62305-3 Table 11)
Also, kc can be calculated from the
following equation:
Where:
n = total number of
down-conductors,
c = distance of a down-conductor
to the next down-conductor,
h = spacing or height
between ring conductors.
Table#4: Values of coefficient km (BS EN 62305-3 Table 12)
Notes to Table#4:
When there are several
insulating materials in series, it is good practice to use the lower value
for km. The use of other insulating materials
is under consideration.
Table#5: Values of coefficient kc (BS EN 62305-3 Table C.1)
Notes to Table#5:
a) Values range from kc = 0.5 where c << h to kc = 1 with h << c (see Figure C.1).
b) The equation for kc according to Figure C.2 is an
approximation for cubic structures and for n≥ 4. The values of h, cs and cd are assumed to be in the range of 5 meters
to 20 meters.
c) If the down conductors
are connected horizontally by ring conductors, the current distribution is
more homogeneous in the lower parts of the down conductor system and kc is further reduced. This is especially
valid for tall structures.
d) These values are valid
for single earthing electrodes with comparable earthing resistances. If
earthing resistances of single earthing electrodes are clearly different, kc = 1 is to be assumed other values of kc may be used if detailed calculations are
performed.
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Example#1:
With reference to below
Figure, and If:
What is the required separation distance from the air rod to
the air conditioning unit?
Solution:
From above Tables for
calculation of separation distance, we find that
ki = 0.06 for LPS Class II (see Table 4.13)
kc = 0.44 (see Table 4.16)
km = 1 for air (see Table 4.15)
l = 25m
So, separation distance can be calculated as follows:
Thus the air rod would
need to be a minimum of 0.66m away from the air conditioning unit to ensure that
flashover did not occur in the event of a lightning discharge striking the
air rod.
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3- Test And Inspection Of The Equipotential Bonding Subsystem
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General Overview of Surge
Protection Subsystem
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4- General Overview of
Surge Protection Subsystem
As we stated before
that Services and metallic items entering the facility may include:
Where permitted,
these items should be bonded directly to the bonding bar. In the cases of
electrical, electronic and tele/data communications services, bonding should
be via surge protective devices.
4.1 What Is A Surge
Protective Device?
Surge
protective device (SPD) is the IEC term given to a device intended to limit
transient voltages and divert surge current. Around the world these products
are referred to by many other names, such as:
Within
some industries and regions these alternative names may apply to a defined
classification, but essentially these devices are all SPDs. SPDs are made
with different technologies, and often these are the basis for other names,
such as:
4.2 Importance of
Surge Protective Devices SPDs
The installation of
the surge protective devices on such services addresses multiple issues:
4.3 Working
Principle for Surge Protective Devices SPDs
4.4 Selection and
Installation Of Surge Protective Devices SPDs
The issues of
selection and installation of surge protective devices are complex, and made
more difficult by requirements being covered in EN 50164-1, -2, -3 & -4,
with reference to other standards including EN 50164-3, EN 61643 series, and
IEC 61000-4-5.
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