Conventional Lightning Protection System Components – Part Seven


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:

  1. Franklin Rod LPS,
  2. Franklin/Faraday Cage LPS.


B- Non-Conventional lightning protection system, which includes:

a- Active Attraction LPS, which includes:

  1. Improved single mast system (Blunt Ended Rods),
  2. Early streamer Emission System.


b- Active Prevention/Elimination LPS, which includes:

  1. Charge Transfer System (CTS),
  2. Dissipation Array System (DAS).


2- LPS for Protection against overvoltage on incoming conductors and conductor systems,

3- LPS for Protection against the electromagnetic pulse of the lightning.





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:

  • Strike Termination Subsystem,
  • Conductor Subsystem,
  • Grounding Electrode Subsystem.


2- The Internal Lightning Protection System, which includes:

  • Equipotential Bonding Subsystem,
  • Surge Protection Subsystem.


Another important components of the Lightning Protection System is the Connection Components which include but not limited to:

  • Clamps,
  • Connectors,
  • Terminal components,
  • Bridging components,
  • Expansion pieces,
  • Measuring points.





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)


  • The correct choice of material, configuration and dimensions of the lightning protection components is essential when linking the various elements of an LPS together. 
  • The designer/user needs to know that the components, conductors, earth electrodes etc will meet the highest levels when it comes to durability, long term exposure to the environmental elements and perhaps most importantly of all, the ability to dissipate the lightning current safely and harmlessly to earth.
  • Various standards series have been compiled with this very much in mind. At present these standards are as follows:



Standards for Lightning Protection Systems


1- Within Europe:

Various standards series have been issued by (2) National Committees which are:

  1. The European Committee for Electrotechnical Standardisation (CENELEC).
  2. The International Electrotechnical Commission (IEC)


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:

  • EN 50164-1 Lightning protection components (LPC) – Part 1: Requirements for connection components,
  • EN 50164-2 Lightning protection components (LPC) – Part 2: Requirements for conductors and earth electrodes,
  • EN 50164-3 Lightning protection components (LPC) – Part 3: Requirements for isolating spark gaps,
  • EN 50164-4: Lightning Protection Components (LPC) – Part 4: Requirements for conductor fasteners,
  • EN 50164-5: Lightning Protection Components (LPC) – Part 5: Requirements for earth electrode inspection housings and earth electrode seals,
  • EN 50164-6: Lightning Protection Components (LPC) – Part 6: Requirements for lightning strike counters,
  • EN 50164-7: Lightning Protection Components (LPC) – Part 7: Requirements for earthing enhancing compounds.


Notes:

  • The standards generally have an IEC prefix to their number (CEI for French versions). IEC standards are produced in English and French languages.
  • IEC and CENELEC generally work in parallel, and CENELEC members vote to adopt new IEC standards as CENELEC standards. The committees of CENELEC may choose to make some alterations to the IEC version.
  • Additionally, CENELEC produce their own standards to which IEC have no counterpart. CENELEC documents are produced in English, French and German and an approved CENELEC standard will have an EN prefix (or NE in the French language versions).


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:

  1. Underwriters Laboratory (UL96 & 96A),
  2. The National Fire Protection Association (NFPA 780)
  3. The Lightning Protection Institute (LPI-175)


Note:

For heavy fault conditions, Conductor Size should be calculated in accordance with IEEE Std 80.






Equipotential Bonding Subsystem - Continued




Components Of Equipotential Bonding Subsystem





1- Components Of Equipotential Bonding Subsystem

Generally, Equipotential bonding subsystem include the following components:

  1. Equipotential bonding conductors,
  2. Equipotential bonding bars,
  3. Connection Components.







1.1 Equipotential Bonding Conductors



Equipotential Bonding Conductors

  • In general, bonding conductors intended for bonding are of smaller cross-section than those intended for the main flow of lightning current.
  • Equipotential bonding conductors do not carry operating currents and can therefore be either bare or insulated.

  • Equipotential bonding conductors should, as long as they fulfill a protective function, if it is insulated, it shall be labeled the same as protective conductors, i.e. green/yellow.

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.



Table#1


Notes On Table#1:

  • In any case, the minimum cross section of the main equipotential bonding conductor is at least 6 mm2 Cu. 25 mm2 Cu has been defined as a possible maximum.
  • The supplementary equipotential bonding must have a minimum cross section of 2.5 mm2 Cu for a protected installation, and 4 mm2 Cu for an unprotected installation.
  • For earth conductors of antennas (according to IEC 60728-11 (EN 60728-11)), the minimum cross section is 16 mm2 Cu, 25 mm2 Al or 50 mm2 steel.







1.2 Equipotential Bonding Bars


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.






1.3 Connection Components

Connection Components include but not limited to:

  1. Clamps,
  2. Connector,
  3. Terminal,
  4. Terminal lug.


The most important component among them is the clamps.


Pipe clamps:



Pipe clamps

  • In order to integrate pipes into the equipotential bonding, earthing pipe clamps corresponding to the diameters of the pipes are used.
  • Pipe earthing clamps made of stainless steel, which can be universally adapted to the diameter of the pipe, offer enormous advantages for mounting.
  • These pipe earthing clamps can be used to clamp pipes that are made of different materials (e.g. steel, copper and stainless steel). These components allow also a straight-through connection.







2- Separation (Isolation) Distance Requirements


2.1 Why a separation distance between the external LPS and the structural metal parts is needed?

  • A separation distance (i.e. the electrical insulation) between the external LPS and the structural metal parts (external and internal) is essentially required because this will minimize any chance of partial lightning current being introduced internally in the structure. This can be achieved by placing lightning conductors, sufficiently far away from any conductive parts that has routes leading into the structure. So, if the lightning discharge strikes the lightning conductor, it cannot ‘bridge the gap’ and flash over to the adjacent metalwork.
  • Hence, the separation distance requirements determine what external and internal metallic items need to be bonded to the LPS.



Separation (Isolation) Distance Requirements


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:

  • If the structure has a metallic framework, such as steel reinforced concrete, or structural steel stanchions and is electrically continuous, then the requirement for a separation distance is no longer valid. This is because all the steelwork is effectively bonded and as such an electrical insulation or separation distance cannot practicably be achieved.
  • l is the length of the down-conductor only; the length of the path of the conductor/metallic item in the structure is not important.
  • Separation distance requirements would apply to the air-terminal and external down-conductor connecting into the natural down-conductor. The connection point is the reference point for measurement of the length.
  • In an isolated lightning protection system, the LPS is designed to maintain the required separation distance to all required items, therefore bonding only occurs at ground level.




Class of LPS
ki
I
0.08
II
0.06
III and IV
0.04
Table #2: Values of coefficient ki (BS EN 62305-3 Table 10)




Number of down-conductors
n
Detailed values (see Table#5)
kc
1
1
2
1 to 0.5
4 and more
1 to 1/n
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.



Material
km
Air
1
Concrete, bricks
0.5
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.



Type Of Air Termination System

Number Of Down Conductors
n

kc
Earthing Arrangement
Type A
Earthing Arrangement
Type B
Single rod
1
1
1
Wire
2
0.66 d)
0.5 to 1
(see Figure C.1) a)
Mesh

4 and more
0.44 d)
0.25 to 0.5
(see Figure C.2) b)
Mesh

4 and more, connected by
horizontal ring conductors
0.44 d)
1/n to 0.5
(see Figure C.3) c)
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.







Example#1:

With reference to below Figure, and If:

  • Number of down conductors = 4,
  • Class of LPS = LPL II,
  • Earthing arrangement = Type A,
  • Length of air termination/down conductor to nearest equipotential bonding bar = 25m.


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.






3- Test And Inspection Of The Equipotential Bonding Subsystem

  • Before commissioning the electrical consumer’s installation, the connections must be inspected to ensure their faultless condition and effectiveness.
  • A low-impedance conductance to the various parts of the installation and to the equipotential bonding is recommended. A guide value of < 1 Ω for the connections at equipotential bonding is considered to be sufficient.








General Overview of Surge Protection Subsystem




4- General Overview of Surge Protection Subsystem

As we stated before that Services and metallic items entering the facility may include:

  • Telephone and telecommunication lines,
  • Cable TV circuits,
  • Antenna feeders,
  • Power lines,
  • Pipe work (water, air, gas, etc),
  • Metal ducts.


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 Devices SPDs


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:

  • Surge Arrestor,
  • Surge Diverter,
  • Arrestor,
  • Suppressor,
  • Diverter,
  • Lightning Arrestor,
  • Voltage Suppressor,
  • Transient Voltage Surge Suppressor
  • Overvoltage Arrestor.


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:

  • Spark gaps,
  • Arc Gaps,
  • Gas Discharge Tubes (GDTs),
  • Metal Oxide Varistors (MOVs).



4.2 Importance of Surge Protective Devices SPDs

The installation of the surge protective devices on such services addresses multiple issues:

  • Eliminating potential differences to service conductors and thereby reducing the risk of flashover and possible resulting fire (IEC 62305-3),
  • Providing protection to structure electrical/electronic equipment against impulses from direct or indirect flashes to the services (IEC 62305-4),
  • Correctly located and installed protection (coordinated protection) will also reduce the risk of equipment damage from impulses generated by switching or faults within the electrical circuits,
  • They are a key part of the Lightning Electromagnetic Impulse LEMP protection measures system which be abbreviated as LMPS.



4.3 Working Principle for Surge Protective Devices SPDs

  • SPDs contain at least one non-linear component, which under specific conditions transitions between a high and low impedance state.
  • At normal operating voltages the SPDs are in a high impedance state and do not affect the system. When a transient voltage occurs on the circuit, the SPD moves into a state of conduction (a low impedance) and diverts the transient energy/current back to its source or ground.
  • This limits (clamps) the voltage amplitude to a safer level. After the transient is diverted, the SPD will automatically reset back to its high impedance state.



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. 


Hence, we will not discuss the issues of selection and installation of surge protective devices and the LEMP Protection Measures System (LPMS) in this course, and they will be discussed later in a separate course.






In the next Article, I will explain The Non-Conventional Lightning Protection Systems. Please, keep following.



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