E.4.2.2.2.1 Architect
Agreement should be reached with the architect on the following items:
routing of all LPS conductors;
materials for LPS components;
details of all metal pipes, gutters, rails and similar items;
details of any equipment, apparatus, plant installations, etc. to be installed on, within or near the structure which may require the moving of installations or may require bonding to the LPS because of the separation distance. Examples of installations are alarm systems, security systems, internal telecommunication systems, signal and data processing systems, radio and TV circuits;
the extent of any buried conductive service which could affect the positioning of the earthtermination network and be required to be placed at a safe distance from the LPS;
the general area available for the earth-termination network;
the extent of the work and the division of responsibility for primary fixings of the LPS to the structure. For example, those affecting the water tightness of the fabric (chiefly roofing), etc;
conductive materials to be used in the structure, especially any continuous metal which may have to be bonded to the LPS, for example stanchions, reinforcing steel and metal services either entering, leaving, or within the structure;
the visual impact of the LPS;
the impact of the LPS on the fabric of the structure;
the location of the connection points to the reinforcing steel, especially where they penetrate external conductive parts (pipes, cable shields, etc.);
the connection the LPS to the LPS of adjacent buildings.
E.4.2.2.2.2 Public utilities
Bonding of incoming services to the LPS directly or, if this is not possible, through isolating spark gaps or SPD should be discussed with the operator or authorities concerned, as there may be conflicting requirements.
E.4.2.2.2.3 Fire and safety authorities
Agreement should be reached with the fire and safety authorities on the following items:
- the positioning of alarm and fire extinguishing system components;
routes, construction material and sealing of ducts;
the method of protection to be used in the case of a structure with a flammable roof.
E.4.2.2.2.4 Electronic system and external antenna installers
Agreement with the electronic system and antenna installer should be reached on the following items:
the isolating or bonding of aerial supports and conductive shields of cables to the LPS;
the routing of aerial cables and internal network;
installation of surge protective devices.
E.4.2.2.2.5 Builder and installer
Agreement on the following items should be reached between the builder, installer, and those responsible for construction of the structure and its technical equipment:
the form, position and number of primary fixings of the LPS to be provided by the builder;
any fixings provided by the LPS designer (or the LPS contractor or the LPS supplier) to be installed by the builder;
the position of LPS conductors to be placed beneath the structure;
whether any components of the LPS are to be used during the construction phase, for example the permanent earth-termination network could be used for earthing cranes, hoists and other metallic items during construction work on the site;
for steel-framed structures, the number and position of stanchions and the form of fixing to be made for the connection of earth-terminations and other components of the LPS;
whether metal coverings, where used, are suitable as components of the LPS;
the method of ensuring the electrical continuity of the individual parts of the coverings and their method of connecting them to the rest of the LPS where metal coverings are suitable as components of the LPS;
the nature and location of services entering the structure above and below ground including conveyor systems, television and radio aerials and their metal supports, metal flues and window cleaning gear;
coordination of the structure's LPS earth-termination system with the bonding of power and communication services;
the position and number of flag masts, roof-level plant rooms, for example lift motor rooms, ventilation, heating and air-conditioning plant rooms, water tanks and other salient features;
the construction to be employed for roofs and walls in order to determine appropriate methods of fixing LPS conductors, specifically with a view to maintaining the watertightness of the structure;
the provision of holes through the structure to allow free passage of LPS downconductors;
the provision of bonding connections to steel frames, reinforcement bars and other conductive parts of the structure;
the frequency of inspection of LPS components which will become inaccessible, for example steel reinforcing bars encapsulated in concrete;
the most suitable choice of metal for the conductors taking account of corrosion, especially at the point of contact between dissimilar metals;
accessibility of test joints, provision of protection by non-metallic casings against mechanical damage or pilferage, lowering of flag masts or other movable objects, facilities for periodic inspection especially for chimneys;the preparation of drawings incorporating the above details and showing the positions of all conductors and main components;
the location of the connection points to the reinforcing steel.
E.4.2.3 Electrical and mechanical requirements
E.4.2.3.1 Electrical design
The LPS designer should select the appropriate LPS to obtain the most efficient construction. This means consideration of the architectural design of the structure to determine whether an isolated or non-isolated LPS, or a combination of both types of lightning protection, should be used.
Soil resistivity tests should be performed preferably prior to finalizing the design of an LPS and should take into consideration the seasonal variations of soil resistivity.
During the completion of the basic electrical design of the LPS, the use of suitable conductive parts of the structure should be considered as natural components of the LPS to enhance or act as essential components of the LPS.
It is the responsibility of the LPS designer to evaluate the electrical and physical properties of natural components of the LPS and to ensure that they conform to the minimum requirements of this standard.
The use of metal reinforcing, such as steel-reinforced concrete, as lightning protection conductors requires careful consideration, and knowledge of the national construction standards applicable to the structure to be protected. The steel skeleton of reinforced concrete may be used as LPS conductors or may be used as a conductive shielding layer to reduce the electromagnetic fields generated by lightning in the structure as the lightning currents are conducted through an isolated LPS. This LPS design makes protection easier, in particular for special structures containing extensive electrical and electronic installations.
A stringent construction specification for down-conductors is required in order to meet the minimum requirements for natural components given in 5.3.5.
E.4.2.3.2 Mechanical design
The lightning protection designer should consult with the persons responsible for the structure on mechanical design matters following the completion of the electrical design.
Aesthetic considerations are particularly important as well as the correct selection of materials to limit the risk of corrosion.
The minimum size of lightning protection components for the various parts of the LPS are listed in Tables 3, 6, 7, 8 and 9.
The materials used for the LPS components are listed in Table 5.
NOTE For selection of other components, such as rods and clamps, reference may be made to the future IEC 62561 series. This will ensure that temperature rise and mechanical strength of such components are taken into account.
Where deviations are made from the dimensions and materials specified in Tables 5, 6 and 7, using the lightning discharge electrical parameters specified for the selected class of LPS given in Table 1, the lightning protection designer or installer should predict the temperature rise of lightning conductors under discharge conditions and dimension the conductors accordingly.
When excessive temperature rise is a concern for the surface on which the components are to be attached (because it is flammable or has a low melting point), either larger conductor cross-sections should be specified or other safety precautions should be considered, such as the use of stand-off fittings or the insertion of fire-resistant layers.
The LPS designer should identify all corrosion problem areas and specify appropriate measures.
The corrosion effects on the LPS may be reduced either by increases in material size, by using corrosion resistive components, or by taking other corrosion protection measures.
The LPS designer and LPS installer should specify conductor fasteners and fixtures which will withstand the electrodynamic forces of lightning current in the conductors and also allow for the expansion and contraction of conductors due to the increase in temperature that occurs.
This could be achieved by using components tested according to the future IEC 62561 series.
E.4.2.3.3 Structure with a cantilevered part
To reduce the probability of a person standing under a cantilevered construction from becoming an alternate path for lightning current flowing in the down-conductor running on the cantilevered wall, the actual distance, d, in metres should satisfy the following condition:
d > 2,5 + s (E.1)
where s is the separation distance in metres calculated in accordance with 6.3.
The value 2,5 is representative of the height at the tips of a man's fingers when he stretches his arm vertically (see Figure E.2).
Кеу
d actual distance >s
s separation distance according to 6.3
I length for the evaluation of separation distance s
NOTE The height of the person with raised hand is taken to be 2,5 m.
Figure E.2 - LPS design for a cantilevered part of a structure
Loops in a conductor as shown in Figure E.2 can produce high inductive voltage drops, which can cause a lightning discharge to pass through a structure wall thereby causing damage.
If the conditions in 6.3 are not met, arrangements should be made for direct routing through the structure at the points of re-entrant lightning conductor loops for those conditions shown in Figure E.2.
E.4.3 Reinforced concrete structures
E.4.3.1 General
Industrial structures frequently comprise sections of reinforced concrete which are produced on site. In many other cases, parts of the structure may consist of prefabricated concrete units or steel parts.
Steel reinforcement in reinforced concrete structures conforming to 4.3 may be used as a natural component of the LPS.
Such natural components must fulfil the requirements of:
down-conductors according to 5.3;
earth-termination networks according to 5.4.
The requirement of a maximum overall resistance of 0,2 О can be checked by measuring the resistance between the air-termination system and a ground plate at ground level using testing equipment suitable for the application capable of measuring in a four lead configuration (two measuring leads and two sensing leads) as illustrated in Figure E.3. The injected measuring current should be in the order of about 10 A.
NOTE 1 When access to test areas or routing of test cables are difficult, dedicated bar from high to low may be provided in order to carry out testing at each point. The total resistance of joints plus the resistance of downconductor can then be calculated.
IEC 2661/10
Figure E.3 - Measuring the overall electrical resistance
Moreover, the conductive steel reinforcement in concrete, when properly used, should form the cage for potential equalization of the internal LPS according to 6.2.
Furthermore, the steel reinforcement of the structure, if adequate, may serve as an electromagnetic shield, which assists in protecting electrical and electronic equipment from interference caused by lightning electromagnetic fields according to IEC 62305-4.
If the reinforcement of the concrete and any other steel constructions of a structure are connected both externally and internally so that the electrical continuity conforms to 4.3, effective protection may be achieved against physical damage.
The current injected into the reinforcing rods is assumed to flow through a large number of parallel paths. The impedance of the resulting mesh is thus low and, as a consequence, the voltage drop due to the lightning current is also low. The magnetic field generated by the current in the reinforcing steel mesh is weak due to the low current density and the parallel current paths generating opposing electromagnetic fields. Interference with neighbouring internal electrical conductors is correspondingly reduced.
NOTE 2 For protection against electromagnetic interference, see IEC 62305-4 and IEC/TR 61000-5-2
When a room is totally enclosed by steel-reinforced concrete walls whose electrical continuity conforms to 4.3, the magnetic field due to lightning current flowing through the reinforcement in the vicinity of the walls is lower than that in a room of a structure protected with conventional down-conductors. Owing to the lower induced voltages in conductor loops installed inside the room, protection against failures of internal systems may be easily improved.
After the construction phase, it is nearly impossible to determine the layout and construction of the reinforcement steel. Therefore, the layout of the reinforcement steel for the purpose of lightning protection should be very well documented. This can be done utilizing drawings, descriptions and photographs taken during the construction.
E.4.3.2 Utilization of reinforcement in concrete
Bonding conductors or grounding plates should be furnished in order to provide reliable electrical connection to the reinforcement steel.
Conductive frames that, for example, are attached to the structure may be used as natural LPS conductors and as connection points for the internal equipotential bonding system.
A practical example is the use of foundation anchors or foundation rails of machines, apparatus or housings, to achieve potential equalization. Figure E.4 illustrates the arrangement of the reinforcement and the bonding bars in an industrial structure.
Key
b
electrical power equipment
steel girder
metal covering of the facade
bonding joint
electrical or electronic equipment
steel reinforcement in concrete (with superimposed mesh conductors)
foundation earth electrode
common inlet for different services
Figure E.4 - Equipotential bonding in a structure with a steel reinforcement
The location of bonding terminations in the structure should be specified at an early planning stage in the design of the LPS and should be made known to the civil works contractor.
The building contractor should be consulted to determine whether welding to the reinforcing rods is permitted, whether clamping is possible or whether additional conductors should be installed. All necessary work should be performed and inspected prior to pouring of the concrete (i.e. planning of the LPS should be carried out in conjunction with the design of the structure).
Е.4.3.3 Welding or clamping to the steel-reinforcing rods
The continuity of the reinforcing rods should be established by clamping or welding.
NOTE Clamps conforming to the future IEC 62561 series are suitable.
Welding to the reinforcing rods is only permitted if the civil works designer consents. The reinforcing rods should be welded over a length not less than 50 mm (see Figure E.5).
IEC 2663/10
Figure E.5a - Welded joints (suitable for lightning current and EMC purposes)
IEC 2664/10
Figure E.5b - Clamped joints to future IEC 62561 (suitable for lightning current and EMC purposes)
Figure E.5c - Bound joints (suitable for lightning current and EMC purposes)
IEC 2666/10
Figure E.5d - Lashed joints (suitable for EMC purposes only)
Figure E.5 - Typical methods of joining reinforcing rods in concrete (where permitted)
The connection to outside components of the lightning protection system should be established by a reinforcement rod brought out through the concrete at a designated location or by a connecting rod or ground plate passing through the concrete which is welded or clamped to the reinforcing rods.
Where joints between the reinforcing rods in concrete and the bonding conductor are made by means of clamping, two bonding conductors (or one bonding conductor with two clamps to different reinforcing bars) should always be used for safety, since the joints cannot be inspected after the concrete has set. If the bonding conductor and reinforcing rod are dissimilar metals, then the joint area should be completely sealed with a moisture inhibiting compound.
Figure E.6 shows clamps used for joints for reinforcing rods and solid tape conductors.
Figure E.7 shows details for connection of an external system to reinforcing rods.
The bonding conductors should be dimensioned for the proportion of lightning current flowing at the bonding point (see Tables 8 and 9).
Figure E.6a - Circular conductor to a reinforcing rod
Figure E.6b - Solid tape conductor to a reinforcing rod
Key
reinforcing rod
circular conductor
screw
tape conductor
Figure E.6 - Example of clamps used as joints
between reinforcing rods and conductor
s
Figure E.7b
Figure E.7d
ІЕС 2670/10
IEC 2672/10
Key
bonding conductor
nut welded to steel bonding connector
steel-bonding connector*
cast in non ferrous bonding point
stranded copper bonding connector
corrosion protection measure
C-steel (C-shaped mounting bar)
welding
* The steel-bonding connector is connected at many points by welding or clamping to the steel reinforcing bars.
NOTE Construction shown in Figure E.7c is not a generally accepted solution in terms of good engineering practice.
Figure E.7 - Examples for connection points to the reinforcement
in a reinforced concrete wall
Е.4.3.4 Materials
The following materials can be used as additional conductors installed in concrete for lightning protection purposes: steel, mild steel, galvanized steel, stainless steel, copper and copper coated steel .
The behaviour of a galvanized layer on steel in concrete is very complicated, particularly in concrete with chlorides, the zinc will corrode quickly on contact with the reinforcement, and can under certain conditions cause damage to the concrete. Galvanized steel should therefore not be used in coastal areas and where there may be salt in the ground water. As the use of galvanized steel in concrete requires evaluation of many external factors this material should be used only after careful analysis. With this in mind the use of the other mentioned materials is preferred over the use of galvanized steel.
In order to avoid confusion between the different types of steel rods in concrete, it is recommended that round steel rods of at least 8 mm diameter with a smooth surface be used as additional conductors in contrast to the ordinary ribbed surface of the reinforcing rods.
E.4.3.5 Corrosion
Where steel reinforcement bonding conductors are brought through a concrete wall, particular attention should be paid to protection against chemical corrosion.
The simplest corrosion protection measure is the provision of a silicon rubber or bitumen finish in the vicinity of the exit point from the wall, e.g. 50 mm or more in the wall and 50 mm or more outside the wall (see Figure E.7c). However this is generally not regarded as a good engineering solution. An improved solution is to use connectors especially developed for this purpose as shown in the other examples of Figure E.7
Where copper and copper coated steel bonding conductors are brought through the concrete wall, there is no corrosion risk if a solid conductor, proprietary bonding point, PVC covering or isolated wire is used (see Figure E.7b). For stainless steel bonding conductors, in accordance with Tables 6 and 7, no corrosion prevention measures need to be used.
In the case of extremely aggressive atmospheres, it is recommended that the bonding conductor projecting from the wall be made of stainless steel.
NOTE Galvanized steel outside the concrete in contact with reinforcement steel in the concrete may, under certain circumstances, cause damage to the concrete.
When cast-in type nuts or mild steel pieces are used, these should be protected against corrosion on the outside of the wall. Serrated lock washers should be used to make electrical contact through the protective finish of the nut (see Figure E.7a).
For more information on corrosion protection, see E.5.6.2.2.2.
E.4.3.6 Connections
Investigations show that lashed joints are not suitable for lightning-current carrying connections. There is a risk of the lashing wire exploding and damaging the concrete. However, on the basis of earlier investigations it can be assumed that at least every third wire lashing forms an electrically conductive link, so that practically all the rods of the reinforcement are electrically interconnected. Measurements carried out on reinforced concrete structures support this conclusion.
So for lightning-carrying connections welding and clamping are the preferred methods. Lashed joints as a connection are suitable for additional conductors for equipotentialization and for EMC purposes only.Connections of external circuits to the interconnected reinforcement should be performed by means of clamps or by welding.
Welds between reinforcing bars (see Figure E.5) within concrete should be at least 50 mm long. Crossing rods should be bent to run for at least 70 mm in parallel prior to welding.
NOTE Where welding is permitted, both conventional welding and exothermic welding are acceptable.
When welded rods need to be cast into concrete, it is not sufficient to weld at crossing points with weld seam lengths of only a few millimetres. Such joints frequently break when the concrete is poured.
