Material Combinations and Dimensions
- Required to use galvanically compatible metals in lightning protection system components and surface materials on which the components are mounted. For example, do not connect copper to aluminum.
- Do not use together metals that are not galvanically compatible. Bad matching accelerates their corrosion in the presence of moisture.
- With aluminum conductors, use only connection devices designed for aluminum. Make sure to use the right fastening torque.
| Different Contact Material | |
| Material | Suitable Contact Material |
| Copper | Nickel /Brass / Tin / Lead / Stainless steel / Monel (nickel–copper alloy) |
| Aluminum | Magnesium / Zinc / Galvanized steel / Stainless steel / Lead / Wrought iron / Galvalume (an aluminum-coated sheet steel product) |
LPS Material
| LPS Materials and Conditions of Use | |||||||
| Table-5 (IEC 62305-3) | |||||||
| Material | Use | Corrosion | |||||
| In Open Air | In Earth | In Concrete | Resistance | Increased by | May be destroyed by Galvanic Coupling with | ||
| Copper | Solid | Solid | Solid | Good in many environments | Sulphur compounds | – | |
| Stranded | Stranded | Stranded | – | Organic materials | – | ||
| – | As coating | As coating | – | – | – | ||
| Hot galvanized steel123 | Solid | Solid | Solid | Acceptable in air, in concrete, and in benign soil | High chlorides content | Copper | |
| Stranded 4 | – | Stranded 4 | – | – | – | ||
| Steel with electro-deposited copper | Solid | Solid | Solid | Good in many environments | Sulphur compounds | – | |
| Stainless steel | Solid | Solid | Solid | Good in many environments | High chlorides content | ||
| Stranded | Stranded | Stranded | – | – | – | ||
| Aluminum | Solid | Unsuitable | Unsuitable | Good in atmospheres containing low concentration of Sulphur and chloride | Alkaline solutions | Copper | |
| Stranded | – | – | – | – | – | ||
| Lead 5 | Solid | Solid | Unsuitable | Good in atmospheres with high concentration of sulphates | Acid soils | Copper | |
| As coating | As coating | – | – | – | Stainless steel | ||
Material Dimensions
- Several lightning protection system codes and standards define minimum dimensions for the components of a grounding system. These standards are designed to protect buildings and other inhabited or otherwise critical facilities.
- Practical minimums are based on field experience and indicate what is needed to protect the installed equipment in a cost-effective way during the foreseeable technical lifetime, typically a few decades, taking into account local regulations. To ensure proper operation of the grounding system, periodic inspection and maintenance is needed
Minimum Dimensions of Earth Electrode as per IEC 623053
- Table 1 and Table 2 are based on standard IEC 62305-3 Ed 2. The tables list minimum dimensions for the lightning protection system equipment.
- The following table lists the different materials and shapes that are used in air terminals, down conductors, and ground electrodes, including the cross-sectional area.
| Minimum Dimensions of Earth Electrodes | ||||
| Table-7, IEC-62305-3 | ||||
| Material | Configuration | Dimensions | ||
| Earth Rod Diameter | Earth Conductor | Earth Plate | ||
| Copper, Tin-plated copper | Stranded | – | 50 Sq.mm (8 mm) | – |
| Solid round | 15 mm | 50 Sq.mm (8 mm) | – | |
| Solid tape | – | 50 Sq.mm (8 mm) | – | |
| Pipe | 20 mm | – | – | |
| Solid plate | – | – | 500 × 500 mm | |
| Lattice plate | – | – | 600 × 600 mm | |
| Hot-dipped galvanized steel | Solid round | 14 mm | 78 Sq.mm (9.96 mm) | – |
| Pipe | 25 mm | – | – | |
| Solid tape | – | 90 Sq.mm (10.7 mm) | – | |
| Solid plate | – | – | 500 × 500 mm | |
| Lattice plate | – | – | 600 × 600 mm | |
| Profile | * | – | – | |
| Bare steel (Shall be embedded in concrete for a minimum depth of 50 mm.) | Stranded | – | 70 Sq.mm (9.4 mm) | – |
| Solid round | – | 78 Sq.mm (9.96 mm) | – | |
| Solid tape | 75 Sq.mm (9.72 mm) | |||
| Copper coated steel | Solid round | 14 mm | 50 Sq.mm (8 mm) | |
| Solid tape | 90 Sq.mm (10.7 mm) | |||
| Stainless steel | Solid round | 15 mm | 78 Sq.mm (9.96 mm) | |
| Solid tape | 100 Sq.mm (11.28 mm) | |||
| Mechanical and electrical characteristics as well as corrosion resistance properties shall meet the requirements of the future IEC 62561 series. | ||||
| In case of a type B arrangement foundation earthing system, the earth electrode shall be correctly connected at least every 5 m with the reinforcement steel. | ||||
| * Different profiles are permitted with a cross-section of 290 mm2 and a minimum thickness of 3 mm, e.g. cross profile. | ||||
Minimum Cross-sectional Area of Air-termination Conductors
| Minimum Cross-sectional Area of Air-termination Conductors | |||
| Table 6 (IEC 62305-3) | |||
| Material | Configuration | Cross-sectional Area | Comments |
| Copper, tin-plated copper | Solid tape | 50 Sq.mm / 8mm * | 2 mm min. thickness |
| Solid round1 | 50 Sq.mm / 8mm * | 8 mm diameter | |
| Stranded 1 | 50 Sq.mm / 8mm * | 1.7 mm min. dia of each strand | |
| Solid round*** | 176 Sq.mm /15mm | 16 mm diameter | |
| Aluminum | Solid tape | 70 Sq.mm* | 3 mm min. thickness |
| Solid round | 50 Sq.mm / 8mm * | 8 mm diameter | |
| Stranded | 50 Sq.mm / 8mm * | 1.7 mm min. dia of each strand | |
| Aluminum alloy | Solid tape | 50 Sq.mm / 8mm * | 2.5 mm min. thickness |
| Solid round | 50 Sq.mm / 8mm * | 8 mm diameter | |
| Stranded | 50 Sq.mm / 8mm * | 1.7 mm min. dia of each strand | |
| Solid round*** | 176 Sq.mm /15mm | 16 mm diameter | |
| Copper-coated aluminum alloy | Solid round | 50 Sq.mm / 8mm * | |
| Hot-dipped galvanized steel ** | Solid tape | 50 Sq.mm / 8mm * | 2.5 mm min. thickness |
| Solid round | 50 Sq.mm / 8mm * | 8 mm diameter | |
| Stranded | 50 Sq.mm / 8mm * | 1.7 mm min. dia of each strand | |
| Solid round*** | 176 Sq.mm /15mm | 16 mm diameter | |
| Copper-coated steel | Solid round | 50 Sq.mm / 8mm * | |
| Solid tape | 50 Sq.mm / 8mm * | ||
| Stainless steel | Solid tape | 50 Sq.mm / 8mm * | 2 mm min. thickness |
| Solid round*** | 50 Sq.mm / 8mm * | 8 mm diameter | |
| Stranded | 70 Sq.mm / 9.5mm* | 1.7 mm min. dia of each strand | |
| Solid round *** | 176 Sq.mm /15mm* | 16 mm diameter | |
| * If thermal and mechanical considerations are important, these dimensions can be increased to 60 mm2 for solid tape and to 78 mm2 for solid round. | |||
| ** The coating should be smooth, continuous and free from flux stains with a minimum thickness coating of 50 μm. | |||
| ***Applicable for air-termination rods only. For applications where mechanical stress such as wind loading is not critical, a 10 mm diameter, 1 m long maximum air-termination rod with an additional fixing may be used. | |||
Minimum values of the cross-section of the bonding conductors with different bonding bars
| Minimum dimensions of conductors connecting internal metal installations to the bonding bar | ||
| Table-8 (IEC-62305-3) | ||
| Class of LPS | Material | Cross-section (mm2) |
| I to IV | Copper | 16 Sq.mm |
| Aluminum | 25 Sq.mm | |
| Steel | 50 Sq.mm | |
| Minimum dimensions of conductors connecting internal metal installations to the bonding bar | ||
| Table-9 (IEC-62305-3) | ||
| Class of LPS | Material | Cross-section (mm2) |
| I to IV | Copper | 6 Sq.mm |
| Aluminum | 10 Sq.mm | |
| Steel | 16 Sq.mm | |
| Table 10: Minimum thickness of metal sheets or metal pipes in air termination systems | |||
| (IEC/BS EN 62305-3 Table 3) | |||
| Class of LPS | Material | Thickness (1) t | Thickness (2) t’ |
| I to IV | Lead | – | 2 MM |
| Steel (stainless, galvanized) | 4 MM | 0.5 MM | |
| Titanium | 4 MM | 0.5 MM | |
| Copper 5 mm 0.5 mm | 5 MM | 0.5 MM | |
| Aluminum 7 mm 0.65 mm | 7 MM | 0.65 MM | |
| Zinc – 0.7 mm | – | 0.70 MM | |
| Thickness t prevents puncture, hot spot or ignition | |||
| Thickness t’ only for metal sheets if it is not important to prevent puncture, hot spot or ignition problems | |||
Minimum Dimensions
| Air Terminal Minimum Dimensions | |
| Material | Dimension |
| Copper, aluminum | Tube with a 16 mm diameter, minimum wall thickness of 2 mm |
| 8 mm (0.31 in) solid round | |
| Steel | 10 mm |
| Down Conductor Minimum Dimensions | |
| Material | Dimension |
| Copper | 25 mm2 solid or stranded wire or solid tape |
| Aluminum | 35 mm2 in solid or stranded aluminum |
| Steel | 35 mm2 solid steel or stranded wires |
| Minimum Thickness of Tapes | |
| Material | Thickness |
| Copper | 1 mm |
| Aluminum | 2 mm |
| Galvanized steel | 2 mm |
| Stainless steel | 2 mm |
| Minimum Thickness of Strand Diameters in Stranded Cables | |
| Material | Thickness |
| Copper | 1 mm |
| Aluminum | 1.6 mm |
| Steel | 1.6 mm |
| Ground Rod Minimum Dimensions | |
| Material | Thickness |
| Copper | Solid round 15 mm |
| Pipe 20 mm diameter with a minimum wall thickness of 2 mm | |
| Copper clad solid steel | 14 mm |
| Galvanized steel | 16 mm |
| Galvanized steel, pipe | 25 mm diameter with a minimum wall thickness of 2 mm |
| Horizontal Ground Electrode Minimum Dimensions | |
| Material | Thickness |
| Copper | 25 mm2 solid/strand/tape with a minimum 2 mm thickness |
| Galvanized steel, round wire | 50 mm2 with a minimum 8 mm diameter |
| Galvanized steel, stranded | 50 mm2 with a minimum strand diameter of 1.7 mm |
| Galvanized steel, tape | 50 mm2 with a minimum thickness of 2 mm |
| Installation Depth of Ground Electrode | |
| Ground Electrode Type | Installation Depth |
| Ground rod | 3 meter |
| Horizontal ground electrode | 0.6 meter |
| Typical Ground Electrode Length and Spacing | ||
| Minimum values | Ground rod | Horizontal ground electrode |
| Length | Typically, 3 Meter | 10 Meter to 30 Meter as per soil type dependent |
| Loop diameter | – | 5 Meter to 6 Meter |
| Spacing | Min. 2 × rod length | – |
Guideline for LPS System:
- The following design guidelines need to be adhered to ensure safer installation of the external LPS.
- Air Terminal:
- Air terminal should be selected and provided only based on the protection angle or rolling sphere method
- Proper safety distance between the air terminal and any metallic object needs to be maintained as per the calculation mentioned earlier to avoid dangerous spark-overs.
- Different Material Jointing & Insulations:
- Wherever incompatible materials to be joined (Ex. Copper with Aluminum), suitable bi-metal connectors should be used.
- Suitable expansion joints must be provided on the horizontal conductors on top to take care of thermal effects.
- Special conductor holders of insulating type need to be provided on top of the terrace floor for routing the conductor to ensure electrocution impact does not happen in case of water stagnation.
- Equip potential Bonding:
- Required measures to ensure shielding, bonding / equipotential bonding techniques are handled properly to avoid LEMPs.
- Establishing connection for equipotential bonding with nearby metallic components need to be taken care of.
- Joints should be mechanically and electrically effective, should be protected against corrosion or erosion from the elements or the environment and should present an adequate contact area.
- Reinforcement Structure:
- In the case of using reinforcement in concrete structures as lightning down conductor details should be decided at the design stage, before building construction begins.
- Good contact between reinforcing bars to be ensured only by using connection clamps tested as per the requirement of IEC 62561-1
- Down Conductor:
- A down-conductor should be installed at each exposed corner of the structure where it is possible.
- The Down conductor should run as straight and vertical as possible so that they provide the shortest and most direct path of a low impedance from the air termination to the earth electrode so that the lightning current can be safely conducted to earth.
- The formation of loops in bring the down conductor shall be avoided, but where this is not possible the distance shall be maintained
- There should be a test joint arrangement to have separation between down conductor and earth termination for safety and for measurement of earth resistance.
- At least two down conductors are mandatory for any size of Building.
- The termination of the down conductor to an earth electrode should be done minimum of 1 meter away from the structure and minimum of 0.5m depth inside the ground.
- Earth electrodes for each down conductor shall be provided.
- Connection of down conductors to gutters or down-spouts even if they are covered by insulating materials.
- Usage of multiple connections with different materials should not be permitted.
- Insufficient conductor dimensions (non-complying material as mentioned in IEC 62305-3 Table – 5) should be strictly avoided.
- When the distance from down conductors to combustible materials cannot be assured, the cross section of the down conductor shall not be less than 100 mm²
