Copper Lightning Arresters, Conductors and Earthing Material

On Indian sites, 'lightning arrester' or 'LA' means the pointed copper rod on the roof, often with one spike or a crown of several. Strictly, the standard calls that an air-termination rod, and the term lightning arrester (or surge arrester) belongs to a device that protects power lines and equipment from overvoltage. Both are needed in a complete scheme, but they are different products. When you order a copper lightning arrester from us, we understand it as the rooftop air terminal and the copper that goes with it.

• Air terminals: copper rods, plain or with spikes, fixed at roof corners, parapets, towers and tanks
• Roof conductors: copper tape or round conductor forming a mesh across the roof and linking the air terminals
• Down conductors: copper tape or conductor running down the walls to the ground, spaced around the building as the design requires
• Test joints: a bolted break near ground level so each earth electrode can be tested separately
• Earth electrodes: copper plates, rods or buried strip that discharge the current into the soil
• Bonding conductors: copper links tying metal structures, pipes and the electrical earth into one system

Table 6 of IS/IEC 62305-3 gives minimum cross-sections for air-termination conductors, air-termination rods and down conductors. For copper and tin-plated copper, solid tape, solid round and stranded conductors must be at least 50 mm². Solid round air-termination rods and earth lead-in rods must be at least 176 mm², which is a 15 mm diameter rod. A note allows 50 mm² (8 mm diameter) conductors to be reduced to 25 mm² where mechanical strength is not essential, and a rod of 9.5 mm diameter and at least 1 m long where wind load is not critical.

In practice, 25 × 3 mm copper tape (75 mm²) and 25 × 2 mm tape (50 mm²) are common choices for roof and down conductors, and 8 mm round conductor for neat runs. The designer's drawing has the final say.

IS 3043, the Indian code of practice for earthing, has long specified copper plate electrodes of at least 600 × 600 mm and 3.15 mm thick, buried with the top edge at least 1.5 m below ground, and copper strip electrodes of at least 25 × 1.6 mm. Lightning earth pits are usually interconnected with the electrical earth so the whole installation rises and falls together during a strike. Plate, strip and wire are covered on our copper sheets and plates and copper wire pages.

Galvanised steel is cheaper and is permitted by the standard, but it needs a larger section for the same duty and its zinc coating is consumed over time, especially underground and in polluted air. Copper conducts far better, survives decades in most soils, and bolts to copper earth bars without a bimetallic joint. Where both materials meet, use proper bimetallic connectors, because copper in contact with galvanised steel or aluminium in damp conditions drives corrosion of the less noble metal.

Theft is the other practical issue. Copper down conductors at ground level are a target on unattended sites, so many designers specify a guard or PVC sleeve over the bottom few metres and tamper-resistant fixings at the test joint.

Bare copper is standard inland. Near the sea, around chemical plants and on sewage works, tinned copper tape and conductor last longer and keep joints clean, and IS/IEC 62305 treats tinned copper at the same sizes as bare. Exposed tape and conductor are usually hard or half hard so they stay straight between fixings; buried strip and conductor can be soft. Spike rods are made from E.C. grade copper round bar.

Send us the drawing or a bill of materials with sizes and quantities. We confirm availability at enquiry and can supply test certificates for consultant approval.