ESE vs conventional lightning arresters: what the standards actually say

How a conventional system works

A conventional lightning protection system (LPS) intercepts a strike with air terminals: rods, horizontal conductors on the roof, or a mesh. It carries the current down through down conductors and disperses it through an earth termination system. IEC 62305-3 sets out three methods for placing the air terminals:

• the rolling sphere,
• the protective angle,
• the mesh method.

The sphere radius, angle and mesh size depend on the lightning protection level (LPL I–IV) chosen from a risk assessment under IEC 62305-2.

What an ESE terminal claims

An ESE air terminal is designed to emit an upward streamer earlier than a plain rod would under the same conditions. This head start is measured in the laboratory as ΔT in microseconds. Under NF C 17-102, a larger ΔT translates into a larger protection radius. That is why a single ESE mast is often proposed to cover an area that would otherwise need many rods or a roof mesh.

Where the standards disagree

• NF C 17-102 and UNE 21186 define how ESE devices are tested and how their protection radius is calculated.
• IEC 62305, the basis of IS/IEC 62305, does not include ESE methods. It defines protection zones only by the physical geometry of the air-termination system. It treats claims of an enlarged zone as unproven.

Field evidence for the ESE protection-radius model is debated in the technical literature. In practice:

• if a tender or consultant specifies IS/IEC 62305, design to it;
• if they specify NF C 17-102, ensure the ESE model has a test certificate to that standard from a recognised laboratory, and that the protection radius has been calculated for the actual mast height and protection level.

What matters whichever you choose

• Down conductors: the number, route and spacing set by the standard. Make them as straight as possible, with no sharp bends.
• Earth termination: a dedicated, low-impedance earth for the LPS, bonded to the building's other earths as the standard requires. See the solar earthing checklist for an example.
• Surge protection: an external LPS does not protect equipment inside from surges. Pair it with a Type 1 SPD at the main incomer. See SPD types explained.
• Strike counters on the down conductor show whether the system is actually being hit, which helps plan inspections.
• Inspection after installation and periodically, including earth resistance and continuity tests.

From Ashima

We supply:

• ESE air terminals from Cirprotec, Protector and Orkou,
• copper and copper-bonded conventional air terminals,
• lightning strike counters,
• the earthing for the LPS: ACME electrodes and backfill, which we manufacture.

Manufacturer test documents are available on request. See the lightning protection range.