NF C17-102 Lightning Protection - Protection of Buildings and Open Areas Against Lightning Using Early Current Emission Air Terminals

The French standard "NF C17-102 Lightning protection - Protection of structures and open areas against lightning by using early current emission air terminals" describes the requirements for the protection of common structures and open areas (such as storage areas, recreation areas) with a height of less than 60 meters from lightning by using early current emission lightning conductors. This procedure includes protection against electrical consequences caused by lightning current passing through the lightning protection system.

This standard does not cover the protection of electrical equipment or systems against voltage surges of atmospheric origin transmitted by networks entering the structure. Other standards describe lightning protection systems using simple rod lightning conductors, stretched wires and stranded conductors. Some administrations, utilities or operators of hazardous facilities may have adopted specific regulations.

This standard provides information for the design, construction, inspection and maintenance of lightning protection systems using early current dissipation lightning conductors. The purpose of these lightning protection systems is to protect persons and property as effectively as possible.

The NF C17-102 standard is an international standard governing the use of early current emission systems. They are an alternative to what many consider to be the traditional type of lightning protection system, the Faraday Cage system, governed by the “EN 62305 Protection against lightning” standard. An early current emission system is a lightning rod with an electronic current emission device that uses the atmospheric gradient to store energy. This then emits high frequency pulses into the atmosphere, which creates a priority channel for the lightning discharge, known as an up leader. The early current emission system header captures the lightning strike and dissipates the current safely into down conductors and into the ground.

The benefits of installing an early-stream emission system include:

• A single lightning rod can cover a protection radius of more than 100 meters.
• At least only two down conductors and grounding are required.
• It is easy to install and cost effective.
• It has a wider protection radius.
• It is designed to withstand adverse weather conditions such as heavy rain and snow.
• It is an innovative design that uses the latest architectural trends.
• It mainly complies with the following standards: NF C17-102, EN 50164-1, CTE SU, UNE 21186, UNE 21185.

An early-stream emission system fully meets the NF C17-102 standard.

For the purposes of the NF C17-102 standard, the following terms and definitions apply:

• A lightning flash to the ground is an electrical discharge of atmospheric origin consisting of one or more current pulses (return pulses) between the cloud and the ground.
• A lightning flash is one or more lightning discharges to the ground.
• The strike point is the point where a lightning flash makes contact with the ground, a structure, or a lightning protection system.
• The protected volume is the effective volume of the early current dissipation lightning rod, where the early current dissipation lightning rod is the impact point.
• Lightning flash density is the annual number of lightning flashes per km2.
• Return flash density is the number of return flashes per km2 per year. A lightning flash consists, on average, of several return flashes.
• Lightning protection system is a complete system used to protect structures and open areas against the effects of lightning. It consists of external lightning protection system and internal lightning protection system, if any.
• The external lightning protection installation consists of an air-termination system, one or more down conductors and one or more earth-termination systems.
• The internal lightning protection installation consists of all devices and measures that reduce the electromagnetic effects of lightning current within the volume to be protected.
• The early current dissipation lightning conductor is a lightning rod equipped with a system that creates a trigger advancement of the upward leader compared to a simple rod lightning conductor under the same conditions.
• The triggering process is the physical phenomenon between the onset of the initial corona and the continued spread of an upward leader.
• Trigger advance is the average gain in trigger time of the upward leader of an early current propagating lightning conductor compared to a lightning conductor under the same conditions and derived from the evaluation test.
• A natural component is a conductive part located outside the structure, embedded in walls or inside a structure and can be used to replace all or part of a down conductor or as an addition to an external lightning protection installation.
• Equipotential bonding rod is a collector used to connect natural components, ground conductors, earth conductors, screens, shields and conductors protecting electrical telecommunication lines or other cables to the lightning protection system.

The need for lightning protection is determined by the lightning flash density of the area under consideration. The probability of a structure being struck by lightning in a one-year period is the lightning flash frequency multiplied by the equivalent collection area.

Lightning is mainly characterized by the parameters related to the electric arc between the cloud and the ground, and therefore by the parameters related to the lightning current flow in the arc and in the conductors. The most important parameters are:

• Amplitude
• Rise time
• Decreasing period
• Current rate of change
• Polarity
• Load
• Specific energy
• Number of impacts per discharge

The first three parameters are statistically independent. Any amplitude, i.e., any decay time, can be encountered.

As an electrical phenomenon, lightning can have the same consequences as any current passing through an electrical conductor or any current passing through a bad conductor or insulator.

The expected effects of characteristic lightning parameters are:

• Optical effects
• Acoustic effects
• Electrochemical effects
• Thermal effects
• Electro-dynamic effects
• Electromagnetic radiation

Our organization, which has been trying to support businesses from every sector with its testing, measurement, analysis and evaluation studies carried out in a wide range for years, has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. In this context, testing services are also provided to businesses in accordance with the standard “NF C17-102 Lightning Protection - Protection of structures and open areas against lightning using early current emission air terminals”.