Lightning Down Conductor Providing Insulation

In our country, lightning protection systems are installed based on the IEC 62305 standard. This standard provides guidance for passive systems such as cages, meshes, air terminals, and catenary wires. Lightning rod systems commonly encountered in our country are designed based on the NFC 17102 standard. In this article, we would like to bring up a very important topic that is included in the standards and must be emphasized while directing lightning discharge with external lightning protection systems: “Insulation”.

While the lightning discharge captured by external lightning protection systems is conducted down to the grounding area, it may jump to power and data lines and often cause serious damage due to coupling effects. In addition, bare conductors installed directly against the building can lead to dangerous outcomes such as fires and risks to human life. Therefore, lightning discharge must be conducted to the ground in an insulated manner, away from the structure. To achieve this, standards provide us with two alternatives.

• Using insulated conductors tested at lightning discharge levels ()
• Maintaining the ‘S’ separation distance calculated by considering the physical characteristics of the building using relevant formulas.

Calculation of the S Distance

Generally, maintaining the ‘S’ separation distance should be ensured with special insulated products. However, due to application difficulties and the risk of contact caused by bare conductors, and especially due to fire hazards in areas such as fuel stations and filling facilities, the use of an insulated lightning discharge conductor is a more common solution.

Calculation of lightning and the S distance

The S distance is calculated according to IEC 62305.

Formula of the S distance

Ki: Protection class

Kc: Number of down conductors

Km: Type of conductor used

Insulated Conductor

Systems using insulated conductors for down conductors provide ‘Safety’ in many respects. This is particularly important for areas where technology and people coexist densely, such as military facilities, ammunition depots, GSM towers, wind turbines, solar panels, filling facilities, hospitals, schools, technological buildings, and subways. Regardless of the external lightning design—whether cage method or Faraday method—ensuring down conductor insulation and providing symmetrical down conductors from two points are extremely important. Insulated conductors provide insulation for impulses up to 200 kA. Considering that the average impulse in our country is 50 kA and can reach up to 100 kA in southern regions, these systems stand out as a significant method for establishing safe lightning protection systems. However, as we always emphasize, we cannot protect our facilities with external lightning protection systems alone. Lightning protection systems are like a table standing on four legs. To maximize facility safety, internal lightning protection systems, equipotential bonding, and a proper grounding system must also be implemented.

In the table below, you can see the difference between systems with and without S separation distance and systems using insulated conductors .

Due to fire hazard risks in areas such as fuel stations and filling facilities, the use of insulated lightning discharge conductors is a more common solution.

An insulated lightning protection system must be implemented as a whole with all its components. Installing only the conductor may cause malfunctions in the system over time. The insulated system consists entirely of corrosion-resistant insulated products. At the locations where the system is installed, lightning impulses passing through the facility are recorded by the Lightning Recording System and can be provided to you as reports upon request.

In conclusion, when lightning protection systems are implemented by providing insulation at the contact surfaces between the structure and down conductors, as stated in the standards, unwanted adverse consequences will be prevented proportionally.

What must not be forgotten is that Lightning Protection and Grounding are systems that must be designed and implemented by expert engineers. Even the smallest clamp used has an impact on the integrity of the entire system; therefore, we kindly ask all sector stakeholders to show due sensitivity on this matter.