The Importance of Internal Lightning Protection Systems and Their Technical Necessity of Use

Lightning protection systems must be established as a result of the integration of four systems when Turkish standards and international standards are taken into consideration. As Yılkomer, as a result of the research we have conducted in the sector, it has been concluded that many engineers and technicians perceive lightning protection systems as consisting only of external lightning protection applications (Faraday cage, air terminal, catenary wire, lightning rod). However, among the lightning protection systems that must be present in a structure, external lightning protection applications are only one of the four pillars of this integration. Just as a table cannot stand on a single leg and collapses, a structure will also be damaged by the effects of lightning discharge when exposed to a lightning strike. Lightning protection systems must be created as a result of the integration of four systems.

Protecting buildings against lightning is of great importance in terms of life and property safety.

These are listed as: a good grounding system, a correctly designed equipotential system, an external lightning protection system selected according to the type of structure to be installed outside the building, and a internal lightning protection (surge protection device) system installed in stages. When evaluated according to standards and technical requirements, these systems must exist in a structure. If we install an external lightning protection system without installing an internal lightning protection system, we will put all our power and data lines and electronic devices at risk. On the other hand, if there is no grounding system in a structure, we cannot integrate an internal lightning protection system into that structure. In addition, a facility with insufficient equipotential bonding may be damaged due to coupling effects of the external lightning protection system. These integration steps can be increased further.

In summary, if you want to protect a structure from lightning, an external lightning protection system must be present to reduce fire risk in buildings and protect living beings, and an internal lightning protection system must be present to protect electronic devices. In this article, we will try to provide information about internal lightning protection systems.

Sudden overvoltages are voltages that occur within a few microseconds to a few milliseconds and cause loss of life and property if precautions are not taken. In terms of their formation, these voltages can be examined in two main groups.

Internal Lightning-Induced Sudden Overvoltages

During a lightning discharge, a current between 2,000 and 200,000 amperes flows. These values cause voltage formation through direct lightning discharge or magnetic field effects on facilities such as power transmission lines, communication lines, security systems, etc., within an area of approximately 2 km. If these voltages exceed the insulation or equipment withstand limits, they manifest as insulation breakdowns, burnings, and explosions.

Sudden Overvoltages Caused by Electrical Switching

Current flowing through a conductor creates a magnetic field, and when the current is interrupted, the magnetic field suddenly decreases. The energy accumulated on the conductor is distributed into the system as voltage through induction. Such voltages are very common.

For lightning-induced sudden overvoltages to occur in a structure, it is not necessary for that structure to have an external lightning protection system. After a lightning discharge reaches the ground, it spreads in circular patterns within a 2 km area and moves toward points with lower resistance. Therefore, we must use the internal lightning protection systems mentioned above in our building even if there is no external lightning protection system.

Today, most social activities in industry, trade, services, healthcare, and human life are strongly dependent on the correct operation of electrical and electronic devices and systems. The most frequent cause of malfunction in these systems is sudden overvoltages that disrupt data transmission and cause damage to this equipment. Many companies may view uninterruptible power supplies (UPS) as surge protection systems. However, although UPS units are installed to regulate changes in circuits, they do not contain any real surge protection system. In most devices claimed to include such protection, there is only a small low-pass filter. This filter only provides protection against radio frequency interference but does not protect against high-amplitude sudden overvoltages that cause damage. In addition, fuses and relays in our panels do not function against lightning-characteristic impulses because they are integrated for long-duration impulses. Lightning discharge, however, has a very short impulse characteristic and dissipates slowly over the ground. Therefore, internal lightning protection systems are required.

How should protection against sudden overvoltage be implemented?

In low-voltage installations, surge protection devices connected between phases-earth and neutral-earth conduct during a surge and extinguish the overvoltage through themselves, preventing damage to the system. For this purpose, a staged protection concept is envisaged in DIN-IEC standards. Each stage reduces the surge voltage step by step, ultimately rendering it harmless to the system. For external lightning strikes, Class B protection is used; for internal sudden overvoltages, Class C protection; and for sensitive protection, Class D protection is used. Class B is also referred to as Class 1 or Type 1, Class C as Type 2 or Class 2, and Class D surge protectors as Class 3 or Type 3.

Surge Protector Classes

At the first point where power enters the building, Class B products are generally installed in the main distribution panels; Class C products are installed in sub-distribution panels where power is distributed within the building; and Class D products are installed in front of devices such as servers, cameras, external lines, data, computers, and other electronic equipment. If a structure has an external lightning protection system, the use of a Class B product in the main panel to protect against direct lightning discharge is considered mandatory. If we assume that a 200 kA lightning strike comes from the external lightning protection system, 100 kA will be dissipated into the ground and the remaining 100 kA will enter the building. By providing a protection level of 50 kA per phase with Class B products, the lightning impulse is prevented from reaching the devices. Class B products limit impulse voltages at the main supply point to levels such as 4.5 kV, 2.5 kV, and 1.5 kV, preventing damage to the system. This protection is applied at the main panel level.

In sub-distribution panels where power is distributed within the building, Class C protection is envisaged. If a Class C product is used without a Class B product in a structure with external lightning protection, the system will be damaged. Class C products prevent sudden overvoltages occurring within the system from damaging devices on the line and limit surge currents up to 40 kA per phase to levels of 2.3 kV, 1.5 kV, and 1 kV. This protection is generally applied at the sub-panel level. For a Class C protector to be applied to the system, the minimum distance between it and the Class B protector must be at least 5 m. However, newly developed B+C class products eliminate this problem.

Class D Surge Protectors

Class D protectors are developed to protect various devices and are considered sensitive protection since they provide direct device-level protection. Socket-type and panel-type versions are available. They offer many options depending on the area of use. However, Class D products used without Class B and Class C products do not function effectively. For example, socket protectors sold in electrical markets form the final stage of protection but are not effective on their own. In addition, there are specially designed modules to protect receiving and transmitting stations of communication systems. These products especially protect antenna inputs against sudden voltage and current surges and have a wide range of applications in radio communication systems and CB radios. In applications where signal transmission is carried out via coaxial cable, such as computers, data processing systems, or video systems, Class D connector adapter modules are used to prevent surge voltages coming from signal lines from damaging devices.

In summary, in order to protect against lightning and also to protect against the effects of switching elements, harmonics, and voltage fluctuations that cause sudden voltage surges, we must use internal lightning protection (surge protection device) systems. To prevent damage to increasingly sensitive devices with advancing technology, to avoid loss of critically important data, and to protect billion-dollar facilities from damage, we must install these systems in our facilities and buildings. It is very important to receive support from expert engineers and technically competent companies when selecting products. Let us remember that it is within our power to prevent small effects such as sudden overvoltage impulses from causing major damage!