Lightning Protection and Grounding of Rail Systems

Rail (railway) systems continue to be an indispensable means of public transportation in our daily lives. Rail system applications such as metro and high-speed trains, which contain many complex communication systems and signaling, must be evaluated and handled separately in terms of both lightning protection and grounding. First of all, electronic systems in a railway station should be taken into consideration, and protection against overvoltage surges should be provided with low-voltage surge protection devices. These systems are listed below.

Electronic systems in railway stations should be protected against overvoltage surges with low-voltage surge protection devices.

•Alarm Systems
•Protection of Power Systems and Security Center
•Passenger Access, Monitoring and Security Center
•Radio & Public Address System
•Signaling Systems
•Interactive Electromechanical Systems
•Track Circuits
•Rail Power Supply Systems
•Lighting Systems
•Data Transmission Systems
•CCTV
•SCADA

In rail systems, the minimum existing danger is internal overvoltage surges rather than direct lightning strikes. Transient voltages and switching surges frequently occur in railway stations and pose a serious risk to electronic systems. Moreover, even if these stations are installed in open areas and do not receive a direct lightning strike, they must be protected against conducted surges.

Protection of electronic systems in rail systems is very important.

In order to provide a complete protection system in railway applications, a four-stage protection must be ensured. This includes external lightning protection, internal lightning protection, grounding, and equipotential bonding. In low-voltage surge protection systems, step-by-step coordination is crucial. B+C class devices should be used in main panels, Class C devices in sub-panels, and Class D devices in front of sensitive equipment.

Grounding in Rail Systems

A sustainable grounding system is mandatory in rail systems. Therefore, grounding in systems where human life is critically important must not be damaged over time and must maintain its values. Connection points are of primary importance, and our preference should always be thermowelded connections. Thermowelding ensures long-term reliability of connection points. All metallic components and reinforcements must be connected to the same grounding system, and equipotential bonding must be maintained throughout the line and stations. The lower the rail-to-ground transition resistance, the faster fault currents will flow.

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On the other hand, current circulation occurring during train acceleration and braking will not damage systems when equipotential bonding is ensured. The corrosion effect caused by traction currents is one of the most critical factors that shortens system lifespan. Therefore, applying corrosion tape at every connection point, designing multiple local equipotential bars, and using spark gap surge arresters in critical grounding points are indispensable steps for system protection.