Security, stability and order are basic needs. In a world of increasingly complex processes sophisticated technical equipment is required to satisfy these basic needs. In this context, both structural and technical measures, such as CCTV systems, are decisive to increase the security in buildings and facilities.
Failure-free operation of these systems is particularly vital in dangerous and extreme situations to ensure that the required information is transferred and the relevant actions are initiated. False alarms may cause unnecessary costs and make the alarmed group of persons used to alarms so that real alarms may no longer be taken seriously. This could have fatal consequences.
False alarms resulting from technical problems can have different causes. One possible cause is electromagnetic interference with the monitoring systems. During a thunderstorm, a particularly dangerous combination of circumstances occurs: On the one hand, there is always an increased risk of fire resulting from the thermal effect of a lightning strike. On the other hand, a lightning discharge is a strong source of electromagnetic interference, which may interfere with the security systems due to conducted interferences and the electromagnetic field. This leads to failure or destruction of the security systems, which are then no longer able to indicate a dangerous situation. Therefore, lightning and surge protection measures are required to ensure safe operation of such systems.
CCTV systems are used to monitor public and private rooms, traffic flows and technical systems. In industrial plants, they are vital to ensure safe and efficient operating procedures. Installed in an outdoor location, CCTV cameras are often vulnerable to direct lightning strikes due to their exposed location. This danger can be avoided by adequately arranging the cameras at the outer walls of buildings or installing lightning protection systems for the cameras.
The lightning protection standards of the IEC 62305 series form the basis for planning and implementing lightning protection measures. The protection goal of the two protection measures mentioned before is to prevent a direct lightning strike to the camera to be protected by an adequate arrangement of air-termination systems. When dimensioning the down conductors for the external lightning protection system of the camera, a sufficiently large separation distance must be maintained between the down conductor of the lightning protection system and the CCTV camera including its supply lines to prevent flashover between the down conductor and the CCTV camera.
The minimum value of the separation distance to be maintained can be calculated based on the calculation scheme provided in the IEC 62305-3 standard. If, for example, CCTV cameras have to be installed on an isolated camera mast to be able to seamlessly monitor an object or an installation, it is often difficult to maintain the separation distance between the CCTV camera and the installations of the external lightning protection system. But there are also practice-proven solutions for this case such as high-voltage-resistance, insulated conductors. No separation distance must be maintained between the CCTV camera and the down conductor if these special conductors are used.
CCTV cameras are typically installed on masts at the periphery of large objects and installations. The resulting larger cable lengths between the central monitoring system and the camera masts are targets for the electromagnetic field of the lightning discharge which may induce impulse-shaped and temporary high voltages in the lines of the CCTV system. These voltages may interfere with or even destroy the CCTV cameras. To prevent this situation, surge protective devices for protecting the supply voltage and the video signal of the camera should be used.
Specific lightning and surge protection measures for security systems such as CCTV systems avoid false alarms in case of uncritical situations and the resulting costs, thus considerably increasing the operational reliability of these systems. Only if all technical boundary conditions are observed, trouble-free operation of security systems and thus the necessary information transfer is ensured.
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