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Economic damages caused by surge voltages
One of the pillars of our technological progress is our highly developed ability to distribute, store and process information by means of electrical devices. Thanks to sophisticated measuring system and automatic control equipment used in production process and also due to the fact that modern EDP technology and telecommunications offer a fast and reliable support to the industry, it has become possible to manufacture high-tech products and to offer highly qualified services. Nowadays, however, the use of modern electronics and EPD system is no longer limited to the industrial applications as it has become a matter of course to all of us, both in our private lives and in business. The negative side to this development comes with the increasing problems of electromagnetic compatibility (EMC), in other words, disturbances occurring in electronic devices and system due to unwanted interferences. These problems increase at the same rate as the frequency of use of highly sensitive equipment, its networking and the integration density of microelectronics. Surge voltage and lightning protection is a part of EMC which is aimed at protecting electronic devices from damages caused by these phenomena.
EMC lightning protection zones
In the recent years, knowledge gathered from research work on lightning effects and surge voltage protection technology has led to the development of a multistage protection system for power supply, MSC and data communications networks called EMC lightning protection zones concept (2). With this system, a building is split into several protection zones, whereby the unprotected zone outside the building is called zone 0. this is where the highest discharge currents appear after a lightning strike. Zones 0/E and 1 are partially protected against lightning strikes (i.e. by building reinforcement or metallic roof covers), which means that only reduced partial lightning currents can occur. Protection zone 2 (for partical reasons, any device or equipment to be orotected is considered to be zone 2 or higher)offers protection against any destructive effect caused by direct lightning strikes. All lines crossing a zone border must be protected by arresters, independently from the current flow direction. The adequate choice of surge protective devices depends on the voltage resistance of the electronic equipment to be protected, on the frequency of signal control checks and the necessary discharge capacity. This means that the use of surge protectors will have to be multistage and selective, whereby the protection level is steadily increasing from zone 0/E resp. zone 1 (main distributor) to zones 2,3 and so on (electronic device to be protected) whilst the discharge capacity is decreasing accordingly. The arresters are normally installed in the main distributor panel and sub-distributor as well as directly on the device to be protected.
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