SURGE PROTECTION AND LIGHTNING PROTECTION SYSTEMS
SURGE PROTECTION Surge protection and lightning protection systems
Surge protection has always been closely linked to lightning protection systemsdue to the logical link between themanagement of, andprotection against, substantial fault currents. It is pertinent to consider that a structure is usually at greater threat fromlightning surge current damage than from the threat of a direct lightning strike.
The previous iteration of the lightning protection standard, BS 6651, held information on integratingsurgeprotectiondeviceswithin an appendix; however BS EN (IEC) 62305 now holds surge protection as a distinct aspect of the standard (part 4), which must be addressed in any structure that claims to be compliant with this standard. BS EN (IEC) 62305-4 recommends a number of methods to protect against transient overvoltages caused by lightning, such as effective earthing and bonding, electromagnetic shielding and line routing, and importantly coordinated surge protection devices; these measures directly impact on the performance of the internal measures of a lightning protection system. The function of the internal lightning protection system is to prevent dangerous sparking between areas of differing electrical potentials, and to prevent the fault currents causing damage in the form of fires, explosions or equipment damage.
A philosophy which underpins the whole of BS EN 62305 is that of lightning protection zones. The concept is that any complex, facility, building or roomcan be split into zoneswhich havedifferent requirements for lightningprotection, and then appropriate protection measures can be broken down into that particular zone. A buildingmay have an external lightning protection systemthat will stop the building frombeing damaged, or catching fire. Inside the building theremay be equipment such as a computer server within a dedicated room. The server will need further protection to ensure that it is protected fromsurges, therefore being a lightning protection zone, within a lightning protection zone. It is always worth remembering to attempt to surge protect locally to equipment to ensure that it is managed effectively, and to avoid allowing fault currents inducting downstreamof the surge protection device.
Surges can carry through data, power and telephone lines and it is prudent to install surge protectionmeasures on the local power supply to vital equipment, any electronic equipment outside themain structure; particular attention should be given to cables which penetrate the external envelope of the structure. Examples of such items can include CCTV systems, air handling units, power, data
and telecom lines,
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