FEATURE SURGE PROTECTION ARE YOU AT RISK?
Despite the dangers of lightning strikes and the critical nature of many business systems, the high numbers of insurance claims for lightning damage indicates that many organisations are still not installing the correct forms of lightning protection devices. This is despite the fact that the BS EN 62305 standard encompasses an enormous amount of detail on how to choose the correct surge protection device. Here, Weidmuller offers some tips
ower surges are an unavoidable occurrence in today’s electrical distribution systems. A number of different things can cause this to happen but the most familiar source is probably lightning. More common sources of power surges can include such things as the operation of high power electrical devices, faulty wiring, problems with the utility company’s equipment, and downed power lines. If you are considering whether you
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should be installing surge protection devices (SPDs), here are some of the key reasons why you should make that investment. If your application falls within certain requirements, and consequences, of section 443: Protection Against Overvoltages of Atmospheric Origin or Due to Switching of the 17th Edition Wiring Regulations, then lightning and surge protection against over voltage must be provided in all cases. If your application falls within the
requirements of Section 534: Devices for Protection Against Overvoltage of the 17th Edition Wiring Regulations, then lightning and surge protection should be fitted. If you have external lightning protection installed, to adhere to BS 62305, you should install a Class I device as close to the point of entrance to the building as practically possible, or the
26 SEPTEMBER 2014 | ELECTRICAL ENGINEERING
main distribution board, and Class II devices at all machine controls panels and distribution boards, which are directly connected back to that MDB. The expanded BS EN 62305 protection
against lightning comprises four parts. Part 1 is General Principles and introduces you to the other parts; Part 2 is Risk Management, which defines the level of lightning protection system required, based on a risk assessment; Part 3 relates to physical damage to structures and life hazards; and Part 4 covers the protection of electrical and electronic systems within structures.
WHAT’S AT RISK? A business should assess how much it is at risk by the types of loss that could incur, should it be struck by lightning or a power surge. There are four types of loss defined in BS EN 62305 - loss of human life, loss of service to the public, loss of cultural heritage and loss of economic value. Once the risk is assessed, you will then
need to look up in the table in the National Annexes, the tolerable risk for these types of losses and calculate the
Above: it is reported that around one million flashes strike the ground each decade in the UK
actual risk. Logically, if the actual risk is higher than the tolerable risk, then the protection requirements are set out in the tables in the standard. Part 4 of the standard has arisen as a
result of the increasing cost of failures of electrical and electronic systems, caused by the electromagnetic effects of lightning. It provides information on protection measures to reduce the risk of permanent failures, as well as information for the design, installation, inspection, maintenance and testing of protection systems for electrical and electronic systems within a structure, and how to reduce the risk
of permanent failures due to lightning
electromagnetic impulse. The scope and diversity of
surge protection devices can be as
Above: Weidmuller can offer advice and information on protection devices
complex as the standard, from lightning arresters, high power varistors and surge monitoring modules, to data interfaces and surge protection for photovoltaic systems. With this clear definition from BS EN 62305, businesses no longer need to be at risk.
Weidmuller
www.weidmuller.co.uk T: 0845 094 2006
Enter 210 / ELECTRICALENGINEERING
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