FEATURE SURGE PROTECTION
SURGE PROTECTION A BUSINESS NECESSITY
Lightning activity during thunderstorms or electrical switching events can have a profound impact on how electronic systems operate. Here, Keith Smith, BEAMA’s deputy director, installation sector, discusses the recognition of the protection of electronic equipment in a society increasingly reliant upon it
A
lmost every aspect of our daily lives, from filling up the car to shopping at
the local supermarket, is permeated by electronic systems, and as such we, as a society, are increasingly reliant on these systems being run efficiently and continuously. The huge rise in the use of computers, electronic process controls and telecommunications over the last 20 years is there for all to see, however, not only are there more systems in existence, but the physical size of the electronics involved has reduced considerably. This reduction in size means less energy is required to damage components. Lightning activity during thunder storms
or electrical switching events can cause very short duration increases in voltage on mains power and/or data communication/signal/telephone lines, with potentially devastating consequences. These increases in voltages are called surges or transient over voltages. A lightning surge is severe enough to present a risk of loss of life through fire and/or electric shock hazards through a dangerous flashover. This can occur when the surge voltage exceeds the withstand rating of the cable insulation or equipment. Products such as LCD screens, computer networks, data servers and industrial equipment including PLCs, provide essential services now crucial to business operational productivity. Protection against the effects of voltage surges in business today is no longer an option, it has become a necessity.
CIRCUIT BREAKERS/FUSES Fuses and circuit breakers (aka over current protective devices - OCPDs) are designed to protect your home, business, equipment, and possibly even your life from an event such as a short circuit or overload. The surge protection device (SPD) is specifically designed to protect equipment from events such as extremely short duration high voltage spikes. These voltage spikes or transients are everyday
24 MARCH 2014 | ELECTRICAL ENGINEERING
occurrences, and can be caused by anything from switching on a lamp to a lightning storm. Most spikes are of low energy, but some spikes could possibly cause irreparable damage to equipment if no SPD is installed to redirect the harmful voltage away from the equipment.
DAMAGE, DISRUPTION AND DEGRADATION Disruption caused by transients can be immediately felt, such as when the logic or analogue levels of the systems are upset, causing data loss, corruption or unexplained computer crashes, or the tripping of residual current devices (RCDs). The system can be reset (often just by switching off and on) and will then function normally. Much of this nuisance may go unreported. Large transient over voltages can cause
damage to components, circuit boards and I/O cards. Severe transient over voltages can physically manifest themselves through burnt out circuit boards. However, ordinarily damage is less
spectacular. Similar degradation can occur to the silicon dioxide insulation in integrated circuits (or microchips). Only in the most severe cases do we see ruptured cases, charring and fire. In fact, much of this more spectacular damage is caused by power follow-on and not by the transient. Degradation is somewhat more serious.
Long term exposure to lower level transient over voltages will, unknown to the user, degrade electronic components and circuitry, thus reducing the equipment’s expected life and increasing the likelihood of failures.
STANDARDS AND REGULATIONS As our reliance as a society on electronic equipment has increased dramatically, BS EN 62305 has specifically recognised the protection of such equipment within a normative part of BS EN 62305-4 which states, ‘Lightning as a source of harm is a very high energy phenomenon.
Lightning flashes release many hundreds of mega-joules of energy. When compared to the milli-joules of energy that may be sufficient to cause damage to sensitive electronic equipment in electrical and electronic systems within a structure, it is clear that additional protection measures will be necessary to protect some of this equipment. ‘The need for this international standard
Above: Keith Smith, BEAMA’s deputy director - installation sector
Below: the operation of electronic systems can be severely affected by lightning activity during thunderstorms or electrical switching events
has arisen due to the increasing costs of failures of electrical and electronic systems, caused by electromagnetic effects of lightning. Of particular importance are electronic systems used in data processing and storage as well as process control and safety for plans of considerable capital cost, size and complexity (for which plant outages are very undesirable for cost and safety reasons).’ Section 443 of the 17th Edition Wiring Regulations assesses surge protection on the probability of lightning days. However, there is some difference between the use of ‘thunderstorm days’ as the sole criterion of tolerable risk and BS EN 62305, which uses many other factors in its risk assessment.
BEAMA GUIDE For busy specifiers, navigating around a variety of standards can be time consuming and complicated. BEAMA, the trade association for the electrotechnical industry, has compiled a Best Practice Guide to assist designers, specifiers and installers to enable them to comply with surge protection requirements in Wiring Regulations BS
7671, as well as assisting those involved in the use of these standards in selecting, erecting and testing, and verification of surge protection devices in accordance with BS 7671, supported by current lightning and surge protection standards. .
BEAMA
www.beama.org.uk T: 0207 793 3000
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