DCN October 2016 - Page 13

centre of attention Recently we have seen an increase in disruption to data centre services due to lightning strikes. The nature of loss in data centres is not only through damage to sensitive equipment, but also the loss of productivity due to disruption in service. The degradation of equipment also leads to loss of time in replacement of parts. Currently in an effort to protect buildings, more than 100 published lightning protection codes and standards are in use by various agencies within countries. In the last two decades, significant information has been gathered and the International Electro-technical Commission (IEC) has made final an authoritative and comprehensive lightning protection standard in four parts, known as the IEC 62305 Series. The dangers of a strike Before exploring methods of protection, it is important to understand the nature of damage that is likely to disrupt or damage the functioning of today’s data centre. The impact of lightning normally causes damage to the equipment in three ways; firstly by direct strike to the installation, secondly by direct strike on to an overhead line or the ground nearby, and lastly by cloud to cloud strike. A direct strike to the installation tends to be protected by the presence of a standard lightning protection system; it is the latter two situations that cause indirect lightning electromagnetic impulses that prove disastrous. When there is a strike at a nearby ground, or cloud to cloud, a series of electrical surges are generated and picked up by the metallic conductors that enter the building. This conductor could be a utility cable, telecom cable or any other cable that supplies power or data to an external device on the building perimeter or rooftop. This could be the external perimeter lighting, camera, ac plant or even a fire alarm device. The transient surge ripples through the power distribution system and damages almost all the electronic components in the installation. Engineering solutions Firstly it would be sensible to reduce the risk by locating the data centre in an area with a low thunderstorm rate, by referring to the global flash density map. Unfortunately in most instances this is not possible. Given there is currently no way of changing natural weather conditions, the next step would be to carry out a risk assessment of the centre. The IEC Lightning Protection Code IEC62305 Part 2 is used to determine the classification of the lightning protection level required, with class I being the greatest. Some properties are more at risk than others, and factors such as the size and height of the building can affect this. Here four main aspects of lightning risks are explored, with the highest being loss of human life. Lightning protection specialists can carry out early stage assessments and will produce full reports, findings, and recommendations. Next in prevention preparations it is standard practice for engineers to design the air termination by following the rolling sphere, mesh and protection angle methods in accordance with IEC 62305 Part 3. This aims to capture the lightning discharge current and enables it to flow to the earth harmlessly, ensuring that the building is now safe ‘for life and property’. Unfortunately though this does not guarantee safety for the electronic equipment within the building. It goes without saying that electronic systems are vital in data centres. The reduction of risk of permanent failure and damage to electrical and electronic equipment is covered in BS EN62305 Part 4. In a shielded environment the correct coordination and installation of surge protection devices will be advised by your appointed lightning protection specialist. This will ensure that sensitive electronic equipment can be protected from damage and continue to operate in the event of a lightning strike. Moving forward For new data centres considering lightning protection, plans must be made early in the design stage to achieve cost effectiveness and sufficient protection. This will allow for maximum use of the natural components of the structure and provide a better choice for the cabling layout and equipment location. For those existing structures the cost of lightning protection measures tends to be higher. Although budget restrictions may raise doubt as to the necessity of protection from natural elements, the risks must be considered and lightning attacks treated with caution. Ultimately the consequences of losing both equipment and time could be catastrophic to your business. Our top three tips to ensure proper protection are as follows: Ensure provisions are defined by a lightning protection expert. Manage effective coordination and communication between the different experts involved in the building construction from the concept stage of the project. Maintain and regularly check the lightning protection system as per the recommendations. 13