FEATURE SURGE & CIRCUIT PROTECTION
Standards surge forwards
In early July the IET will publish the 18th Edition Wiring Regulations, containing important changes to requirements and test standards for surge protection. Samad Khan, global product and standardisation manager for ABB Furse, explains how to prepare for the upcoming changes
WHY ARE THE SURGE PROTECTION REQUIREMENTS AND TEST STANDARDS CHANGING? There are two main drivers for the changes to surge protection standards. The first is that the use of electronic devices has grown exponentially while electronic components have become smaller. This means that less energy is required to damage them, meaning more need for surge protection devices (SPDs). Secondly, surge protection is also needed for solar photovoltaic (PV) panels and wind turbines. They are often installed on rooftops or exposed hilltops and can be a route to earth for lightning. SPDs are needed to protect the electronic inverters, converters and condition monitoring systems in these renewable energy installations.
WHAT ARE THE CAUSES OF ELECTRICAL SURGES? Also known as transient overvoltages, electrical surges are large short-lived (a
38 MAY 2018 | ELECTRICAL ENGINEERING
few thousandth of a second) spikes in voltage that can cause damage to power, data and telecommunications systems. Lightning can create overvoltages of up to 6,000V within a low-voltage installation. Even a strike up to a kilometre away can be devastating. The other major source of surges is due to the electrical switching of large loads such as motors or transformers. While switching transients are smaller in size, they are more frequent and cause stress to electronic systems. The result of either type of surge is disruption, degradation, damage and downtime. These lead to unplanned outages, loss of data, tripping of residual current devices (RCDs). These cause lost productivity, delays to customers, product spoilage, staff overtime and lost sales.
HOW ARE THE REGULATIONS CHANGING? There will be an important update in Chapter 44 of the IET Wiring Regulations
18th Edition (BS 7671:2018). This covers protection against voltage disturbances and electromagnetic disturbances, as well as protection against transient overvoltages due to lightning or switching. Previously, the ‘AQ criteria’ was used to determine the need to protect against transient overvoltages. This was based on the likelihood of lightning at different locations across the UK. However, in the 18th Edition, the AQ criteria has been replaced with a requirement to install surge protection devices (SPDs) in instances where electrical surges may lead to serious injury, loss of life, interruption to public services or commercial activity, damage to cultural heritage. This means that SPDs will be needed for many commercial, public and industrial buildings. However, for installations where these consequences do not apply, a simplified risk assessment should determine whether SPDs are needed. The exception to the requirement is single dwellings in some situations. Special care is needed at high risk
sites such as nuclear or chemical facilities, where the result of transient overvoltages could be more significant and harmful. A full risk assessment is required for these, as described in BS EN62305-2, the overarching European standard for lightning protection. Continues on PG41...
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