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Samad Khan, Global Product and Standardisation Manager for Furse, answers a few questions about why the changes are coming and what to do about them.
What challenges does the industry face from electrical surges?
There is greater dependency than ever before on electronics in everyday system applications and these require effective protection against surges. Sensitive electronics require enhanced levels of surge protection, particularly in critical environments such as chemical plants.
Electrical surges, also known as transient overvoltages, are large, brief and potentially destructive spikes in voltage in electrical supplies.
The largest overvoltages are caused by lightning strikes. These can lead to spikes of up to 6,000 V lasting no more than a millisecond on a low-voltage network.
Another major source of surges is electrical switching of large inductive loads such as transformers, or motors and drives. These are common in HVAC, lifts, conveyors and other commercial and industrial equipment. While such switching transients are less intense than lightning, they are more frequent and if left unchecked will lead to continual stress on electronic components.
No matter how they arise, the results of surges are the same and are characterised by four D’s: disruption, degradation, damage and downtime. The effects include unexpected outages, data loss and tripping of residual current devices (RCDs). However the costs to business can be lost productivity, product spoilage, staff overtime, delays to customers and lost sales.
What are the big trends driving changes in surge protection?
Significant growth in renewable energy has led to more need for surge protection. Solar photovoltaic (PV) and wind turbine installations can be particularly vulnerable to electrical surges. The physical structures of turbines and rooftop or field PV installations makes them a route to earth for lightning. Therefore the electronics in inverters, converters and condition monitoring systems all need to be protected.
Recognising this, global surge protection standards and surge protection designs have been updated to ensure optimised system protection for renewables.
The other big trend is that electronic systems now pervade almost every aspect of our lives. Not only are there more systems, the physical size of the electronics has reduced considerably. This reduction in size means less energy is required to damage components, therefore more systems are under threat from surges and as such drive the growth for surge protective devices.
How are these changes being reflected in the regulations?
The incoming 18th Edition will contain an important change to Chapter 44, which covers protection against voltage disturbances and electromagnetic disturbances. This chapter deals with protection against transient overvoltages due to lightning or switching.
Previous editions of the regulations used “AQ criteria”, to take into account external conditions that influence lightning. This determined if protection against transient overvoltages was needed. However this AQ criteria method has been removed from the 18th edition. Instead, designers and installers must include protection against transient overvoltages where there may be serious consequences such as serious injury or loss of life, interruption to public services or commercial activity, damage to cultural heritage, or impact on a site with a large number of people.
For all other cases, a simplified risk assessment must be performed to determine whether surge protection devices (SPDs) are required to protect against transient overvoltages. However, there is an exception not to provide protection for single dwellings in some situations.
At high risk sites such as nuclear or chemical sites, the consequences of transient overvoltages could be more significant and harmful. Therefore the new edition of the IET Wiring Regulations requires a full risk assessment for these facilities, as described in BS EN 62305-2.
Beyond high risk installations, the 18th edition requires that SPDs be installed up to the level specified in BS EN 62305 if there is a risk of direct lightning strike to the structure itself or to overhead lines connected with the structure.
It’s also worth being aware there are also changes planned to BS EN and IEC 62305 standards. The International Electrotechnical Committee (IEC) looks likely to publish Edition 3 of the IEC 62305 standard for protection against lightning before the end of 2018. The UK and European markets use the BS EN version, which should be published shortly after CENELEC (European Committee for Electrotechnical Standardisation) has reviewed and amended the changes to the IEC standard so that they are suited to the UK and European markets.
What should panel builders do to make sure they meet the new requirements?
Suppliers like Furse are constantly developing products to meet the needs of surge protection product standards, particularly in terms of safety.
Furse regularly tests its SPDs for mains, signal and telecoms lines to the latest product standards to ensure that they are capable of protecting against repeated “worst case” transients.
Panel builders should be aware of the three Types of power SPD and that there are also Combined Types.
Type 1 SPDs should be installed at the service entrance to protect against loss of life in the case of direct lightning strikes. They prevent dangerous sparking arising from lightning surges, where voltage exceeds the impulse voltage rating of the cable or equipment. They are also called equipotential bonding SPDs in the BS EN 62305 standard.
However, Type 1 SPDs cannot be used alone as they do not protect sensitive electrical or electronic systems.
To achieve this, panel builders should also use Type 2 and Type 3 overvoltage SPDs. Type 2 SPDs protect against switching transients and indirect lightning, whereas Type 3 SPDs are for local protection of sensitive loads. These further reduce transient overvoltages to safe levels for equipment protection
Cumulatively Type 1, 2 and 3 SPDs are referred to as a coordinated SPD set.
It is also possible to purchase Combined Type SPDs, which combine two or more types. These handle high surge current as well as overvoltage protection and offer significant technical, practical and economic benefits over single Type SPDs.
Selecting the right product can seem complex and so Furse publishes detailed guidance on the application of SPDs to protect electrical and electronic systems and this can be downloaded free of charge from www.furse.com.
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