Lee Dickinson

Lightning strikes can be a major cause of destruction to buildings, people and the environment. The secondary effects of lightning (known as transient overvoltages) can be equally destructive and damage the electronic systems inside a building.

Most buildings have some form of structural lightning protection to their building, which channels the lightning strike in a safe and controlled manner to the earth termination network. This is designed to protect the fabric of the building and the people inside it. However, this type of lightning protection does not guard the electronic systems within a building from transient overvoltage damage.

Over the past three decades, electronic systems have played an increasingly important part in modern life. The consequences of being without them, even for an hour, for some businesses or organisations can be catastrophic. Employers are therefore very keen to protect their assets and reduce their risks. One of the greatest risks to electronic systems is from electrical surges in a lightning storm.

The British Standard BS 6651 ‘Code of practice for the protection of structures against lightning’ was the original standard covering Surge Protection. This was superceded in September 2008 by the European Standard BS EN 62305. Under BS EN 62305, Surge Protection is a fundamental part of a lightning protection system. The purpose of  HYPERLINK "http://www.omegaredgroup.com/lightning_current_spds.asp" Surge Protection is to safeguard against sparking, therefore minimising the risk to life and damage to the structure and systems in a building.

This standard requires that, in the first instance, a risk assessment is carried out to determine what level of lightning protection is required in order to protect a building and its occupants.

There are four different types of risk to be assessed:

• Risk of loss of human life, This covers buildings that run life-saving equipment, such as hospitals or hospices
• Risk of loss of service to the public Eg. Banking services, transport, schools and such like
• Risk of loss of cultural heritage Including museums, art galleries and historical monuments
• Risk of loss of economic value This relates to businesses, particularly those that trade heavily online.

In many cases, structures that were built prior to BS EN 62305 being implemented in 2008 often do not have adequate Surge Protection within their lightning systems. As a result their electronic systems are vulnerable during a lighting storm.

Aside from the obvious risk to life-saving equipment in the health sector, without adequate Surge Protection, the result can be fire and electric shock hazards because of the risk of flashover. This is where the voltage exceeds the amount that the cable and equipment is able to withstand. The best approach for the building owner or occupier (if they are in any doubt about the buildings Surge Protection) is to request a survey from a specialist lightning protection company.
When our lightning protection team carries out an initial inspection, we determine the risk level and recommend an appropriate Surge Protection system. As a minimum, service entry Surge Protection devices are required where a structural lightning protection system is fitted.

There are several techniques which can be used to minimise the lightning threat to electronic systems. Like all security measures, they should, wherever possible, be viewed as cumulative and not as a list of alternatives. This may include such measures as Earthing and Bonding, Electromagnetic shielding and line routing, co-ordinated SPD’s (Surge Protection Devices) and use of isolating interfaces (eg fibre optic cables).

In some cases, we recommend over-voltage Surge Protection to protect electrical and electronic systems and equipment from the secondary effects of indirect lightning.

Each of these measures can be used to form a complete SPM (Surge Protection Measures) system. All SPM systems require documented inspections according to manufacturers’ instructions (normally at least on an annual basis) and maintenance to ensure it meets all requirements.

It is therefore recommended that a complete lightning protection solution must include both structural lightning protection and a transient overvoltage/surge protection system. This ensures complete protection of building occupants, the structure of the building and the electronic systems inside.

Lee Dickinson, lightning protection manager, Eurosafe Solutions