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The New Standard



EN 62305 2006


For many years BS 6651 was the standard for "Faraday Cage & Taught Wire Lightning Protection Systems". As of the 31st of August 2006 the lightning protection standard is to be European Standard EN 62305.

However, Europe recognises that the lightning protection industry is different in each member state and therefore a member state was permitted to excercise their right to ammend or augment the base standard in order to better reflect the needs of the lightning protection industry in that member state.

It should be noted that Ireland, for the first time, has its own standard for lightning protection and that standard is IS EN 62305 parts 1-4 2006. As a result, the industry is obliged to use this standard in all its aspects ie risk assessment, design, installation etc. The standard came into immediate effect with no overlap/grace period. An overlap period took place in the UK as there was already an existing standard for taught wire and faraday cage lightning protection systems (ie BS 6651 1999). As Ireland had no pervious conflicting standard , IS EN 62305 came into immediate effect.

ADS currently perform all risk assessments and designs to IS EN 62305 2006


IS EN 62305 is a direct translation of the European standard EN 62305. Therefore the standard has not been amended or augmented in any way from the original to suite the conditions and/or the lightning protection industry in this country. However, its British counterpart (BS EN 62305) has been, primarily in part 2 of the standard dealing with risk assessment as it was believed that a greater risk should be attributed to the various factors and elements which make up the risk assessment calculation.

What does this mean ?

Briefly, this means that a building may require a different (usually higher)  level of protection if assessed under the BS EN 62305 than if assessed under IS EN 62305.


BS 6651 1999 Vs IS EN 62305 2006


Although there are a number of small differences which have a bearing on a design, these differences are of no real concern from a conceptual view point and should only be considered by, and are of importance to,  the Lightning Protection Specialist.

The standard is broken into four parts and they are

Part 1       General Principles

Part 2       Risk Management

Part 3       Phyisical Damage To Structures And Life Hazard

Part 4       Electrical And Electronic Systems Within Structures


Part 1

Part 1 outlines the types of damage and losses. Basic design criteria and protection measure are also outlined. This section also outlines the four different levels of protection.

Part 2

The section has the most profound effect on the industry. This section is where IS EN 62305 leaves BS 6651 behind. The Risk Assessment on a structure determines the overall design in terms of,

  • Grid Size
  • Earth Spacing
  • Surge Protection

It is worth noting that one, now designs, not necessarily to protect a structure, but to mitigate the risk to the structure and its end use against the effects of lightning.

Grid Size

The old 10X20 M grid set out in BS 6651 is now a thing of the past. The grid size is determined by a risk assessment calculation. The calculation is an exhaustive one, and hence software packages are used to determine the level of risk for a particular structure for a particular senario. It is important to be aware that there are a number of software packages on the market that will perform the risk assessment to the BS standard (which will give inaccurate results) and not the IS standard. We perform all our risk assessments in house and to the correct and or appropriate standard for the given senario, (ie ADS can perform risk assessment calculations for any EU member State).

Earth Spacing

The same applies for earth spacing as does for the grid size, ie this is determined by the risk assessment.

Surge Protection

As outlined on our web page entitled "Surge Protection and The New Satndard" the area of surge protection has now been incorporated into the main part of the standard and this now means that one can not have a full lightning protection system without the inclusion of surge protection devices. The level of surge protection to be applied to a structure is again determined by the risk assessment. The risk assessment atributes values for the failure of electrical equipment (resulting in possible fire) as a result of a direct and/or indirect strike causing over voltages. As a result of these calculations a level of surge protection is asertained. It is worth noting at this time that ADS are reluctant to install surge protection devices for a number of reasons under the new standard. Reasons for this reluctance are outlined on our web page entitled "Surge Protection and The New Satndard".

Part 3

This section outlines the various criteria for each of the lightning protection levels (levels 1-4 as determined by the risk assessment). It is also concerned with the external lightning protection and outlines the various types of lightning protection system (LPS) that a building (commercial or private) or plant area can have and the various ways in which the design can be assessed and created. These systems are briefly, grid, isloation and catenary LPS. This section goes into great detail and provides practical equations to determine the optimum solutuion to any given senario.

Part 4

This section deals with the protection of electrical equipment from over voltage. This area can be of importants to human life when one considers an explosive environment, or an intensive care unit in a hospital. This section outlines the importance of considering the various zones to be employed both at the design and the risk assessment stage within a structure, remembering that every structure has at least two zones (ie the internal and external). This section also deals with the the protection from LEMP (Lightning Electro Magnetic Pulse).


This page is under construction and will be completed as soon as possible

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