Lightning protection system for buildings, Protection of buildings, etc. damaged by lightning and of human and animal life

Technical information

Lightning protection system for buildings

Lightning protection system for buildings
LPS(Lightning Protection System)

Objective : Protection of buildings, etc. and human and animal life damaged by lightning strikes

JIS Z 9290-3:2019 [Physical damage to buildings, etc. and danger to human life], which defines procedures for protecting physical damage to buildings, etc. and human life from lightning strikes, consists of an “external lightning protection system” and an “internal lightning protection system”.

Selection of lightning protection systems for buildings and other structures

Step 1Select an external lightning protection system (external LPS)

An external LPS is a system that reliably captures approaching lightning strikes and safely discharges them to the ground in order to prevent physical damage to the building itself, as well as to life and its contents. Depending on the importance of the building or equipment, the protection class is determined based on JIS Z 9290-3, and the external LPS is designed.

Step①Selection of lightning protection level (LPL) and determination of LPS class

Considering the importance of the building, the density of lightning strikes in the area and the location conditions, the decision is made in consultation with the client and designer.

Step②Selection of each system for external LPS
  • ◎Lightning receiving part system
    • ・Lightning receiving part layout (rotating sphere method, protection angle method, mesh method)
    • ・Components of lightning receiving part (piercing needle, horizontal conductor, mesh conductor)
  • ◎Down conductor system
    • Direct method, structure use method (simplified method)
  • ◎Earth electrode system
    • A type earth electrode (horizontal earth electrode, vertical earth electrode, plate earth electrode, foundation earth electrode that does not form a closed loop, combination of horizontal and vertical)
    • B-type earth electrode (ring earth electrode, mesh earth electrode, foundation earth electrode forming a closed loop)
      Structure-used earth electrode
Step 2Select an internal lightning protection system (internal LPS)

Internal LPS is a lightning equipotential bonding and isolation (separation distance) from external LPS to reduce dangerous spark discharge and electromagnetic effects by lightning.

Step①Safety measures using lightning equipotential bonding (EB)

To prevent the generation of overvoltage that may cause electric shock or fire, connect the external LPS to other metal parts directly by bonding or indirectly by using SPD.

Step②Secure the safety isolation distance

Perform magnetic shielding and examine the wiring route.

Setting the lightning protection level (LPL)

The lightning current parameters (Lightning Impulse current peak value) for direct lightning strikes specified in IEC62305-1-2010 are classified into four levels namely Lightning Protection Level (LPL) I to IV. In addition, lightning current parameters such as the maximum current peak value and the minimum current peak value of the lightning current are defined according to each level.

■Setting the lightning protection level
Setting the lightning protection level
■Probability of lightning occurrance within the limit values of the lightning current parameters
Probability of lightning occurrance within the limit values of the lightning current parameters

The range of protection levels according to IEC 62305-1

Source: “Lightning and the Advanced Information Society,” Institute of Electrical Equipment and Components Engineers. Added to Figure 1.4.2 in 1999.

■The range of protection levels for cumulative frequency distribution of lightning current surges

Arrangement of lightning receiving parts

In order to design a lightning protection system (LPS) which meets the requirements of LPS class in accordance with IEC 62305-2 (EN 62305-2), the following methods may be used individually or in combination:

  • ①Rolling sphere method
    A method in which the protected object’s side is protected by being in the area enveloped by a sphere’s surface when the sphere is rotated such that it touches two or more lightning receiving points or one or more lightning receiving points and the earth at the same time.
  • ②Mesh method
    A method by which a specific area is protected by being covered with a mesh conductor.
  • ③Protection angle method
    A method where the specified protection angle measured from vertical lightning receiving rod at the upper end is the protected range.

Protection range of lightning receiving area on the side wall

With the increase in high-rise buildings, IEC 62305-3:2010 stipulates that a lightning receiving area should be ensured on the side wall that is on the upper 20% height of a building which exceeds 60 m in height.

Installation example of external lightning protection system