Lightning Protection Systems (Part 2 of 3) - Down Conductor System by Kingsmill Earthing

By Chris Dodds on 18th December, 2014

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Lightning Protection Systems (Part 2 of 3) - Down Conductor System by Kingsmill Earthing

Basic Overview Of A Lightning Protection System

 

Part 2 - Down Conductor System

Kingsmill Guest Blog for T&D by Jason Leatherland, UK Sales & Business Development Manager.

Part 1 Air Termination System - Risk Assessment & Air Termination Components & Important Remarks

Down Conductor System

  • The purpose of the down conductor is to provide the low impedance path from the air termination system to the earth system.
  • Any good conductor which forms part of the building structure can be employed as a down conductor with appropriate connection to the air termination and earthing systems.
  • For down leads not part of the structure, copper and aluminium earth tapes are the most widely used materials, these are sometimes PVC sheathed for aesthetic purposes only.
  • Where practical they should be routed directly from the air termination to the earth system and be spaced symmetrically around the outside walls of the structure.
  • At all times consideration must be given to the possibility of side flashing. Each down conductor should also be provided with a test point as a means of isolating the earth electrode for test purposes.

Design of Down Conductors

  • Dictated by the initial risk assessment, as the risk assessment will inform you as to what level of protection is required.
  • There is typically one down conductor for every 20m or part thereof the building perimeter at roof or ground level.
  • If the building is above 20m in height or of an abnormal risk this distance should be reduced to 10m.

Pictured: Down Conductors Typical Distances In Lightning Protection Systems


Down Conductors Typical Distances In Lightning Protection Systems

What can be used as Down Conductors?

 

Using Structural Re-Bar as a Down Conductors

  • When using structural re-bars as down conductors you need to ensure the electrical continuity of the re-bars from the Air Termination System down to the Earth Termination System.

Earthing - Typical Structural Rebar Connection

Down Conductor Test Point

  • Each down conductor should have a test point located at minimum height of 2 m for earthing test purposes.

Pictured: Test Clamps For Down Conductor Test Points


Test Clamps For Down Conductor Test Points

Down Conductors Important Remarks

  • These are responsible for transmitting the lightning current from the Air Termination System to the Earth Termination System.
  • Distance between down conductors is subject to risk assessment and also architectural & practical constraints.
  • Down Conductors shall always provide the shortest & most direct to Earth (Earth Termination System)

Coming Soon - Basic Overview Of A Lightning Protection System - Part 3 - Earth Termination System




Category:  Earthing & Lightning Protection

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