Week 11

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LIGHTNING PROTECTION SYSTEM (LPS)

What are LPS?
  • ·        A lightning protection system provides a safe pathway for energy from a lightning strike to find its way to earth, encouraging the bolt to bypass building components that might otherwise to damaged.



Example of A Lightning Protection System (LPS)

Why using LPS?
Lightning protection is essential for the protection of humans, structures, contents within structures, transmission lines, and electrical equipment by controlling a variety of risks resulting from thermal, mechanical, and electrical hazards of the lightning flash current. These risks can be categorized as follows:
  • Risk to persons (and animals),
  • Risk to structures & internal equipment
1.      Risk to persons (and animals)

  • Direct flash,
  • Step potential,
  • Touch potential,
  • Side flash,
2.  Risk to structures & internal equipment
  • Fire and/or explosion triggered by heat of lightning flash, its attachment point or electrical arcing of lightning current within structures,
  • Fire and/or explosion triggered by ohmic heating of conductors or arcing due to melted conductors,
  • Punctures of structure roofing due to plasma heat at lightning point of strike,
  • Failure of internal electrical and electronic systems,
  • Mechanical damage including dislodged materials at point of strike.
What is The Effective Lightning Protection System?
The effective lightning protection system which eliminates the above risks must be designed to:

  • Intercept lightning flash (i.e. create a preferred point of strike)
  • Conduct the strike to ground safely through purpose designed down conductors,
  • Dissipate the lightning energy into the ground with minimum rise in ground potential,
  • Eliminate ground loops and hazardous potential differentials between LPS, structure and internal elements/circuits by creating low impedance, equipotential ground system,
  • Protect equipment from surges and transients on incoming power lines to prevent equipment damage and costly operational downtime,
  • Protect equipment from surges and transients on incoming telecommunications and signal lines to prevent equipment damage and costly operational downtime,
  • Not cause thermal or mechanical damage to the structure,
  • Not cause sparking which may cause fire or explosion,
  • Limit step and touch voltages to control the risk of injury to occupants.

Types of Lightning Protection Systems LPS

Lightning protection systems for buildings and installations may be divided into three principal types as follows:
  1. LPS for Protection for buildings and installations against direct strike by lightning,
  2. LPS for Protection against overvoltage on incoming conductors and conductor systems,
  3. LPS for Protection against the electromagnetic pulse of the lightning.

First: LPS for Protection for buildings and installations against direct strike by lightning
This type of LPS protects the building from damage by direct strike lightning but doesn’t prevent the lightning striking the building.
This type of LPS can be divided into:-
  1. Conventional lightning protection system,
  2. Non-Conventional lightning protection system.


Conventional Lightning Protection System
Properly designed conventional lightning protection systems for ground-based structures serve to provide lightning attachment points and paths for the lightning current to follow from the attachment points into the ground without harm to the protected structure.

Convetianal Lightning Protection System

Such systems are basically composed of three elements:
  • Air terminals at appropriate points on the structure to intercept the lightning,
  • Down conductors to carry the lightning current from the air terminals toward the ground, and
  • Grounding electrodes to pass the lightning current into the earth.

Types of Conventional Lightning Protection System

1. Franklin Rod LPS:
Other names for this type of Conventional Lightning Protection System are:
  • Sharp pointed rods,
  • Single mast system,
  • Franklin Cone / protective Angle cone.
Franklin Rod LPS

  • A pointed lightning rod or air terminal or a single mast will help prevent lightning from striking in the immediate vicinity because it will help reduce the difference in potential between earth and cloud by "bleeding off" charge and therefore reducing the chance of a direct strike.
  • This lightning rod or air terminal or a single mast will provide a cone shaped zone of protection with angle of 45 degree forming a circular base on the ground around a building or part of a building.
  • Many decades of experience shows that by combining Franklin rods located at critical points on a structure with a proper down conductor and grounding system the damage due to lightning could be reduced significantly.
2. Franklin/Faraday Cage LPS:

A faraday cage is an enclosure fixed to the outside of the building made of conductors laid out on a grid pattern to produce an external mish. If the building is steel formed, the job can be made considerably easier as the steel frame itself can be used as part of the cage, but air termination devices are needed if the upper external surface of the roof is not metal and continuous with the steel frame.

Franklin/Faraday Cage Principle

Advantages of The faraday cage LPS:
  • The faraday cage, if designed correctly, will form an electromagnetic shield. This means that there will be no electric fields inside the cage resulting from currents flowing to earth on the surface of the cage.
  • Each one of numerous down conductors will be earthed to ground.
  • The air termination network can easily be made suitably extensive.
  • This is the type of protection which is likely to be the most reliable in terms of lightning protection.


Non-Conventional Lightning Protection System



Components of Non-Conventional Lightning Protection System
Non-Conventional lightning protection system includes (2) main types as follows:

1. Active Attraction LPS, which includes:
  • Improved single mast system (Blunt Ended Rods),
  • Early streamer Emission System.

2. Active Prevention/Elimination LPS, which includes:
  • Charge Transfer System (CTS),
  • Dissipation Array System (DAS).






General Information About Non-Conventional Lightning Protection System

In the 1970s, two types of unconventional air terminals had been commercially reinvented and introduced in the world market under a variety of trade names. They are:

1. The lightning Active Attraction air terminal: 
  • the lightning attracting air terminal is claimed to be able to attract the lightning to it (and hence away from the building) in order to protect the building that it was installed on.
2. The lightning Active Prevention/Elimination air terminal:

  • the lightning prevention air terminal is claimed to be able to prevent lightning from occurring and hence protect the building.


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