Lightning Protection System

LIGHTNING PROTECTION SYSTEM (LPS)

Lightning system used in Malaysia can be divided into 2 category which is conventional lightning system and unconventional lightning system.

·         Conventional lightning system

-          known as a standard LPS.

-          It comply with the technical standards and codes of practice.

Source:Google Images

·         Unconventional lightning system

-          It known as a system that not comply with the standard technical practice.

-          It also more cheaper than the conventional system.

-          Accident will be easily occur by using this system.

 

Source:Google Images

The Components of the lightning system

 

Source:Google Images

Damages by Lightning

There are many accident occur because of getting hit by lightning. It normally are happen at the upper part of the structure. For example:

Ø  it pointed apex roofs, spires and protrusions

Ø  also to the gable roof ends and outer roof corners.

Basic Principle of Lightning Rod

A lightning rod or lightning conductor is a metal rod mounted on a structure and intended to protect the structure from a lightning strike. It consisted of a pointed metal pole, extending upward above the building. The conducting rod is attached by a copper cable to a grounding rod which is buried in Earth below.

            As lightning hits the structure, instead of passing through the structure, it will strike the rod and conducted to ground through a wire. If not, it could cause fire or electrocution.Intense electric fields surrounding a pointed object serve to ionize the surrounding air, thus enhancing its conductive ability. As a storm cloud approaches, there is a conductive pathway established between statically charged cloud and the lightning rod. Static charges gradually migrate along this pathway to the ground, thus reducing the likelihood of sudden and explosive discharge. Therefore, the primary role of a lightning rod is to discharge the cloud over a onger length of time, thus preventing the excessive charge build up which is characteristic of a lightning strike.

When there is positive charges in the ground, the copper rod acts as perfect conductor and direct the charges into lightning rod.

Storm cloud carrying concentrated negative charge will hit the positive charges (lightning rod).

As the lightning rod charges take place, it will safely conduct back to ground (Earth) safely.

The function of lightning rod is not to attract lightning, but to provide path least resistance for lightning to safely travel to the ground.

Earth Protection System

Factors that should be incorporated when selecting an earth protection system for a building include:

1. The contents of the building and any personnel that may be working inside.
2. The risk posed by a full lightning strike and the full lightning electromagnetic field.
3. Requirements for emergency protection device.
4. Any of the buildings natural components that can be considered as part of the lightning protection system.
5. The four key components of the lightning protection system are: Roof termination system, down conductor configuration, earth termination network, bonding.

External Lightning Protection System

Source : Google Images

The function is to protect buildings from direct lightning strikes, potential fire as well as the effects of injected lightning currents (non-incentive flash). As well as it was external protection, so the building area that need protection include the various systems used to cover the structures or buildings, as well as open and people against direct lightning strikes areas. It consists of air-termination systems, down conductors and an earth-termination system as shown above. 

Air termination Systems

• Located over the highest points of the building to intercept lightning stroke s before they strike the fabric itself. 
• A single point air terminatiom is considered to give a zone of protection defined by a cone,; the apex of the cone is formed by the air termination and the base of the cone has a radius equal to the height of the air termination. 
• The probability of structure penetration by a lightning current is considerably decreased by the presence of a properly designed air - termination system. 
• Air termination systems can be composed of any combination of the following elements : - rods (including free-standing masts); catenary wires; and meshed conductors. 
• Positioning : - Air termination components installed on a structure shall be located at corners, exposed points and edges (especially on the upper level of any facades) in accordance with one or more of the following methods 
• the  rolling sphere method 

• the mesh method

• the protection angle method

Down-conductor Systems

In order to reduce the probability of damage due to lightning current flowing in the LPS, the down-conductors shall be arranged in such a way that from the point of strike to earth: -

• several parallel current path exist
• the length of the current paths is kept to a minimum
• equip potential bonding to conducting parts of the structure is performed according to the requirements.
• the down-conductors shall be installed straight and vertical such that they provide the shortest and most direct path to earth. the formation of loops shall be avoided.
• down-conductors shall not be installed in gutters or down-spouts even if they are covered by insulating material.

Earth-termination System

• To disperse the lightning current into the mass of the earth.
• To reduce any potentially dangerous over voltages.
• In general, an earthing below 10 ohms, measured at low frequency is recommended
• single integrated structure earth-termination system is preferable and is suitable for all purposes such as lightning protection, power systems, and telecommunication systems.

For earth-termination systems, two basic types of earth electrode arrangements apply:

1. Type 'A' arrangement
2. Type 'B' arrangement