30-12-2010, 04:28 PM
By: D.S.P. Edirisinghe
LIGHTENING PROTECTION.pptx (Size: 834.04 KB / Downloads: 156)
Outline.
Introduction
Types of lightening strokes
Lightening protection system
What is LFA-M?
Block Diagram
Design of LFA-M
How LFA-M protects the system?
Advantages
Disadvantages
Lightening…
What is it…?
Takes place when clouds are charged to a high potential
Electrical discharge between a cloud and earth
A huge spark...
Types of Lightening Strokes...
Direct stroke
Indirect stroke
Lightening - Direct Stroke
Lightening discharge is directly from a cloud to overhead line.
From the line, current path may be over at the ground.
The over voltage setup due to the stroke may be large enough to flashover this path directly to the ground.
Lightening - Indirect Stroke
Results from electro statically induced charges on the conductors.
(+ve) ly charged cloud induces (-ve) charge right under the cloud on the line and (+ve) charge away from it.
When cloud discharges to earth, (-ve) charge rushes along both directions in form of travelling wave.
Lightening protection system
A system designed to protect a structure from damage due to lightening strikes.
Intercepts such strikes and safely passes their extremely high voltage currents to “ground".
Provides a low-impedance path for the lightning current to lessen the heating effect.
Lightening protection system...
Traditional Designs...
Majority of nowadays- traditional “Franklin System”-providing low impedance path
“Franklin System”-A system of
lightning protection conductors
lightning rods -installed on the roof of the building to intercept any lightning before it strikes the building.
This has 3 main parts.
The roof circuit
Interconnection to grounding electrodes
Grounding electrodes
Lightening protection system...
Non-traditional Designs...
Aim is to reduce the number of air terminals required by a traditional Franklin-type system.
Reduce the overall cost of the protection system.
Mainly in two categories.
Systems that provide an increased zone of protection
Systems that eliminate lightning strikes altogether.