A lightning protection system is designed to protect a structure from damage due to lightning strikes by intercepting such strikes and safely passing their extremely high currents to ground.

1. BRINDAVAN
INSTITUTE OF TECHNOLOGY & SCIENCE (BITS-KNL)
(Approved by AICTE & Affiliated to JNTUA)
NH-7, PEDDATEKUR, KURNOOL
Technical Seminar on :
LIGHTNING PROTECTION USING LFA-M.
Name of the Student : Shaik Mohammed Mustaq.
Roll Number : 192N5A0407.
Under the esteemed Guidance of,
Mrs. K. Divya,
Assistant Professor
Department of ECE.

2. Overview of the Presentation
• Introduction
• What is a Lightning Stroke ?
• Types of Lightning Strokes
• What is a LFA-M ?
• Block Diagram
• Design of LFA-M
• How LFA-M protects the system ?
• Advantages and its disadvantages
• Applications
• Future Expansion
• Conclusion
• Reference

3. Introduction
• A lightning protection system is designed to protect a structure from damage due
to lightning strikes by intercepting such strikes and safely passing their extremely
high currents to ground.
• A new simple, effective and inexpensive method for lightning protection of
medium voltage overhead distribution line is using long flashover arresters
(LFA).
• The important feature of this modular long flashover arrester (LFA-M) is that it
can be applied for lightning protection of overhead distribution line against
both induced overvoltage and direct lightning strokes.

4. What is a Lightning Stroke ?
• Lightning is an electrical discharge between cloud and the
earth or between clouds or between the charge centers of the
same cloud.
• Lightning is a huge spark and that take place when clouds
are charged to at a high potential with respect to earth object
(e.g. overhead lines) or neighboring cloud that the dielectric
strength of the neighboring medium (air) is destroyed.

5. Types of Lightning Strokes
There are two main ways in which the lightning may strike the power system . They
are :
1. Direct Stroke.
2. Indirect Stroke.

6. Direct Stroke
• Lightning discharge is directly from cloud to overhead line.
• From the line, current path may be over the insulators down to the pole to
the ground.
• The over voltage set up due to the stroke may be large enough to flashover this
path directly to the ground.

7. Types of Direct Strokes :
1. STROKE A -
• The lightning discharge is from the cloud to the subject equipment(e.g. overhead
lines).
• The cloud will induce a charge of opposite sign on the tall object.
• When the potential between the cloud and line exceed the breakdown value of air,
the lightning discharge occurs between the cloud and the line.
2. STROKE B -
• Lightning discharge occurs on overhead line due to stroke-A.

8. 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.

9. What is a LFA-M ?
• Long flashover arrestors are those devices
which capture the high voltage sparks resulting
out of lightening.
• "M" indicates that LFA-M is for the protection of
medium overhead transmission lines.
• It can be applied for protection of distribution
lines.

10. • Induced over voltages can be counteracted by installing a single arrestor on an
overhead line support.
• For direct lightning – arrestors are connected between poles and all the phase
conductors in parallel with the insulators.

11. Block Diagram
a) block diagram b) electric schematic c) arrester testing

12. Design of LFA-M
• An LFA_M arrester consists of two cables like pieces.
• Each cable piece has a semi conductive core of
resistance R.
• The cable pieces are arranged so as to form three
flashover modules 1,2,3 as shown in figure.
• Semiconductive core of upper piece, whose resistance
is R.

13. How LFA-M protects the system ?
1) A lightning impulse causes a spark over of
the spark gaps.
2) Resistance carries a
high potential U
3) Same resistance
applies a 0 potential.
4) All three
modules are
assured of
creeping
discharges into a
single long
flashover
channel.

14. Advantages
• Extend the working life of high voltage circuit breakers.
• Reliable.
• Inexpensive.
• It protects from 0.4 to 10 kV power distribution.
• Used for both induced overvoltage's and direct lightning strokes.
• No need for maintenance.

15. Disadvantages
• Efficiency can only be increased by number of flash over modules.
• Cost of installation.

16. Applications
1. The LFA-Insulation Tube (LFA-IT) :
1.power line conductor
2.insulation tube
3.metal tube clamp
4.insulator
5.structure
6.flashover channel
7.sparkover horn
8.S-sparkover gap
figure :

17. 2. The LFA – Loop :
• A piece of a steel rod covered with insulation is bent in a loop and connected to
the pole with a clamp.

18. Future Expansion
• This can be used for lightning protection of very high voltage lines.
• The number of flash over modules increases by increasing the cable pieces.
• When the modules increases the total arrester stressing is distributed these
modules also. Then it can withstand very high over voltages.

19. Conclusion
• LFA comprising three flash over modules, using the creeping discharge effect.
• The LFA-M is a simple, low weight and convenient apparatus.
• To protect a line against induced over voltages; a single arrestor must be mounted
on a pole.

20. References
1) IEEE TRANSACTIONS ON POWER DELIVERY
VOL.18,NO 3,JULY 2003 PAGE NO. 781-787
2) PRINCIPLES OF POWER SYSTEM BY V.K. MEHTA
ROHIT MEHTA

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