Fundamentals of Lightning General Principles lightning protection Lightning Parameters Measurements Of Peak currents Advanced Approaches to Lightning Protection Lightning Discharge Downward flash Upward Flash General principle Of lightning Protection

1. Lightning Discharge and
Fundamentals of lightning
Protection
Presented By
Chittaranjan Behera
EEE-B

2. Contents:-
 Introduction
 Fundamentals of Lightning
 General Principles lightning protection
 Lightning Parameters
 Measurements Of Peak currents
 Advanced Approaches to Lightning Protection
 Summery and Conclusion
 References

3. Introduction
The principles of modern lightning protection technology
emphasize the protection, comprehensive treatment and
successive lines of defence. External lightning protection facilities
shall be installed for the external of buildings, and corresponding
lightning protection devices shall be installed for systems inside
buildings. Thunder and lightning is one of the Most destructive
natural disasters. Therefore, lightning protection is an important
systematic work. Only the lightning protection is carried out well for
a long term, the effects of lightning protection and disaster
reduction can be truly realized by some modernised protection
system

4. Lightning Flash:-
Lightning is the visible discharge of static electricity within a cloud, from cloud to
cloud, or between the earth and a cloud.
It can be divided into two types
1. lightning Discharge
2. lightning strokes
Lightning Discharge
Lightning flashes to earth (discharges) lead to a neutralization of charge between
the cloud charges and the electrostatic charges on the ground.
Two types of lightning Discharge
 Downward flashes (cloud-to-earth flashes)
 Upward flashes (earth-to-cloud flashes)
Downward flash:-
Flash starts from cloud and moves towards ground

5. Downward flashes are of two types:-
1. –ve Discharge
2. +ve Discharge
Upward Flash:
Flash starts from earth and move towards cloud
It is also of two types
1. –ve flash
2. +ve flash
Lightning waveform

6. General principle Of lightning Protection
There are generally two aspects of Lightning Protection
1. Diversion and shielding, primarily intended for
structural protection but also serving to reduce the lightning
electric and magnetic fields within the structure
2. The limiting of currents and voltages on electronic, power, and communication systems via surge
protection
Lightning Protection System:-
A Lighting Protection System (LPS) is the system that provides a means by which a lightning discharge
may enter or leave earth without passing through and damaging personnel, electrical equipment, and
non-conducting structures such as buildings
Ground based Structure:-
Properly structural 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

7. It basically composed of three elements
 Air terminals
 Down conductors
 Grounding electrodes
Side Flash:-
During the lightning flash the rapid rate of current
rise can cause the inductive voltage rise of the
conductor to reach a magnitude where sufficient
voltage exists for the conductor to flashover to a
nearby conductive and earthed object
Side flashing can be controlled by:
1. Using a number of parallel down-conductors to
reduce the current in each, ensuring the
separation distance between the two objects is
sufficient not to break down the intervening
medium

8. Lightning Parameters
There are four important parameters which can cause damage due to lightning
1. Peak current
2. Maximum rate of change of current
3. Integral of current over time
4. Action integral
Peak current:-
For resistive impedance
Ohm’s law
V=RI
If a peak current of 30 KA injected through a long power line phase conductor with a resistance
of 400 ohm then it produces a line voltage of 6MV
Maximum rate of change of Current:-
For inductive loads voltage is proportional to rate of change of current by the relation
V = L dI/dt

9. Integral of Current over Time:-
 The severity of heating or burn-through of metal sheets such as airplane wing surfaces and
metal roofs is proportional to the lightning charge transferred which is in turn proportional to
the energy delivered to the surface.
 Large no of charge is transferred due to longer duration of time and due to this heating and
burning will be occur
Action Integral:-
 The time integral of joule heating power (I2(t) R) cause melting and explosion of poorly
conducting material
 The produced heat vaporises the internal material and the resultant gas pressure causes
explosion
 It also cause some mechanical effects such as causing of hollow metal
 Current induces due to electromagnetic fields from lightning
1.the peak values of electric and magnetic field
2.max rate of change of fields

10. Lightning Protection Standard:-
>CIGRE distribution
>IEEE distribution
 For the CIGRE distribution, 98% of peak currents
exceed4 kA, 80% exceed 20 kA, and 5% exceed 90
kA
 For the IEEE distribution, the “probability to exceed”
values are given by the following equation

11. Advanced Approaches to Lightning Protection
Electrogeometrical Model(EGM):-
Striking distance:-
The striking distance can be defined as the distance
from the tip of the descending leader to the object to
be struck at the instant when an upward connecting
leader is initiated from this object
>The geometrical construction of this surface can be
accomplished simply by rolling an imaginary sphere of
radius equal to the assumed striking distance across
the ground and across objects on the ground

13. Striking Distance
I=peak current(KA)
rs=striking distance(meters)
>The main application of the rolling sphere method is positioning air terminals on an ordinary structure,
so that one of the terminals, rather than a roof edge or other part of the structure, initiates the upward
leader that intercepts the descending leader and, hence, becomes the lightning attachment point

14. Objectives:-
 To force the current to flow to ground
 To reduce the hazardous potential
The distance between an LPS down-
conductor and the protected object in air
should be greater than Dair given in meters by
Dair=Distance b/w air terminal and protected object
Z=impedance of LPS grounding system
L=distance b/w LPS grounding system and point of
intrest
Bonding vs isolation approaches in lightning protection:-

15.  The distance between the LPS grounding system and buried metallic services should be
greater than Dsoil given by
I=Lightning Peak current
Z=impedance of LPS grounding system
Eb=Breakdown electric field

16. CONCLUSION:-
 Any design of Direct Lightning Stroke Shielding depends on the probabilistic nature of
lightning phenomena. There is no method available to provide 100% shielding against
direct lightning stroke of the substation equipment and bus structures.
 EGM method is more appropriate for large and important substations at 230 kV and
above voltage level. In order to arrive at some practical solutions, many assumptions
are made in the different design techniques

17. References
 A.M. Mousa, The Applicability of Lightning Elimination Devices to Substations and Power
Lines, IEEE Trans. on Power Delivery, Vol. 13, No. 4, October 1998, pp. 1120-1127.
 D. W. Zipse, Lightning Protection Systems: Advantages and Disadvantages, IEEE Trans. On
Industry Applications, Vol. 30, No. 5, Sept/Oct. 1994, pp. 1351-1361.
 IEEE Std. 998-1996, Section 6, pp. 42-43.
 www.wikipidia.in

18. THANK YOU