WELCOME LIGHTNING PROTECTION USING LFA-M Submitted By:Somi.P. Chacko Class: S7-EEE Roll no: MCET CONTENTS. Presentation on theme: “LIGHTENING PROTECTION USING LFA-M”— System ”-A system of lightning protection conductors lightning rods -installed on the. effective and inexpensive method for lightning protection of medium voltage overhead distribution line is using long flashover arresters (LFA).

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The over voltage set up due to the stroke may be large enough to flashover this path directly to the ground.

Are not stressed by operational voltage and do not require maintenance. How does LFA-M protect the overhead lines?: When the central part of the arrester flashes over at instant t 3the arrester sparks over through a single spark channel of very low resistance.

The roof circuit Interconnection to grounding electrodes Grounding electrodes. It offers great number of technical and economical advantages. The induced overvoltages can be counteracted by installing a single arrester on an overhead line support pole. The result is that charge on cloud R suddenly become free and it then discharges rapidly to earth, ignoring tall object. If the channel length is greater or equal to the module length, a flashover is assumed to have occurred for that particular module and the equivalent arrester resistance abruptly becomes equal to the resistance of the respective semi conductive cable section.

The direct stroke can be of two types. Phase to phase lightning flashover is also highly probable to protrction resulting to a power arc accompanied by heavy short circuit currents, which causes immediate line tripping.

OK Rate of flow of electrical charge is called lightnng P2 4. The induced over voltages can be counteracted by installing pprotection single arrester on an overhead line support pole. Each cable piece has a semi conductive core of resistance R. Thus the total voltage is applied to each flashover module at the portection moment, and all the three flashover modules 1, 2 and 3 are assured conditions for simultaneous initiation of creeping discharges which,with respective modules flashed over, develop a single long flashover channel PowerPoint Presentation: First, a lightning impulse causes a spark over of the spark lightnning Next, the semiconducting core of the upper cable protecfion, whose resistancecarries the high potential to the surface of the lower piece at its middle.


In this design, the total arrester stressing voltage is applied simultaneously to all of the three modules so that the voltage-time characteristics of the arresters are improved.

Lightning is an electrical discharge between cloud and the earth, between clouds or between the charge centers of the same cloud. A delta arrangement of conductors maximizes direct lightning strokes on the top center phase, which acts as shielding wire for the bottom outer phases.

Edirisinghe T Department of EE. 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 overvoltages and direct lightning strokes.

Thus, the number of outages caused by direct lightning strokes can be lowered with the use of LFA arresters by an order of magnitude or more even for high values of grounding resistance.


It protects from 0. In stroke A, the lightning discharge is from the cloud to the subject equipment e. It offers great number of technical and economical advantages. Thus, t tr is larger than t usibg. Thank you 5 months ago.


Thank you for providing the great information on a Lightning Protection System The pictorial representation is very helpful for every new user.

Electricity The movement of charge from one place to another Requires energy to move the charge Also requires conductors. Published by Sherman Lindsey Modified over 2 years ago. It is stressed usinh fairly steep over voltage impulses associated with direct lightning strokes on a conductor.



Where n 0 is the number of lightning outages on an LFA protected line caused by direct lightning strokes on the phase conductors and P I lcr is probability of a lightning current with steepness greater or equal to I lcr.

Next, the insulators and arresters voltage-time characteristics VTCs are ussing in an analytical form. Since the resistance of the flash over channel is low compared to other resistance affecting lightning over voltages surge impedance of the conductor and of the lightning channel, etc. Then it can withstand very high over voltages.

In stroke B the lightning discharge occurs on the overhead line as the result of stroke A between the clouds. Majority of the surges in a transmission lines are caused by indirect lightning stroke. The general pattern is as follows. From the line, current path may be over the insulators down to the pole to the ground.

We think you have liked this presentation. This is the reason lf-am the calculation takes into account the critical values of the lightning current steepness I l l ,cr at which the insulator flashes over for a given set of parameters.

The over voltage setup due to the stroke may be large enough to flashover this path directly to the ground. Mainly in two categories. The conditions for the efficient protection of a medium voltage e. Systems that provide an increased zone of protection Systems that eliminate lightning strikes altogether.

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