17 Dec Explore Lightning Protection Using LFA-M with Free Download of Seminar Report and PPT in PDF and DOC Format. Also Explore the Seminar. Presentation on theme: “LIGHTENING PROTECTION USING LFA-M”— System ”-A system of lightning protection conductors lightning rods -installed on the. 13 Jan The important feature of this modular long flashover arrester (LFA-M) is that it can be applied for lightning protection of overhead distribution.
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It can be clearly seen that as the grounding resistance increases, the critical lightning current steepness I l l ,cr decreases. There are three clouds P,Q and R having positive, negative and positive charge respectively.
Seminar for you: Lighting protection using LFA-M
The induced over voltages can be counteracted by installing a single ligthning on an overhead line support pole. The suggested LFA accomplishes this principle. Where U l is the maximum operating line voltage; E cr is the critical gradient of the power frequency voltage that rules out PAF.
It was also shown that, after the LFA A arrestors has successfully operated, the voltage rate of rise on phase B insulator and its arrestor becomes low and this facilities successful operation of the LFA B arrestor, at least, over the 10 to W grounding range.
When the cloud discharges to earth or to another cloud, negative charge on the wire is isolated as it can not flow quickly to earth over the insulator. Opposite charges attract, like repel Charged objects can cause electrons to rearrange their positions on a neutral object.
The LFA-M described here consists of three flashover modules. The flashover length, L is greater for lines with wooden structures rather than steel or concrete structures, because wooden Cross-arm increases the flashover path. How lightning is formed.
LIGHTENING PROTECTION USING LFA-M
It follows from the previously described sequence of events that direct lightning stroke causes flashover of all the insulators on the affected pole.
The general pattern is as follows. The induced over voltages can be counteracted by installing a single arrester on an overhead line support pole. If the cloud P shift too nearer to cloud Q,Then lightning discharge will occur between them and charges on both these cloud disappear quickly. It offers great number of technical and economical advantages.
The next step is to calculate flashover voltages for the individual discharge components or modules. Semi conductive core 1 2 3. Lightning is an electrical discharge between cloud and the earth, between clouds or lca-m the charge centers of the same cloud. It can be calculated from the formula.
The cable pieces are arranged so as to form three flashover modules 1,2,3 as shown in figure1. Types of lightning II. Tests have been shown that, as the line conductor is stressed usng lightning over voltage impulse, flash over channel develop at different rates. The over voltage set up due to the stroke may be large enough to flashover this path directly to the ground. At this point, the calculation is stopped and the output is printed, including the steepness of the protectiion current I 1 1 at which the insulator flashed over.
Due to different propagation rates of flashover channels for lightning impulses of positive and negative polarity, the first lightnint to flashover is module 1 with a flashover length of l 1. Profection cable piece has a semi conductive core of resistance R.
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 llfa-m lightning current with steepness greater or equal to I lcr The efficiency of LFA lightning protection against direct lightning strokes can be expressed as the ratio of the number of lightning outages n 0 for unprotected line to n 0 for lines protected by LFA arresters.
If the cloud P shift too nearer to cloud Q,Then lightning discharge will occur between them and charges on both these cloud disappear quickly. How does LFA-M protect the overhead lines?: It offers great number of technical and economical advantages. The roof circuit Interconnection to grounding electrodes Grounding electrodes. Charge on the cloud Q is bound by cloud R. Modules1 and 3 flashover lightninh, followed by module 2 ,and thus, forming a rather long flashover channel along the LFA.
Induced over voltages can be counteracted by installing a single arrestor on an overhead line support.
After a top lf-m LFA flashes over, lightning current will flow, through the affected conductor and through the pole to the ground. Lightning is an proyection discharge between cloud and earth, between clouds or between the charge centers of same cloud. A new long flashover arrester model has been developed.
When cloud discharges to earth, -ve charge rushes along both directions in form of travelling wave. The result is that charge on cloud R suddenly become free and it then discharges rapidly to earth, ignoring tall object.
It was found that the main factor, which determines the probability of PAF, is the mean gradient of operational voltage along the flashover path. A new simple, effective and inexpensive method for lightning protection of medium voltage overhead distribution line is using long flashover arresters LFA. The result is that negative charge rushes along the line is both directions in the form of traveling wave. LFAs should be mounted on the pole usinb parallel with each line insulator.
Direct stroke Indirect stroke. Lightning is an electrical discharge between cloud and the earth, between clouds lf-m between the charge centers of the same cloud. At instants t 4t 5and t 6 the first, third, and second modules of arrester LFA B flash over, respectively, changing the resistance of the arrester.
A long flashover arrester LFAwhich comprises of three flashover modules using the creeping discharge effect, is described in this paper. The over voltage set up due to the stroke may be large enough to flashover this path directly to the ground.
The voltage causes the insulator to flashover. It is seen from Fig. It offers great number of technical and economical advantages.