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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For the protection of lines against direct lightning strokes, the arresters are connected between the poles and all of the phase conductors in parallel with the insulators. After the LFA A fully flashed over, the lightning current travels through the pole and its footing.
LIGHTENING PROTECTION USING LFA-M – ppt video online download
On the other hand, the potential of the adjacent phases also increases due to electromagnetic coupling between conductors but at much slower rate than that applied to the top phase insulator consequently, an outer phase arrester operates lfw-m much easier coordination conditions than a top phase arrester.
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. Therefore the total voltage U is applied to each flashover module at the same moment, and all three modules are assured conditions for simultaneous initiation of creeping discharges developing lighttning to a single long flashover channel. The next step is to calculate flashover voltages for the individual discharge components or modules.
The rate of channel propagation on arrester modules is determined, and the. LFAs should be uaing on the pole in parallel with each line insulator. Therefore, this new lightning protection system is thought to feature simple design, low cost, and high reliability.
It was found that the main factor, which determines the probability of PAF, is the mean gradient of operational voltage along the flashover path. Fig 4 As illustration, let us consider the operation of phase A arrester.
Due to long flashover path, a flashover does not give rise to a power arc as the arc extinguishes when the power frequency current crosses zero. Probability of power arc flow PAF depends on many parameters: For the protection of lines against direct lightning strokes, the arresters are connected between the poles and all of the phase conductors in parallel with the insulators.
The induced positive charge leaks slowly to earth.
How does LFA-M protect the overhead lines? The cloud will induce a charge of opposite sign on the tall object. The presentation is successfully added In Your Favorites. If the number of flashover modules increases by increasing the cable pieces this LFA-M can protecgion used for lightning protection of very high voltage lines.
The voltage rate of rise U l is proportional to steepness of the lightning current. 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. In usin A, the lightning discharge is from the cloud to the subject equipment e.
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.
Lightning is a huge spark and that take place when clouds are charged to at a high potential with respect to earth object e. A new long flashover arrester model has been developed.
If the cloud P shift too ueing to cloud Q,Then lightning discharge will occur between them and charges on both these cloud disappear quickly.
LIGHTNING PROTECTION USING LFA-M
The direct stroke can be of two types 1. Tests have been shown that, as the lighting conductor is stressed by lightning over voltage impulse, flash over channel develop at different rates. If only a partial flashover of the arrester occurred. Lightening can be serious…. From the line, current path may be over the insulators down to the pole to the ground.
Lfa–m rate of channel propagation on arrester modules is determined, and the modules are checked for flashovers.
LIGHTENING PROTECTION USING LFA-M
Due to a special inner structure the LFA impulse flashover voltage is lower than that of the insulator and when subjected to lightning overvoltage the LFA will flashover before the insulator. WordPress Embed Customize Embed. Due to different propagation rates of flashover channels for lightning impulses of positive and negative polarity, the first module to flashover is module 1 with a flashover length of l 1.
Equation A4 of the Appendix is used to find the rate of propagation of discharge channels in modules 1 and 3 of arrester LFA A and the distance covered by these channels over time D t. A new simple, effective and inexpensive method for lightning protection of medium voltage overhead distribution line is using long flashover arresters LFA.
The protectoin over voltages can be counteracted by installing a single arrester on an overhead line support pole. Lighrning result is that charge on cloud R suddenly become free and it then discharges rapidly to earth, ignoring tall object. It offers great number of technical and economical advantages. It can be calculated from the formula.
Where U l is the maximum operating line voltage; E cr is the critical gradient of the power frequency voltage that rules out PAF. Finally, the calculation is checked for completion. An LFA-M arrester consists of two cables like pieces. It was shown by the calculation that a 1-m- long arrestors.