lightning protection using lfa-m presentation
TRANSCRIPT
WELCOME
DEPT OF ELECTRONICS & COMMUNICATION
1
MEA ENGG COLLEGE,PMNA
BY MOHAMED SHALOOB T K REG NO:-CEAGEEC 050 S7 ECE-1
LIGHTNING PROTECTION USING LFA-M
2 DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
3
CONTENTS
INTRODUCTION
WHAT IS A LIGHTNING STROKE?
TYPES OF LIGHTNING STROKES.
WHAT IS LFA-M?
BLOCK DIAGRAM
DESIGN OF LFA-M
HOW LIGHTNING AFFECTS OVERHEAD TRANSMISSION?
THE LFA-M PRINCIPLE
HOW CAN IT BE PROTECTED?
FUTURE EXPANSION
AVANTAGES & DISADVANTAGES
CONCLUSION
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
4 INTRODUCTION
• 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
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
5
WHAT IS LIGHTNING STROKE
?
Lightning is an electrical discharge between cloud and the earth, 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
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
6
TYPES OF LIGHTNING STROKES
DIRECT STROKE
INDIRECT STROKE
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
7 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
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
8DIRECT STROKE-
TYPES
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.
STROKE-B – Lightning discharge occurs on overhead line due to stroke-A.
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
9 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.
Most commonDEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
10 WHAT IS 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 lightning protection of overhead distribution line against both induced over voltages and direct lightning strokes.
The induced over voltages can be counteracted by installing a single arrester on an overhead line support (pole).
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.
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
11 BLOCK DIAGRAM
ff
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
a) block diagram; b) electric schematic c) arrester testing
12DESIGN 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
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
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HOW DOES LFA-M PROTECT THE
OVERHEAD LINES?
First, a lightning impulse causes a spark over of the spark gaps
Next, the semiconducting core of the upper cable piece, whose resistance , carries the high potential to the surface of the lower piece at its middle. Similarly, the semiconducting core of the lower piece of the same resistance applies the low potential 0 to the surface of the upper piece, also at its center.
Thus the total voltage is applied to each flashover module at the same 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
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
14THE LFA
PRINCIPLE
Probability of power arc flow (PAF) depends on many parameters: nominal voltage of the line Unom, length of the flashover path L,
The probability of PAF sharply decreases with a decrease in E
An analysis of available data on spark over discharge transition to PAF concluded that for E=7 to 10 kV/m probability of PAF is practically zero.
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
15 LFA LOOP-TYPE
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
16 ADVANTEGE
LFA-Ls help avoid both conductor burnouts and overhead power lines outages caused by lightning induced overvoltages.
Eliminate the consequences of lightning flashovers without damaging lines and substations equipment, as opposed to arcing horns, which transform single-phase shorting into two-phase one, thus creating a powerful electrodynamic blow on the equipment.
Extend the working life of high voltage circuit breakers.
Protect electric networks against arc overvoltages.
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
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Cannot be destroyed by lightning currents and power follow currents as metal oxide arresters, gapped silicon carbide arresters or expulsion tubes since currents are flowing outside of LFAs.
Are not stressed by operational voltage and do not require maintenance.
It protect from 0.4 to 10 kv power distribution
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
18 DISADVANTEGE
We can improve only it efficiency by increasing the number of flashover modules then only it can withstand very high over voltages
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
19FUTURE
EXPANSION
The LFA-M described here consists of three flashover modules. We can increases the flashover modules. If the number of flashover modules increases by increasing the cable pieces this LFA-M can be used for lightning protection of very high voltage lines.
When the modules increases the total arrester stressing is distributed these modules also. Then it can withstand very high over voltages
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
20 CONCLUSIONS
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
The voltage-time characteristics of this modular arrestor assure reliable protection of medium voltage overhead lines against both induced over voltages and direct lightning strokes.
A long flashover arrestor (LFA) comprising three flashover modules using the creeping discharge effect was presented in this report. Its resistors assure application of the total arrestor-stressing voltage simultaneously to all the modules.
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
21REFERENCES
PRINCIPLES OF POWER SYSTEM BY V.K. MEHTA ,ROHIT MEHTA
IEEE TRANSACTIONS ON POWER DELIVERY .VOL.18,NO 3,JULY 2003 PAGE NO. 781-787
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
END
22 DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
23 THANK YOU
DEPT OF ELECTRONICS & COMMUNICATIONMEA ENGG COLLEGE,PMNA
QUESTIONS?