14.09.13 PPT on System Transients

8/12/2019 14.09.13 PPT on System Transients

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PPT on System Transients


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1) Some natural destructive phenomena :-Some natural destructive phenomena are cyclones, lightning, earthquakes etc.

Lightning is streaks of bright light and sound caused by electric discharge

between clouds and earth or between different clouds.Earthquake is a sudden shaking or trembling of the earth caused by a

disturbance deep inside the earths crust.

Lightning and earthquakes cause a lot of damage to human life and property.


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3) Types of charges and their interaction :-There are two types of charges. They are positive charge (+) and

negative charge (-).

Two charged bodies may attract or repel each other.

Like (similar) charges repel each other and unlike (dissimilar)charges attract each other.


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7) Lightning :-During thunderstorms air currents move upwards and water droplets move

downwards. This movement causes separation of charges in the clouds. Thepositive charges collect at the upper part and negative charges collect at the

lower part of the clouds. Some negative charges collect near the ground also.When a large amount of charge is formed, then the charges pass from the cloudsto the earth producing streaks of light and sound. The light produced is calledlightning and the sound produced is called thunder.

It was Benjamin Franklin who first discovered that lightning was electric

discharge.


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It takes about 1,000,000volts/meter to cause a

spark.Thats 10,000 volts per

centimeter.


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National Grid 115 kV Line without Surge Arresters

SWEDE Conference - April 2011


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National Grid 115 kV Line with Surge Arresters



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Traveling Wave/ Overvoltage Protection

Lightning hits mid-span

Current divides and thenpropagates

V = I x R


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Lightning


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8) Lightning conductor :-A lightning conductor is a device used to protect buildings from damage due to

lightning.

A lightning conductor has a metallic rod. The upper end is pointed and thelower end is joined to a metal plate buried inside the ground. When lightningstrikes, the electric charges pass through it to the earth without causing anydamage to the building.


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http://www.youtube.com/watch?v=pXasvq1ivnw

http://www.electricalquizzes.com/Transmission_Distribution/Transmission_Distribution_Theory_1.htm
http://www.youtube.com/watch?v=pXasvq1ivnwhttp://www.youtube.com/watch?v=pXasvq1ivnwhttp://www.youtube.com/watch?v=pXasvq1ivnwhttp://www.youtube.com/watch?v=pXasvq1ivnw


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How does lightning kill ?

A. Severe burnsB. Blast trauma (head injuries)C. External bleeding from woundsD. Internal bleeding from ruptured blood vesselsE. Cardiac arrest (heart attack)

h h ll h


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The atmosphere normally has avoltage gradient of 100 volts/meter

which maysound like a

lot, but whathappens when you stand one

meter from a110 volt outlet?


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Outdoor Safety Rules

If you are outdoors when a thunderstorm threatens go as quicklyas you can to a safe shelter

What constitutes as a safe shelter

Safe buildings are buildings that are fully enclosed with a

roof, walls, and floor. They are considered safe because they have wiring and plumbing Safe vehicles are those with hard tops.

Make sure all doors are closed and windows rolled up and do nottouch any metal surfaces

Large Boats with Cabins Best policy is if you are on the water and a storm is approaching is to

get out of the water


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Outdoor Safety Rules

The question begs to be asked: What do you doif there is no safe shelter nearby to go to.

Move away from tall trees Keep away from metal objects and fences If you are in a group spread out with at least 15

ft between you so that there is someone toassist the struck victim.

If you feel your hair rising or your skin feelprickly you are about to be struck so assume thecrouching position shown This position where the heels are touching

encourages the lighting to return to groundwithout going through your whole body

Protect your ears from the resulting thunder bycovering them with your hands


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Langley F106B research aircraft: Where paint is missing.lightning attachment points


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Transmission of Electricity

From power station to consumer

Yardtransformer

RegionalSubstation

ZoneSubstation

DistributionSubstation

TypicalVoltage

11kV, 17kV,

22kV, 23kV

330kV,

500kV

60kV,

132kV

11kV,

33kV

GenerationPrimaryTransmission

SecondaryTransmission

High VoltageDistribution

Final low-voltagedistribution toconsumers

230/400V

Power Station


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Distribution of Power

High Voltage and low voltage distribution system

1 2 3 4

Delta/Startransformer

Three phase four wire distribution lowvoltage 230/400V

Consumer 1 and 2: 230V two wire

Consumer 3 : 230/400V three wire

Consumer 4 : 230/400V four wire

Three phase, highvoltage distribution

Bulk Supply Consumer

Line 1(A)

Line 2(B)

Line 3(C)

Neutral

Three Phase

Star System


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Aluminum conductor


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Aluminum strands

d


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ACSR conductor

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14.09.13 PPT on System Transients