Lightning and Lightning Protection
Todd H. Hubing
Michelin Professor of Vehicular Electronics
Clemson University
Course Topics
„
Lightning Formation
„
Lightning Safety
„
Lightning Protection
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Dielectric Breakdown
V
-V+
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Dielectric Breakdown
V
-V+
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Dielectric Breakdown
-+
V
-V+
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Dielectric Breakdown
-+
V
-V+
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Dielectric Breakdown
+
+
+
V
-V+
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Dielectric Breakdown
+
PLASMA
+
+
V
-V+
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Lightning Formation
Warm Humid Air
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Lightning Formation
Water Droplets
Warm Humid Air
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Lightning Formation
Ice Crystals
Water Droplets
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Charge Separation
+
+
+
Ice Crystals
-Water Droplets
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+ ++
-
+
-
-
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+
+ +
+ +
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-
-
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12
Charge Separation
+
+
+
--
+
+ ++
-
+
-
-
+
+
+ ++
+
+
-
-
-
+ + + + + + ++ + + + + + + + +
+
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Charge Separation
-
-
-
- -
-
-
-
-
+ + + + + + ++ + + + + + + + +
+
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Stepped Leaders
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-
-
- -
-
-
-
+
+
-
+
+ +
+ +
+
+
+ +
+ + +
+ + + + + + ++ + + + + + + + +
+
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Streamers
-
-
-
- -
-
-
-
+
+
-
+
+ +
+ +
+
+
+ +
+ + +
+ + + + + + ++ + + + + + + + +
+
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Attachment
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-
-
- -
-
-
-
+
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-
+
+ +
+ +
+
+
+ +
+ + +
+ + + + + + ++ + + + + + + + +
+
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Return Stroke
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-
-
- -
-
-
-
+
+
+
+
-
+
+
+ +
+ ++ +++ + + + + + +
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Mean Number of Thunderstorm Days in the
United States
5
30
20
5
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50 40
10
20
20
50
40
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50
70
90
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Lightning Statistics
„
Peak currents are generally 10 kA
to 20 kA, but may exceed 100 kA.
„
First strokes generally have more
current than subsequent strokes.
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Lightning Statistics
„
Approximately 2000 thunderstorms
are in progress in the world at any
given time.
„
Commercial aircraft are struck by
lightning every 5,000-10,000 flying
hours (on average).
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Boeing 747 over Narita Airport
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Lightning Statistics
„
Lightning kills approximately 100
people in the U.S. every year.
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Lightning Dangers
„
Electrical Shock
„
Burns
„
Secondary Effects
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Where is the safest place to be in a thunderstorm?
a) at home, taking a shower
b) in your car, talking on your cell phone.
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Where is the safest place to be in a thunderstorm?
a) on a golf course
b) standing under a power line
c)
standing under a tree
d) in a Boeing 777 flying through the storm
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You’re in a canoe in the middle of a large lake
when a thunderstorm approaches. What should
you do?
a) row towards shore
b) prop your paddle up in one end of the
canoe and crouch down in the other
c)
swim towards shore
d) turn the canoe over and get under it
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Part II: Lightning Protection
Todd H. Hubing
Michelin Professor of Vehicular Electronics
Clemson University
Lightning Protection
„
Protection from currents
„
Protection from arcs
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Lightning Protection
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Lightning Protection
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Lightning Rods
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Lightning Rods
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Lightning Rods
“Cone of protection”
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Lightning Protection
PHONE LINE
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Lightning Protection
PHONE LINE
ELECTRIC LINE
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Lightning Protection
PHONE LINE
ELECTRIC LINE
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Lightning Protection
PHONE LINE
ELECTRIC LINE
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Lightning Protection
PHONE LINE
ELECTRIC LINE
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Lightning Protection
PHONE LINE
ELECTRIC LINE
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Building Ground
All wires and
pipes that
connect the
inside of the
building to
the outside
should have a
common
ground.
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PHONE LINE
ELECTRIC LINE
PLUMBING
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Building Ground
All wires and
pipes that
connect the
inside of the
building to
the outside
should have a
common
ground.
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PHONE LINE
ELECTRIC LINE
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Note: This
doesn’t
include the
lightning rod
ground, since
this does not
enter the
building.
42
Building Ground
All wires and
pipes that
connect the
inside of the
building to
the outside
should have a
common
ground.
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Inductance
Lightning currents will prefer a low inductance
(straight) path.
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Lightning Protection for Aircraft
Relying of “Faraday Cage” to protect everything
inside.
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Lightning Protection for Boats
Provide a safe current path to the water.
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Primary Lightning Protection
Protection where a cable penetrates the building
PHONE LINE
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Arc Suppressors
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Gas Discharge Tubes
10’s of volts to 1000’s of volts
High Energy
Low Capacitance (< 1 pF)
Fail open
Crowbar device
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Thyristors
0.5 volts to 10’s of volts
Medium Energy
Higher Capacitance (10’s of pF)
Fail open or short
Crowbar device
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Varistors
0.5 volts to 10’s of volts
Low Energy
Higher Capacitance (10’s of pF)
Usually fail short
Voltage limiting device
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Diodes
0.5 volts to ~10 volts
Lowest Energy
High Capacitance (10’s of pF)
Usually fail short
Voltage limiting device
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Course Summary
„
Lightning Formation
„
Lightning Safety
„
Lightning Protection
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