SLIDE 1 www.scvemc.org Title : The Lightning Phenomenon Guest Speaker : Marcos Rubinstein (DL)
Abstract: Lightning is one of the primary causes of damage and malfunction of telecommunication and power networks and one of the leading causes of weather-related deaths and injuries. Lightning is composed of numerous physical processes, of which only a few are visible to the naked eye. This lecture presents various aspects of the lightning phenomenon, its main processes and the technologies that have been developed to assess the parameters that are important for engineering and scientific applications. These parameters include the channel-base current and its associated electromagnetic fields. The measurement techniques for these parameters are intrinsically difficult due to the randomness of the phenomenon and to the harsh electromagnetic environment created by the lightning itself. Besides the measurement of the lightning parameters, warning and insurance applications require the real-time detection and location of the lightning strike point. The main classical and emerging lightning detection and location techniques, including those used in currently available commercial lightning location systems will be described in the lecture. The newly proposed Electromagnetic Time Reversal technique, which has the potential to revolutionize lightning location will also be presented.
SLIDE 2
The Lightning Phenomenon
Marcos Rubinstein
SLIDE 3 Outline
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What is lightning and the main lightning processes
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How are its parameters measured
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Lightning detection and location
SLIDE 4
What is lightning?
Li Lightni ning ng is a a trans ansien ent, hi high-cur curren ent el elect ectric c di dischar charge e who hose e pa path h leng ength h is me measured in kilome meters
SLIDE 5 Lightning Effects
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About 30%-60% of all power outages annually are lightning-related, on average, with total costs approaching $1 billion dollars. (Source: EPRI)
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Lightning strikes cost nearly $1 billion in insured losses in 2012 (source: Insurance Information Institute)
SLIDE 6 Kamatzu Airforce Base, Japan
Lightning initiation by an aircraft
SLIDE 7 Kamatzu Airforce Base, Japan
Lightning initiation by an aircraft
SLIDE 8
Cattle Killed by Step or Touch Potential
SLIDE 9 A complete lightning is called a “lightning flash”
Major Types of Lightning
SLIDE 10 Types of Cloud-to-Ground lightning
Both of these types can transfer either positive or negative charge to the ground.
SLIDE 11 Cloud-to-Ground Lightning
Downward negative Upward negative Downward positive Upward positive
Adapted from Berger, 1977
SLIDE 12 Downward negative Upward negative Downward positive
Upward positive
About 90% or more of global Cloud-to-ground lightning
Cloud-to-Ground Lightning
SLIDE 13 Downward negative Upward negative Downward positive
Upward positive
About 10% or less of global Cloud-to-ground lightning
Cloud-to-Ground Lightning
SLIDE 14 Downward negative Upward negative Downward positive Upward positive
Occur only from tall objects (>100 m or so) or from
- bjects of moderate height
located on mountain tops
Cloud-to-Ground Lightning
SLIDE 15 Cloud-to-Ground Lightning
Adapted from Berger, 1977
SLIDE 16
Separation of charge
SLIDE 17 Separation of charge
Graupel
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Ice crystals
SLIDE 18
Cloud-to-Ground Lightning
SLIDE 19 Cloud-to-Ground Lightning
Downward negative Upward negative Downward positive Upward positive
Adapted from Berger, 1977
SLIDE 20 Downward negative Upward negative Downward positive Upward positive
Cloud-to-Ground Lightning
SLIDE 21 Downward Negative Cloud-to-Ground Lightning
Stepped leader
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t = 0 Preliminary discharge
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t = 1.2 ms Upward connecting discharges Attachment process First return stroke
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time
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t = 20.1 ms
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Dart leader Subsequent return stroke time
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Adapted from Uman, 1987
SLIDE 22 22
High speed video (7,200 images per second) of a negative ground flash captured on August 15, 2008 near Rapid City, South Dakota
SLIDE 23 The three processes we saw in the video
❖ Preliminary breakdown ❖ Stepped Leader ❖ Attachment process ❖ Return stroke ❖ Continuing current ❖ M components ❖ Inter-stroke processes (K and J changes)
SLIDE 24 There are other processes in downward CG lightning
❖ Preliminary breakdown ❖ Stepped Leader ❖ Attachment process ❖ Return stroke ❖ Continuing current ❖ M components ❖ Inter-stroke processes (K and J changes)
SLIDE 25 Typical Channel-Base Current Waveform Associated with a Downward Negative Flash
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First Return Stroke Subsequent Return Stroke Subsequent Return Stroke M Components M Component
CC
t
Tens to hundreds of ms Of the order of a hundred µs Of the order of a hundred µs First RS ~ 30 kA Subsequent RS ~ 12 kA CC ~ tens to hundreds of A M- comp. ~ hundreds of A
SLIDE 26
Lightning is a Very Long Antenna
SLIDE 27 Lightning Return-Stroke Fields: 1-5 km
Typical vertical electric field intensity (left column) and azimuthal magnetic flux density (right column) waveforms for first (solid line) and subsequent (dashed line) return strokes at distances of 1, 2 and 5 km. Adapted from Lin et al. (1979).
Solid Line: First Strokes Dashed Line: Subsequent Strokes
SLIDE 28 Lightning Return-Stroke Fields: 10-200 km
Typical vertical electric field intensity (left column) and azimuthal magnetic flux density (right column) waveforms for first (solid line) and subsequent (dashed line) return strokes at distances of 10, 15, 50, and 200 km. Adapted from Lin et al. (1979).
SLIDE 29 Upward Lightning
❖ Only from tall objects or from moderate height objects on mountains ❖ It is becoming more frequent ❖ Above a certain height, tall structures produce their own lightning
SLIDE 30 Upward Lightning
Upward negative Upward positive
Adapted from Berger, 1977
SLIDE 31
High-Speed Video of Upward Lightning
SLIDE 32 Upward Negative Lightning
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Return Stroke Return Stroke ICC pulses M Component
CC
t
CC ICC
Tens to hundreds of ms Of the order of a hundred µs
SLIDE 33
How are Lightning Measurements Made, Given its Inherent Randomness and Harsh EM environment?
SLIDE 34 Direct Channel-Base Measurements
❖ Artificially initiated lightning ❖ Rocket-triggered ❖ Laser triggered? ❖ Instrumented tall grounded objects ❖ Towers, buildings, wind turbines
SLIDE 35 Rocket-Triggered Lightning
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Camp Blanding, Florida
Launcher Rockets
SLIDE 36 Camp Blnding, Florida
- F. Rachidi and C.A. Nucci, 2005
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SLIDE 37 Tall Grounded Objects
Slide courtesy of Prof. V. Rakov 37
SLIDE 38 Instrumented Towers Around the World
Slide courtesy of Prof. V. Rakov 38 2502 m ASL 124 m Morro do Cachimbo 60 m 1430 m ASL Gaisberg 1288 m ASL 100 m Eagle Nest 2537 m ASL 25 m Peissenberg CN Tower Skytree 940 m ASL 76 m ASL 37 m ASL 160 m 553 m 634 m Säntis
SLIDE 39 39 Säntis mountain: 2502 m; Säntis Tower: 123.5 m
- Instrumented in May 2010
- The highest lightning incidence (100+
times a year).
SLIDE 40 control room
B-dot sensors 82 m 24 m Rogowski coils
Säntis mountain: 2502 m; Säntis Tower: 123.5 m
SLIDE 41
EMC Box Design
SLIDE 42
Equipment Installation
SLIDE 43 Flat-Plate Sensor for Electric Fields
46 Cut-out disk Metallic box
SLIDE 44 Cross-Loop Magnetic Field Sensor
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NS EW
SLIDE 45 Electric and Magnetic Fields
Slide courtesy of Prof. V. Rakov 48 Flate-plate antenna (vertical E-field) Two loop antennas (Horizontal H-field)
SLIDE 46 How is Lightning Located?
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❖ Well-known (patented) Time-to-Thunder ❖ Direction Finding (DF) ❖ Time of Arrival (TOA) ❖ Interferometry ❖ Peak Amplitude Method ❖ Field Component Methods ❖ Time reversal
SLIDE 47 Time to Thunder
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d = Number of seconds × Speed of sound
Light T h u n d e r
The light is 1 million times faster than sound
d = Number of seconds 3 km
𝑒 = 𝑂𝑣𝑛𝑐𝑓𝑠 𝑝𝑔 𝑡𝑓𝑑𝑝𝑜𝑒𝑡 5 𝑁𝑗𝑚𝑓𝑡
SLIDE 48 Time to Thunder
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❖ Advantages: ❖ Can be used as single station ❖ It does not require any special equipment ❖ Disadvantages: ❖ Low accuracy ❖ Limited range
SLIDE 49 Direction Finding
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The radiated magnetic field is perpendicular to the direction of propagation
H E
SLIDE 50 Direction Finding
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SLIDE 51 Time of Arrival (ToA or DToA)
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SLIDE 53 Commercial LLS sensor
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GPS Antenne Rahmenspulen
GPS antenna
SLIDE 54 European Cooperation for Lightning Detection
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www.euclid.at
IMPACT 181T IMPACT ES IMPACT ESP LPATS III LPATS IV LS 7000
SLIDE 55 Emerging LLS Technology: Time Reversal
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SLIDE 56 Time Reversal Invariance
❖ It is the property of some laws of physics to remain invariant under the T-
Symmetry Transformation
❖ The T-Symmetry Transformation:
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T :t → −t
SLIDE 57 Time-reversal Invariance of Maxwell’s Equations
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∇⋅ ε( r ) E( r,t)
( ) = ρ(
r,t) ∇⋅ µ( r ) H( r,t)
( ) = 0
∇ × E( r,t) = −µ( r) ∂ H( r,t) ∂t ∇ × H( r,t) = ε( r ) ∂ E( r,t) ∂t + J( r,t)
- Maxwell’s equations in vacuum are time-reversal invariant
SLIDE 58 EMTR and Lightning Location
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❖ Record magnetic field at sensors
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- Time-reverse the measured field
- Transmit the time-reversed waveforms back into the
medium by simulation
- Find the point of maximum constructive interference
SLIDE 60 Thank you for your Attention!
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