roadmap for assessment of lightning mitigation technologies
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Non-Conventional
Lightning Mitigation:
Fact or Fiction?
IEEE PES
2003 General Meeting
July 16, 2003
A Roadmap for
Evaluation of
Lightning EliminationTechnologies
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Purpose of Talk
Review methods that have been used to observeperformance:
Small or large-scale high-voltage tests usingelectrostatic or switching-impulse excitation
Anecdotes and Lack of Damage
Visual Inspection for Damage
Visual Observations during Storms
Measurements of DC or impulse current
Remote measurements from lightning location
systems
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Introduction
Lightning control or mitigation has beenproposed with a wide range of treatments:
The Franklin Rod, a conductive electrode
that provides a preferred path for lightning.
Multiple shells of conductive material,providing increased protection to the interior
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Conventional Protection IEC 61312
Dehn & Shne, 1995
Zone 1
Zone 0
Zone 2
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Introduction
Lightning control or mitigation has beenproposed with a wide range of treatments:
Small conductive electrodes that modify theelectric field, making them more attractive tolightning than a conventional lightning rod.
-Concept of critical radius in switching surge testing
- Rocket triggered lightning
Largeconductive electrodes that modify theelectric field to make a structure less attractiveto lightning.
- Rod-plane versus sphere-plane gap flashover
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Introduction
Lightning control or mitigation has beenproposed with a wide range of treatments:
Semiconductive electrodes intended to limitpeak current and rate of current rise.
Semiconductive electrode extensions such
as laser plasma, liquid jets, glow discharge orstreamers, ionizing radiation
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Laboratory Studies
High-voltage facilities and resources for adequatestudy of leader development are not widely
available.Unfortunately, extrapolation of reduced-scalecorona and nonlinear field effects from small to
larger physical scales has usually beenproblematic.
streamer formation process dominates the impulse
flashover of 0.1-m gaps flashover of 1-m gaps is dominated by leaderformation, with streamer formation contributing a
minor time delay.
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Laboratory Studies Small Scale
200 kV/m
570 kV/m
300 kV/m
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Typical Laboratory Study - Grounding
800 kV, 2us impulse, http://www.deutsches-museum.de/ausstell/dauer/starkst/e_strom2.htm#top
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Typical Field Observations
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Laboratory Studies
Physics of switching-surge flashover at 3-15 m scale hasbeen extrapolatedto the final jump of the lightning,a process that occurs over a 30 to 200-m gap.
Positive switching-surge leaders have speeds of 104 m/s,currents of 0.4A, and linear charge of about 40C/m.Corresponding values for natural lighting are 105 m/s,100A and 1000C/m.Even so, the resulting models [Rizk, Dellera-Garbagnatiadapted by Tarchini] describe many of the same features
as the Electrogeometric model (EGM) that relates theobserved reach of the final jump to the current in theresulting flash.
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Laboratory Studies
Laboratory tests of spherical tips or enhanced airterminals in large rod-to-plane gaps have been usedto address questions of theoptimal size and shapeoftreatments, whether intended to increase or decreasestroke incidence.
Comparison tests of treated and untreated rods are
sensitive to height: An advantage of less than 0.03mwas noted in tests comparing a 72-Curie radioactivesource treatment to a rod.
There is increased leader inception and switching-surge flashover voltage in a 7-m gap for a criticalelectroderadius of greater than 0.4m.
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Typical Field Observations
Lightning triggered by
airplane- Upward branching to sky- Downward branching to
ground- Commercial airplanestypically struck once a year
- Most flashes triggered bythe presence of the airplane
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Electric Field Mapping
LAUNCH PAD LIGHTNINGWARNING SYSTEM (LPLWS)
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Electric Field Mapping
LAUNCH PAD LIGHTNINGWARNING SYSTEM (LPLWS)
Total of 36 flashesin 100 km2
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Anecdotal Interpretation
There was lightning all around.
The flash-to-bang time was less than 15 seconds.
My 220-m (720) tower, recently treated, was notstruck.
The treatment works.
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-7.3 kV/m
Models for Flash Incidence to Towers
96.0248.0
600211.0)9.25(
10hNh
NN g
g
d
Downward Flashes
hkVEgc 1600
Upward Flashes
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Quantitative Interpretation
There was a storm flash density of 0.36/km2.
The expected number of downward flashes to a220-m tower on flat ground would be0.13, basedon the storm flash density.
The expected number of upward flashes from a220-m tower on flat ground would be0.033,based on the observed ground-level field
strength values.
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Quantitative Interpretation
To see a conclusive (2-) difference in treatment, onewould need to observe for a period that would haveproduced n flashes, where
This means that:
4/0.13 = 31 similar storms need to be observed to
comment on the treatment for downward flashes.121 storms would need analysis for upward flashesbased on this distribution of ground-level electric fields.
4
220
n
nnn
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Quantitative Interpretation
Year-to-year variations in storm exposure canbe large: Ng at Bruce NGS
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Example of Adequate Comparison Study
N. Kuwabara, T. Tominaga, M. Kanazawa, and S. Kuramoto, Probability Occurrenceof Estimated Lightning Surge Current at Lightning Rod before and after InstallingDissipation Array System (DAS),1999 IEEE Intl EMC SymposiumPaper 00476,Seattle WA, ISBN 0-7803-5638-1
Before Treatment:26 surges recorded in three years.
After Treatment*:
16 surges recorded in one year.
After Correction for Storm Exposure:
No difference, treated / untreated.* The treatment was penetrated by a 2-m lightning rod, which wouldhave been enveloped by any corona envelope greater than 2 m.
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Example of Adequate Comparison Study
N. K uwabara, T. Tominaga, M. Kanazawa, and S. Kuramoto, Probability Occurrence ofEstimated Lightning Surge Current at Lightning Rod before and after Installing Dissipation ArraySystem (DAS), 1999 IEEE Intl EMC SymposiumPaper 00476, Seattle WA, ISBN 0-7803-5638-1
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Lightning Location Systems
In continental USA/Canada, a sophisticatedand accurate network of receivers has
provided lightning location and amplitudedata since the mid 1990s.
The technology is based on GPS time ofarrival and direction finding based on the
strong radiation from a vertical lightningchannel.
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199906111330.000000
30 kA
Lightning Location Technology
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199906111330.000420
199906111330.0004216 118.6 45.0
Lightning Location Technology
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199906111330.000960
199906111330.0004216 118.6 45.0
199906111330.0009613 52.0 135.0
Lightning Location Technology
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199906111330.001080
199906111330.0004216 118.6 45.0
199906111330.0009613 52.0 135.0
199906111330.0010536 47.4 270.0
Lightning Location Technology
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199906111330.0004216 118.6 45.0
199906111330.0009613 52.0 135.0
199906111330.0010536 47.4 270.0
T=92.3 s
T=539.7 s T=632.0 s
Lightning Location Technology
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199906111330.0009613 52.0 135.0
Lightning Location Technology
199906111330.0010536 47.4 270.0
199906111330.0004216 118.6 45.0
DD+28 km
Hyperbola withT=92 s (28 km)
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Lightning Location System Performance
Location accuracy ofmeasured data from
ALDIS (GAI) lightningdetection network forcorrelated strokes to a
100-m tower inGaisburg, Austria.
The tower is centeredat the origin.
G. Diendorfer, W. Hadrian, F. Hofbauer, M. Mair, W. Schultz, Evaluation of Lightning Location Data Employing
Measurements of Direct Strikes to a Radio Tower, CIGRE Session 2002, paper 33-206
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LLS Observation of Treated Area
FEDEX installation in Memphis, TN
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LLS Observation of Treated Area
FEDEX installation in Memphis, TN
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LLS Observation of Treated Area
FEDEX installation in Memphis, TN
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LLS Observation of Treated Area
FEDEX installation in Memphis, TN
Correct Size of Dots,
Based on 400-m Uncertainty
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Conclusions
Anecdotal data: There was lightning allaround but the treatment was not struck is
inconclusive for typical structure heights andtypical reporting periods.
Quantitative data: The ground-level electricfield Ez >(1600/h) , the treatment reacted and
was/was not struck, instead a nearbystructure/ground was struck.
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Conclusions
Transfer functions are needed between:
Excitation (local static or dynamic
vertical electric fields) and
Treatment effects (visible, UV corona or
related currents)
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Conclusions
Lightning location system data are essential:
For validating time-tagged records of structure
currentsFor normalizing observations of performance
However, holes in the data before and aftertreatment need to be larger than 400-mobservation error and should have enough samplesto be convincing. Locally,
While globally, nafter= nbefore
beforebeforeafterafter nnnn 22
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Conclusions
Direct rather than indirect measurements areneeded to assess treatments.
Before and after treatment, with a minimumof four responses in one group and noresponses, for the same lightning exposure, in
the other group, is convincing.Damage to equipment is a poorly-calibratedmeasure of response, since replacement
equipment often has different (and higher)surge absorption capability.