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Recent Researcwith Implications
illia
Professor of ElecNew Mexico Institute o
Socorro,
on Lightning,or Air Terminals
Risonr
ical EngineeringMining and Technologyew Mexico
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Recent LightninImplications fo
Computer Modeling of
Process
High Speed Videos of t
g Research withAir Terminals
the Lightning Attachment
e Lightning Attachment
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Video by Tom Warner, June 17, 20
High SpeeNegative Cloud to
7,100 Frame
7, near Devils Tower, Wyoming
d Video ofGround Discharge
s per Second
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Video by Tom Warner, June 17, 20 7, near Devils Tower, Wyoming
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Video by Tom Warner, August 4, 2
High Spee
AttachmentNegative Cloud to
7,100 Frame
500 foot tall tower
07, near Rapid City, South Dakota
d Video of
rocess for aGround Discharge
s per Second
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History of Attemptfor ESE Ai
1980s --- Laboratory e
100 s time advantage
Early 1990s --- Push b
1990s --- Prolonged prover proposed NFPA st
Early 2000s --- NFPAstandard and retain NF
2005 through 2008 ---ESE manufacturers
to Pass a StandardTerminals
periments indicate
or ESE air terminals
ESE manufacturers for
cedural and legal fightndard
ecides to reject ESEA 780
ederal court rules against
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History of Attemfor ESE Ai
ESE based on three ass
1) Laboratory time advanpresent in real lightnin
upward leader
3) Upward leader speed i
If these three assumptioESE terminals a 100 m
No input from scientifi
development of standar
t to Pass StandardTerminals
mptions
tage of about 100 s will alsog
about 1 x 106 m/s
ns are true, they will giveter capture radius
community on
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History of Attemfor ESE Ai
No scientific consensus
when the standard was
t to Pass StandardTerminals
on ESE assumptions at
roposed
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Validity of ES
1) Laboratory time advantage of 1
No scientific research indic
Golde (1941), The ValiditModels
there is a question regatest designed to simulatleader and the attachmelengths, tens of meters,
experiment (Rakov & Becerra and Cooray (2008),
be Utilized to Justify the A
Terminals
Assumptions
00 s also present in real lightning
ting that this is the case
of Lightning Tests with Scale
rding the validity of any laboratorythe physics of the lightning steppedt process, since typical leader stepxceed the size of the laboratory
man, 2003)Laboratory Experiments Cannottion of Early Streamer Emission
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Validity of ES
2) Initial early streamer
successful upward lea
No research at time st
oore e aRod Responses to Neastreamers ineffective
Assumptions
ill develop into
er
ndard proposed
easuremen s o g n ngrby Strikes shows early
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Validity of ES Assumptions
Early
streamers donot develop
into leaders
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Validity of ES
3) Upward leader speed i
Not many measuremetime standard propose
,speed of about 1 x 105
Tom Warner tower str1.2 x 105 m/s
Speed of 1 x 105 m/s gradius
Assumptions
s about 1 x 106 m/s
ts of upward leader speeds at
m/s
ke video: average speed of
ives only 10 meter capture
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Validity of ES
Research since the ES
shows all three ESE a
There have been no in
There is now scientifiterminals are ineffecti
It was premature to adterminals in early 199
Assumptions
standard was proposed
sumptions are incorrect
dependent field studies
consensus that ESEe
opt a standard for ESEs
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CVM
Idea initially proposed by
Theory was further devel
Gumley(2000) and DAle
Tested by DAlessandro iKon Petro & DAless
and Petrov, 2006)
istory
Eriksson (1979)
ped by DAlessandro and
ssandro (2002)
Kuala Lumpur and Hongndro 2 1 DAlessandro
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CVM As(DAlessandro a
1) Electric field intensificati
formation of upward lead
2) Critical radius of 38 cm f
the critical value must be
b) [T]he criterion for the inia stable upward leader is tcritical radius
3) Ratio of velocity of dowis about 1.2
umptionsd Gumley, 2000)
on by structures affects
er
om laboratory measurements
rounded off to this value
tiation of corona and consequentlye attainment of 3.1 MV/m at the
ward leader to upward leader
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CVM As(DAlessandro a
1) Electric field intensificati
formation of upward lead This is correct, from basic
umptionsd Gumley, 2000)
on by structures affects
erfreshman physics
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CVM As(DAlessandro a
2) Critical radius of 38 cm f
a) Any sharp geometrical fcritical value must be ro
Moore et al (2000) show
much less than a few cendifferently from those wi
umptionsd Gumley, 2000)
om laboratory measurements
atures with a radius of less that thended off to this value
d air terminals with radius of
imeters behave quiteh radius of a few centimeters
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CVM As(DAlessandro a
2) Critical radius of 38 cm f
b) [T]he criterion for the inia stable upward leader is tcritical radius
It is necessary for the field bedownward leader to be strong
No field measurements to confi
Becerra & Cooray (2007) mo
leader and found this not to b
It is shown that the collectionlightning protection areas of ai
umptionsd Gumley, 2000)
om laboratory measurements
tiation of corona and consequentlye attainment of 3.1 MV/m at the
ween the critical radius and theenough to sustain propagation
rm this
eled development of upward
the case:
olume concept overestimates theterminals placed on complex structures
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CVM As(DAlessandro a
3) Ratio of velocity of dow
about 1.2:1
umptionsd Gumley, 2000)
ward leader to upward leader
During initial upward
leader, velocity ratio is
about 10 to 1
Overall, velocity ratiois about 3 to 1
DAlessandro: [A]higher velocity ratio
yields a smaller
attractive radius
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CVM As(DAlessandro a
3) Ratio of velocity of dow
is about 1.2 During critical initial lea
of upward leader) velocit
This is when other objectswith the air terminal
DAlessandro & Gumley
In fact, if one attempts todoes not have a real soluti
umptionsd Gumley, 2000)
ward leader to upward leader
er development (first 100 feetratio is about 10:1
on the structure are competing
(2001)
use a ratio of 4 [or higher], Eq. (9)n.
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Field Valida(Petrov & DAl
(DAlessandro a
Studies in Hong Kong an
Buildin s rotected b E
according to CVM calcul
Claim to show protection
2 to 15% of low intensity
lightning protection syste
ion of CVMessandro, 2000)d Petrov, 2006)
d Kuala Lumpur, Malaysia
ICO D nas heres laced
ations
levels in the 85-98% range
flashed under 10 kA could bypass
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Field Valida(Petrov & DAl
(DAlessandro a
Study in Kuala Lumpur
Data in stud has been dis
Lightning Research Pte. LtThis review shows that the fis invalid and should not be uof air terminal placement.
No independent verification o
ion of CVMessandro, 2000)d Petrov, 2006)
uted b Hartono & Robiah of
d. of Kuala Lumpureld data given in the above studyed to validate the CVM method
f CVM method
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Field Valida(Petrov & DAl
(DAlessandro a
Two problems with methodo
1 Two different techni ues
with no way to differenti
2) There was no control
ion of CVMessandro, 2000)d Petrov, 2006)
ogy of field study:
were tested with one stud
te between the two
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Field Valida(Petrov & DAl
(DAlessandro a
1) Two different techniquesway to differentiate betw
Study used ERICO DynaCVM technique
If there was an effect, wa
to the CVM?
ion of CVMessandro, 2000)d Petrov, 2006)
tested with one study, with noen the two
spheres placed according to
s it due to the Dynasphere or
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Field Valida(Petrov & DAl
(DAlessandro a
ion of CVMessandro, 2000)d Petrov, 2006)
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Field Valida(Petrov & DAl
(DAlessandro a
2) There was no control
Onl CVM lacement w
Would the results have bplacement method?
ion of CVMessandro, 2000)d Petrov, 2006)
s tested.
en different with another
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Critique Lightning research does
assumptions of CVM
No field study confirmingcritical radius reaches 3.1
Contrary to laboratory stumatter when smaller than
Recent high-speed video ithat leader velocity ratios
Problems with field verif
Having only two field tesby proponents of CVM, iscientific consensus
of CVMot support most of the
leader will develop when field atMV/m
dies, field studies show radius doescritical radius
s in conflict with the assumptionare about 1:1
cation need to be resolved
ts, with same methodology,s not sufficient to meet
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Critique There is no consensus in
CVM is valid
IEEE standards should bby the scientific commun
of CVMthe scientific community that
based on principles acceptedity