SLIDE 1 Recent Research with Implications f
William William
Professor of Elect New Mexico Institute of Socorro, Ne
ch on Lightning, s for Air Terminals
am Rison am Rison
ectrical Engineering
, New Mexico
SLIDE 2 Recent Lightning Implications for
Computer Modeling of t
Process
High Speed Videos of th
Process Process
ing Research with for Air Terminals
f the Lightning Attachment f the Lightning Attachment
SLIDE 3
Video by Tom Warner, June 17, 2007, ne
High Speed Negative Cloud to G 7,100 Frames
17, 2007, near Devil’s Tower, Wyoming
eed Video of to Ground Discharge es per Second
SLIDE 4
Video by Tom Warner, June 17, 2007, ne 17, 2007, near Devil’s Tower, Wyoming
SLIDE 5
Video by Tom Warner, August 4, 2007, ne
High Speed Attachment P Negative Cloud to G 7,100 Frames
500 foot tall tower 4, 2007, near Rapid City, South Dakota
eed Video of t Process for a to Ground Discharge es per Second
SLIDE 6 History of Attempt for ESE Air
1980’s --- Laboratory ex
100 µs time advantage fo
Early 1990’s --- Push by
adoption of an ESE stand adoption of an ESE stand
1990’s --- Prolonged pro
Early 2000’s --- NFPA d
standard and retain NFP
2005 through 2008 --- Fe
ESE manufacturers
pt to Pass a Standard ir Terminals
experiments indicate e for ESE air terminals by ESE manufacturers for andard andard procedural and legal fight standard decides to reject ESE FPA 780 Federal court rules against
SLIDE 7 History of Attempt for ESE Air
ESE based on three assu
1)
Laboratory time advant present in real lightning
2)
Initial early streamer w
2)
Initial early streamer w upward leader
3)
Upward leader speed is
If these three assumption
ESE terminals a 100 met
No input from scientific
development of standard
pt to Pass Standard ir Terminals
sumptions
antage of about 100 µs will also ing will develop into successful will develop into successful is about 1 x 106 m/s
ions are true, they will give eter capture radius fic community on ard
SLIDE 8 History of Attempt for ESE Air
No scientific consensus
when the standard was p
pt to Pass Standard ir Terminals
us on ESE assumptions at s proposed
SLIDE 9 Validity of ESE
1)
Laboratory time advantage of 100
- No scientific research indica
- Golde (1941), “The Validity
Models”
- “there is a question regar
test designed to simulate leader and the attachment lengths, tens of meters, e experiment” (Rakov & U
- Becerra and Cooray (2008),
be Utilized to Justify the Act Terminals”
SE Assumptions
100 µs also present in real lightning ndicating that this is the case dity of Lightning Tests with Scale garding the validity of any laboratory te the physics of the lightning stepped ent process, since typical leader step , exceed the size of the laboratory Uman, 2003) 2008), “Laboratory Experiments Cannot ction of Early Streamer Emission
SLIDE 10 Validity of ESE
2) Initial early streamer w
successful upward lead
- No research at time sta
- Moore et al (2000) “Me
- Moore et al (2000) “Me
Rod Responses to Near streamers ineffective
SE Assumptions
r will develop into ader
standard proposed Measurements of Lightning Measurements of Lightning earby Strikes” shows early
SLIDE 11
Validity of ESE SE Assumptions
Early streamers do not develop into leaders
SLIDE 12 Validity of ESE
3) Upward leader speed is
time standard proposed
- Now, several measurem
- Now, several measurem
speed of about 1 x 105
1.2 x 105 m/s
radius
SE Assumptions
d is about 1 x 106 m/s
ents of upward leader speeds at sed rements of upward leaders show rements of upward leaders show m/s trike video: average speed of gives only 10 meter capture
SLIDE 13 Validity of ESE
shows all three ESE as
showing ESE terminals showing ESE terminals
terminals are ineffectiv
terminals in early 1990
SE Assumptions
SE standard was proposed assumptions are incorrect independent field studies als are effective als are effective fic consensus that ESE tive adopt a standard for ESE 90’s
SLIDE 14 CVM H
- Idea initially proposed by
- Theory was further develo
Gumley(2000) and D’Ales
- Tested by D’Alessandro in
Kong (Petrov & D’Alessan Kong (Petrov & D’Alessan and Petrov, 2006)
History
y Eriksson (1979) eloped by D’Alessandro and lessandro (2002) in Kuala Lumpur and Hong sandro, 2001, D’Alessandro sandro, 2001, D’Alessandro
SLIDE 15 CVM Assu
(D’Alessandro and
1)
Electric field intensificatio formation of upward leade
2)
Critical radius of 38 cm fr
a)
“Any sharp geometrical fea
a)
“Any sharp geometrical fea the critical value must be “
b)
“[T]he criterion for the init a stable upward leader is the critical radius”
3)
Ratio of velocity of downw is about 1.2
ssumptions
and Gumley, 2000) tion by structures affects ader from laboratory measurements
features with a radius of less that of features with a radius of less that of be “rounded off” to this value” nitiation of corona and consequently s the attainment of 3.1 MV/m at the
nward leader to upward leader
SLIDE 16 CVM Assu
(D’Alessandro and
1)
Electric field intensificatio formation of upward leade
- This is correct, from basic
ssumptions
and Gumley, 2000) tion by structures affects ader
ic freshman physics
SLIDE 17 CVM Assu
(D’Alessandro and
2)
Critical radius of 38 cm fr
a)
“Any sharp geometrical fea critical value must be “rounde
- Moore et al (2000) showed
- Moore et al (2000) showed
much less than a few centi differently from those with
ssumptions
and Gumley, 2000) from laboratory measurements
features with a radius of less that the
- unded off” to this value”
ed air terminals with radius of ed air terminals with radius of ntimeters behave quite ith radius of a few centimeters
SLIDE 18 CVM Assu
(D’Alessandro and
2)
Critical radius of 38 cm fr
b)
“[T]he criterion for the init a stable upward leader is the critical radius” It is necessary for the field bet
- It is necessary for the field bet
downward leader to be strong
- No field measurements to confir
- Becerra & Cooray (2007) mode
leader and found this not to be
- “It is shown that the collection v
lightning protection areas of air
ssumptions
and Gumley, 2000) from laboratory measurements
nitiation of corona and consequently s the attainment of 3.1 MV/m at the between the “critical radius” and the between the “critical radius” and the
- ng enough to sustain propagation
firm this
- deled development of upward
- be the case:
n volume concept overestimates the air terminals placed on complex structures”
SLIDE 19 CVM Assu
(D’Alessandro and
3)
Ratio of velocity of downw about 1.2:1
ssumptions
and Gumley, 2000) nward leader to upward leader
leader, velocity ratio is about 10 to 1 about 10 to 1
is about 3 to 1
higher velocity ratio yields a smaller attractive radius
SLIDE 20 CVM Assu
(D’Alessandro and
3)
Ratio of velocity of downw is about 1.2
- During critical initial leade
- f upward leader) velocity
- This is when other objects
with the air terminal
- D’Alessandro & Gumley (
- “In fact, if one attempts to
does not have a real solution.”
ssumptions
and Gumley, 2000) nward leader to upward leader ader development (first 100 feet ity ratio is about 10:1
ts on the structure are competing
y (2001)
to use a ratio of 4 [or higher], Eq. (9) ution.”
SLIDE 21 Field Validat
(Petrov & D’Ale (D’Alessandro an
- Studies in Hong Kong and
- Buildings protected by ER
- Buildings protected by ER
according to CVM calcula
- Claim to show protection
- 2 to 15% of low intensity f
lightning protection system
ation of CVM
lessandro, 2000) and Petrov, 2006) and Kuala Lumpur, Malaysia ERICO Dynaspheres placed ERICO Dynaspheres placed ulations
- n levels in the 85-98% range
ty flashed under 10 kA could bypass tem
SLIDE 22 Field Validat
(Petrov & D’Ale (D’Alessandro an
- Study in Kuala Lumpur
- Data in study has been disp
- Data in study has been disp
Lightning Research Pte. Ltd “This review shows that the fie
is invalid and should not be us
- f air terminal placement.”
- No independent verification of
ation of CVM
lessandro, 2000) and Petrov, 2006) sputed by Hartono & Robiah of sputed by Hartono & Robiah of
field data given in the above study used to validate the CVM method
SLIDE 23 Field Validat
(Petrov & D’Ale (D’Alessandro an Two problems with methodolo
1)
Two different techniques
1)
Two different techniques with no way to differentia
2)
There was no control
ation of CVM
lessandro, 2000) and Petrov, 2006)
es were tested with one study, es were tested with one study, tiate between the two
SLIDE 24 Field Validat
(Petrov & D’Ale (D’Alessandro an
1)
Two different techniques way to differentiate betwe
CVM technique
- If there was an effect, was
to the CVM?
ation of CVM
lessandro, 2000) and Petrov, 2006) es tested with one study, with no ween the two naspheres placed according to as it due to the Dynasphere or
SLIDE 25
Field Validat
(Petrov & D’Ale (D’Alessandro an
ation of CVM
lessandro, 2000) and Petrov, 2006)
SLIDE 26 Field Validat
(Petrov & D’Ale (D’Alessandro an
2)
There was no control
- Only CVM placement wa
- Only CVM placement wa
- Would the results have be
placement method?
ation of CVM
lessandro, 2000) and Petrov, 2006) was tested. was tested. been different with another
SLIDE 27 Field Validat
(Petrov & D’Ale (D’Alessandro an
- Data from field study hav
- If there were an effect, there is
- If there were an effect, there is
was due to CVM or Dynasphe
- No control
- No independent verification of
ation of CVM
lessandro, 2000) and Petrov, 2006) ave been disputed.
e is no way to determine if the effect e is no way to determine if the effect phere
SLIDE 28 Critique o
- Lightning research does n
assumptions of CVM
- No field study confirming
critical radius reaches 3.1 M
- Contrary to laboratory studi
matter when smaller than c matter when smaller than c
- Recent high-speed video is
that leader velocity ratios a
- Problems with field verifi
- Having only two field test
by proponents of CVM, is scientific consensus
e of CVM
s not support most of the
ng leader will develop when field at 3.1 MV/m tudies, field studies show radius does n critical radius n critical radius
- is in conflict with the assumption
- s are about 1:1
ification need to be resolved ests, with same methodology, , is not sufficient to meet
SLIDE 29 Critique o
- There is no consensus in t
CVM is valid
by the scientific communi
- It is premature to adopt CV
- It is premature to adopt CV
e of CVM
n the scientific community that be based on principles accepted unity CVM into IEEE standard CVM into IEEE standard
