roadmap for assessment of lightning mitigation technologies

7/29/2019 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


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


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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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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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



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199906111330.000960

199906111330.0004216 118.6 45.0

199906111330.0009613 52.0 135.0



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199906111330.001080

199906111330.0004216 118.6 45.0

199906111330.0009613 52.0 135.0

199906111330.0010536 47.4 270.0



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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



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199906111330.0009613 52.0 135.0


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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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.

roadmap for assessment of lightning mitigation technologies

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