CHANGCHUN INSTITUTE OF TECHNOLOGY

Lightning Risk on Wind Turbine Generator

Systems

202s� 01.F.J 18 B
Extended Summary *Xii pp.1219-1224

Lightning Risk on Wind Turbine Generator Systems

Takaloshi Shindo Senior Member (CRIEPI. shindo@criepi.dcnken.or.jp)

Tomotaka Suda Senior Member (CRIEPI. 1-suda@criepi.denken.or .jp)

Keywords� lightning, wind turbine. recc-ptor, lightning protection

As the number of \\;nd turbine generator systems is incn:asing, and that in winter are about I (/kn\J) and 0.2(/km2). respectively.
howev er, lightning-caused outngcs are also incn:asing, especially in According to the equntion of the number of lightning strikes l}ascd
lhc coasta1 nrca of the Sen of Japan. In order to establish a rational on the field data. estimated numbers of strikes in summt:r and in
lightning protection design form them. risk management scheme as winter are about 0.5 and 12.6. respectively.
shown in Fig.I i s inevitable. The probability of occurrence of lightning that causes damage on
ln this paper. the basic concept of lightning risk management for a wind rurbine blade: in summer and thnt in winter are 0.1 % aod 5%,
wind turbine generator systems is introduced and present status of if w e assume that the charge of lightning current exceeds 300C,
the research on the lightning risk management is described. Finnlly. which is the proposed ch urge of the protection level I of the CEC
a simplified lightning risk assessment algorithm for wind turbine Technical Rcpon No.61400-24 published in 2002, intolerable dam­
generation systems is proposed. age generates. Therefore the occurrence frequency of damage of
Lightning risk of wind turbine blades without any special protec­ wind turbine blades N r is cnlculatcd as follows.
tion mcasun::s, the risk R is calculated.as follows.
Nr = N .i. · P, +NJ ,,.· P.,.
R = Nr -C = 0.5 · 0.0001 + 12.6 · 0.05
= Nd ·P·C····-· ·····. = 0.68 ... ..... .. ............... ... ... .. ..... ... ...( 3)

where N, is the number of occurrence frequency of damage of wind There wen: reponcdly IO events of damage related to wind tur­
turbine blades, Nd is the nwnbcr of Lightning strikes to the blades, P bine blndcs in the Nikaho-Kogen Wind Farm is in two winter sea­
is the occurrence probabilily of lightning strikes thqt cause damage sons. which is 0.3 3 events per turbine year. This vnJue is somewhat
and C is the cost by the damage of wind turbine blades. smaller than the calculated resulL One of the reasons of this differ­
Co nsidering the difference of lightning chamcteristics in summer ence is \hat the value shown is not included the number (!f repairing
and in winter, E.q.(I) is rewrinen as follows. due to panial destruction of blades but the number of cxchn.nge of
R = CNw · P, + N&- · P.,.) ·C · ..·· .. , ... ... ... ......... (2) blades due to serious destruction of blades.
-If the lightning risk R of n wind turbine blade exceeds a toler­
where suffixes s n.nd w indicate summer nnd winter, respectively. able levd, some meas= ore neccs.sruy. If we set C.,, tbe cost of
ln the Ni.kabo-Kogen IIIt:II, 1J1c ground llnsh density in summer the additional measures including the neccs..<.:1ry maintenance cost
and Km the risk reduction factor by the measures, we get following
n::lationship to be sntisfied for applying the measures.

C111 < Nr · Km ·C ·· ........ ............. ...·······---- (4)

Evnluotion where, K.,. = 0 indicates that there is no effoc1i1� lightniug prot�--c-

tion measure and Kci = I indicates there is n perfect ligbuting pro­
tection mcnsure.
Eq. (4) shows that the re.:isonuble cost of tho additional lightning
protection measures depends on the po."5iblo ris.k reduction ruto th.:it
Is 1111aincd by the rncasurcs. If the cost oflho measurcs i.s larger than
expected. another meas11ru such as tmnsfcr of ri.sk by insurance etc.
should bo con<luc(ed.
l11e concept is 1101 only npplicnblo to the lightning protection of
wind turhino blad.:s but also other components. of w ind turbine gcn­
crntor systems und ligh1ning risk manngcmcat should be cooduc1cd
Fig. I. 8115ic conccpl ligh111ing risk munagcmc111 us 11 10111) power gcncmtion S)'slcm.
 Paper I

Lightning Risk o n Wind Turbi ne Generator Systems

· Takatoshi Shindo' Senior Member
Ton1otal<:a Suda' Senior Member

Recent l y, t)1c nu mber of outages of \v iml turbine generntor systems hns been increa�ing. For rational ligh tning pro­
tec tion design. the concept o f l i ghtning risk mnn ngcme nt has been proposed. fn this paper, l i ghtning risk assessment
of the wind tw-binc gcncrntor systems is cnrried out and it is compnred wi th field experiences, Futthermorc , lightning
risk mnnngement scheme is d iscussed .

KcY"'-oi-<ls: lightning. risk, risk nrnnngc111c11l, wind turbine

■ O o r m a n y ( ( 4 50 , Y/ ) ■ O or m o n y () 4 5 0 kW)
1. Introduction O O e n m o r � ( ( 4 50kW ) Cll D o n m o r k ( > 4 50kW)

A lot of wind turbine generator systems have been con­ 60

structed in Jupan as one of altcrnntive power sources that
arc in hurmony wit h envi ronment. As the number of wi nd
50
,,...__
turbi ne gener.1tor systems is increasing. however, l i ghtn ing­ 40
couscd outages are also increasing, espec ial ly i n the coastnl ::::,
30
n.rcn of the Sea of Japan. In order to csniblish a r:1t ioaa l l ight­ LL 2 0
(lJ

n i ng prot ection design fom1 them, risk management scheme

is i nevitable.. 10
ln this pnper. the basic concept of lightning risk mana ge­ 0
ment for wind turbine generator systems is introduced and B la d e s E le c tric C o n tro l
prese nt stntus of the research on the lightning risk �anage­ s y s te m s s y s te m s
ment is descri bed. Finally. a simpli fied l ightning ri s.k .assess­
Pig. I . Faults by components and size 111
ment nlgorithm for wind turbine generation systems 'IS' p'ra;­
poscd. Tobie I. Damage occum:ncc rates of wind turbine
2. Damage of \Vmd Turbine Generator:- �ystcn,is generator systems in Japan °'
Caused by Lightning Dumagc related LO Dwnngc of control
wind turbine blades systems
2.1 Lightning Damage Frequency Assessment
(/ I OOs) seems/y ear) (/ I OOsvstcms/vcar)
LighLning damage frequencies of wind turbine generator
Total 5. 1 7.6
sys.terns in European countries from I 990 to 1 998 'are 3.9�
Arca or winter l -'-0 6. I
8.0 per I 00 turbine YCfilS '"- Wada ct al. reported tho( field lightning
cxpcric:nces io the coast.al area of I.he Sen of Japan in w i nier 01hcr urea 3.1 7.9
season show thut dumage frequency of wind turbine blades is
nbouJ 36 per J OO turbine yean; a,. which is much lnrger Limn
the vuluc:; in Europe. The vlllues, however, are not nomrnl­ On the other htmd, damage to I.be blnde is the most com­
izcd by the l ightning freq uency in the observed nrca�. mon type of dumnge wi Lh larger turbines (more than 30% in
According lo I.be duUlbose of Lurbinc fou l Ls shown in Ref. Ocm1any und more thun 40% in Denmark). These values a.re
( I ) , mnin components Lhllt ure damaged by lightning directly larger thnn those of smaller turbines in both Germany and
or indirectly llfC blndcs., control systems and electric sys1ems. Denmark . This is because larger turbines 1trc more likely to
'fhc number of fnulLS of .the wind Lurbine generalor sy6tcms be struck by l ig hLning.
below 450kW i1, l nrgar tbllll lllil1 above 450 kW. However, I n Japan, lightning dumuge of wind turbine gcne.rntor sys­
1.hc dnmngc pirttcm i& guite different for I.urger (ocv.-c r) tur­ tems is also i nvestigated by NEDO "\ Ba.scJ. on i nquiri�
bi □cb und r,mullor (older) turbin�. Figure I snows the (uul ls recen t lightni ng dillll,Jgc charactcrisLics an:: su mmarized u.�
of for d 11fcrc111 compoocn� illld r--iz.e of wind turbine gencrn- shown in Tub lc I . The lot al J.nmago occurre lll'e rate of con­
1 or liYbl.CTI�- Wi th t.mallcr turbines (below 4 50 kW), Lhc most trol sys1cms is larger than Lhal rc lulc d 10 w ind turbine blnde.�.
common d uma.gc Will 10 lhc canLrol &y&tCill5 (rn.011: than 30% Ln the area of winte r lightning. however, the dumugo occur•
in Gcm1uny and mme Llwn 50% io DClll.l.Wt) and the faults rcncc rule rclaLeJ to w iJJd turbino bluJcs is much large r than
rutcli urc reduced for lil.f"gor 1urhinc s ( llbO\'C 450 k W ). tlul rclaJcJ Lo co111rol sy �tcrn:;.
' Ccmr al H.cc:u ch lo, i.n1!<' "I .IJ::'..,nt r\.111 r.r ivJJ.:>\f)' 2.2 Co:;t of l>llnwgo 1110 ll\'C rngo repai r co:;t of u 1uu -
2-(>. J , N O,J; ,.,,,..W. YII.Lu»tl.ll :14\l-\\l V(> ugc � cuu�cJ. by lightning fur vnnu11!\ components i� 1115 0
surveyed i n Ref. ( I ) . It is shown that b lade damage is the consideration.
most expensive to repair · (about 3 8000 DEM for turbines Let the numbers of occurrence of the damage shown abov
above 450 kW) . The cost is about ten times larger than those be N 11 , N 12 , No, they are formulated as follows_
of other components and the l arger turbines are more expen­
Nn == A1.sNg, Ptc1s
sive to repair for most types of d amage. Once fn ult of blades
by l i ghtni ng occurs, it also results in large downtimes. It is + A 1,..Ngw P 1 i1w · · · · · · · · · · · - · · · · · · · · · · · · · · · ( I )
same in Japan according to the NEDO report <JI . N12 == Ni;s (A1.sP2c1s + AasP21, )
From these statistics, it i s concluded that the lightning pro­
+ Ngw (A 1w P2dw + Aow P.aw ) . . . . . . . . . . . . . . . ( 2 )
tection o f win d turbine blade is the most important problems
No == Ngi(A1.sPJc1s + AasPJu )
for rational li ghtning protection design of wind turb\ne gen­
erator syste ms. + N gw (A 1w P3d w + Aow PJ;w ) . • • • , . . . . • . . . . . (3)

3. Ligh tnin g Risk Assessment of Wind Turbine where,

Generator Systems N g : ·ground flash density
3.1 Basic Concept or Lightning Risk Management A 1 : Equivalent collection area of a wind turbine
of "rmd Turbine Gene rator Systems B as ic concept ge rierator
of lightning risk management has bcco proposed and the A0 : Equivalent collection area of other systems con­
application to wind turb ine generators systems has been necting to the wind turbine generator
shown '')-{"'· As shown in Fig. 2, l ightning risk management P 1 cli , P2d i , P3cli : Ratio of occu rrence of damage by
cons i s ts of three phase, which are lightning hazard evalua­ the direct lightning hit to the wind turbine gen erator
tion (LHE), lightning risk assessment (LRA) and lightning P 1 1, Pi; , P3i : Ratio of occurrence of damage by the
risk management (LRM). · lightning to other systems connecting to Lhe wind
In the case of wind turbine generator systems, three kinds turbine generator.
of damage sbou Id be considered ''', which are Su ffixes s and w indicate summer and winte r, respectively.
( I ) damage to blades The total risk is defined as follows.
( 2 ) damage to control and communication systems
( 3 ) damage to power systems R == L Nr, C; . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (4)
Let the ground flash densities in summer and in winter b e
where,
N :;;, and N !;"., respectively . Damage to a blade occurs b y di­
rect ligbming to the blade and the number of liijhtning strokes R: total lightning risk of the object
to the blade is evaluated by an equivalent collection area. The N n : number of occurrence of i -Lh damage
collectio area o f an object is defined as an area that when C i': cost by Lhe i-th damage
lightning comes within, l i ghtni ng strikes the object. This
Considering the various measures to reduce the damages
definition considers a downward leader from a thundercould .
b� lightning, Eq . (4) can be rewri llen as follows.
In the case of winter lightning, however, upward lead ers de­
LN
J

velop from earthed objects. Even in that case, an equivalent R == r; · C1 · ( I - Pi) · . . . . · · . . · · · . . . . · · · · · · - - (5)
collection area can be defined as the ratio of the number of
lightning strokes to an object to the ground flash density of where Pi is defined as a risk reduction factor. In the case Lhat
the site. there is no protection, Pi == 0 and if the object is completely
On the oLher h and , oLher two cases may occur by a protected from lightning, Pi == I .
lightning stroke to other wind turbine generators or to the Because the cost of damage of turbine blades is much
ground of the wind farm and such possibility is taken into larger than that of other components and its occurrence fn.'--
quency is also larger for large turbines which have been con­
structed in recent years, only the damage of blades are con­
sidered hereafter.
3.2 Lightning Hazard E\'aluation (LHE) for Wind
1\U"binc Blades Lightning hazard is considered as Ligb!­
oing seve rity and it is di ffe rent for different kinds of damage.
Jo other words, lightning hazard depends oa not only Light­
ning frequency but also the ch..1.racteristics of li ghtning that
L1ghtning cuuses damage on the object. As stated above, lighlniog haz­
ard Lh is not the munber of ligh tning fh1ilics but the possibil­
ity of c,nisi ng a dmnugo is taken in to considcrntion.
Lh == N� · P · · · · · · · · , , · · · · , · , · - · · , · · · · · · · · · , • , · · · (6)
where, N� is the ground flash de nsity and P is the mtio of oc­
currence of lightning that cnuscs damage to an obj(.-Cl in the
area.
In the case of wind turbine blades, the energy of Lightning
fig.. 2. Ba6ic concepl lig,h!Jling ri,k mrumgement ls considered to be imporurn t for the dturn1.gc of wind turbine

1220 tEEJ llnnR PE, Vol. 1 29, No. 10, 2009

 Lightning Risk on Wind Tu1binc Gener.liar S),ecrm

Sun1n1cr lightning

0
I,i:tru,m, frcq<KnC) nup
(1>�()1.,\)
•
\loll we lOlm , 20'.m
�
" 0 I 0-2J</ I •

J�
0

JI:>
�
I 2�•19

I
I I
,I.

I
0
0 150-

\Vin1cr lightning

u�fs�aup

.�
(f>'({)U)
\fall we l<n.m , lOLm

,, " 0 I 0-,'1 I
I I
0
<�N

I
' 0
• ]
I I 1$0- l

Fil l /\J1 u..unpk of llg.hu11111 h.uanl m:ip: lbc u,o of circle 11nd color lntlk!lle Ille nur�, of"111d turb&ne­
and ,�-en1y ,,( the J.un.ap:. J\dup1cJ l111111 NC!OO tcpoll "'

.!Tl.II 8. 12ll '.I 10 ll, 2000 ti 1221

_J
l1fflll
L
0 l
100

t
rd
II(' :.,

J
'll dI
d ll l
O dOl
0 0001
Ill 100 ,aoa
µ.,od-1 cl :tluclDl'ir Cm)

Fit.5. E'srimnred numbc� or gtrike.<I to high structarcs-:

Nomml Im! by ground· Oru;h dcmllry of 1/kn,'1 yenr

Though the average height of a wind turbine is the hu

b height plus 86% of one rotor blade length, it is recom
mended that all wind turbines are modeled as a tall mas
t with a height(h) equal to the hub height plus one rotor
radius.
Therefore number of lightning strikes to wind turbine
�•.1------iiiiiiiiiii---------�
Ill: ,ec ,:,;- •?-' •!II'• ttw" ,cir 1q 144· 146' .
No is expressed as follows.
Nc1 =N2 •91rb 2 ·10- 6 (8)
where h is the wind turbine height in meters.
too of lightn ing current over l00kA in summer The physical background of this equivalent collection
and light- ning frequency, As to lightning in win area is not shown in Ref.(l), though.
ter season, occur- from Rel.(8) Using nu merous field data all over the world, Eriksso
n pro- posed that annual incidence of lightning strikes t
biades. o tall struc- tu res N, is expressed by the fo llowing equati
An example of lightning hazard map for wind turbine on "
gen- which the frequency of lightning of large peak curr N5 =Ng •2. 4x l0-5 ,H:!U5 (9)
ent is considered . Figure 5 shows such lightning freque
ncy maps. Though number of lightning flashes is larger i where Ng is the ground flash density and H is the struc
n summer. only the number of lightning flashes whose c ture height in meters.
urrent peak ex- ceed a critical value is not enough to ev Since 9rr is about 28.3, Eqs.(8) and(9) give similar resul
aluate lightning haz- and. ts.
Figure 4 is an example of lightning hazard map in whi These equations are for lightning in summer season a
ch both charge of lightning c ument and lightning occur nd it is well known that lightning stri king characteristics
rence fre- quency are considered " . This map clearly sh in the coastal area of the Sea of Japan in winter season i
ows the severity of lightning in the coastal area of the s s completely different from those in summer. In the case
ea of Japan in winter season. of winter light- ning, a relationship between the height o
For the evaluation of lightning hazard for wind turbin f structure and num- ber of lightning to the structure(N
e blades, however, the lightning striking cha racteristics a) is proposed'm from the observation results at Fukui,
to them should also be considered. Kashiwazaki, Nakanoto, which are the sites on the coast
As shown previously, lightning striking characteristics of the Sea of Japan.
of tall structures are evaluated by a concept of equivale N 2=H/8. (10)
nt collec- tion area A. Nu mber of lighting strokes to a tal
I structure No is calculated as follows with the equivale where N 4 is the number of lightning strokes in winter
nt collection area. season and H is the structure height in meters.
N4= N2 Ao (7) Considering that the flash density in these areas i n wi
nter season is about 0.2/km 2, the number of strikes to hi
gh struc- tures normalized by flash density is expressed
in the IBC Technical Report " , the equivalent collecti as follows.
on area A. is the a rea exciosed with a border line obtain
ed from the mienection between the g ronud surface an (11)
d a straight line with a 1: 3 alope which passes from the
upper parts of the sincian and relating around it. Figure 5 shows the height dependence of number of str
ikes to high structures in summer and in winte The critic
al current value that causes damage to wind turbine gen
erator systems depends on the protection mea- sures eq
ui pped on the system. Model experiments with im- pulse
voltages shows da mage on blade surface esily oc- press
ure increase due to the arc discharge inside the blade is

7 I
 Lightning Risk on Wind Turbine Generator Systems

As an example, we will calculate the occurrence frequency

or damage or wind turbine blades of the N i kabo-Kogen Wind
99.9 ♦ .Conlinuou5
Fnrm , There arc 15 wind !Urbine generators in 1hc Nikaho­
99
•• .& :\\'Ith pulse
O :Totnl
Kogen Wind Farm and !he maximum height of these wind
o
turbines is nboul I 00 meters. Jn lhc Nilw ho-Kogcn area. the
90 ground nosh density in summer and Iha! in winter arc abou1
.: � '
I (/km2 ) mid 0.2 (/km2 ), respectively. According to Fig. 5. es­
70 Limn ted numbers of strikes in summer and in winier are about
so \t 0.5 und 1 2 .6, respectively. The probability of occurrence of
30 lightning Iha! causes damage on a wind turbine blade in sum­
&\
10 & mer and thal in winter arc 0. 1 % and 5%. as shown in the pre­
&
vious section. Therefore the occu rrence frequency of damage
of wind turbine bl odes Nr is calculated as fol l ows.
�- Nr = Nw · P, + Ndw · Pw
0.01 OJ 10 1 00 1 000 = 0.5 · 0.000 1 + 1 2.6 · 0.05
Charge nmounl (C) = 0.68 . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ✓ - • ( 1 4)
Fig. 6. Cumu !alive frequency distribution of charge
nmount of lightning currents striking wind turbine in win­ There were reportedly 1 0 events of damage related to wind
ter season ,,., turbine blades in the Nikaho-Kogen Wind Farm is in two win­
ter seasons <n, wh ich is 0.33 events per !Urbine year. This
unlikely to occur i f the down conductor system is sufficiently value is somewhal smaller than !he calculated resul1. One
ins1al l ed "J) . Though 1hc damage on blade su rface depends of the reasons of th is wfference is !hat the value shown in
on the energy of l ightning, mechanical stress to the blades by Ref. (2) is not included 1he number of repairing due to partial
wind or rotation of the b lade itself is also important for the deslruction of blades but the number of exchnnge of blades
destruction of b lades. due 10 serious destruction of blades.
Because there is not enough data 10 determine the critical O1her possible reasons of 1he difference arc as foll ows_
current or energy al presenl, it is assumed that !he charge ' ( I ) Recenl wind !Urbine blades have receptors 10 i nter­
of ligblning currenl exceeds 300C, which is the proposed cept lightning strokes and they lessen the damage o f wind
charge of !he protection level I oflhe IEC Technical Report <ll , !Urbine bl odes even for l ightning strokes of which ch arge ex­
intolerable damage generates. ceeds 300 C. Th is hypothese is partly supported by the fact
. 9
Figure 6 shows the charge distnbution of ligh_tn ing to wmcf !hat recent survey indicates smaUer clamnge rate of wind tur­
t urbine generator systems observed at !he ·Nikaho- Kogen bine blades Lhan the estimated value even i n the area of winter
Wmd Farm o •i_ lightning as shown in Table I .
Considering cbe data shown in Fig. 6 and observation re­ ( 2 ) It is known !hat detection efficiency of Lightning lo­
sul ts of lightning al Fukui Lherrnal power plant 0 " , the proba­ cation systems is smaller that that of summer l.ightning. Ob-­
bility that cbe charge amoun1 is more Lhan 300 C is aboul 5 % served l ightning flash density of winier lightning observed
in the case o f win ier lightning. by l ightning location systems may be Lhe�fore smaller than
In the case of Ligb1ning strokes in summer, the chnrge nctunl flash density.
amount is usually much smal ler Iha! in winter. From sto­ Though '!here is not enough data for Lightning risk assess­
t.istical data obt.ai ned so far"0' , the probabi lity that the charge ment of wind turbine generator.;; systems a1 present, obser­
amount exceeds 300 C is considered to be less 1hnn 0. 1 %. vation of winter lightning to wind turbine generator systems
3.3 Lightning Rlsk Assessment (LRA) for Wi nd Tur­ has been carried oul at seveml sites in Japan. The results will
bine Blades Lightning risk of wind turbine blades with­ reveal detailed l ightning striking chantctcristics 10 wil.Hl tur­
out any speciul protect.ion measures, the risk R is calculoted bine gcnerntor systems, 1he level of dwnage caused by light­
us foUows. ning, and the elkcl of various lightning protection methods
R = Nr · C equipped on wind turbine gcncrn!Or systems. B:ise<l on Lbcse
dn1a, more precise risk assessment will be nl:lde in future.
== Nd · P · C · · · · · · · · · · · · · · · · , , • • · , · , , , , , · , , · · · ( 1 2) 3 .4 Ligh lnlng Risk l\lanagcmcnt (LRi\l) for Wind
where N r is I.be number of occurrence frequency of damage 1\1rbine Generator Systems If the ligh11ung risk R of a
of wind turbine bludcs, N d i.i; I.he number of lightning strikes wind turbine blade exceeds a tokrublo lcvd, some mc::isl.J.fCs
10 the blades, P is the occurrence probabi lity of lightning ure ncc�ssnry. The lightning risk w i th ad<l itiooul ligbLning
strikes IJlll.l cuusc damage and C is the cost by !he danwge protection mca:;un:s Rm is cxp1cssc<l a.� foUows,
of wind turbine blades.
Considering !be di fference of lightn.iug charnctcri.s1ics in R = Nr · C · ( I - Km) + Cm · · · · · · · · · · , . . · · · . . . . ( 1 5)
111

summer and in winter, Eq . ( 1 2) is rewriuen ai; folLows. whcrn Cm is the cost of the 11d<li tionul me:i.sures indud.ing the
R == (N d, · P, + N dw • P,.. ) · C . . . , . . . . . . . . . . . . . . - - ( 1 3) neccssury muintcnanco cost and K m i.s the risk reduction fac­
tor by the measures . K111 ;= 0 indicates tbut the IC is no effective
when: sulfi xe1, 6 and w indicate sununcr an.d winter, rcs peF­ lightning protection mctt:mre und K 111 = I i.J1d icute;:; th ere is u
t.ivcly. perfect lightning protection mcasw-c.

-�·I.ii B, 128 4 10 ij , 2008 If- 1 223

 The value R m should be less than R in Eq. ( 1 2) ; that is, Omferrna: on Lightning Pmu:cti00 (ICLP). Vlll..J, 1um,.,,..,. 0)06)
( 6 ) I. S hiruJo and T. Sud>: "A Sa:,dy of Ligbmmg Ri>t for V.u:ioa,< F.rilitio".
N f · C > N f • (I - Km) · C + Cm · · · · · . . · . . . . · . . • · ( I 6) The P:,pcr af Join1 T<elmioJ Mo:tia: on EkctJX� Di.KllJrj;c,.. s ..-iu:t,.
ing mJ Pro<ccting Engino::ring and High \'o!t,gc Eogicccriog. IEE l'1{X11l.
Eq. ( 1 6) is transfom1cd as follows. Na.ED-07-1 46. SP--07.SJ. IN--07- 1 26 (]!JJ7) (ii, h!""cx)
( 7 ) "/\ OuiJclinc of wiod turbine gcocnt>r ')�tan• in J,pan", NEDO Report
Cm < N f • Km · C · · · · · · · · · • · · · · · , , · · · · · , • , , , , · · · ( 1 7 ) (2008) (lo J,p:,nc:,c)
( 8 ) T. Shindo nnd T Sudr tllliic coocc� of lightning rhk m:inagrnroC,
OUEPI Rcpo�. NoJ10600!! (2J1J7J (In h p:i ocsc)
Eq. ( 1 7) shows that the reasonab le cost of the ndditionaJ (9) /\J. Em.Suon: "lk in cide nce or lightning suilc1 lo power liad". IEEE
· l ightning protection measun:!s depends on the possible risk Trunt /lm,r D<lli,ry, ¼IJ'WRD-2. Na.J. pp.859-870 ( 1997)
reduction rate that is attained by the measure s. If the cost of '( 10) ll'orl:ing Grou p on Lightning l'Jotectioo for T=<mUSWO Sy<tcm<: "Llgb!­
the measures is lnrger thnn expected, another mcnsttrc such ning ob,cm,tions on Japan Sc coasl in winier, CRIEPI Report. No.TIO
( 1989) (in Jop:ioc:sc)
us transfe r of risk by insurance etc. should be conducted. (11) T. N,b. NJ. Vasu. S. Yolo�rm. A. W,cu. /\. A<:tuwa. H. Hood:>, K.
In this p aper, we have cnrricd out lightning risk assessment Tsutsumi, and S. Arin.iga: --Srudy on lightning pro tecti on mc1ho<ls for u.�ncf
and lightning risk management for on ly wind turbine blades. 1urbinc bbdc<. /EEJ Tru,u. PE:.. Voll 25. No. 10. pp-99J.-9?9 (2005-IO)'
Iii,..
'\"1 12 ) I. Shinda. A. /\siliwa. und M. Mil:i: "A <1udy of llgblning urik.Jng ch.ace,,
The concept is, however, applicable to the lightnin g protec­ 1erhtics of wiod lurbinc,", 19!h lnlcrnll<iorul Confcrcocc on Li g h<ning Pro-
tion of other components of wind turbine generator systems 1cctioo (]CLP). No.9c-1, Upp s:ila (200!l )
and lightning risk management should be conducted as a total ( I) ) )'. Goda. S. Tu=b. and T. Oh<ili: •/\re lesu of wiod !Urbine hl.xle< <imo­
power gcncrntion system. L,ting high energy lighllling strikes, 29th lntcmlliorul Conference on Ug h<•
ning Protection (10.P). No.9c-S. Upp,ai, (2008)
As to the lightning risk assessment of control systems and ( 14 ) A. /\s:il.:awa.. A. Wod:J., S. Yolo)'ama. T. Shindo, K. Hochiya. and H.
communication systems, damage by civervoltages generated Hyodo: "DcYelopmcn< of "idc fn:qucncy bond RogowskJ coil and cv:ilao­
by lightning strokes to wind turbine gene rator systems are tion of electric ch:lrgc in 1<1n<cr lightning-Li ghtning obsCtY.llioa n:sulL< for
dominant. l11e study of these overvoltages also have bee n winJ 1urbinc ,t Ni.Ii.oho Wind Pork in 2005 win<cr so.son-". CRIEPI Rcpon,
1':o.H060IO (2005) (ia Japan=)
carried out both e x perimentally and theoreticaJly < •n_ Based ( 15) I. Shindo. S. Yol:oymn,. T. Sunaµ. I\. l\s.;ibwa. H. Motoy:>nU. /\. WJd:>.,
on these studies. the critical current that exceeds the toler­ and H. Ga>himJ.: "Lightning c:lunc<cri<1ics in wia<cr ,co.sou ,o a high
.ance level of the low voltage system will be determi ned. st:1cl:-Tcn-rcar obscrntion n:suli. from 1989-1991l w Fukui obsc:rv-Jlion
.J1c-". CRJEPI Rcpon. No.TS8 ( 1999) (in fa pan=)
4. Conclusions ( 16) K. Berger. R.a /\odcnoo. and H. Kroniagcr: ·P:iramc:la of lightning
O:><hcs". ELECTRA. No.4 1 . pr-:D-37 (1 975)
The lightning risk assessment is carried out and the calcu­ ' ( 17) K. Yam:imo<o, cl ,I: "Etpcrimcnul and analytical s<udics of ligh<ning OV'Cl'­
volu;c-s in 'io\lod turbine gcncralor ��cnu. .., 2007 Intcrnalionnl Coafcn:ncc
lated damage occurrence rate of wind turbine blade shows
on Power Sy,1cnu Trun�cnts OPST). Lyon (2007)
reasonable agreements with field ex perience. In the view
of lightning risk munagement, the reisonable cost exjsts for.7
l igbtrung protection measures and if it is ·not attainable, other
measures such as risk transfer is needed'. Tnkntoshl Shindo (Senior Member) was born in Tol..'Yo, Japan on
For future study, we will propos� .� ,lighrning risk manage November 2 1 . 1 953 .. He rccei\'cd lhe B.S. degree
and M.E. degree in eleclTical engineering and Pb.D.
scheme for the Lola) wind turbine power generation system. degree in engineering from the Univcr,ity of Tok'Yo,
Acknowledgment Tokyo. Jupan in 1976, 1 978, and 1 992. rcspc"-"li,-ely.
The authors would like to express their sincere· thank to the He joined !he CcnlTUI Research Institute of Electric
members of the Lightrung Risk Workfog Group of the Cen­ Power Industry. Tokyo. J:ip:in. in 1978. He 11:is been
tral Electric Power Council for the valuable discussion and engaged in the study of c." tcrnal ins:ulurion of power
n pparatus.. p:inicubrly with regard to ligh tning pro­
comments. tection. phys ics of clisch.:trge in long uir gaps. From
(Man uscript received Jan. 6, 2009, 1987 10 1988. he wns u Rcsc.·uch Associate in the Department of Elccaicul
revised Feb. 25, 2009) Engineering. Universi1y of Florida Dr. Shindo tS a member of the Society
of At mospheric Electricity of fap:m. the lnsti1u10 of Engin=-s on Electrical
Di.,churgc rn Japan, itnd a Fellow of JEIIB.
References

( I J -Wmd turbmc g,:na:uJ.orsy•�un vi: Uglurnmg protcaloo", IECTcch­ Tomolnku Sudu (Senior Member) wus born in Naga no Prefecture in
ruc.,I P..cpo<t. No TI 61 400-24 (2002) Jap.m on October 30. 1950, Ho fC\.--C i\'es B.S. dc-­
( 2 J A. Wod.1. S Yol:Dyonu., T. Nwuuc,. Y l,,WlllrJ1I, aruJ T. l l lrnl<l: "IJghtninn grc., and I\LS. degree in clcctricul cngin<Xring fro111
c:1:u.n� u1 �'lod wrb1oc bWdc in �\Ula lo J�p;11)-Uglu11i11g oh,cn1Jliou Pl Toho"l.l Uni\'crsity, Sendai. Jupau in l973 and 1976,
1bc �ho--Y.ogc:o wltld farm-", 27111 lrucmallonal Con/c1cncc on Llghl• rc.spc,."liYcl)', ond n D- Eng. cL:;,rr<-e in ckcttioJ en­
rune Pru1a1100 (10.J'J. l\o.9� 7, A>·ig.oon (lDOl) gineering from KyU>hu Unhcc;ily, Full.lok:i.. fop:in
f 1 J '"2001 · Ile, ,c. cA �J;nlnUl8 p<w:= mclboJ, for -..u.J twbiru: �OlCr.>tor
"J'IKlllD". NEDO Rq,on (2U06) lto J,flo'lloc) In 19(}.l. In 1 97 6. ho joiocd the Ccntr.>I Rcseun:b

ccpt l>od tlc Loti:,:J cA •=·.

( 4 J I. 5lundo and T Sud... -Ugi,lilU\g ri» mo1111J6""10ll-Tbc fund,olC'illUI con•
Tbc Pupc, ur laiul Tochnkol Ma:llllJJ on
Elactnc»I Du.d>;,ri;c>. Swllc:hin; and l'Jow::tlng E.o[µx:crws anJ lllgh Voll•
lll.Slilulo of Elo:ttic I\Jwcr lndU>Uy. Tokyo, Jo.pan,
nm) ,inru lhcn. ho b.J.S \\Otkod on Ibo �tudy uf ion
now clcc11i llca1 iun phcnoru.,na on HY d,;: a--'1ll>lilis­
� En,.=nut- � J"!=, Nu .l'.JH)� I J 2. Sl'-0.l- .10. IIV-0.l-� aoo.11 (111 •ion lines. i mulamr c,mta111ina1io1� oud lighlnlng phcnomcru. Dr. Sud.li Is.
J.,fllll'CC) � mc111hcr of the Socio !)' of AlmL'>ph<1ric Elc-, trk ily of lu(lillt und a Senior
( � J T Sbiodo Aod T. Suda; "On Ui;liwu1g ruk ""'ll.>;!O:llcuf". 28th ln1<m1ui<m11I Mc111b.,r or IEllH.

1 224 IEEJ Ttil/15. PE, Vot 129, No. 10, 2009

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