IEC TR 62874 Edition 1 0 201 5 05 TECHNICAL REPORT Guidance on the interpretation of carbon dioxide and 2 furfuraldehyde as markers of paper thermal degradation in insulating mineral oil IE C T R 6 2[.]
Trang 1IEC TR 62874
Editio 1.0 2 15-0
Guidance on t he int erpret at ion of carbon dioxide and 2- fur uraldehyde as
markers of paper t hermal degradat ion in insulat ing mineral oi
Trang 2THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyr ight © 2 15 IEC, Ge e a, Switzer la d
Al rig ts r es r ve Unle s oth rwis s e ifi d, n p rt of this p blc tio ma b r epr od c d or uti z d in a y form
or b a y me n , ele tr onic or me h nic l in lu in p oto o yin a d microfim, with ut p rmis io in wr itin from
eith r IEC or IEC's memb r Natio al Commite in th c u tr y of th re u ste If y u h v a y q e tio s a o t IEC
c p r i ht or h v a e q ir y a o t o tainin a ditio al ri hts to this p blc tio , ple s c nta t th a dr es b low or
y ur lo al IEC memb r Natio al Commite for ur th r informatio
Th Intern tio al Ele trote h ic l Commis io (IEC) is th le din glo al org niz tio th t pr ep res a d p bls e
Internatio al Sta d r ds for al ele tri al ele tr onic a d relate te h olo ie
Abo t IEC p blc tio s
Th te h ic l c nte t of IEC p blc tio s is k pt u d r c n ta t r eview b th IEC Ple s ma e s re th t y u h v th
late t e itio ,a c rr ig n a or a ame dme t mig t h v b e p bls e
IEC Cat alo ue - webst ore.e ch/ cat alo ue
Th st an -alo e a plc t io for c n ultin th e tire
biblo ra hic l informat io o IEC Intern tio al Sta d rd ,
Te h ic l Sp cific tio s, Te h ic l R ep rts a d oth r
d c me ts A v aia le for P , Ma OS, A ndroid Ta let s a d
iPa
IEC p blc t i ns s arch - www ie ch/ se rch u
Th a v an e s arc e a le t o fin IEC p blc t io s b a
variety of crit eria (efere c n mb r, t ext, t ec nic l
c mmitt e,…) It als gives informatio o projec t s, re la e
a d wit hdrawn p blc tio s
IEC Just P blshed - webst ore.e ch/ just pu lshed
St ay u to d te o al n w IEC p blc tio s Ju t Pu ls e
d t ais al n w p blc t io s rele s d A v aia le o ln a d
als o c a mo t h b emai
Ele t ro edia - www ele t ro edia.org
Th world's le din o ln dic t io ary of elec t ro ic a d
ele t ric l t erms c ntainin more t ha 3 0 0 terms a d
d finitio s in En ls a d Fre c , wit h e uiv ale t t erms in 15
a ditio al la g a e Als k nown a t he Int ern t io al
Elec t rot ec nic l Vo a ulary (IEV ) o ln
IEC Glos ar y - st d.e ch/ glos ary
More t ha 6 0 0 ele t rot ec nic l termin lo y e t rie in
En ls a d Fre c e tra t ed fom t he Terms a d Definitio s
cla s of IEC p blc t io s is u d sin e 2 0 Some e t rie
h v e b e c le t ed fom e rler p blc tio s of IEC TC 3 ,
7 ,8 a d CISPR
IEC Cust omer Servic Cent re - webst ore.ec ch/ csc
If y ou wis to giv e u your fe d a k o t his p blc tio or
n e furt her a sista c , ple s c nta t t he Cu tomer Serv ic
Ce t re:c c@ie c
Trang 3IEC TR 62874
Edit io 1.0 2 15-0
Guidance on t he int erpret at ion of carbon diox ide and 2- fur uraldehyde as
markers of paper t hermal degradat ion in insulat ing mineral oi
Trang 4FOREWORD 4
INTRODUCTION 6
1 Sco e 7
2 Normative ref eren es 7
3 Sig if i an e 8
3.1 General 8
3 2 Thermal an mec anical degradation of p p r
8 3.2.1 General 8
3.2.2 Imp ct of temp rature 8
3.2.3 Imp ct of h midity an ox gen 9
3.3 Symptoms of p p r agein in in ulatin oi 10 3.3.1 General 10 3.3.2 Volati e by-prod cts 1
3.3.3 Soluble by-prod cts 1
3.3.4 In oluble by-prod cts 1
3.4 Op rational p rameters in uen in p p r thermal agein 1
3.5 Role of oi typ an con ition 12 3.6 F ult con ition that may af fect thermal agein 12 3 7 Maintenan e o eration that may aff ect thermal agein in icators 1
3 3.7.1 General 13 3.7.2 Ef fects of oi recon itionin 13 3.7.3 Ef fects of oi reclamation 13 3.7.4 Ef fects of oi c an e 13 4 Monitorin protocol 14 4.1 General 14 4.2 Parameters 14 4.2.1 Basic monitorin 14 4.2.2 Complementary monitorin 14 4.3 Recommen ed testin f req en ies 14 5 Typical values of p p r agein s mptoms 15 5.1 General 15 5.2 F mi es of eq ipment 15 6 Estimation of p p r thermal degradation an agein rate 16 6.1 General a pro c 16 6.2 Practice 16 7 Action 17 An ex A (informative) Typical values ta les 19 A.1 General warnin 19 A.2 2-FAL typical values 19 A.2.1 General 19 A.2.2 F miy: GSU (generation ste -up u its) 19 A.2.3 F miy: network tran mis ion u its 2
A.2.4 F miy: large distribution u its 2
A.2.5 F miy: in u trial distribution u its 2
A.2.6 F miy: LVDC u its 21
Trang 5A.3 Carb n dioxide typical values 21
A.3.1 General 21
A.3.2 F mi y: GSU (generation ste -up u its) 21
A.3.3 F mi y: network tran mis ion u its 21
A.3.4 F mi y: large distribution u its 2
A.3.5 F miy: in u trial distribution u its 2
A.3.6 F miy: LVDC u its 2
Biblogra h 2
Fig re 1 – Sc ematic diagram s owin rate of agein k, de en in on dif ferent agein mec anisms 9
Fig re 2 – Relation hip b twe n mec anical pro erties of in ulatin p p r an p per degre of p lymerization (DP) [5] 10 Fig re 3 – Example of f low-c art f or the estimation of p p r degradation con ition 17 Ta le A.1 – 2-FAL typical values for GSU tran f ormers, fi ed with u in ibited mineral oi (b sed on a p pulation of 1 8 0 u its) 19 Ta le A.2 – 2-FAL typical values for GSU tran formers, f il ed with in ibited mineral oi (b sed on a p pulation of 17 units) 19 Ta le A.3 – 2-FAL typical values for network tran mis ion tran formers, fi ed with u in ibited mineral oi (b sed on a p pulation of 2 8 5 u its) 2
Ta le A.4 – 2-FAL typical values for large distribution tran formers, with o en bre thin con ervator, f il ed with u in ibited mineral oi (b sed on a p pulation of 7 10 u its) 2
Ta le A.5 – 2-FAL typical values for large distribution tran formers, with se led con ervator, fi ed with u in ibited mineral oi (b sed on a p pulation of 2 8 u its) 2
Ta le A.6 – 2-FAL typical values for in u trial distribution tran formers, fi ed with u in ibited mineral oi (b sed on a p pulation of 3 8 5 u its) 2
Ta le A.7 – 2-FAL typical values for LVDC tran formers, f il ed with u in ibited mineral oi (b sed on a p pulation of 3 0 u its) 21
Ta le A.8 – CO 2 typical values for GSU an ex itation tran f ormers, fi ed with u in ibited mineral oi (b sed on a p pulation of 1 0 8 u its) 21
Ta le A.9 – CO 2 typical values for network tran mis ion tran f ormers, fi ed with u in ibited mineral oi (b sed on a p pulation of 4 5 u its) 21
Ta le A.10 – CO 2 typical values for large distribution tran formers, f iled with u in ibited mineral oi (b sed on a p pulation of 7 2 1 u its) 2
Ta le A.1 – CO 2 typical values for in u trial distribution tran formers, fi ed with u in ibited mineral oi (b sed on a p pulation of 4 5 6 u its) 2
Ta le A.12 – CO 2 typical values for LVDC tran f ormers, fi ed with u in ibited mineral oi (b sed on a p pulation of 2 3 u its) 2
Trang 6INTERNATIONAL ELECTROTECHNICAL COMMISSION
1 Th Intern tio al Ele trote h ic l Commis io (IEC) is a worldwid org niz tio for sta d rdiz tio c mprisin
al n tio al ele trote h ic l c mmite s (IEC Natio al Commite s) Th o je t of IEC is to promote
intern tio al c -o eratio o al q e tio s c n ernin sta d rdiz tio in th ele tric l a d ele tro ic f i ld To
this e d a d in a ditio to oth r a tivitie , IEC p bls e Intern tio al Sta d rd , Te h ic l Sp cific tio s,
Te h ic l Re orts, Pu lcly Av ia le Sp cif i atio s (P S) a d Guid s (h re f ter refer e to a “IEC
Pu lc tio (s)”) Th ir pre aratio is e tru te to te h ic l c mmite s; a y IEC Natio al Commite intere te
in th s bje t d alt with ma p rticip te in this pre aratory work Intern tio al g v rnme tal a d n n
-g v rnme tal org niz tio s laisin with th IEC als p rticip te in this pre aratio IEC c la orate clo ely
with th Intern tio al Org niz tio f or Sta d rdiz tio (ISO) in a c rd n e with c n itio s d termin d b
a re me t b twe n th two org niz tio s
2) Th f ormal d cisio s or a re me ts of IEC o te h ic l maters e pre s, a n arly a p s ible, a intern tio al
c n e s s of o inio o th rele a t s bje ts sin e e c te h ic l c mmite h s re re e tatio fom al
intere te IEC Natio al Commite s
3) IEC Pu lc tio s h v th form of re omme d tio s f or intern tio al u e a d are a c pte b IEC Natio al
Commite s in th t s n e Whie al re s n ble ef forts are ma e to e s re th t th te h ic l c nte t of IEC
Pu lc tio s is a c rate, IEC c n ot b h ld re p n ible for th wa in whic th y are u e or f or a y
misinterpretatio b a y e d u er
4) In ord r to promote intern tio al u if ormity, IEC Natio al Commite s u d rta e to a ply IEC Pu lc tio s
tra s are tly to th ma imum e te t p s ible in th ir n tio al a d re io al p blc tio s An div rg n e
b twe n a y IEC Pu lc tio a d th c re p n in n tio al or re io al p blc tio s al b cle rly in ic te in
th later
5) IEC its lf d e n t pro id a y ate tatio of c nf ormity In e e d nt c rtific tio b die pro id c nf ormity
a s s me t s rvic s a d, in s me are s, a c s to IEC mark of c nf ormity IEC is n t re p n ible f or a y
s rvic s c rie o t b in e e d nt c rtific tio b die
6) Al u ers s o lde s re th t th y h v th late t e itio of this p blc tio
7) No la i ty s al ata h to IEC or its dire tors, emplo e s, s rv nts or a e ts in lu in in ivid al e p rts a d
memb rs of its te h ic l c mmite s a d IEC Natio al Commite s f or a y p rs n l injury, pro erty d ma e or
oth r d ma e of a y n ture wh ts e er, wh th r dire t or in ire t, or for c sts (in lu in le al f ee ) a d
e p n e arisin o t of th p blc tio , u e of, or rela c u o , this IEC Pu lc tio or a y oth r IEC
Pu lc tio s
8) Ate tio is drawn to th Normativ refere c s cite in this p blc tio Us of th refere c d p blc tio s is
in is e s ble for th c r e t a plc tio of this p blc tio
9) Ate tio is drawn to th p s ibi ty th t s me of th eleme ts of this IEC Pu lc tio ma b th s bje t of
p te t rig ts IEC s al n t b h ld re p n ible f or id ntif yin a y or al s c p te t rig ts
The main tas of IEC tec nical commit e s is to pre are International Stan ard However, a
tec nical commit e may pro ose the publ cation of a Tec nical Re ort when it has col ected
data of a diff erent kin f rom that whic is normaly publs ed as an International Stan ard, f or
example "state of the art"
IEC TR 6 8 4, whic is a Tec nical Re ort, has b en pre ared by IEC tec nical commit e
10: Fluid f or electrotec nical a pl cation
The text of this stan ard is b sed on the f ol owin doc ments:
En uiry draft Re ort o v tin
Ful information on the votin for the a proval of this Tec nical Re ort can b f ou d in the
re ort on votin in icated in the a ove ta le
Trang 7This publ cation has b en draf ted in ac ordan e with the ISO/IEC Directives, Part 2.
The commit e has decided that the contents of this publ cation wi remain u c an ed u ti
the sta i ty date in icated on the IEC we site u der "ht p:/webstore.iec.c " in the data
related to the sp cif i publ cation At this date, the publ cation wi b
Trang 8The cel ulosic sol d in ulation of tran f ormers an other electrical a p ratu is s bject to
thermal degradation d rin their o erational lfetime This res lts in a progres ive los of
p p r’s mec anical pro erties, s c as ten i e stren th, whic are related to the d ration of
the tec nical l fe of the eq ipment [3,4]
1
Durin its thermal degradation proces (also cal ed “agein ” in this Tec nical Re ort ,
cel ulose forms several by-prod cts, some of whic may b detected by me n of in ulating
oi s c emical analy is [1,2] The con entration an rate of in re se of those by-prod cts can
b u ed as a to l to estimate the progres of p p r thermal degradation in tran f ormers an
other electrical a p rata in service
For this re son, IEC tec nical commit e 10 has pre ared this Tec nical Re ort for the
monitorin of in ulatin oi p rameters related to celulose agein an the interpretation of
res lts, as a g idan e to the thermal degradation evaluation of in ulatin p p r
This Tec nical Re ort is b sed on the evaluation of cel ulose agein by-produ ts content in
in ulatin oi , an their rate of f ormation d rin the l fe of the oi-immersed electrical
eq ipment Statistical referen e values re orted in An ex A of this Tec nical Re ort are
b sed on data col ected by TC10 The final re ort of CIGRE WG D1.01.TF13 [7] was taken as
a source of inf ormation con ernin mec anisms an p rameters influen in the formation of
furanic comp u d
NOT Meth d f or th e timatio of a tu l d gre of p lymeriz tio (DP) v lu s of p p r, whic are wid ly
a aia le in lterature, were n t a ple within this Te h ic l Re ort This is d e to th f act th t a n mb r of
diff ere t mo els h v b e d v lo e a d re orte , a d th y of te le d to dif fere t re ults More v r, th
a plc bi ty of th s mo els h s n t b e s f ficie tly pro e b c mp ris n with f i ld e p rie c to b in lu e
into a IEC sta d rd
He lth a d s fety
This Tec nical Re ort do s not purp rt to ad res al the safety pro lems as ociated with its
u e It is the resp n ibi ty of the u er of the Tec nical Re ort to esta ls a pro riate he lth
an safety practices an determine the a pl ca i ty of reg latory l mitation prior to u e
The mineral oi s whic are the s bject of this Tec nical Re ort s ould b han led with d e
regard to p rsonal saf ety an h giene Direct contact with eyes may cau e sl g t ir itation In
the case of eye contact, ir igation with co iou q antities of cle n ru nin water s ould b
car ied out an medical ad ice sou ht
Some of the tests sp cified in this Tec nical Re ort in olve the u e of proces es that could
le d to a hazardou situation At ention is drawn to the relevant stan ard f or guidan e
En ironme t
This Tec nical Re ort in olves mineral oi s, c emicals an u ed sample containers The
disp sal of these items s ould b car ied out in ac ordan e with c r ent national legislation
with regard to the imp ct on the en ironment Every precaution s ould b taken to prevent the
rele se into the en ironment of mineral oi
_ _ _ _ _ _
1
Fig re in s u re bra k ts refer to th Biblo ra h
Trang 9GUIDA NCE ON THE INTERPRETA TION OF CARBON DIOXIDE
IEC TR 6 8 4, whic is a Tec nical Re ort provides g idan e f or the estimation of con umed
thermal l f e of tran formers' cel ulosic in ulators, throu h the analy is of some comp u d
dis olved in the in ulatin mineral oi A comp rison b twe n analytical res lts of 2-f urf ural
(2-FAL) an carb n oxides an their cor esp n ent typical values estimated f or diff erent
f ami es of eq ipment gives information on the estimated thermal degradation of p p rs
The agein rate of in ulatin p p rs can b evaluated, in s ort time ran es (e.g 1 ye r), by
reg larly monitorin 2-FAL an carb n oxides content in the oi an by comp rin them to
typical rates of in re se
A statistical a pro c for the estimation of p p r thermal degradation, an the evaluation of
agein rate is given
Typical values for con entration an rates of in re se of the p rameters related to p p r
agein were extra olated f rom a statistical data ase col ected, an are re orted in An ex A
They may b u ed as a rou h g ide, but they s ould not b con idered as thres old values
This Tec nical Re ort is only a pl ca le to tran formers an re ctors f il ed with in ulatin
mineral oi s an in ulated with Kraft p p r The a proac es an proced res sp cified s ould
b taken as a practical g idan e to in estigate the thermal degradation of cel ulosic
in ulation, an not as an algorithm to calc late the actual degre of p lymerization (DP) of
p p rs
The p p r thermal l fe evaluation protocol des rib d in this Tec nical Re ort a pl es to
mineral oi impreg ated tran formers an re ctors, in ulated with Kraf t p p r An eq ipment
f il ed with in ulatin lquid other than mineral oi (i.e esters, si cones) or in ulated with sold
materials other than Kraft p p r (i.e TUP – thermal y upgraded Kraf t p p r, s nthetic
p lymers) is outside of the s o e of this Tec nical Re ort
This Tec nical Re ort is a pl ca le to eq ipment that has b en s bmit ed to a reg lar
monitorin practice d rin the service, an for whic maintenan e an f ault history is k own
The f ol owin doc ments, in whole or in p rt, are normatively ref eren ed in this doc ment an
are in isp n a le f or its a pl cation For dated ref eren es, only the edition cited a ples For
u dated referen es, the latest edition of the referen ed doc ment (in lu in an
amen ments) a pl es
None
Trang 103 Signif icanc
This Tec nical Re ort des rib s a statistical a pro c to p p r thermal l f e evaluation This
me n that al typical values are o tained f om p pulation of tran formers b lon in to the
same fami y for tec nical c aracteristic an a pl cation (se An ex A)
The a pro c u ed to col ect statistical data, des rib d in 6.1, can b a pl ed by uti ties or
owners havin a large p pulation of u its, to calc late in ivid al ref eren e values related to a
sp cific fami y of tran f ormers or re ctors This is very imp rtant b cau e dif ferent p pulation
of tran f ormers (i.e o eratin in dif ferent clmates or u der diff erent o erational con ition )
may have dif ferent typical values
NOT For a e te siv s rv y o fura ic c mp u d a mark rs f or dia n sis of p p r in ulatio d gra atio ,
s e CIGRE Bro h re 4 4/2 12[7]
3.2 Thermal a d me ha ic l de ra ation of paper
There are main factors: desig an materials, contaminants in the in ulation s stem an
o erational con ition , that wi determine the agein of a tran former [1,2] F r the sold
in ulation – p p r an pres b ard – it me n a combination of mec anical an dielectric
p rorman e, whic are interl n ed an s nergetic F r a tran f ormer, in the context of
thermal agein , it is the mec anical stren th of the p p r that mat ers The agein of p p r
res lts in a decre sed mec anical stren th an is as umed to red ce the a i ty of the
tran former to with tan s ort circ it stres This, however, has not b en statistical y
demon trated, yet
Ten i e stren th, elon ation an foldin stren th al decay with time, an more q ic ly at
hig er temp ratures
The mec anical p r orman e of cel ulosic in ulation is given in terms of ten i e in ex or
degre of p lymerization (DP), whic are stron ly influen ed by agein The DP value is an
average value of c ain len th of the cel ulose molec les given as a n mb r of glu ose rin s
in a cel ulose c ain It is me s red throu h me s rement of the vis osity of a p p r solution,
ac ordin to IEC 6 4 0 [8]
It is more con enient to p rf orm DP than ten i e in ex, b cau e of the lmited amou t of
p p r ac es ible f or tests; theref ore it is widely u ed for the evaluation of the cel ulosic
3.2.2 Impa t of temperature
Temp rature af fects the rate of degradation This fact is reflected in IEC 6 0 6-7 [3] an
IEEE Std C5 91 [4] tran former lo din g ides
IEC 6 0 6-7 [3] s g ests in ac ordan e with Montsin er that the lfe of a tran former can b
Trang 11p is a con tant (a value of 6 is s g ested in the ran e 8 °C to 14 °C)
θ is the temp rature in degre s Celsiu
This is a simpl f ied version of Ar heniu law u ed in IEEE Std C5 91 [4]
Sin e a precise en -of lne criterion f or a tran former is not re l y avai a le, IEEE an IEC
stan ard u e an a pro c where agein rate is con idered This is the in erse of l f etime –
in Montsin er f orm:
Rate of a eing = c nstant
θ
×p
(2)
The con tant in Eq ation (2) is de en ent on man p rameters, e.g original q alty of
cel ulosic prod cts as wel as environmental p rameters (moisture content and ox gen in the
s stem) A gra hical re resentation of these influen es is s own in Fig re 1
Fig re 1 – Sc ematic dia ram s owing rate of a eing k,
depe ding on dif f ere t a eing me ha isms
3.2.3 Impa t of h midity a d ox ge
Humidity an ox gen in res (oxidation) have an imp rtant imp ct on the agein of Kraft
p p r This me n not only that the mec anical stren th of p p r ra idly decre ses u der
in res of moisture an air, but practical y cau es an in re sin contamination of the
combined l q id-sol d in ulation u der these con ition It is a con eq en e of the
degradation prod cts formed f rom oi an p p r le din to a f urther degradation
Durin the agein of the combined cel ulosic an oi in ulation man by-prod cts are formed –
carb n oxides, water, acid , slu ge an furanic comp u d Man of these degradation
prod cts, e.g furanic comp u d , are soluble in oi an sta le enou h to b u ed as
diag ostic markers Furanic are f ormed by deh dration re ction fol owin h droly is of the
cel ulose an hemicel ulose as wel as by oxidative pyroly is of cel ulose Their analytical
determination is wel k own an rela le (se IEC 61 9 [12])
In a tran f ormer al these proces es – h droly is, oxidation an pyroly is – act
simultane u ly, res ltin in a non-l ne r mec anism (se Fig re 1) Whic proces wi
dominate de en s on the temp rature an the o erational p rameters In fact the a plcation
of one activation energy, althou h of ten practiced, is very dif fic lt b cau e of the complexity
of the degradation proces es
IEC Oxid tio
Trang 123.3 Symptoms of paper a eing in in ulating oi
The agein of p p r can b detected by direct in estigation on the p p r or by the
me s rement of by-prod cts dis olved in the oi
Cel ulose degradation mainly af fects the mec anical pro erties ( en i e stren th, elon ation,
burst stren th, double f old stren th, etc.) of p p r (se Fig re 2), but a direct me s re of
those p rameters req ires the sampl n of a large amou t of p p r, whic is normal y
imp s ible d rin the o erational l f etime of a tran former However, the relation hip b twe n
the mec anical in exes an the degre of p lymerization (DP) is wel k own Degradation of
p p r do s not sig ificantly aff ect its resistan e to the compres ion f orces mostly an
contin ou ly a pl ed to tran former win in s throu h clampin
Figure 2 – Relations ip betwe n me ha ic l propertie of
ins latin paper a d paper de re of polymerization (DP) [5]
The DP value is the average n mb r of gly oside rin s in the cel ulose p lymer; in the native
cel ulose DP may b as hig as or more than 10 0 0 u its but after the purification proces
an other tre tments the DP value of the electrical Kraft p p r decre ses to arou d
1 0 0 u its ( ypical value: 1 2 0)
DP is me s red in ac ordan e with IEC 6 4 0 [8] throu h me s rement of the sp cific
vis osity of a very smal amou t of p p r dis olved in c pri-eth lene-diamine (CuED) From
this me s rement the intrin ic vis osity of solution is ded ced an f rom this, u in the
Martin’s formula, the DP value is e si y calc lated
By-prod cts of aged p p r may b clas ified as volati e, soluble an in oluble, an are
de en ent on the sp cif i decomp sition proces : pyroly is, h droly is or oxidation
Relativ d gre of p lymerisatio
Trang 133.3.2 Volati e by-products
Carb n oxides (CO an CO
2) are the ultimate prod cts of cel ulose degradation an are
me s red with dis olved gas analy is (DGA) in ac ordan e with IEC 6 5 7 [9] It mu t b
taken into ac ou t that b th CO an CO
2can b generated fom oi oxidation as wel
Water can re c several p r cent of the p p r weig t Most of the water f ormed is ad orb d
an retained in the sol d in ulation of the tran f ormer an only a l tle p rt is dis olved in oi
Of course another contribution to total water is the in res of moisture f rom atmosphere
The detection of water in oi is p rf ormed in ac ordan e with IEC 6 814 [10]
3.3.3 Soluble by-products
A large n mb r of oi soluble comp u d (acid , alcohols, etc.) are generated f rom p p r
degradation The most commonly u ed comp u d for diag osis is 2-f urf ural (2-FAL) an its
related comp u d :
– 5 hy rox meth l 2- urural (5-HMF)
– 2 f ururylalcohol (2-FOL)
– 2 acetylfuran (2-ACF)
– 5 meth l 2-f urf ural (5-MEF)
The detection of 2-FAL an related comp u d in oi is p r ormed in ac ordan e with
IEC 61 9 [12]
In the same way as with water, a relevant amou t of generated furanic comp u d is retained
in the bulk of the p p r The ratio b twe n the con entration of furanic comp u d in the
p p r an in the oi dif fers for e c sin le comp u d, an is aff ected by temp rature
In reased temp rature forces the eq i brium of f uranic comp u d to a hig er con entration
in the oi Decre sed temp rature forces the eq i brium of f uranic comp u d to a hig er
con entration in the p p r, especial y in the case of dry p p r
Pa er h midity an typ of p p r also in uen e the oi -to-p p r con entration ratio of furanic
comp u d A wet p p r ten s to retain a larger amou t of furanic comp u d , th s red cin
the oi -to-p p r con entration ratio
Furanic comp u d are not hig ly sta le, an may b degraded by oxidation, mostly in ois
with hig ox gen content Decay in the con entration of 2-FAL was o served in tran formers
d rin their o eration, d e to its in erent in ta i ty
Acid comp u d may b f ormed either by celulose an /or oi oxidation, an a hig acidity
of ten ac omp nies other s mptoms of p p r agein
3.3.4 In oluble by-products
Severe p p r agein can final y le d to the f ragmentation of p lymeric celulose, an smal
p p r fibres can b detac ed fom the p p r mas
The celulose f ibres can b detected as p rticles present in in ulatin oi , in ac ordan e with
IEC 6 9 0 [1 ]
3.4 Operational parameters influe cing paper th rmal a ein
In ad ition to tran former hours of service as a key p rameter in def i in “re l age” of p p r
in ulation in normal workin regimes, other o erational p rameters s c as lo d, typ of
co l n an tran f ormer s b-typ have a major in uen e on p p r thermal agein The nature
Trang 14The hig -lo d of a tran former, implyin elevated o eratin temp ratures, promotes the p p r
thermal degradation proces , o served with some typ s of tran formers that are of ten
overlo ded (s u t re ctors, HVDC, generator ste -up (GSU) in thermal p wer plants (TPP),
hig voltage inter tie tran mis ion tran formers)
The typ of co ln , in terms of co l n media (water or air) an typ of flow a pl ed (forced or
natural con ection), aff ects eff i ien y of he t removal, th s influen in the rate of p p r
thermal degradation The most ef ficient co l n can b ac ieved by a plyin water as co lant
in f orced oi flow
For example, it was o served in most cases that the degre of p p r degradation with GSU
tran formers in hy ro p wer plants (HPP) is lower than with thermal p wer plant GSU u its,
havin a simi ar service d ration These fin in s are cor elated to dif ferent types of co l n
(OFWF vers s ONAF an OFAF), hours of service an lo din history of HPP an TPP u its
[6]
Amon dif ferent tran f ormer s b-typ s, air bre thin tran formers are s bjected to more
inten ive p p r degradation than se led ones, d e to hig er ox gen an moisture content
Elevated con entration of ox gen an water ac elerate the p p r degradation proces
Sin e the p p r degradation proces is temp rature driven, every en ironmental an
o erational con ition that may aff ect the temp rature can also modify the degradation rate of
the sol d in ulation An elevated en ironmental temp rature or a hig lo din can th s
in rease the rate of p p r degradation, res ltin in a s d en in re se of 2-FAL, CO
2, CO an
other by-prod cts
3.5 Role of oi type a d condition
Oi typ may af fect the agein rate of p p r In ibited oi s s ow a lower ten en y to form
acidity, an the oxidation proces is slac ened; the ef fect of ox gen in the p p r oxidation
proces is red ced
Tran formers impreg ated with in ibited oi may s ow a lower content of 2-FAL if comp red
with u its in ulated with an u in ibited oi , even if s owin the same degre of p lymerization
(DP) of the p p r
The ef fect of p s ivators ( riazole derivates) in the agein of celuloses is sti not wel
defined By definition, metal p s ivators may in u e a lower rate of the oi degradation
proces by de ctivatin the co p r cataly t in oxidation proces es, theref ore slowin down
the p p r degradation proces , but in uen e of metal p s ivators on 2-FAL con entration in
the oi may not b straig tforward Some la oratory stu ies have s own that p p rs
impreg ated with oi s to whic a p s ivator has b en ad ed, may have a lower ten en y to
f orm f uranic comp u d ; this may le d to o timistic estimation of agein in presen e of
triazol c p s ivators
The agein con ition of the oi may also aff ect the p rtition of furanic comp u d b twe n
sol d and l q id in ulation; acidic oi s may res lt in an in re sed 2-FAL con entration in oi,
d e to its au mented ca a i ty to extract p lar comp u d f rom the p p r
3.6 Fa lt condition th t ma af f ect thermal a eing
In tran f ormers where the degradation mec anism may b either thermal or electrical, the rate
of p p r degradation may in re se ra idly as a con eq en e of sig ificant temp rature rise
Hig energ thermal an electrical f aults in olvin ex es ive c r ents circ latin throu h the
in ulation an large c r ent fol ow-throu h le d to exten ive destru tion an carb nization of
p p r
In presen e of local thermal degradation d e to a fault, the estimation of the p p r’s
con umed thermal l fe may b come very dific lt, sin e the exten ion of the p p r volume