No 28 Xianning West Road, Xi an No 70 Yuhua East Road, Shijiazhuang.

Transcription

1 On-Ln Dynamc Cabl Ratng for Undrground Cabls basd on DTS and FEM Y.C.Lang *, Y.M.L School of Elctrcal Engnrng * Dpartmnt of Elctrcal and Informaton X an Jaotong Unvrsty Hb Unvrsty of Scnc and Tchnology No 8 Xannng Wst Road, X an No 70 Yuhua East Road, Shjazhuang CHINA CHINA yongchunlang@hotmal.com Abstract: - Th dvlopmnt of surfac tmpratur on-ln montorng tchnqus for 0kV and abov XLPE powr cabl gvs a strong support to powr cabl load dynamc adjustmnt. Howvr, th problm s how to dtrmn th conductor tmpratur from th surfac tmpratur. A tchnqu basd on dstrbutd tmpratur snsng (DTS) and fnt lmnt mthod (FEM) s prsntd to stmat th sol thrmal proprts by matchng th computd thrmal flds to that obtand from masurmnt and prdct th raltm currnt carryng capacty by tratv mthod n ordr to prvnt ovrhat of nsulaton. Compar wth th thrmal crcut modl, th mthod basd on DTS and FEM s mor accuracy. Ky-Words: - Onln montorng, Dynamc cabl ratng, Dstrbutd tmpratur snsng, Fnt lmnt mthod, currnt carryng capacty, Undrground cabls Introducton In dnsly populatd aras, lctrcty s usually transmttd and dstrbutd through burd cabls. Th man dsadvantag of burd nstallatons s to obtan, wth suffcnt accuracy, th maxmum valus of currnt that can flow through th cabls n stady stats wthout nsulaton dtroraton. For modrn HV cabls, ol-flld papr-nsulatd cabl can b opratd at maxmum tmpratur of 85 C and XLPE nsulatd cabl at a maxmum tmpratur of 90 C. Thr ar svral factors dtrmnng th currnt carryng capacty of a spcfc cabl crcut, namly, th cabl constructon, cabl surroundng sol, ambnt tmpratur and shath-bondng mthod. Of ths factors, th thrmal proprts of sol ar always varyng whras th othrs ar rlatvly stabl. Bcaus th thrmal proprts of sol chang wth tm dpndng on th wathr n dffrnt sasons and th hatng n th cabl, th currnt carryng capacty could chang sgnfcantly from tm to tm. Thrfor, t s mportant to dtrmn th dynamc ratng of a cabl crcut so that ts full capacty can b utlzd all yar around, and t s always a challng for powr systm oprators to assgn adquat powr load to undrground cabls wthout xcdng thr currnt ratng [-5]. Nowadays mor and mor powr utlts hav rcognzd th mportanc of thrmal condton montorng of burd cabl crcuts and nstalld advanc dstrbutd tmpratur snsng (DTS) systms to montor cabl surfac tmpratur [6-4]. In [], th cabl surfac tmpratur s usd to mprov th calculaton modl basd on IEC 6087 and McGraph/Nhr mthod. Howvr, analytcal mthod s basd on som assumpton condtons and can t smulat th ral condton. Th cabl surfac tmpratur s just an ndrct ndcaton for th cabl nsulaton thrmal stats. From th vwpont of cabl opraton, cabl conductor tmpratur s th most dsrd and usful quantty, whch drctly rflcts th cabl thrmal condton [5]. In [6], th conductor tmpratur s calculatd from cabl surfac tmpratur by thrmal crcut mthod. Howvr, dynamc ratng systms hav a lmtd numbrs of dscrt snsors-typcally thrmocoupls-that ar placd at rprsntatv locatons on th cabl systm. Thr can b svral hotspots n a cabl crcut, whch act as bottl ncks to lmt th load-carryng capacty. It s vtal for a utlty to locat and rctfy all hotspots n a cabl crcut so that t can b drvn to ts ratng lmt comfortably. Unfortunatly, th systm can do a suprb job of dynamcally ratng th cabl-basd upon masurmnts at th wrong locaton. Th tmpratur dstrbuton of th most usd confguratons for burd cabls undr normal loadng condtons s shown n fgur [7]. For th mddl cabl, th maxmum tmpratur dffrnc ISSN: Issu 4, Volum 7, Aprl 008

2 of th cabl surfac s 0.6 C. For th outr cabl, th maxmum tmpratur dffrnc of th cabl surfac s.3 C. How to slct th corrct hot pont on th surfac of cabl s vry dffcult to calculat th conductor tmpratur and dtrmn th currnt carryng capacty. In rcnt yars, numrcal mthods, such as FEM, hav bn dvlopd for calculatng th tmpratur dstrbuton of lctrcal qupmnt [8] [9]. Compard wth th analytcal mthods, numrcal mthods not only allow bttr rprsntaton of th mutual hatng ffcts, but also prmt mor accurat modlng of th rgon s boundary. Fgur. A sngl-loop burd cabl s tmpratur fld dstrbuton In ths papr, w us DTS to montor th surfac tmpratur and stmat th sol thrmal proprts by FEM and prdct th ral-tm currnt carryng capacty by tratv mthod. Compar wth th tradtonal thrmal crcut, th poston of hot pont dos not nflunc th computatonal accuracy of th conductor tmpratur. Ovrvw mthod of th thrmal crcut A typcal sngl-cor powr cabl s composd of at last four man componnts, namly, lctrcal conductor, conductor nsulaton, shath, and xtrnal covrng as shown n fgur. Conductor nsulaton Elctrcal conductor sh ath Extrnal covrng In ordr to dtrmn hatng of undrground cabl systm, th systm losss hav to b known. Th currnt dpndnt losss of cabls wth th sold shaths can b calculatd by fnt lmnt mthod. For th lctrc-magntc fld n powr cabls, th problm can b calculatd n two-dmnsonal Cartsan coordnat systm and spac charg and dsplacmnt currnt can b nglctd. A snglcor powr cabl structur s gvn n Fgur. Thr ar two knd of rgon: mtal and othrs. Th Magntc-vctor potntal can b dscrbd by Lapalac s and Posson quaton dffrntly n ths aras. Magntc-vctor potntal quaton of cabl n dffrnt parts undr th Coulomb norms s as follows: Cabl conductor rgon: A 0 J s, J s s th currnt dnsty of conductor rgon. Cabl nsulaton rgon: A 0. Cabl shath rgon: A 3 0 J, J s th Eddy currnt dnsty of mtal packag rgon. Cabl xtrnal covrng rgon: A4 0. Sol rgon: A5 0. Th contnuty quaton btwn dffrnt mdum s: Fgur. Th structur of a typcal sngl-cor cabl A A j () ISSN: Issu 4, Volum 7, Aprl 008

3 A A n j A, j,,3,4,5 j A n () (3) whr and j rprsnt fnt lmnt nghborng rgon. Magntc vctor potntal can b calculatd usng FEM [0]. Th ddy currnt n cabl conductor and mtal packag can b calculatd by magntc vctor potntal as follow: J j 3 A 3 (4) whr J rprsnts th currnt dnsty n mtal packag; A3 rprsnts th magntc vctor potntal of mtal packag rgon. Thn th conductor lctromagntc loss can b calculatd as follow: W c ( [( ( J J s s( ) J s( ) J ) dv J ( ) j ) r S 3 3, A ) r S ] (5) whr Wc rprsnts th losss n th conductor; rprsnts th conductor conductvty; r rprsnts th dstanc from th cntr to th axs of ach unt; S rprsnts th unt ara. Thn th shath lctromagntc loss can b calculatd as follow: W s J [( J ( ) 3 c dv r S 3, A ) r S ] RT (6) whr W s rprsnts th ddy currnt loss n th shath; 3 rprsnts th shath conductvty. Th calculaton of th dlctrc losss s consdrd as a rathr straghtforward task, and dtals can b found by standard Nhr/McGraph and IEC 6087 procdurs. Dlctrc loss of pr unt lngth n ach phas can b calculatd as follow: W d 0 c U tg (7) whr f ; c, th D 9 8 ln 0 d capactanc n pr unt lngth cabl ; tg, th nsulaton loss factor n powr systm and workng tmpratur; U, th phas voltag ;, th 0 dlctrc coffcnt of nsulaton matral; D, th nsulaton damtr; d c, th conductor damtr. Aftr th losss n th cabl s known, th conductor tmpratur and th currnt carryng capacty can b calculatd by th thrmal crcut mthod basd on th standard Nhr/McGraph and IEC 6087 procdurs, wth th furthr d-ratng for potntal hot spots, as shown n fgur 3. Now, many powr utlts nstalld advancd DTS systms to montorng th cabl surfac tmpratur w. Whn currnt flow through cabl s known, th conductor tmpratur can b calculatd as follow. ( W W ) ( R R ) ( W W ) RT (8) c w c d Tj whr c s th conductor tmpratur, RT thrmal rsstanc of th conductor nsulaton, and RT thrmal rsstanc of th xtrnal covrng. RT w RT 3 Tw s d Wc W d W d W s a Fgur3. Th thrmal crcut modl ISSN: Issu 4, Volum 7, Aprl 008

4 Th dffcult problm n th thrmal crcut mthod s how to dtrmn th surfac tmpratur. Dffrnt surfac tmpratur may rsult n dffrnt conductor tmpratur. But th surfac tmpratur s not an sothrm as shown n Fgur. Wth th dvlopmnt of th numbr of powr cabls, th surfac tmpratur s mor dsprs and t s mor dffcult to dtrmn th corrct surfac tmpratur to rsult corrct conductor tmpratur. Othrws, bcaus th sol thrmal conductvty s hghly dpndnt on mostur contnt of sol, thrmal rsstanc RT 3 s dynamc and th currnt carryng capacty calculatd by th tradtonal thrmal crcut modl as shown n Fgur 3 may b not accurat. 3 Prncpl 3..Fnt lmnt formulaton On of th most usd confguratons for burd cabls conssts of thr ndvdual cabls at th sam lvl wth a typcal sparaton btwn thm of on cabl damtr as shown n Fgur 4. Ths cabls ar usually burd drctly n th arth or n a backfll matral such as concrt or sand. Th analyss prsntd n ths papr s basd on th followng assumptons: a.th cabl systm s nfntly long, so that th problm bcoms a two-dmnsonal on. b. Stady-stat condtons xst. c. All matrals hav constant thrmal proprts. d. Th ambnt ar s statonary. ground surfac conductor nsulator s a n d O a r s o l Fgur 4 Gomtrc Modl of a Typcal Burd Cabl Installaton Basd on th abov assumptons, f th systm cross-scton ls on th x-y plan, th assocatd L stady-stat hat conducton quaton for a twodmnsonal burd cabl systm, as shown n Fgur 4, can b dscrbd as T T ( ) q x y (9) whr s th thrmal conductvty W m C, T s th unknown tmpratur, q s th hat sourcs gnratd by cabls. Equaton (9) s subjctd to th followng boundary condtons: a. In th sol whch s far nough away from th cabls, both to th sds and undrnath, tmpratur s not affctd by th cabls prsnc. In th aras far nough away undrnath th cabls, a tmpratur sothrm s consdrd to b qual to th dp sol tmpratur ( Ts ).In th aras far nough away to th sds from th cabls, calorfc flow s: T 0 l (0) b. At th sparaton surfac btwn sol and ar, convcton losss ar consdrd, whch mans that tmpratur at ths surfac s obtand by takng nto account Nwton s law: Q h( T Ta) () whr h s th convctv hat transfr coffcnt ( W / m C) ), T s th tmpratur at th surfac, and Ta s th ar tmpratur. c. In th sparaton btwn th dffrnt matrals of th cabl, btwn th surfac of th cabls and th surroundng mdum, and btwn th dffrnt matrals surroundng th cabls, calorfc flow contnuty s fulflld at th sparaton surfac: T T l l () whr l s th normal to th sparaton surfac, and and rprsnt th thrmal conductvty of mdum and mdum, rspctvly. Lkws, th tmpratur n ISSN: Issu 4, Volum 7, Aprl 008

5 both matrals at th bordr ponts must b th sam. Th fnt lmnt modlng of quatons s obtand by usng wak Galrkn s procdur and prforms ovr all th lmnts [-]. J T l J T l J T l jm Wl T Wl T [( )] dxdy x x y y Wl T Wl T [( )] dxdy x x y y Wl T Wl T [ ( )] dxdy x x y y W ( T T ) ds l f (3) (4) (5) Th tmpraturs of vry nod can b dscrbd by quatons (6). kk k kk k knk n k n n nn T P T P Tn Pn (6) Whr, k and P ar gvn by soluton of quaton j (3), (4) and (5). T ar th tmpratur of nods. Thy ar varabls dsrd to solv. ~ n, j ~ n. n s th numbr of dssctng nod. Dscrtzng th fld doman s usually th most tdous work durng mplmnt of FEM. Trangular lmnts ar usd n formng th ntwork modlng th cabl and surroundng nvronmnt. Fgur 5 shows th dscrtsd cabl doman. 3.Estmaton of sol thrmal proprts Onc th cabl constructon, nstallaton, shath bondng mthod, cabl load and th ambnt tmpratur ar dtrmnd, th tmpratur dstrbuton only dpnds on th thrmal proprts of th surroundng sol. Th thrmal proprts of sol ar always varyng. Our st sol tst shows that sol thrmal conductvty s hghly dpndnt on th mostur contnt. Undr unfavourabl condtons, hat flux from th cabl ntrng th sol may caus sgnfcant mgraton of mostur away from th cabl. A drd-out zon may dvlop around th cabl, n whch th thrmal conductvty s rducd by a factor of thr or mor ovr th conductvty of th bulk. Ths n turn may caus an abrupt rs n tmpratur of th cabl shath and conductor whch may lad to damag of cabl nsulaton. How to dtrmn th thrmal proprts of sol s vry dffcult usng FEM to calculat th thrmal fld too. On th mddl cabl of Fgur 3, a DTS optc fbr s nstalld at pont O. Suppos th tmpratur at surfac pont O s masurd wth DTS and th sol s takn as a homognous thrmal mdum, th conductor tmpratur and th ffctv thrmal conductvty of sol can b calculatd basd on th FEM undr th unqunss thorm of th thrmal fld. Th tmpratur at pont O calculatd by FEM s dnotd by T F. Th tmpratur at surfac pont O masurd wth DTS s dnotd by T m. In ths study, th ffctv thrmal proprts of sol ar dtrmnd by mnmzng th followng objctv functon. F T T F m (7) Fgur 5 Dscrtsd cabl doman: trangular mshs Hr, w us subtns truncaton approach to calculat th ffctv thrmal conductvty of sol. Th ltrat quaton of th subtns truncaton approach s quaton (8). T F (k) s th tmpratur at pont O calculatd by FEM. s th ffctv thrmal conductvty of sol. k s th nxt stp rsult, k s th tmporary stp rsult, k s th last stp rsult. ISSN: Issu 4, Volum 7, Aprl 008

6 ( Tm T ( k ) ( k) T F F ( k)) ( ( k) ( k )) ( k) T F ( k ) (8) In ordr to vrfy th ffctv th mthod prsntd n ths papr, w us thr burd hat pps to vrfy th mthod as shown n Fgur 6 Th traton procss s trmnatd f th followng condton s satsfd: Th objctv F s not gratr than 0. C. E 5 0 c m 3.3Prdcton 3Prdcton of th currnt carryng capacty Th ffctv thrmal conductvty of sol was adjustd untl th calculatd tmpratur was th sam as th masurd tmpratur, and th conductor tmpratur was calculatd. A currnt carryng capacty was calculatd untl th conductor tmpratur s qual to 90 C (XLPE powr cabl) for thos condtons by tratv mthod. Th ltrat quaton of th subtns truncaton approach s quaton (9). T C (k) s th conductor tmpratur calculatd by FEM. I s th thrmal conductvty of sol. k s th nxt rsult, k s th tmporary rsult, k s th last rsult. (90 TC ( k)) ( I( k) I( k )) I( k ) I( k) T ( k) T ( k ) C C (9) It s mportant to not that tmpratur n a cabl systm at any tm ar a functon of loadng at that tm plus th loadng for th last wk or so bcaus of th vry long thrmal tm constant of th cabl/arth systm. For xampl, a cabl that has bn opratng at 700 amprs constantly for 00 hours wll b much hottr than a cabl that has bn opratng at 00 amprs for th last 90 hours, thn 700 amprs th last tn hours. So, th currnt carryng capacty should b calculatd for dffrnt tms, usng xpctd changs n ambnt arth tmpratur and backfll and sol thrmal conductvty at thos tms by th subtns truncaton approach. 4 Tst and Rsults 4. Mthod vrfy N 0 c m 0 c m Thrmalcoupl Hat pp Fgur 6 Tst modl of hat pp Thr burd hat pps covrd wth rubbr ar placd horzontally at 0.5 m dpth and sparatd 0.m btwn th pp cntrs. Th lngth of hat pp s.5m and th radus s 0.006m. Th thcknss of rubbr s 0.004m. Th thrmal conductvty of sol and rubbr ar.664 W /( m C) and 0.5 W /( m C). Th tmpratur of ar s 8 C. Whn th powr of hat pp s 9W, th tmpratur of pont N aftr 0 days s 96 C and th tmpratur of pont E aftr 0 days s 83 C. Usng th mthod prsntd n ths papr, th tmpratur of pont E s 8.93 C and th tmpratur of pont N s C. Th ffctv thrmal conductvty of sol s.9 W /( m K). Th rsult shows that th mthod s ffctv to calculatd th conductor tmpratur of powr cabls and prdct th currnt carryng capacty of powr cabls wth hghly accuracy. 4. Sngl loop powr cabls n horzontally In ths scton, th thrmal crcut mthod and th mthod prsntd n ths papr ar appld to stmat th conductor tmpraturs of sngl loop undrground cabls. In ordr to dscrb th dsprs of th surfac tmpraturs, w masurd four pont tmpratur on th surfac of cabl as shown n fgur 7. ISSN: Issu 4, Volum 7, Aprl 008

7 4 3 Fgur7. Th postons of th four ponts on th cabl surfac Thr 800mm 0kV YJLW0 cabls ar placd horzontally at 0.7m dpth and sparatd 0.m btwn th cabl cntrs. A 35 ambnt tmpratur s spcfd. Th currnt supplyng th cabls s 500A. Whn th shaths ar bondd at both nds, th losss n th conductors of dffrnt phass ar 5.699W/5.6989W/5.699W Th losss n th shaths of dffrnt phass ar 9.60W/0.0839W/3.5855W Th dlctrc losss ar 0.69W. Th ambnt thrmal conductvty of sol s sol W /( m C) Th thrmal rsstvty of nsulaton and xtrnal covrng ar 3.5 W /( m K) 6 W /( m K) Th thrmal rsstanc of nsulaton and xtrnal covrng ar R Tj R Tw For th mddl cabl, th four pont tmpraturs on th surfac and th cabl conductor tmpraturs rsultd from th cabl surfac tmpratur n (8) ar shown n tabl. From dffrnt surfac tmpratur, th conductor tmpratur s dffrnt. Th maxmum dffrnc s 0.5 C. Th ffctv thrmal conductvty of sol calculatd by FEM and traton mthod s W /( m C) and th conductor tmpratur calculatd by FEM s Th rsult by FEM and traton mthod s mor accuracy. By traton mthod, th currnt carryng capablty of sngl loop powr cabls placd horzontally wth shath bondd at both nds s 597A at ths tm. Tabl Th cabl surfac tmpratur and th cabl conductor tmpratur Cabl structur Cabl surfac Tmpratur ( C ) T T T3 T Cabl cor Thr loop powr cabls n horzontally In ths scton, th thrmal crcut mthod and th mthod prsntd n ths papr ar appld to stmat th conductor tmpraturs of thr loop undrground cabls. Nn 800mm 0kV YJLW0 cabls ar placd horzontally at 0.7m dpth and sparatd 0.m btwn th cabl cntrs. Th ambnt tmpratur and th thrmal conductvty of all thrmal mdum s th sam as abov. Th currnt supplyng th cabls s 500A. Whn th shaths ar bondd at both nds, th losss n th conductors of dffrnt loop and phas ar Loop:5.734W/5.976W/5.76W Loop:5.7566W/5.7567W/5.7587W Loop3:5.754W/5.7670W/5.7376W Th losss n th shaths of dffrnt loop and phas ar Loop:6.0379W/6.7763W/5.7846W Loop:5.7045W/5.73W/5.6367W Loop3:6.39W/4.733W/.5W. Tabl shows th surfac tmpraturs of vry cabl. For dffrnt loop, th currnt carryng capacty dpnds on th hottst cabl. Tabl 3 shows th cabl conductor tmpraturs from dffrnt surfac ponts by thrmal crcut mthod. Th maxmum dffrnc for phas C s.7 C. Th maxmum dffrnc for phas B s. C. Th maxmum dffrnc for phas A3 s.5 C. Wth th ncras of th numbr of th powr cabls, th dffrnc of th cabl surfac tmpratur s mor dsprs and t s mor dffcult to dtrmn th corrct surfac hot pont to calculat th corrct conductor tmpratur by thrmal crcut mthod. Th ffctv thrmal conductvty of sol calculatd by th mthod prsntd n ths papr s ISSN: Issu 4, Volum 7, Aprl 008

8 0.773 W /( m C). Tabl 4 shows th cabl conductor tmpraturs usng FEM. Tabl Th cabl surfac tmpraturs of thr loop undrground cabls placd n horzontally Pont Tmpratur ( C ) A B C A B C A3 B3 C3 T T T T Tabl 3 Th conductor tmpraturs of thr loop powr cabls placd n horzontally usng thrmal crcut mthod Pont Tmpratur ( C ) C B A3 T T T T Tabl 4 th conductor tmpratur of thr loop powr cabls placd n horzontally usng FEM Mthod Tmpratur ( C ) C B A3 Fm By traton mthod, th currnt carryng capablty of thr loop powr cabls placd horzontally wth shath bondd at both nds s 459A at ths tm. 4.3 Sngl loop powr cabls n trangular Thr 800mm 0kV YJLW0 cabls ar placd n trangular at 0.7m dpth. A 35 ambnt tmpratur s spcfd. Th currnt supplyng th cabls s 500A and th shaths ar bondd at on nd. Th losss n th conductors of dffrnt phass ar W/5.9604W/5.95W Th losss n th shaths of dffrnt phass ar.7407w/.9506w/.8698w Tabl 5 shows th surfac tmpraturs of vry cabl. Tabl 6 shows th conductor tmpraturs of vry cabl by thrmal crcut mthod. Th maxmum dffrnc of phas A s.4 C. Th maxmum dffrnc for phas B s. C. Th maxmum dffrnc for phas C s.0 C. Th ffctv thrmal conductvty of sol calculatd by th mthod prsntd n ths papr s W /( m C). Th conductor tmpratur of phas A s 53.0 C. Th conductor tmpratur of Phas B s 53.7 C. Th conductor tmpratur of Phas C s 53.5 C. ISSN: Issu 4, Volum 7, Aprl 008

9 By traton mthod, th currnt carryng capablty of sngl loop powr cabls placd n trangular wth shath bondd at on nd s 763A at ths tm. Tabl 5 Th cabl surfac tmpraturs of sngl loop undrground cabls placd n trangular Cabl T T T 3 T4 Th mthod basd on DTS and FEM can mprov th dfct. Whn w know th tmpratur and th poston of th hot pont on th cabl surfac, w can calculat th conductor tmpratur wth hgh accuracy. At th sam tm, w can prdct th ffctv thrmal conductvty of sol and calculat th currnt carryng capacty of th powr cabls by tratv mthod. Phas A Concluson Phas B Phas C Tabl 6 Th cabl conductor tmpraturs of sngl loop undrground cabls placd n trangular by thrmal crcut mthod Cabl T T T 3 T4 Phas A Phas B Phas C Dscusson Tabl and tabl show that th dffrnc of th surfac tmpratur ncrass wth th ncras of th numbr of powr cabls. Tabl and tabl 5 show that th dffrnc of th surfac tmpratur of th powr cabls placd n trangular s largr than th powr cabls placd n horzontally. Tabl, tabl 3 and tabl 6 show that t s dffcult to slct th corrct surfac hot pont to calculat th corrct conductor tmpratur. It mans that th accuracy of th conductor tmpratur calculatd by thrmal crcut mthod hghly dpndnt on th slcton of th hot pont of th cabl surfac. It may gv a worst rsult. DTS systms hav bn nstalld by numrous powr utlts to montor n ral tm th cabl surfac tmpratur. To mak full us of advancd DTS, a tchnqu basd on FEM and surfac tmpratur of cabl has bn dvlopd to calculat th cabl conductor tmpratur and prdct th currnt carryng capablty. Th computatonal rsults show that th conductor tmpratur can b dtrmnd mor accuratly. Ths tchnqu wll b usful for th futur dvlopmnt of an onln dynamc ratng systm for th undrground cabls basd on DTS. Rfrncs: [] G.J.Andrs, J.M.Braun, S.Rsstto and D.Casslman, Ral Tm Montorng Systm for 30 kv Cabls n Tunnls. IEEE PES Transmsson and Dstrbuton Confrnc and Exposton, Vol.3, 003, pp [] Dal A. Douglass and Abdl-Aty Edrs, Raltm Montorng Dynamc Thrmal Ratng of Powr Transmsson Crcut, IEEE Transactons on Powr Dlvry, Vol., No.3, 996, pp [3] Stvn P.Walldorf, John S.Englhardt and Frank J.Hopp, Th Us of Ral-tm Montorng and Dynamc Ratngs for Powr Dlvry Systms and th Implcatons for Dlctrc Matrals, IEEE Elctrc Insulaton Magzn, Vol.5, No.5, 999, pp.8-33 [4] S.Nakamura, S.Morooka and K.Kawasak, Conductor Tmpratur Montorng Systm n Undrground Powr Transmsson XLPE Cabl Jonts, IEEE Transactons on Powr Dlvry, Vol.4, No.4, 99, pp [5] Q.Su, H.J.L, K.C.Tan, Hotspot Locaton and Mtgaton for Undrground Powr Cabls, IEE Procdngs of Gnraton, Transmsson and Dstrbuton, Vol.5, 005, pp ISSN: Issu 4, Volum 7, Aprl 008

10 [6] H.J.L, Estmaton of Thrmal Paramtrs and Prdcton of Tmpratur Rs n Cran Powr Cabls, IEE Procdng of Gnraton, Transmsson and Dstrbuton, Vol.5, 004, pp [7] Guns Yllmaz, Sat Esr Karlk, A Dstrbutd Optcal Fbr Snsor for Tmpratur Dtcton n Powr Cabls, Snsors and Actuators A, Vol.5, 006, pp [8] John Downs, CEng, H Y Lung, Dstrbutd Tmpratur Snsng Worldwd Powr Crcut Montorng Applcatons, 004 Intrnatonal Confrnc on Powr Systm Tchnology POWERCON 004, pp [9] V.Dubckas and H.Edn, On-ln Tm Doman Rflctomtry Masurmnts of Tmpratur Varatons of an XLPE Powr Cabl, 006 Annual Rport Confrnc on Elctrcal Insulaton Dlctrc Phnomna, pp [0] J. H. Zhao, H. Y. Yuan and W. C. Fan, Surfac tmpratur fld basd onln dagnoss study for lctrc cabl s conductor tmpratur, Procdngs of th CSEE, Vol.,999,pp.5-55 [] Z. W. Gao, X. F. W and Q. G. Chn, 005 Rsarch on forcast and alarm systm of ampacty on-ln for powr cabl, Hlongjang Elctrc Powr, Vol., 005, pp.96-99,07 [] Goff Noks, Optmzng Powr Transmsson and Dstrbuton Ntworks usng Optcal Fbr Dstrbutd Tmpratur Snsng Systm, Powr Engnrng Journal, Vol.3, 999, pp.9-96 [3] Vaslou.D K-E, Agors.D, Pyrgot.E, A Rvw on th Applcaton of Fbr Optcs on Hgh Voltag Lns, WSEAS Transactons on Crcuts and Systms, Vol.3, No.5, 004, pp.9-96 [4] Jay A.Wllams, John S.Coopr, Thomas J.Rodnbaugh, t al, Incrasng Cabl Ratng by Dstrbutd Fbr Optc Tmpratur Montorng and Ampacty Analyss, IEEE Transmsson and Dstrbuton Confrnc, Vol., 999, pp.8-34 [5] H.J.L, Estmaton of Sol Thrmal Paramtrs from Surfac Tmpratur of Undrground Cabls and Prdcton of Cabl Ratng, IEE Gnraton Transmsson and Dstrbuton, Vol.5, No. 6, 005, pp [6] Shun-Hsn Huang, W-Jn L, Mng-Ts Kuo, An Onln Dynamc Cabl Ratng Systm for an Industral Powr Plant n th Rstructurd Elctrc Markt, IEEE Transactons on Industry Applcaton, Vol.43, 007, pp [7] Carlos Garrdo, Antono F.Otro and Jos Cdras, Thortcal Modl to Calculat Stady- Stat and Transnt Ampacty and Tmpratur n Burd Cabls, IEEE Transactons on Powr Dlvry, Vol.3, 003, pp [8] C.C.Hwang, J.J.Chang, H.Y.Chn, Calcualton of Ampacts for Cabls n Trays usng Fnt Elmnts, Elctrc Powr Systms Rsarch, Vol.54, 000, pp.75-8 [9] Sharfan Attar.S, Yagoub.MCE, Mohammad.F, Smulaton of Elctro-thrmal Effcts n Dvc and Crcut, WSEAS Transatons on Crcut and Systms, Vol.5, No.7, 006, pp (fem) [0] D.Labrds, V.Hatzathanassou, Fnt Elmnt Computaton of Fld, Forcs and Inductancs n Undrground SF6 Insulatd Cabls usng a Coupld Magnto-Thrmal Formulaton, IEEE Trans.Magn, Vol.30,994, pp [] G.J.Andrs, M.Caaban, N.Bdard, t al, Nw Approach to Ampacty Evaluaton of Cabls n Ducts usng Fnt Elmnt Tchnqu, IEEE Transactons on Powr Dlvry, vol. PWDR-, 987, pp [] J.Nahman, M.Tanaskovc, Dtrmnaton of th Currnt Carryng Capacty of Cabls usng th Fnt Elmnt Mthod, Elctrc Powr Systms Rsarch, Vol.6, 00, pp.09-7 ISSN: Issu 4, Volum 7, Aprl 008