Aalborg Universitet. Published in: IEEJ Transactions on Power and Energy. DOI (link to publication from Publisher): /ieejpes.129.

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1 Aalborg Unverstet Resstor Type Superonutng Fault Current Lmter: Optmum Shunt Resstane Determnaton to Enhane Power System Transent Stablty Hooshyar, Hossen; Heyar, Hossen; Savagheb, Meh; Sharf, Reza Publshe n: IEEJ Transatons on Power an Energy DOI (lnk to publaton from Publsher): /eejpes Publaton ate: 2009 Doument Verson Early verson, also known as pre-prnt Lnk to publaton from Aalborg Unversty Ctaton for publshe verson (APA): Hooshyar, H., Heyar, H., Savagheb, M., & Sharf, R. (2009). Resstor Type Superonutng Fault Current Lmter: Optmum Shunt Resstane Determnaton to Enhane Power System Transent Stablty. IEEJ Transatons on Power an Energy, 129(2), General rghts Copyrght an moral rghts for the publatons mae aessble n the publ portal are retane by the authors an/or other opyrght owners an t s a onton of aessng publatons that users reognse an abe by the legal requrements assoate wth these rghts.? Users may ownloa an prnt one opy of any publaton from the publ portal for the purpose of prvate stuy or researh.? You may not further strbute the materal or use t for any proft-makng atvty or ommeral gan? You may freely strbute the URL entfyng the publaton n the publ portal? Take own poly If you beleve that ths oument breahes opyrght please ontat us at vbn@aub.aau.k provng etals, an we wll remove aess to the work mmeately an nvestgate your lam. Downloae from vbn.aau.k on: november 08, 2018

2 Paper RESISTOR TYPE SUPERCONDUCTING FAULT CURRENT LIMITER: OPTIMUM SHUNT RESISTANCE DETERMINATION TO ENHANCE POWER SYSTEM TRANSIENT STABILITY H. Hooshyar, H. Heyar, M. Savagheb, an R. Sharf *, Non-member In power systems, Resstor type Superonutng Fault Current Lmters (RSFCL) an lmt the prospetve short-rut urrents to lower levels, so that the unerrate swthgears an operate safely. Beses, RSFCLs an enhane the power system transent stablty f they are aompane by approprate shunt resstanes. Ths paper presents a metho of optmum shunt resstane etermnaton for transent stablty mprovement. The metho s base on mnmzaton of rotor knet energy osllatons. Meanwhle to make t more omprehensble, the metho s utlze to etermne the shunt resstanes of three RSFCLs nstalle n a 9-bus 3-generator sample network. All of the smulatons have been arre out by EMTP/ATP. The paper begns by moelng an RSFCL. Then RSFCL rtal urrent etermnaton s susse n a moel system. Fnally, a metho of optmum shunt resstane etermnaton for transent stablty mprovement s presente. Keywors : Resstor type Superonutng Fault Current Lmters (RSFCL), Hgh Temperature Superonutor (HTS), Transent Stablty, Dret Searh Metho 1. INTRODUCTION As eletr power systems grow an beome more nteronnete, at some ponts, the avalable fault urrents levels may eee the mamum short-rut ratngs of the swthgear. As a onsequene, the fault urrent nrease leas to more serous transent stablty problems. Tratonally, to allevate the ost of swthgear an bus replaements, the most ommon ways to lmt hgh-level fault urrents are: upratng of swthgear an other equpment, splttng the power gr an ntroung hgher voltage onnetons (AC or DC), usng urrent-lmtng fuses or seres reators or hgh-mpeane transformers, an usng omple strateges lke sequental network trppng. Nevertheless, these alternatves may reate other problems suh as loss of power system safety an relablty, hgh ost an nreasng power losses [1]. In the past few years, many kns of fault urrent lmtng eves have been move forwar n aorane wth the evelopment of power eletrons, magnet tehnology an superonutng materals [2-4]. In reent years, Resstor type Superonutng Fault Current Lmters (RSFCL) as the eves fault urrent lmtng have been progressng ue to the avanement of superonutng tehnology [2,5,6]. Ther man avantages are: neglgble nfluene on the network uner normal ontons, nstantaneous lmtng of fault urrent an automat response wthout eternal trgger. Furthermore, they an also mprove the power system transent stablty f sutable shunt resstane s use as the lmtng element [7-10]. Ths s beause the fferene between the mehanal nput power an the eletral output power n the generator after a fault s erease ue to effetvely absorpton of the real power by the shunt resstane. Over the last eae, some researhes have been evelope on Center of Eellene for Power System Automaton an Operaton, Eletral Engneerng Department, Iran Unversty of Sene an Tehnology, Tehran, Iran. the RSFCL mpat on the transent stablty mprovement. For eample, n 2000, Yokomzu et al. nvestgate the nfluene of an RSFCL on the transent stablty of a 4-bus network [11,12]. They emonstrate the postve mpat of the RSFCL on the transent stablty by llustratng the generators output atve power osllatons wth an wthout RSFCL. In 2001, Tsua enorse Yokomzu s lam by llustratng the generator loa angle osllatons wth an wthout RSFCL n a sample network [13]. Also, he showe the neessty of optmum shunt resstane etermnaton for ahevng the mamum transent stablty. Smlar results have been emonstrate n [14-17]. In 2005, Ye nvestgate the effet of RSFCL loaton on ts apablty to mprove the transent stablty. The results showe that the less the stane between generator an RSFCL, the hgher the stablty. As an be learly nferre from the above paragraph, the researhes are restrte to emonstraton of RSFCL postve effet on the transent stablty an a omprehensve stuy on optmum shunt resstane etermnaton s requre. To ompensate for the shortage of researh n ths fel, a metho for optmum shunt resstane etermnaton s presente n ths paper. The metho s base on mnmzaton of rotor knet energy osllatons. Meanwhle to make t more omprehensble, the metho s utlze to etermne the shunt resstanes of three RSFCLs nstalle n a 9-bus 3-generator sample network. All of the smulatons have been arre out by EMTP/ATP. The paper s organze as follows. In seton II, theoretal bases an moelng of RSFCL s presente. Seton III presents the metho of rtal urrent etermnaton of RSFCLs nstalle n the moel system whh s ntroue n appen I. Fnally, a metho of optmum shunt resstane etermnaton for transent stablty mprovement s presente n seton IV. 2. THEORETICAL BASES AND MODELING OF RSFCL An RSFCL has three stanar operatng zones: the superonutng zone when the transport urrent an the 1

3 temperature of the Hgh Temperature Superonutor (HTS) are both uner ther rtal ponts, the flu flow zone when the transport urrent eees the rtal urrent level (I ) uner the onton that the temperature of the HTS s less than the rtal temperature (T ), an the normal zone when the temperature of the HTS eees the T [18]. In the frst zone (superonutng), t an be easly nferre that: R RSFCL = 0, f s < I an T < T ( where R RSFCL s the resstane of the RSFCL. In the seon zone (flu flow), the rtal urrent ensty an generatng haratersts of flu flow resstane epen on the HTS temperature (T). The flu flow resstane also hanges wth the nstantaneous value of transport urrent ensty (j). Suh temperature an flu ensty epenenes have to be taken nto the onseraton n the smulaton of the lmtng performane of the RSFCL. Detale formulaton an be foun n [19]. The HTS resstane n the flu flow zone follows the followng formula: 2 J T T ρ b f J V 0 0 s R = { ( RSFCL + 1}, 2 j T Tb I (2) f s > I an T < T where T b, J 0, j, ρ f, V s, an A s are the temperature of lqu ntrogen, the rtal urrent ensty, the transport urrent ensty, the flu flow state resstvty, the HTS volume, an the HTS ross-seton respetvely. In the thr zone (normal), resstane of HTS s only a funton of the temperature [20], that s: T V R =, f T > T RSFCL ρ (3) s n ( ) 2 T As where ρ n s the normal state resstvty. Detale esrpton of the equaton an be foun n [21,22,23]. The temperature of the RSFCL s alulate by the followng equatons: RRSFCL 2 W = t V T s W P = C V ( t t C ool f Tb (5) s where C, P ool, t f, an t are the spef heat of the HTS, the oolng system power, the fault start tme, an the total smulaton tme respetvely. It s worthy to be note that n transmsson systems, the RSFCL shoul be aompane by a shunt resstane rather than beng alone [24-28]. RSFCL shoul be esgne n suh a way that t goes mmeately to ts normal zone after a fault ourrene. RSFCL operaton n normal zone leas to a hgh resstane whh fores the fault urrent to go through the shunt resstane. The shunt resstane value shoul be etermne n suh a way that t has the mamum postve mpat on the transent stablty. Some of the most mportant reasons of shunt resstane utlzaton for fault urrent lmtaton are as follows: The fault urrent level s very hgh n transmsson systems. So, t leas to a great nrease of RSFCL temperature. Consequently, t takes a long tme for the RSFCL to be oole enough to return ) (4) to ts superonutng zone after the fault has been leare. By usng the shunt resstane as the lmtng eve, the fault urrent runs through the shunt resstane. So the RSFCL temperature nrease wll be reue an t wll ool own muh faster after the fault has been leare. Hene the RSFCL returns to ts superonutng zone n a shorter pero. In other wor, It an reat faster. The hgh fault urrent level an the subsequent temperature nrease may be so great that they eterorate the hemal struture of the HTS. The HTS eteroraton may prevent t to return to ts superonutng zone forever. The optmum value of shunt resstane s retly epenent on the power network onfguraton. As the power network grows an beomes more nteronnete, the optmum value hanges. So, t s neessary to alulate an nstall the upate optmum value whenever major hanges have been ourre n power network. Replang the resstanes wth the upate values s muh smpler an heaper than replang the RSFCLs. In ths stuy, YBCO oate stanless steel tapes ntroue n [29] are use as the HTS. Table 1 summarzes the tape parameters. The oolng system power (P ool ) s equal to 23kW. 3. DETERMINATION OF CRITICAL CURRENT VALUE Crtal urrent value of an RSFCL s ts most mportant parameter. Generally, the rtal urrent value shoul be etermne n orer to satsfy the followng ontons [30]: RSFCL shoul not operate n steay state. RSFCL shoul not operate aganst the transent urrent after the fault learane. The power system moel use n ths stuy s ntroue n Appen I. It shoul be note that the selete moel system s only a sample. The propose metho for optmum shunt resstane etermnaton s not epenant to the moel system an the sample s use only to make the metho more omprehensble. Ths sample s small enough to be eplanable n a paper. The probable faults are shown n Fg. 1. Sne the network s a sample not a real network, the probable faults are suppose to be 3-phase to groun faults loate at two ens of all transmsson lnes. Ths s only a supposton. It s obvous that ntermeate ponts of the lnes or any other ponts an be suppose as the loaton of probable faults. But t shoul be emphasze that the metho s not epenant to the kn an loaton of the faults. All fault types an all fault loatons an be taken nto onseraton whle usng ths metho. In a real network, these faults shoul be etermne by revewng the reports on the faults (reore by fault reorers) Table 1. HTS parameters Crtal temperature T 107 K Lqu ntrogen temperature T b 77 K Crtal urrent ensty J kA/m 2 Flu flow state resstane ρ f Ωm Normal state resstane ρ n 0.3Ωm Speal heat C 1.5MJ/m 3 Length l m Cross seton A s m 2 2 IEEJ Trans. EIS, Vol., No.,

4 RSFCL: OPTIMUM SHUNT RESISTANCE DETERMINATION TO ENHANCE POWER SYSTEM TRANSIENT STABILITY Fg. 1. moel system. whh have been ourre urng the prevous years n the network. The tme sequene of smulaton s organze as follows: a three phase lne to groun ours at eah fault pont (F1 to F12) at t=0.5s whle the phase voltage angles are ϕ = 0, ϕ = 2π, b ϕ = + 2π, an the rut breakers, CBs, on 3 3 the faulte lne are opene at t=0.6s. Fg. 2 shows the nstantaneous mamum value of fault urrent, after-cb-openng urrent an steay state urrent flowng nto Y se of transformers for eah fault pont, when RSFCLs are not nstalle. In orer to satsfy the above ontons an by onserng Fg. 2, the rtal urrent of RSFCL1, RSFCL2, an RSFCL3 are set to 7p.u, 6p.u., an 4.5p.u., respetvely. Consequently, the three RSFCLs o not operate n steay state an also aganst the transent urrent after the fault learane. The p.u. values are base on transformers Y se steay state urrent. Table 2 summarzes the operatng state of the RSFCLs for eah fault pont. 1 an 0 represent operaton an no operaton of RSFCLs, respetvely. Fgs. 3, 4, an 5 show the fault urrent of phase 'a' orgnate from F1 flowng to Y se of Tr. 1, Tr. 2, an Tr. 3, respetvely. As shown n these fgures, the fault urrents an the transent urrents after CB openng are effetvely lmte by the RSFCLs. It s worthy to be note that the RSFCLs reats n the frst yle after the fault ours, whle no CB s able to reat. In our stuy the CBs of the faulty lne lear the fault at t=0.6s (5 yles after the fault ourrene). Fg. 6 an Fg. 7 show the resstve behavor an temperature varaton of the RSFCL1 HTS respetvely, whle F1 ours. As shown n these fgures, the RSFCL1 goes mmeately to ts normal zone after the fault ourrene at t=0.5s through the flu flow zone. In fat the mle step s the flu flow zone. After the fault ours, the RSFCL transport urrent eees the rtal urrent level. So t goes to ts flu flow zone from the superonutng zone. Sne the resstane of RSFCL has a non-zero value n the flu flow zone, ts temperature nreases mmeately. After the temperature nreases from the rtal value, the RSFCL goes to ts normal zone from the flu flow zone. Ths suen reaton s beause of the RSFCL1 HTS mmeate temperature nrease, beomng more than the rtal temperature value whh s 107 K. In ths zone, t s possble to reah 7kΩ by usng a seres of moules ntroue n [29]. Meanwhle, ths a Fg. 2. mamum values of urrents for eah fault pont. resstane an be muh more than 7kΩ. It may be so hgh that RSFCLs are sometmes moele wth an open swth when they are n normal zone. Ths type of moelng has been use n [24-28]. After the fault learane at t=0.6s, the RSFCL1 HTS s oole own to less than the rtal temperature value. Subsequently, the RSFCL1 returns to ts superonutng zone an ts resstane ereases suenly. 4. OPTIMUM SHUNT RESISTANCE FOR TRANSIENT STABILITY IMPROVEMENT 4.1 THEORETICAL DISCUSSION Conserng a generatng unt onsstng of a three phase synhronous generator an ts prme mover, the rotor moton s etermne by Newton s seon law, gven by [31]: 3

5 m = T T T α (6) m m e = where m, α m (t), T m (t), T e (t), an T a (t) are total moment of nerta of the rotatng masses (kgm 2 ), rotor angular aeleraton (ra/s 2 ), mehanal torque supple by the prme mover mnus the retarng torque ue to mehanal losses (Nm), eletral torque that aounts for the total three phase eletral power output of the generator plus eletral losses (Nm), an net aeleratng torque (Nm), respetvely. By multplyng equaton 6 by rotor angular veloty ( ω (t) ), the followng equaton an be m obtane: m ωm = Pm Pe Pa t ω (7) m = where P m (t), P e (t), an P a (t) are mehanal power supple by the prme mover mnus mehanal losses (Watt), eletral power output of the generator plus eletral losses (Watt), an net aeleratng power (Watt), respetvely. As the knet energy of the rotatng masses (W(t)) s equal to 1 mω 2 ( ) 2 t m, equaton (7) an be wrtten as: W Pm Pe = Pa t a = (8) Followng a fault ourrene, P e (t) ereases rastally an subsequently the rotatng masses aelerate. Ths aeleraton leas to generator nstablty. An RSFCL aompane by an approprate shunt resstane an absorb the real power effetvely an mprove the power system transent stablty. 4.2 OPTIMIZATION METHOD STABILITY CRITERION In orer to evaluate the shunt resstane nfluene on the power system transent stablty, a rteron shoul be efne to quantfy the stablty onept. Conserng equaton 8, the rteron s efne base on the knet energy of the rotatng masses. Ths rteron s as below: 3 ts W = W t (9) = 1 t 0 where W, W, t S, an are stablty rteron, knet energy of the rotatng masses of the th generator, smulaton tme, an weghtng fator of the th generator, respetvely. In fat, the t epresson W (t) alulates the absolute fferental value of the th generator knet energy n eah moment. By usng the ntegral operator, these values are aumulate urng the smulaton tme. Fnally, the sgma as the ntegral operator fnal values for fferent generators together. Hene the value of W s an ne to the knet energy osllatons of the network generators. It s lear that W s equal to zero n power system steay state operaton beause the knet energy of the generators are onstant an have no osllaton. Also, the more severe the sturbane, the greater the W. So, the optmum shunt resstane value s the value whh mnmzes W. The smulaton tme, t S, s 10s whh s long enough to show the ampng behavor of the knet energy osllatons. In fat, The slmulaton pero shoul be selete so long that t shows the tren through whh the osllatons amp own or verge. The weghtng fator,, s alulate usng the followng equaton: S (10) = 3 = 1 S where S s the rate apparent power of the th generator. In ths way, the greater s alloate to the generator wth greater rate power OPTIMUM SHUNT RESISTANCE DETERMINATION The Dret Searh Metho ntroue n [32] has been utlze to fn the optmum shunt resstane value whh mnmzes W. Ths metho searhes a set of ponts aroun the urrent pont, lookng for one where the value of the objetve funton s lower than the value at the urrent pont. The parameters of the Dret Searh Metho, aapte for solvng ths problem, are as below: Table 2. operatng state of RSFCLs Phase F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 a RSFCL1 b a RSFCL2 b a RSFCL3 b IEEJ Trans. EIS, Vol., No.,

6 RSFCL: OPTIMUM SHUNT RESISTANCE DETERMINATION TO ENHANCE POWER SYSTEM TRANSIENT STABILITY Fg. 3. fault urrent of phase 'a' orgnate from F1 flowng to Y se of Tr 1. Fg. 4. fault urrent of phase 'a' orgnate from F1 flowng to Y se of Tr 2. 5

7 Fg. 6. resstve behavor of RSFCL1 HTS whle F1 ours. Fg. 7. temperature varatons of RSFCL1 HTS whle F1 ours. Fg. 5. fault urrent of phase 'a' orgnate from F1 flowng to Y se of Tr 3. Pattern: A pattern s a olleton of fe reton vetors that the Dret Searh Metho uses to etermne whh ponts to searh at eah teraton. The mamal bass pattern (2N vetors) has been selete for ths problem. Sne the objetve funton of ths problem (W ) has three nepenent varables (R1, R2, R3), the pattern onssts of the followng vetors: v1 = [1 0 0], v2 = [-1 0 0], v3 = [0 1 0] v4 = [0-1 0], v5 = [0 0 1], v6 = [0 0-1] Stoppng Crtera: The followng onton has been onsere as Stoppng Crtera of the problem k k + 1 optmzaton: ( W W ) 1 C ( R1, R 2, R3) C ( R1, R2, R3) < Bouns: The results of the optmzaton shoul satsfy the followng onton: 0 p. u. ( R1, R2, R3) 1p. u., frstly beause the eletral resstane s a postve value an seonly beause usng values greater than 1p.u. leas to eessve fault urrent lmtaton. Ths unesrable lmtaton makes the proteton relays unable to stngush the fault urrent from the steay state urrent. Intal Pont: For ths problem, the Intal Pont has been onsere equal to (R1, R2, R3)=(0.5p.u., 0.5p.u., 0.5p.u.) whh s the mle pont of the bouns. It s worthy to be note that by seletng the mamal bass pattern (2N) an by seletng proper length for vetors, the Dret Searh metho tests the target funton values for fferent ponts 6 IEEJ Trans. EIS, Vol., No.,

8 RSFCL: OPTIMUM SHUNT RESISTANCE DETERMINATION TO ENHANCE POWER SYSTEM TRANSIENT STABILITY Table 3. Optmum Resstane Canates an Fnal Values of the Stablty Crteron F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 (R1, R2, R3) p.u. 0.7, 0.95, 0.3) 0.95, 0.2) (0.3, 1, 0.9, 0.975, 0.95) 0.975, 0.95) 0.9, 0.9, 1, 0.95) 1, 0.95) 0.7, W fnal Table 4. Fault Weghtng Fators F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 a nse the bouns whh have been efne for (R1, R2, R3) values. In ths way, the Dret Searh Metho moves towars the global mnmum rather than loal mnmums. Table 3 shows the shunt resstane values mnmzng W, obtane by the Dret Searh Metho, whle eah of the probable faults (F1 to F12) ours. In orer to selet the shunt resstane optmum value from the values mentone n table 3, the followng equaton s evelope: = 12 fnal ( j) = 1 W a W ( j) (1 where W fnal ( j), a, an W ( j) are the fnal values of the stablty rteron, weghtng fator of the th fault, an stablty rteron value for the jth ase (R 1j, R 2j, R 3j ) (the values mentone n table 3) whle the th fault ours, respetvely. In fat, the equaton 11 etermnes the optmum value by nvestgatng the effet of the W - mnmzng shunt resstane of eah fault (the values mentone n table 3) on the network stablty whle the other faults our. The weghtng fator, a, shoul be efne aorng to the probablty of the th fault ourrene. Thus, a s alulate usng the followng equaton: n a (12) = 12 k = 1 n k where n s the yearly number of the th fault ourrene, whh has been obtane from the network statsts. In ths way, the more probable the th fault, the greater the a. Table 4 shows the fault weghtng fators of the sample network use n ths stuy. Table 3 shows the fnal values of the stablty rteron ( W fnal ), obtane by the equaton 11, whle eah of the values mentone n ths table s nstalle. As shown n ths table, the fnal W has been mnmze when (R1, R2, R3) = (0.2p.u., 0.9p.u., 1p.u.). So 0.2p.u., 0.9p.u., an 1p.u. are the optmum values of R1, R2, an R3, respetvely. Fg. 8 shows the flowhart of the mentone metho. In orer to emonstrate the metho effetveness, the knet energy of the G1 rotatng masses, whle F1, F2, an F3 ours, s shown n Fg.s 9, 10, an 11 respetvely for the followng ases: Fg. 8. flowhart of metho of optmum shunt resstane etermnaton. 1. When no fault ours. 2. When the fault ours whle the shunt resstanes has the best values. 3. When the fault ours whle the shunt resstanes has the 7

9 optmum values. 4. When the fault ours whle no RSFCL has been nstalle. By onserng the Optmum Case n Fg.s (9-1, t an be seen that the osllatons of G1 knet energy, whle F1 ours, s muh severe than the osllatons whle F2 or F3 ours. It s beause; the stane between the loaton of F1 an G1 s shorter than the stane between the loaton of F2/F3 an G1. Also, sne the loaton of F2 an F3 s appromately the same (at two ses of Fg. 9. knet energy of G1 rotatng mass whle F1 busbar no.5), the behavors of G1 knet energy, whle F2 an F3 ours, are the same. It s worthy to be note that the shunt resstane optmum values are not neessarly equal to the best values of eah fault loaton. Beause the optmum values are obtane to mamze the transent stablty for all fault loatons, whereas the best values are obtane onserng a spef fault. 5. CONCLUSION A metho of optmum shunt resstane etermnaton of resstor type superonutng fault urrent lmters for transent stablty mprovement was presente. The metho was base on the mnmzaton of the rotor knet energy osllatons usng the Dret Searh Metho. The metho was apple to a sample network an ts effetveness was emonstrate by showng the knet energy of the rotatng masses n fferent ases. APPENDIX I The power system moel use n ths stuy s shown n Fg. 1 [33]. It onssts of three generators (G1, G2 an G3), transformers an ouble-rut transmsson lnes. In ths fgure, the lne parameters are numerally shown n the form R+jX (jb/2) per phase wth one lne. Conserng the transent stablty mprovement as the target of ths stuy, the RSFCLs shoul be nstalle eatly after the generators to reat aganst all the fault urrents passng through the generators. So, three RSFCLs wth shunt resstane are nstalle at Y se of the transformers, Tr. 1, Tr. 2, an Tr. 3. The moels of AVR (Automat Voltage Regulator) an GOV (Governor) are shown n Fg. 12. Table 5 shows the parameters of the generators [30]. Fg. 10. knet energy of G1 rotatng mass whle F2 ours. Fg. 12. AVR an governor moels. Fg. 11. knet energy of G1 rotatng mass whle F3 ours. 8 IEEJ Trans. EIS, Vol., No.,

10 RSFCL: OPTIMUM SHUNT RESISTANCE DETERMINATION TO ENHANCE POWER SYSTEM TRANSIENT STABILITY Table 5. generator parameters (a) G1 S (MVA) q V (kv) 16.5 q r a l q q q H (b) G2 S (MVA) 192 q V (kv) 18 q r a l q q q H 0.83 () G3 S (MVA) 128 q V (kv) 13.8 q r a l q q q H 0.4 Referenes ( A. J. Power : An overvew of transmsson fault urrents, Colloquum on Fault Current Lmters A Look at Tomorrow: IEE Lonon, Dgest 1995/026 (1995) (2) R. F. Gese : Assessment stuy of superonutng fault urrent lmters operaton at 77K, IEEE Trans. Power Delvery, vol. 8; no. 3, pp (July 1993) (3) R. K. Smth : Sol state strbuton urrent lmter an rut breaker applaton requrements an ontrol strateges, IEEE Trans. PWRD, vol. 8, no. 3, pp (July 1993) (4) E. Thures : Towar the superonutng fault urrent lmter., IEEE Trans. on Power Delvery, vol. 6, pp (Apr. 199 (5) T. Hara, T. Okuma, T. Yamamoto, an D. Ito : Development of a new 6.6kV/1500A lass superonutng fault urrent lmter for eletr power systems, IEEE Trans. on Power Delvery, vol. 8, no. 1, pp (1993) (6) M. Leung : Superonutng fault urrent lmters, IEEE Power Engneerng Revew, pp (Aug. 2000) (7) M. Sjostrom, R. Cherkaou, an B. Dutot : Enhanement of power system transent stablty usng superonutng fault urrent lmters, IEEE Trans. on Apple Superonutvty, vol. 9, no. 2, pp (1999) (8) M. Yagam, T. Murata, J. Tamura : Stablzaton of synhronous generator by superonutng fault urrent lmter, IEEE/PES Wnter Meetng, vol. C, (2000) (9) M. Yagam, T. Ounsh, T. Murata, an J. Tamura : Enhanement of power system transent stablty by superonutng fault urrent lmters, IASTED Conf. on Power an Energy Systems, pp (200 (10) M. Yagam, T. Murata, an J. Tamura : An analyss of superonutng fault urrent lmter for stablzaton of synhronous generators uner unbalane faults, IEE Trans. of Japan, vol. 119-B, no. 12, pp (1999) (1 Y. Yokomzu, K. Yukta, an K. Mzuno : Epermental stues on power system transent stablty ue to ntrouton of superonutng fault urrent lmters, IEEE Power Engneerng Soety Wnter Meetng,, vol. 2, pp (Jan. 2000) (12) Y. Yokomzu an K. Yukta : A stuy on power system transent stablty ue to ntrouton of superonutng fault urrent lmters, IEEE Internatonal Conferene on Power System Tehnology, vol. 1, pp (De. 2000) (13) M. Tsua, Y. Mtan, an K. Tsuj : Applaton of resstor base superonutng fault urrent lmter to enhanement of power system transent stablty, IEEE Trans. on Apple Superonutvty, vol. 11, no. 1, pp (Mar. 200 (14) L. Ye an L. Ln : Applaton stues of superonutng fault urrent lmters n eletr power systems, IEEE Trans. on Apple Superonutvty, vol. 12, no. 1, pp (Mar. 2002) (15) M. Yagam, T. Murata, an J. Tamura : Stablzaton of synhronous generators by superonutng fault urrent lmter, IEEE Power Engneerng Soety Wnter Meetng, vol. 2, pp (Jan. 2000) (16) N. Hayakawa, H. Kagawa, an H. Okubo : A system stuy on superonutng fault urrent lmtng transformer (SFCLT) wth the funtons of fault urrent suppresson an system stablty mprovement, IEEE Trans. on Apple Superonutvty, vol. 11, no. 1, pp (Mar. 200 (17) S. Lee : Stablty analyss of a power system wth superonutng fault urrent lmter nstalle, IEEE Trans. on Apple Superonutvty, vol. 11, no. 1, pp (Mar. 200 (18) T. Artake an T. Noa : Relaton between rtal urrent ensty an flu flow resstane n B2223 bulk element for fault urrent lmter, IEEE Trans. on Apple Superonutvty, vol. 13, no. 2, pp (June 2003) (19) H. Shmzu an Y. Yokomzu : A stuy on requre volume of superonutng element for flu flow resstane type fault urrent lmter, IEEE Trans. on Apple Superonutvty, vol. 13, no. 2, pp (June 2003) (20) P. Taor an D. Buzon : Superonutng fault urrent lmter wth bulk materals, Elsever Physa Journal, pp (2002) (2 H. Km an H. Cho : Resstane of superonutng fault urrent lmters base on YBa 2Cu 3O 7 thn flms after quenh ompleton, Elsever Physa Journal, pp (2002) (22) H. Km an H. Cho : Cryogens, Elsever Physa Journal (200 (23) L. Ye an K. Juengst : Moelng an smulaton of hgh temperature resstve superonutng fault urrent lmters, IEEE Trans. on Apple Superonutvty, vol. 14, no. 2, pp (June 2004) (24) Y. Yokomzu, K. Yukta, an K. Mzuno : Epermental stues on power system transent stablty ue to ntrouton of superonutng fault urrent lmters, IEEE Power Engneerng Soety Wnter Meetng, vol. 2, 9

11 pp (Jan. 2000) (25) M. Yagam, T. Murata, an J. Tamura : Stablzaton of synhronous generators by superonutng fault urrent lmter, IEEE Power Engneerng Soety Wnter Meetng, vol. 2, pp (Jan. 2000) (26) Y. Goto an K. Yukta : A stuy on power system transent stablty ue to ntrouton of superonutng fault urrent lmters, IEEE Internatonal Conferene on Power System Tehnology, vol. 1, pp (De. 2000) (27) M. Tsua, Y. Mtan, an K. Tsuj : Applaton of resstor base superonutng fault urrent lmter to enhanement of power system transent stablty, IEEE Trans. on Apple Superonutvty, vol. 11, no. 1, pp (Mar. 200 (28) N. Hayakawa, H. Kagawa, an H. Okubo : A system stuy on superonutng fault urrent lmtng transformer (SFCLT) wth the funtons of fault urrent suppresson an system stablty mprovement, IEEE Trans. on Apple Superonutvty, vol. 11, no. 1, pp (Mar. 200 (29) A. Usoskn, H. Freyhart, an A. Issaev : SUPERPOLI fault urrent lmters base on YBCO oate stanless steel tapes, IEEE Trans. on Apple Superonutvty, vol. 13, no. 2, pp (Jun. 2003) (30) M. Yagam, T. Murata, S. Shbata, an J. Tamura : Improvement of power system transent stablty by superonutng fault urrent lmter, IEEE Transmsson an Dstrbuton Conferene an Ehbton, vol. 1, pp (Ot. 2002) (3 J. Glover, M. Sarma : Power system analyss an esgn, PWS Publshng Company (1993) (32) R. M. Lews an V. Torzon : A globally onvergent augmente lagrangan pattern searh algorthm for optmzaton wth general onstrants an smple bouns, SIAM Journal on Optmzaton, vol. 12, no. 4, pp (2002) (33) P. M. Anerson an A. A. Foua : Power system ontrol an stablty, Iowa Sate Unversty Press (1977) Meh Savagheb was born n Karaj, Iran, n He reeve hs B.S. egree from Tehran Unversty, n 2004 an M.S. egree wth hghest honors from Iran unversty of Sene an Tehnology (IUST), n 2006, both n eletral engneerng. He s now perusng hs PhD n IUST. Hs man researh nterests nlue nuton motors rve, loang apablty of power system omponents, power qualty an artfal ntellgene applaton n power systems. Reza Sharf was born n Tehran, Iran n He reeve hs B.S. egree n eletron engneerng from Glan Unversty an hs M.S. egree n eletral engneerng from Iran Unversty of Sene an Tehnology (IUST) n 1995 an 1999, respetvely. He s urrently pursung hs PhD egree at the epartment of Eletral Engneerng, IUST. Hs major researh nterests are superonutng fault urrent lmters an ther applatons n eletral networks. superonutvty. Hossen Hooshyar was born n He reeve hs B.S. egree n eletral engneerng from Unversty of Tehran an hs M.S. egree n power engneerng from Iran Unversty of Sene an Tehnology n 2004 an 2007, respetvely. He s now perusng hs PhD n North Carolna State Unversty. Hs researh nterests nlue spee ontrol of nuton motors an apple Hossen Heyar obtane the BS egree on Eletral Engneerng n 1985 an then an MS n Power Eletron at Loughborough Unversty n A PhD n transformer ore losses at Unversty of Wales n Followng grauaton, he was employe by IUST as an aaem member (Leturer) of Eletral Power group an he also was apponte as the Dretor of Hgh Voltage & Magnet Materals Researh Center. Hs leture utes are: Eletral Mahnes, Eletral Measurement an Instrumentatons an EMC Applatons n Eletral Power Systems. Hs researh nterests are n EMC Conseratons n Eletral Power Systems, FCL, Superonutors, Eletral Mahne Core Losses. 10 IEEJ Trans. EIS, Vol., No.,