Effect of the Series Resonance LC Tank on the Mitigation of Fault Current in Radial Distribution Networks

Transcription

1 Indian Journal of Science and Technology, Vol 9(7), DOI:.7485/ijt/6/v9i7/43495, February 6 ISSN (Print) : ISSN (Online) : Effect of the Serie Reonance LC Tank on the Mitigation of Fault Current in Radial Ditribution Network Amir Heidary *, Hamid Radmaneh and G. B. Gharehetian 3 Electrical Engineering Deartment, Amirkabir Univerity of Technology, Tehran, Iran; amir.owery@gmail.com Electrical Engineering Deartment, Aeronautical Univerity of Science and Technology, Tehran, Iran; hamid.radmaneh@aut.ac.ir 3 Electrical Engineering Deartment, Amirkabir Univerity of Technology (Tehran Polytechnic), Tehran, Iran; grtian@aut.ac.ir Abtract Thi aer rooe a novel Fault Current Limiter (FCL) for the alication on ower ytem to control voltage ag at the Point of Common Couling (PCC) during fault. Thi new FCL i a reonance tranformer, whoe rimary ide i connected to a erie caacitor and tranmiion line. Alo, the econdary ide of the tranformer i witched by a emiconductor device to change the imedance of the rimary ide of the tranformer. The main control comonent i a fat-cloing witch connected in arallel with the econdary ide of the tranformer, which i driven by the ower electronic witch. It can reond within mec. When a fault occur, the witch cloe and byae the tranformer econdary ide and fault current i limited by the reactor. So, by increaing the exiting reonant frequency, the fault current i limited. The imulated and exerimental reult how that it i feaible to develo the FCL with low cot and high reliability. The exerimental reult how the caability of the rooed FCL, too. Keyword: Fault Current Limiter (FCL), Point of Common Couling (PCC), Power uality, Reonance Tranformer. Introduction The fault current in the ower ytem tend to increae over time for different reaon; e.g., electric ower demand increae (load growth) and ubequent increae in generation, new arallel conducting ath, new interconnection within the grid and new ditributed generation unit. The fault current, flowing from the ource to the fault, lead to high dynamical and thermal tree being imoed on equiment like overhead line, cable, tranformer and witchgear 4. Therefore, there i a coniderable interet in device, which are caable of limiting fault current. Alo, variou tye of Suerconducting Fault Current Limiter (SFCL) have been reented 5 7. A Fault Current Limiter (FCL) can limit the fault current aing through it within the firt half cycle. The imlet way to limit the hort-circuit current would be the ue of an imedance (Z S ) in erie with the current ath. The drawback of thi olution i that it alo obviouly influence the ytem during normal oeration, i.e. it reult in coniderable voltage dro at high load current 8. The concet of FCL i limited to the fault current before it firt eak, although the reone eed i of greatet imortance. Since the 97, everal tye of cheme have been alied in ower ytem uch a the fue with fault-current limitation and uerconducting FCL 3. In recent year, ower electronic baed FCL have been rooed 6, which ha the feature of a erie comenation under normal condition. A new hybrid FCL ha been rooed for rimary ditribution ytem, which i a high temerature uerconducting element in arallel with two other branche 4. Suerconducting Fault Current Limiter (SFCL) can limit *Author for correondence

2 Effect of the Serie Reonance LC Tank on the Mitigation of Fault Current in Radial Ditribution Network the roective hort-circuit current to lower level, o that the underrated witchgear can be afely oerated 5. The neceity and rocedure for the alication of FCL and bu ectionalizing ytem have been dicued in 4. A rectifier SFCL with non-inductive reactor ha been reented in 6. In normal oeration mode, the imedance of the FCL i much le, while in the current limiting mode, the imedance i higher than the imedance of the network 7. There are different FCL technologie that have been uggeted by reearcher uch a: urely reitive SFCL, hybrid reitive SFCL, aturable core SFCL, hielded-core SFCL, olid-tate (SSFCL-CB), fue and bridge tye FCL. The combination of the bridge tye FCL and ower converter for voltage quality imrovement ha been uggeted in 8, where common diode bridge Fault Current Limiter and ower converter have been linked by a common DC link in the ower ytem. Fat-cloing witch baed FCL with erie comenation ha been invetigated in 9. Alo, in, it i mentioned that a DC reactor tye FCL in erie with a downtream circuit breaker can be a olution to control fault current level in electrical ditribution ytem. Sytem tudie how that the DC reactor tye FCL can not only limit the fault current to an accetable value, but alo can mitigate the voltage ag. In thi aer, the FCL tructure, reented in i carefully invetigated and it roblem are olved in a new cheme of FCL, which ha a fat-cloing witch. It effectivene i verified by imulation and meaurement. It i hown that the fat-cloing witch baed FCL ha more advantage, lower cot and higher reliability in comarion with other FCL. It can imrove the ytem tability by it fat reone after fault occurrence and erie comenation after fault clearing. The reult are comared with the FCL rooed in too.. Prooed FCL In thi ection, a None-Suerconducting Fault Current Limiter (NSFCL) baed on reonant tructure i invetigated and reult are comared with. In, the imedance of the erie reactor i very low, o it cannot control the fault current. The FCL controlled the fault current and decreaed it to 5% of it initial value, which i not enough and the tranient reone of the voltage and current of the caacitor can caue the dielectric failure and damage of devie. Advantage of the rooed FCL to the FCL introduced in are lited a follow: The magnitude of the limited current in i.65 time of the fault current, while the limited current, in thi aer, i.5 time of the fault current. Thi mean that the uggeted FCL can effectively control the fault current. Switching delay i 3 mec in, while in current aer, thi delay i decreaed to mec. In, the eak current and ark of voltage on the witch i high and caue damage to the caacitor, but in thi aer there are no ark and urge current. During the fault, the current of the witch i coniderable and can reult in witch failure. Alo, the fault overvoltage on the metal oxide urge arreter can caue it failure. In thi aer, all of the roblem are olved uing the rooed FCL. During normal oeration mode of ower ytem, the imedance of the reonance circuit include erie caacitor and the rimary winding of a erie tranformer. When the fault i haened, the emiconductor witch i cloed in the econdary ide of the tranformer and caue an increae in the imedance of the reonant circuit and a a reult the fault current limitation. A hown in Figure, in the arallel feeder, which i connected to the Point of Common Couling (PCC), the downtream fault of the faulty feeder could reult in large fault current flow, which not only might damage the erie equiment but alo can caue voltage dro at PCC. Thi voltage dro can affect other load on arallel feeder connected to PCC. A ignificant advantage of FCL technologie i their ability to remain virtually inviible to the grid under nominal oeration, introducing negligible imedance in the ower ytem until a fault event occur. Ideally, once the limiting action i no longer needed, an FCL hould quickly return to it nominal low imedance tate. Alo, an ideal FCL hould have the following characteritic: low imedance at normal oeration, a very hort recovery time, large imedance in fault condition, fault current limitation before the firt eak, roerly reond to any fault magnitude and/ or hae combination and finally high reliability and low cot. The uggeted FCL i hown in Figure. There are Generator Z PCC Load Load Figure. Sytem with load connected to PCC through arallel feeder. IL IL Fault V load V load Vol 9 (7) February 6 Indian Journal of Science and Technology

3 Amir Heidary, Hamid Radmaneh and G. B. Gharehetian three FCL, intalled in each hae of the tranmiion line for controlling the over current of each hae earately, where C i erie caacitor. Alo, tranformer are reented by T and connected in erie with the tranmiion line. In addition, the emiconductor witch, T, i connected in erie with the econdary of tranformer. In the normal oeration mode of the ower ytem, the erie caacitor and rimary winding of the tranformer have reonance frequency the ame a the ower ytem frequency, while the econdary ide of the tranformer i oen. So, the tranformer work a an AC reactor and the imedance of the FCL, i.e., C and AC reactor i near to zero. In order to decreae the flux linkage of the tranformer and voltage of the econdary, thi equiment i deigned by lowet turn of winding u to oible value. When the fault occur, the emiconductor witche intantly on and the tranformer econdary ide i hort circuited. In thi mode, the imedance of the inductor decreae uddenly, o erie caacitor limit the fault current and control the voltage of PCC. 3. FCL Control Circuit During fault, the voltage of PCC and the voltage of the downtream bue decreae uddenly. The fault detector circuit i connected to the oint n a hown in Figure 3. It conit of one bridge circuit, caacitor and a reitor. In thi circuit, the voltage on the caacitor i comared with the DC reference voltage. In the cae of decreae of the voltage of the caacitor from the reference voltage, the fault detector witch turn on the FCL witch. Uing thi control circuit, FCL can uccefully control and limit the fault current a will be hown in imulation and exerimental reult. 4. Dynamic Modeling of Prooed FCL In the rooed FCL, the emiconductor witch, T, i aumed to be an ideal witch. Alo, the turn ratio of the tranformer, T, i equal to /. The rooed FCL tranformer model i hown in Figure 4. The imedance of the load and ource i lited in Table and we have: z = R jw L () zl = RL jw LL () 4. The FCL Normal Oeration Mode In the econdary winding of the tranformer i oen circuit and the current of the emiconductor witch i equal to zero. By alying Kirchhoff Voltage Law (KVL) to the equivalent circuit hown in Figure 3, the nonlinear dynamic equation of the ower ytem can be written, a follow: inwt = Ri L di L dt C idt L (3) PCC n if C D D4 : D3 D T Fault Det ector C n if R R R3 Vref V a V b Z Z C C T load load Figure 3. diagram. a) FCL tructure and b) Controlling circuit S T R L L t R t Switching ule V c Z C load 3 S T 3 V rimary L m V terminal S 3 Figure. Prooed FCL and ytem equivalent circuit. Figure 4. Tranformer model. Vol 9 (7) February 6 Indian Journal of Science and Technology 3

4 Effect of the Serie Reonance LC Tank on the Mitigation of Fault Current in Radial Ditribution Network Table. Then, we have: Electrical network arameter Parameter Value Decrition R.5 Ω Source reitance L.9 H Source inductance C 5μf Serie caacitor L. H Primary inductance of tranformer L m.8 H magnetization inductance of tranformer L t. H econdary inductance of tranformer R Ω Primary reitance of tranformer Rt Ω econdary reitance of tranformer R L Ω Load reitance L L.H Load inductance N 3 Primary turn ratio N 3 econdary turn ratio w co wt R di L L di il = (4) dt dt C By olving Equation (4), the line current (i L ) can be written, a follow: w w = R L C i L (5) i L = w w R L C (6) Where, the equivalent reitance i R= R RL R and the equivalent inductance i L= L LL L Lm. 5. Simulation Reult of rooed FCL By olving Equation (6), the line current, i L, can be determined. In the fault oeration mode, the econdary winding of the tranformer i hort-circuited by the emiconductor witch. In thi mode, the current of the econdary ide i equal to the line current; in other word, i T = i L and i L = i (t=t ). Thi equivalent circuit i hown in Figure 5. Z ource V a According to Figure 5, Equation are written, a follow: ( ) t R = R x (7) = xt (8) xt = (9) R By uing above mentioned Equation, the right hand ide erie branch of Figure 5 i changed to arallel branch. Now, L m in Figure 5 i aralleled with L. The reduced equivalent circuit can be driven by changing the arallel branch to the erie branch, a follow: R x tt tt t = R () = x () x = () R Where, x = x xmand R R. By olving the Equation (3) we have: Where, and then, R V rimary _ R L L t R t Figure 5. Equivalent circuit of ytem conidering tranformer model. w co wt R di L L di il = eq eq (3) dt dt C Req = R R Rtt (4) Leq = L Ltt (5) In thi tudy, the fault occur at t = 4 mec. The imulation reult indicate that there i no voltage ag L m Short circuited 4 Vol 9 (7) February 6 Indian Journal of Science and Technology

5 Amir Heidary, Hamid Radmaneh and G. B. Gharehetian during the fault. After fault occurrence, the voltage of the load decreae to zero and becaue of very low imedance of emiconductor witch in on tate, the voltage of the econdary winding of the tranformer almot reache to zero. There i no any unwanted henomenon and the ytem i working under normal oeration mode. Figure 6 how the imulated load voltage. In thi figure, the fault i occurred at 4 mec and the amlitude of the load voltage reached to zero. Figure 7 how the line current during normal and fault oeration mode. Figure 7(a) rereent the line current when there i no intalled FCL in the line. Figure 7(b) Load Voltage (kv) Time (m) Figure 6. Voltage of load during normal and fault oeration condition. 6 4 how the line current while the uggeted FCL i utilized in the line. The fault current amlitude deend on the oeration of the FCL comonent. According to thi figure, the amlitude of the fault current reduce from 4 ka to 6 A. When the fault occur, FCL limit the fault current and the voltage on the Point of Common Couling (PCC) remain in an accetable level a hown in Figure 8. In thi alication, FCL can uccefully control the fault current and limit the tranient overvoltage. 6. Exerimental Reult In order to verify the FCL effectivene on the fault current, a low voltage (V rm ) laboratory rototye i built a hown in Figure 9. To verify the imulation reult, the limited fault current and the voltage of the PCC are meaured in the rototye for normal and fault oeration mode. Figure how the line current (lower waveform) and load voltage (uer waveform) before and after fault Voltage (kv) 4 - Current (ka) Time (m) a) Time (m) Figure 8. PCC voltage during the normal and fault oeration mode while FCL i connected in erie with the line. Current (A) Firt current eak Normal oeration tate Fault oeration tate Time (m) b) Figure 7. Line current during the normal and fault oeration mode a) Without FCL effect and b) With FCL effect. Figure 9. Laboratory tet etu. Vol 9 (7) February 6 Indian Journal of Science and Technology 5

6 Effect of the Serie Reonance LC Tank on the Mitigation of Fault Current in Radial Ditribution Network occurrence. Before the fault occurrence, the line current amlitude i A and the load voltage i V. The load voltage and line current are inuoidal and ytem work under normal oeration mode. In thi cae, ower electronic witch i in off tate and the voltage dro on FCL i near zero. In the intant of the fault incetion, the ower electronic witch driver change the gate ignal and thi witch i turn on. So, the erie tranformer i byaed and the erie caacitor i connected in erie with the line and fault current i decreaed to A a hown in Figure. It i aumed that the fault duration i 3 ec and then the fault i removed. In thi cae, the fault current i decreaed to the normal current and again witche turn off imultaneouly. After fault removal, the FCL voltage dro i zero and the ytem can work under normal oeration mode. Figure how the PCC voltage during the normal and fault oeration mode. Thi figure clearly how the FCL effect on the fixing the PCC voltage level to an accetable level during the fault. In the teady tate condition, the voltage dro of the FCL i equal to zero. During fault, the voltage dro i equal to the ource voltage. The voltage dro of the comonent during the fault deend on the tructure and toology of the FCL. During fault, the emiconductor witch turn on and the econdary ide of the tranformer i hort circuited. Thi witch can limit the fault current, control the voltage of the PCC and kee the amlitude in the accetable range. 7. Concluion In thi aer, a new FCL toology ha been rooed, modeled and imulated. It ha been hown that the rooed FCL can limit the fault current and adjut the voltage of PCC. The time delay of thi FCL oeration i very low, the fault detection circuit delay i le than one mec. So, FCL can limit the fault current before it firt ick. The imulation reult have been comared with imulation reult. The good agreement between the imulation and meaurement reult verifie the effectivene the rooed FCL. 8. Reference Figure. Line current (lower waveform) and load voltage (uer waveform) during the normal and fault oeration mode. Figure. PCC voltage during the normal and fault oeration mode.. Falcone CA. Beehler JE, Mekolite WE, Grzan J. Current limiting device - A utility need. IEEE Tranaction on Power Aaratu and Sytem. 974 Nov; PAS-93(6): Kamal A, Sankar S, Soundaraandian R. Otimal over current relay coordination of a real time ditribution ytem with embedded renewable generation. Indian Journal of Science and Technology. 4 Nov; 7(S7): Akthar SKJ, Chandra Sekhar G. Mitigation of voltage ag uing uerconductor Fault Current Limiter. Indian Journal of Science and Technology. 5 Se; 8(3): Elavarai R, Saravanan P. Imact of ditributed generation on ditribution ytem and it rotection. Indian Journal of Science and Technology. 4 Nov; 7(S7): Li B, Li C, Guo F, Xin Y, Wang C, Pang X. Coordination of Suerconductive Fault Current Limiter with zero-equence current rotection of tranmiion line. IEEE Tranaction on Alied Suerconductivity. 4 Oct; 4(5): Li B, Li C, Guo F, Xin Y. Over current rotection coordination in a ower ditribution network with the active Suerconductive Fault Current Limiter. IEEE Tranaction on Alied Suerconductivity. 4 Oct; 4(5): 4. 6 Vol 9 (7) February 6 Indian Journal of Science and Technology

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