PRACTICAL IMPLEMENTATION OF FSC OF A 400KV TRANSMISSION LINE-CASE STUDY

Transcription

1 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: PRACTICAL IMPLEMENTATION OF FSC OF A 400KV TRANSMISSION LINE-CASE STUDY Mr. N.M.G. KUMAR 1,Dr.P.SANGAMESWARA RAJU 2,Mr.P.VENKATESH 3,Ms.N.NEHA 4 1 Assocate Professor, Department of E.E.E., Sree Vdyankethan Engneerng College, 2 Professor, Department of E.E.E., S.V.U. College of Engneerng, 3 Asstant Professor, Department of E.E.E., Sree Vdyankethan Engneerng College, 4 PG Student, Department of E.E.E., Sree Vdyankethan Engneerng College, E-mal: nmgkumar@gmal.com, rau_ps_2000@yahoo.com, venkateshp.engg@gmal.com, nehanagam@yahoo.co.n ABSTRACT Ths paper presents a case study of practcal mplementaton of fxed seres compensaton (FSC) for relable and effectve power flow n the specfed lne. The method for adustng the lne reactance as parameters by TCSC (Thyrstor Controlled Seres Compensator) n load flow studes. Proper adustment of transmsson lne reactance as a parameter to regulate the requred power flow n a desred lne to the specfed value. The ablty to regulate power flow through certan paths n a power system networks s of partcular mportance, especally n deregulated electrcty market. The proposed approach s a rgorous model wthout any approxmatons. It does not demand any extra row or column n Jacoban matrx of NR (Newton-Raphson) for accountng the adustments of the lne reactance s placed n requred lnes. The proposed technque has been tested on IEEE 30 bus system. The results are very accurate and method converged wthout any numercal convergence problems. The proposed method can be used to estmate the requred level of compensaton n a sngle lne, multple numbers of lnes and group of lne. Here power flow and optmum power flow s per formed for reduced fuel cost and total losses n the system Keywords:-Thyrstor Controlled Seres Compensator,Thyrstor Controlled Phase Shfter, Newton - Raphson, Optmal Power Flow. controllablty of power flow and voltage are 1. INTRODUCTION termed as FACTS Controllers. It s to be noted that power electronc controllers were frst ntroduced n HVDC transmsson for not only regulaton of Modern power systems are hghly complex and are expected to full the growng demands of power wherever requred, wth acceptable qualty and costs. The economc and envronmental factors necesstate the locaton of generaton at places away from load centres.. The restructurng of power utltes has ncreased the uncertantes n system operaton. The regulatory constrants on the expanson of the transmsson network has resulted n reducton of stablty margns and ncreased the rsks of cascadng outages and blackouts. Ths problem can be effectvely tackled by the ntroducton of hgh power electronc controllers for the regulaton of power flows and voltages n AC transmsson networks. Ths allows flexble' operaton of AC transmsson systems whereby the changes can be accommodated easly wthout stressng the system. Power electronc based systems and other statc equpment that provde 252 power flow n HVDC lnks, but also for modulaton to mprove system stablty (both angle and voltage). The technology of thyrstor valves and dgtal controls was ntally extended to the development of Statc Var Compensator (SVC) for load compensaton and voltage regulaton n long transmsson lnes In 1988,Dr.Naran G. Hngoran ntroduced the concept of Flexble AC Transmsson Systems (FACTS) by ncorporatng power electronc controllers to enhance power transfer n exstng AC transmsson lnes, mprove voltage regulaton and system securty wthout addng new lnes. The FACTS controllers can also be used to regulate power ow n crtcal lnes and hence, ease congeston n electrcal networks.

2 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: FACTS does not refer to any sngle devce, but a host of controllers such as SVC, Thyrstor Controlled Seres Capactor (TCSC), Statc Phase Shftng Transformer (SPST), and newer controllers based on Voltage Source Converters (VSC) and current source converters (CSC) Statc synchronous Compensator (STATCOM), Statc Synchronous Seres Compensator (SSSC), Unfed Power Flow Controller (UPFC), Interlne Power Flow Controller (IPFC) etc. The advent of FACTS controllers has already made a maor mpact on the plannng and operaton of power delvery systems. The concept of Custom Power ntroduced by Dr.Hngoran n 1995 has extended the applcaton of FACTS controllers for dstrbuton systems wth the obectve of mprovng power qualty. An understandng of the workng of ndvdual FACTS controllers and ssues that affct ther operaton under varous condtons s essental for both students and engneers (n ndustry) who are nterested n the subect. FACTS Controllers n Power Transmsson and Dstrbuton comprehensve and up-to-date coverage of the FACTS controllers that have been proposed and developed both for transmsson and dstrbuton. Ths paper proposes a relable and effectve method to adust the varable parameters of by seres FACTS devces. 2. BASIC CONCEPTS AND PROBLEM FORMULATION 2.1. N-R method: The most wdely used method for solvng smultaneous nonlnear algebrac equatons s the Newton-Raphson method (NR).Newton s method s found to be more effcent and practcal. The number of teratons requred to obtan a soluton s ndependent of the system sze, but more functonal evaluatons are requred at each teraton. Snce n the power flow problem real power and voltage magntude are specfed for the voltage-controlled buses, the power flow equaton s formulated n polar form. Ths equaton can be rewrtten n admttance matrx as I n 1 Y V In the above equaton, ncludes bus. expressng ths equaton n polar form, we have (1) I n 1 Y V (2) The complex power at bus s * P Q V I (3) Substtutng form equaton 2 for I n eq3 n (4) P Q V Y V 1 Separatng the real and magnary parts, n. (5) P V V Y cos( ) Q 1 n 1 V V Y sn( ) (6) P J J (7) Q J J 3 4 V By runnng the load flow analyss usng NRmethod we can fne the Power flows n ndvdual lnes and loss Economc Dspatch Problem The obectve of conventonal economc dspatch (ED) problems s to fnd the optmal combnaton of power generaton that mnmzes total generaton costs whle satsfyng an equalty constrant and several nequalty constrants. The most smplfed type of obectve functon n the ED problem can be expressed as a summaton of all generatng unts operatng cost n the shape of a smooth functon : Mnmze Ʃ F (P ) (8) F (P )= α +β P + γ P 2 Where α, β, and γ represent cost coeffcents of generatng unt, P the electrcal output of generatng unt, and I ndcates the set for all generatng unts. Whle mnmzng the total generaton cost, the followng constrants should be satsfed. For energy balance, the followng equalty constrant should be satsfed as the followng equaton: Ʃ P =D+ P loss (9) Where D mples the total system demand, and P loss means the total network losses. However, the transmsson losses are not consdered n ths study. Also, generaton of power from each unt 253

3 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: should be between ts maxmum and mnmum lmts: P, mn P P, max ұ I, Where P mn corresponds wth the mnmum output of unt and P,max corresponds wth the maxmum output of unt.to consder a more realstc and accurate representaton of the obectve functon, non smooth cost functons wth a few shapes have been appled to ED problem.that s, the obectve functon of an ED problem has dscontnuous and non dfferentable ponts accordng to valve loadng, change of fuels, and prohbted zones. Therefore, t s more realstc to treat the cost functon as a set of pecewse quadratc functons as llustrated n below fgure when consderng mult fuel problems, whch are defned as follows Fgure1 pecewse quadratc cost functon of the generator (10) Where α, β, and γ correspond wth the cost coeffcents of generatng unt for the th power level, respectvely Modellng of TCSC: Consder a transmsson lne wth ts ABCD parameters and end bus voltages as shown below V V cos( ) A V P2 B. (11) Z A ( 1 Y * ) A CP 2... (12) 1 X B Z, tan R... (13) 1 2 cos( )...(14) If seres compensaton s provded, then : 1 X X C tan R... (15) Now assume that power flow n a lne s to be regulated to a desred value (P specfed ) P sp, then the correspondng new value of B.e B new can be found out usng the equaton gven below: B new.. (16) 1 2 ) V V2 cos( ) A V cos( P specfed Note that B new s also gven by the equaton from whch Xc can be calculated.consder the ntal lne reactance X=X lne of uncompensated. Wth the Xc n the lne the resultant lne reactance s gven by X=X-X c.. (17) The equaton (16) s a hghly nonlnear equaton and need to be solved teratvely and update X usng eqn. (17) accordngly. Wth the seres compensaton n the lne wll be small compared to β of the uncompensated lne. Keepng ths fact n mnd, the X c calculatons can be made n three stages as mentoned below Stage 1 Calculate β=tan -1 (X lne / R lne ), from uncompensated condton. Then cons-derng ncremental approach to avod the hgher correcton step, take Fgure2. Two port model of a Transmsson lne The power at the recevng end P2 s gven by... (18) β 1 =75% of β old Then solve equaton (16) for fndng B new usng the of the desred lne 254

4 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: obtaned from the converged voltages of base case loads flows. The correspondng X c wll be X-X c = (B 2 new R 2 ) 1/2 (19) X c -X = (B 2 new R 2 ) 1/2 (20) Wth ths X c n the lne, the resultng reactance s X=X-X c.. (21) Stage 2 Wth the above resultng X=(X-X c ) as the effectve or net reactance of the desred lne, rerun the load flow soluton. Now latest values of voltages of the lne end buses.e. are avalable. Re compute the parameters A= A α and B= B β 2, where β 1 from equaton (18), and X gven by equaton (21) As the soluton of equaton (13) s nearer to the fnal soluton, β 2 s to be taken as B= B β 2, Where β 3 from equaton (23), X s the latest net reactance of the lne. As the soluton of β 3 s much more nearer to the fnal optmal soluton take β 3 =100% of β 2... (24) Re-run the load flow and compute the X c and X fnal.by the completon of the 3 rd stage calculatons, the accurate value of X c s avalable. At every stage of the above approach calculate the power flow (P calflow ) of the lne under consderaton and ts msmatch between Psp and P calflow. Calculate the %error of the flow n the lne at the end of 3rd stage. Ths error ndcates the level of accuracy observed n the results produced by the newly proposed algorthm. 3. TEST CASE STEADY β 2 =90% of β 1 (22) Once agan solve equaton (16) for fndng B new usng latest values of and update the value of X usng equatons (20) and (21) Stage 3 Wth the above resultng X=(X- X c ) as the effectve or net reactance of the desred lne, rerun the load flow soluton. Now latest values of voltages of the lne end buses.e. are avalable. Recompute the parameters A= A α and B= B β 2 ; where β 2 from equaton (22), and X gven by equaton (21) As the soluton of equaton (13) s nearer to the fnal soluton, β 3 s to be taken as β 3 =95% of β 2.(23) Once agan solve equaton (16) for fndng B new usng latest values of and update the value of X usng equatons (20) and (22) Stage 4 Wth the latest value of X (obtaned n stage 3) n the desred lne, re-run the load flow soluton. Estmate the modfed values of A= A α and Fgure 3. IEEE 30 bus system 3.1 Results for IEEE 30 Bus System Comparson between power flow and optmal power flow wth Beta Compensaton Table1. Power Flow Results for the Lne 2-4 wth N-R Method 255

5 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: Table 2. Optmal Power Flow Results for the Lne 2-4 wth N-R Method Table 5.Power Flow Results for the Lne2-4 and 6-8 and 6-28 wth N-R Method Table3. Power Flow Results for the Lne 2-4 and 6-8 wth N-R Method Table 6. Optmal Power Flow Results for the Lne 2-4 and 6-8, 6-28 wth N- R Method Table 4.Optmal Power Flow Results for the Lne 2-4 and 6-8 wth N-R Method From the above sx tables.e. table 1 to table 6.It s dentfed that the real and reactve power flow s mproved and the optmal power flow s also mproved when compared to power flow wth 256

6 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: beta compensaton concept the varous combnatons of beta compensaton for ndvdual and group of lnes s performed. It s also observed that the ncremental fuel cost and total generaton cost s also consderable reduced. 4. PRACTICAL CASE STUDY The network for whch these FSC systems are beng nstalled n between Kadapa(YSR Dstrct) -Nagarunsagar,Andhra Pradesh,Inda lnes s as follows The man components of ths FSC are: 1.Capactor bank 2.MOV (Metal Oxde Varstor) 3.Spark Gap 4.Dampng Crcut 5.Bypass Breaker Data for the transmsson lne as follows: Lne parameters Resstance Inductance Range Ohm/km Ohm/km 5. PROTECTION OF CAPACITOR BANK: The capactor bank s the prmary equpment. For protecton of the capactor bank, the equpment provded and ther functons are lsted below: Fgure 4.Practcal test system Fgure 5.Implementaton Scheme for transmsson lne The MOV lmts the voltage rase across the capactor n cases of nternal and external faults. The spark gap of the FSC s requred for bypassng and protectng the capactors and MOV s wth n 1ms, snce the Bypass Breaker needs to approx. 52ms closng tme. The used spark gap s forced trggered and non-self extngushng. The trgger sgnal s generated by the protecton system by supervsng currents and MOV energy status. The spark gap s controlled by the Gap Trgger Electroncs (GTE), whch s duplcated. The Bypass Breaker (BBR) bypasses the FSC and thereby controls the power flow of the lne. Also the bypass breaker wll be closed to protect the bank aganst stresses due to overload or other fault stuatons. The bypass breaker s optmzed to handle ths knd of swtchng operaton. The dampng crcut s connected n seres to the spark gap and bypass breaker. Man purpose of the dampng crcut s to lmt and dampen the dscharge current of the capactor durng bypass operatons to prevent damage on other equpment. The dampng crcut conssts of a parallel connecton of dampng reactor and dampng resstor. In seres wth the dampng resstor there s a small spark gap, whch wll swtch the resstor nto the crcut durng the operaton of the forced trggered spark gap of closng of the Bypass Breaker only. Current transformers are provded at dfferent locatons to measure the current for dfferent 257

7 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: protecton system. The dsconnectors DS 1 and DS 2 (the platform dsconnectors) are used for connectng the platform & platform equpment to the lne or solatng the platform & platform equpment from the lne. The man bypass swtch s an off load dsconnectors and can be used for keepng the lne n servce wth the seres capactor banks bypassed. The earth swtches ES 1 and ES 2 are used for ear thng the platform & platform equpment after the platform has been solated from the lne. Fgure 8.Capactor Arrangement 5.1 Sngle lne dagram of FSC: Fgure 9.Capacor banks The segments C31, C32, C33 and C34 represent each 5 parallel and 5 seral capactor cans. The capactors are nternally fused. T31 s the current transformer for measurement of the unbalance current. Table 7.Techncal Data of Capactor Banks: Fgure 6.Sngle lne dagram of FSC Man Data of the Capactor Kadapa Unt bank Rated mpedance 36.9 Ohm Capactance F Rated current 1350 A Overload currents -for 8h n a 12h perod - for 30 mn n a 6h perod -for 10 mn n a 2 h perod A A A Rated Power 3 Phases MVA Protectve Level R Pu KVp Fgure 7. Layout of FSC 5.2 Component Ratngs and Capactor banks: The capactor bank s dvded nto four capactor segments whch are connected to an H-scheme per phase. Please refer to fgure below. 258

8 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: Table 8.Techncal data of MOV unts: Nomnal voltage Rated voltage V r MCOV Lmtng voltage Max. MOV current Arrester heght Creepage MO dsk type Parallel columns Seral blocks 5.3 Metal oxde varstor: 49.8 KV 84KV 58KV 156.1KV 14.5KA 1180mm 3005 mm E78SR123 (N2) 4 18 Metal Oxde Varstors are typcally placed n parallel wth seres capactors. These devces, known as MOV s are crucal n the protecton n the protecton schemes of these capactors. When a fault occurs and lne current surges to a level sgnfcantly hgher than normal, damage to the delectrc n the capactor can occur. The MOV placed n parallel wth the capactor prevents ths by actng n a manner smlar to a zener dode. Fgure 11. Inner Vew of Spark Gap Flash over range -90 to 160 kv (peak) Settng of the forced trggered operaton (U 1m )-156.1kV (peak) Tolerance - +5 % Thermal fault current carryng capablty 40 ka (rms), 1s 5.5 Dampng crcut: Dampng reactor s provded to lmt the peak value current of the dschargng capactor. The dampng resstor s connected n parallel wth the dampng reactor for obtanng the approprate dampng. Due to ths a dampng frequency s evolved whch can be used for the dampng resstor, a small spark gap s also ncluded n seres wth the dampng resstor whch fres for over voltages of the capactor. 5.4 Spark gap Fgure 10. MOV on the platform The spark gap of an FSC nstallaton s used to protect the MOV arresters and capactors aganst short tme over voltage /overload durng nternal and external faults and durng system contngences. The spark gap s connected n parallel to the capactors and the MOV arrestors Fgure 12.Dampng crcut 6.0 CALCULATIONS AND RESULTS Fxed seres compensaton for varous degree of compensaton s shown n the table Seres compensaton for nagaruna sagar to kadapa lne: 259

9 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: The transmsson lne parameters are as follows: Resstance = Ω / Km Capactance = nf / Km Inductance = Ω / Km Length of Nagaruna Sagar to Kadapa lne = 278 Kms Lne reactance of Nagaruna Sagar to Kadapa lne X L = * 278= Ω Degree of Compensaton fxed = 40% Capactve reactance requred for Nagaruna Sagar to Kadapa lne= X C1 = 0.4 * = Ω Capactance of Nagaruna Sagar to Kadapa lne C = 1 / (ω X C1 ) = μf Rated current = 1350 A Rated voltage / phase = 1350 * 36.9 = KV Rated lne voltage = * 3 = KV Rated power = 3 * * 1350 = MVAR Protectve level = 22.2 Pu= 22.2 * 2 * = KV (peak) Power transfer capablty before compensaton, P 1 = 3 * 400 * 1350 = MVA Power transfer capablty after compensaton, P 2 = (X 1 / X 2 ) * P 1 = ( / ( )) * = MVA S. No. Therefore power ncrease s nearly 66%. Table 9. Practcal results for degree of compensaton Degree Of Compens aton (%) Power before compens aton (MVA) Power after compens aton (MVA) Incre ase n Powe r (%) CONCLUSIONS In ths paper a practcal mplementaton of FSC of a 400 Kv transmsson lne s consdered and varous degree of compensaton for the lne wth ncreased power transfer capablty s also presented n table no.10 and t relable and effectve method of compensaton. An algorthm has been consdered n ths paper for estmaton of requred level of seres compensaton to regulate the specfed amount of power flow n selected lne or lnes. The mathematcal model s derved on strong fundamentals usng ABCD parameters wth no approxmatons. Ths method does not modfy the structure or sze of the Jacoban matrx of conventonal N-R method. It can be used for sngle lne or mult lnes compensaton calculatons wthout much extra computatonal burden. The method s hghly relable and fast as t retans the quadratc convergence characterstcs of N-R method. Ths new method can also be used for estmaton of the requred phase angle of a phase shfter to regulate the lne flow of the selected lne. In fact t has been tested on IEEE 30 bus system. Here an optmal power flow wth equalty and nequalty constrants s performed for optmal fuel cost, ncremental fuel cost and the results are presented n tables. REFERENCES: [1] Maheswarupu Sydulu,Elect.Eng.Dept., A new relable and effectve approach for adustment of varable parameters of TCSC and TCPS n Load flow Studes, IEEE Trans. On Power Systems,2004 [2] N. Hngoran, Flexble AC transmsson, IEEE spectrum, v.30, no. 4, pp , Aprl [3] R. Nelson, J. Ban, S. Wllams, Transmsson Seres Power flow Control IEEE Power Delvery,V.10, No.1, pp , an [4] M. Noroozan, G. Anderson, Power flow control by use of Controllable Seres components, IEEE Trans.Power Delvery vol. 8, No.3, pp ,July [5] K. L. Lo, Y.J. Ln and W.H. Sew, Fuzzy Logc Method for Adustment of Varable Parameters n Load flow Calculaton, IEE Proceedngs

10 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: [6] Yng Xao, Y.H.Song, Power Flow Control Approach to Power Systems wth Embedded FACTS Devces, IEEE Trans. On Power Systems, Vol. 17, No. 4, PP Nov [7] S.Rao EHV-AC & HVDC transmsson engneerng & practce Khanna Publcatons,2004 [8] Vadhera Power System Analyss And Stablty Khanna Publcatons, 2 nd Edton,2003 [9] H.Saadat, Power System Analyss, Tata McGraw-Hll Edton, 2001, [10] D P Kothar, I J Nagrath, Modern Power System Analyss, Tata McGraw-Hll Thrd Edton, [11] G.W. Stagg and A.H.El-Abad. Computer Methods n Power System Analyss. McGraw-Hll, IstEdton. [12] D.M.Tagorae Electrc Power Capactors,TMH,2001 [13] Semens Tranng Manual For Power Grd,2004 [14] Relay Manual (Englsh Electrc) for power Grd, 2003 [15]T.Orfanogann and R.Beacher, steady state optmzaton n power systems wth seres FACTS Devces IEEE Trans. On Power Systems,vol.18,pp.19-26,2003 [16] Kwang Y. Lee and Mohamed A. El- Sharkaw, Modern Heurstc Optmzaton Technques Theory And Applcatons To Power Systems, IEEE Press Seres on Power Engneerng,

11 Journal of Theoretcal and Appled Informaton Technology JATIT & LLS. All rghts reserved. ISSN: E-ISSN: AUTHOR PROFILES: Mr. N.M.G.Kumar Currently workng as Assocate Professor n Sr Vdyankethan engneerng College, trupat. Obtaned hs B.tech n Electrcal and Electroncs Engneerng from Bangalore Unversty at S.M.V.I.T.S., Bangalore. Obtaned M.Tech (PSOC) at S.V.U.college engneerng, trupat.area of nterest are power system plannng, power system optmzatons, relablty studes, applcaton of power system lke nonlnear controllers. Dr.P.sangameswara Rau He s presently workng as professor n S.V.U.college engneerng, trupat. Obtaned hs dploma and B.Tech n Electrcal Engneerng, M.Tech n power system operaton and control and PhD n S.V.Unversty,trupat. Hs areas of nterest are power system operaton, plannng and applcaton of fuzzy logc to power system, applcaton of power system lke nonlnear controllers. P.Venkatesh Currently workng as Assstant Professor n Sr Vdyankethan engneerng college, trupat. Obtaned hs B.Tech n Electrcal and Electroncs Engneerng from JNTU Hyderabad Unversty at S.V.P.C.E, T. Putter. and Obtaned hs M.Tech n Electrcal Power System from JNTU Anantapur Unversty at Sr Vdyankethan Engneerng College, trupat. Areas of nterest are power system analyss, applcaton of FACTS devces usng n Transmsson systems. 262