Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. ٢ Year 2009 ٤٧٧ IMPROVING TRANSIENT STABILITY IN CASE OF FAULTS IN HADITHA - QAIM LINE Dr. Samir S. Mustafa Technical Institute / Kirkuk Abstract Iraqi National Super Grid suffers from out of synchronism of the system due to short circuit in the lines. The main goal of this work is to study the effect of optimum generation and reconfiguration of some transmission paths on transient stability improvement for Iraqi Network in case of short circuit in Haditha-Qaim line because it is one of the wrest lines. A programmable package build under Matlab5.3 was used to determine synchronous machines rotor angles as an indicator of transient stability. Sad Al- Mosul, Haditha and Nasiriya power plant were chosen to notice the situation of stability. Keywords- Power Losses, Transient Stability, Stability, Reconfiguration. ����� ا�����ار�� ا ����ة �� � � ا ��� �� �� ���� أ ��! – �ون ()'&%. د �� ��,� � أ���ذ (��- آ�آ3ك/ أ ,�0� أ ��/� ا �56� � ��� ا ��ا� وذ� ������ ��اق � ����� ��وج ا � ا� !"# � )'�� ا &%$ ا)"�. دا!�ة /.� �� ا�� �-�ط ا �'���وث* 34' ;إ�89ف ه5ا ا �< �� �D� E"راإ�"دة و*<=>� اAB�C درا?� *<=>� اF A<��* ��"�Fة �� )'�� ت ا G-�ط � ا�I�?Jار�9 ا� آ��� ا!"�� ���B9 و ، *L ا��>"ر �4-"ت *� >� ?� ا ��AX. ا ������ ����Z أ?��Iار�9 ا �9�X"� .ا Introduction Power System Stability The importance of power system stability is increasingly becoming one of the most limiting factors for system performance. By the stability of a power systems we mean the ability of the system to remain in operating equilibrium, or synchronism, while disturbances occur on the system(Kundur2004). There are three types of stability namely, steady-stat, dynamic, and transient stability. 1) Steady-State stability: refer to the stability of a power system subject to small and gradual changes in load and the system remains stable with conventional excitation and governor controls. Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. ٢ Year 2009 ٤٧٨ 2) Dynamic-Stability: refer to the stability of a power system subject to a relatively small and sudden disturbances .The system can be described by linear differential equation, and the system can be stabilized by a linear and continuous supplementary stability control. 3) Transient stability T.S : refer to the stability of power system subject to a sudden and sever disturbance beyond the capability of the linear and continuous supplementary stability control, and the system may lose its stability at the first swing unless a more effective countermeasure is taken, usually of the discrete type, such as dynamic resistance braking or fast valving for the electric energy surplus area, or load shedding for electric energy deficient area. For T.S analysis and control design, the power system must be described by non linear differential equations. T.S concern with the matter of maintaining synchronism among all generators when the power system is suddenly subjected to sever disturbances such as faults or short circuits caused by lightning strikes, the sudden removal from the transmission system of a generator and/or a line, and any sever shock to the system due to a switching operation. Because of the severity and suddenness of the disturbance, the analysis of transient stability is focused on the first few seconds, or even the first few cycles, following the fault occurrence or switching operation (Shin2004),(Selman2005). First swing analysis is another name that is applied to transient stability studies. If the generators can get through it without losing synchronism, it is said to be transient stable. On the other hand, if the generators losses its synchronism and can not get through the first swing, it is said to be transient unstable. There is a critical angle within which the fault must be cleared if the system is to remain stable( Demetrios2005) . The Transient Stability calculations were carried out using the step by step modified Euler iterative solution of the differential equations describing machines second and total solution time period of 1.5 second. The programmable package performs transient calculations with different behaviors of the system. The solution took into account a time step of 0.05 types of faults at any point on the system with 0.15 second clearing time (tc). Rotor angles were taken as an indicator of transient stability. Iraqi National Network Iraqi national super grid contains19 busbar,27 transmission lines and six generating sets of various types units, thermal and hydro turbine kinds, with different capabilities of MW and MVAR generation and absorption as shown in Figure 1.Using the load data collected on 2/1/2003 in Appendix A, the system line data as shown in Appendix B which can be obtained from the Iraqi Control Center (Afaneen2004). Iraqi electrical network suffered from serious problems. A great damage happened to the Iraqi power system at all levels, the generation, the transmission and the distribution. There are tow dangerous regions , Baiji and Haditha because the loss of Baigi or Haditha busbars cause Sad Al -Mosul to separate from the network, leaving it with high generation and low loading, and causing the instability of the bus. While the separation of Haditha causes the losses of large amount of power feeding the Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. ٢ Year 2009 ٤٧٩ middle area , and forcing the network to overcome this loss from Sad Al -Mosul. This lead Sad Al- Mosul to swing highly reaching the instability. Improving the Stability. The following steps were tried by (Afaneen 2004) to overcome this problem: 1 Recovery of damaged transmission line. Those are (Mosul – Kirkuk line, one of the double lines of Sad Al Mousil – Baiji, one of the double lines of Hartha- Khour Al-Zubair ……etc). Table 1, represents the type of stability and the critical clearing time(Tcr) for each step of generating units cancellation with and without the recovery of the separated transmission lines (T.L). Although the installation of the recovered transmission lines will lead to improvement in the power flow in the north and middle regions, they did not affect the stability situation of the network. Increasing the generating power of the generating units. ٢ 3. As shown in Table 2, increasing the generating power has no effects on the stability of the system when removing Haditha. The Effect of Optimum Power Generation on Transient Stability Three buses(Sad Al-Mosul, Haditha and Nasiriya) power plants were chosen to study the effect of three phase fault in the middle of the line Haditha-Qaim. The system is unstable in case of ordinary load flow because SDM plant is out of synchronism. The system becomes more stable (but still unstable)with optimum power generation using the data of optimum power generation in Appendix C (Samir2007). 1 Stability improvement calculations for Sad Al-Mosul The difference in the rotor angle for the swing curve in case of ordinary generation as shown in Figure 2= 330-20 =310degree. The difference in case of optimum generation as shown in Figure 3 = 100-5= 95degree. The stability improvement between ordinary and optimum generation= 310 95310 − = 69.35% 2 Stability improvement calculations for Haditha The difference in the rotor angle for the swing curve in case of ordinary generation as shown in Fig4= 15-(-75)=90degree. The difference in case of optimum generation as shown in Figure5 = 10-(-15.5)=25.5degree. The stability improvement between ordinary and optimum generation= 90 5.2590 − = 71.6% 3 Stability improvement calculations for Nasiriya The difference in the rotor angle for the swing curve in case of ordinary generation as shown in Figure 6= 10-(-85)=95degree. The difference in case of optimum generation as shown in Figure 7 = 7.5-(-22.5)=30degree. The stability improvement between ordinary and optimum generation= 95 3095 − = 68.4% Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. ٢ Year 2009 ٤٨٠ The Effect of Paths Reconfiguration on Transient Stability As shown before the network is the unstable, during both ordinary and optimal load flows, in case of three phase fault in the Haditha-Qaim because this fault will lead Sad Al-Mosul bus to swing away from the stability and cause instability of the system. To overcome this problem a new configuration of the network will solve this problem. If the radial path (Baiji-Haditha-Qaim) as shown in Figure(1) is changed to a loop path (Baiji-Qaim-Haditha-Baghdad East-Baiji), the system becomes stable for both ordinary and OPF as shown in swing curves Figures (8-13). Stability Improvement Calculations The improvement calculations are done in procedure similar to that in 4.1, 4.2 & 4.3. In case of ordinary generation, the improvements in stability using the new configuration are equal to 96.4%, 63.8% and 59.6% for Sad Al-Mosul, Haditha and Nasiriya respectively with respect to ordinary generation without new configuration as shown in Figures8, 9 & 10. In case of optimum generation, the improvements in stability using the new configuration are equal to 97.4%, 67.9% and 50.8% for Sad Al-Mosul, Haditha and Nasiriya respectively with respect to optimum generation without new configuration as shown in Figures11, 12 & 13 . Conclusion 1) Comparison between stability with optimum generation and ordinary generation according to the rotor time angle curve indicates that transient stability is much better with optimum generation. 2) In case of 3-phase fault in the middle of line Haditha-Qaim, transient stability can be enhanced using optimum generation but the system remains unstable. 3) The system becomes stable if a new configuration is used. References • Afaneen A. Abood (2004), Implementation of Geographic Information System in Real- Time Transient Stability, Ph.D Thesis, University of Technology, Baghdad. • Demetrios A. Tziouvaras(2005), Out-Of-Step Protection Fundamentals and Advancements, wwselinc.com/6163 pdf. • Kundur K(2004).,System Stability, www.ee.und.ac.za/ course main. • Samir S. Mustafa (2007), Minimum Power Losses Based Optimal Power Flow for Iraqi National Super Grid and its Effect on Transient Stability, Ph.D Thesis, University of Technology, Baghdad. • Selman N. H.(2005), Minimum Energy Loss Based Reactive Power Flow, M. Sc. Thesis, University of Technology • Shin-Min Hsu (2004), Power Systems-Basic Concepts and Application,www.PDHcentre.com. . Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. ٢ Year 2009 ٤٨١ Table (1)The stability situation during the recovery of the separated transmission lines Tcr(sec)with the recovery of T.Ls The system stability The separated bus-bar ٠.٠٠١٢٣١٢ Unstable Baiji ٠.٦٩٤٧٠٢١ Stable Sad Al-Mosul ٠.٠٠١٢٣٠٦ Unstable Haditha ٠.٧٧٧٠٢٤٩ Stable Mussayab ٠.٤٠٥٦٤٠٥ Stable Nasiriya ٠.٥١٠٤٢٥٣ Stable Hartha Table (2)The stability situation after increasing generated power of the generating bus-bar Tcr(sec) The system stability The generated power(Mw) The separated bus-bar ٠.٦١٥٢١٠١ Stable ٨٠٠ Baiji ٠.٦٨٠٢٤٥٧ Stable ٨٠٠ Sad Al-Mosul ٠.٠٠١٢٣١٥ Unstable ٦٠٠ Haditha ٠.٥٥٥٥٩١٤ Stable ١٠٠٠ Mussayab ٠.٤٦٥٢٥٩٢ Stable ٧٥٠ Nasiriya ٠.٢٤٤٨٤٤٩٦ Stable ٧٠٠ Hartha Figure (1) Iraqi National Super Grid Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. ٢ Year 2009 ٤٨٢ Figure 2: Swing Curve for (Sad Al-Mosul) Generator Figure 3: Swing Curve for (Sad Al-Mosul) Generator with ordinary power generation with OPF Figure 4: Swing Curve for (Haditha) Generator Figure 5: Swing Curve for (Haditha) Generator with ordinary power generation with OPF Figure 6: Swing Curve for (Nasiriya) Generator Figure 7: Swing Curve for (Nasiriya) Generator 0 0.5 1 1.5 -80 -60 -40 -20 0 20 40 Rotor Angle in degree for gen. HAD4 Time[sec] 0 0.5 1 1.5 -20 -15 -10 -5 0 5 10 15 20 Rotor Angle in degree for gen. HAD4 Time[sec] 0 0.5 1 1.5 -100 -80 -60 -40 -20 0 20 Rotor Angle in degree for gen. NSR4 Time[sec] 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 -20 -15 -10 -5 0 5 10 15 20 25 Rotor Angle in degree for gen. HAD4 Time[sec] mid 3-4 fault(mod) 0 0.5 1 1.5 0 50 100 150 200 250 300 350 Rotor Angle in degree for gen. SDM4 Time[sec] 0 0.5 1 1.5 0 10 20 30 40 50 60 70 80 90 100 Rotor Angle in degree for gen. SDM4 Time[sec] Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. ٢ Year 2009 ٤٨٣ with ordinary power generation with OPF Figure 8: Swing Curve for( Sad Al Mosul) Generator Figure 9: Swing Curve for (Haditha) Generator with ordinary generation& new configuration with ordinary generation& new configuration Figure 10: Swing Curve for( Nasiriya) Generator Figure11: Swing Curve for (Sad Al Mosul) Generator with ordinary generation& new configuration with optimum generation& new configuration 0 0.5 1 1.5 -25 -20 -15 -10 -5 0 5 10 Rotor Angle in degree for gen. NSR4 Time[sec] 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 10 15 20 25 30 35 40 45 50 Rotor Angle in degree for gen. SDM4 Time[sec] mid 3-4 fault(mod) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 -30 -25 -20 -15 -10 -5 0 5 10 15 Rotor Angle in degree for gen. NSR4 Time[sec] mid 3-4 fault(mod) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 5 10 15 20 25 30 Rotor Angle in degree for gen. SDM4 Time[sec] mid 3-4 fault(mod) Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. ٢ Year 2009 ٤٨٤ Figure 12: Swing Curve for(Haditha) Generator Figure13: Swing Curve for (Nasiriya) Generator with optimum generation& new configuration with optimum generation& new configuration Appendix A: INSG System Load Data Generation Load Bus Bar Number Bus Bar Name Type MW MVAR MW MVAR 1 BAJ Slack 570.592 100.4455 200.00 98.00 2 SDM P,V 700.00 - 23.2248 5.00 2.00 3 HAD P,V 500.00 - 0.8474 100.00 60.00 4 QAM P,Q .00 .00 60.00 40.00 5 MOS P,Q .00 .00 300.00 180.00 6 KRK P,Q .00 .00 70.00 40.00 7 BQB P,Q .00 .00 150.00 80.00 8 BGW P,Q .00 .00 500.00 360.00 9 BGE P,Q .00 .00 500.00 360.00 10 BGS P,Q .00 .00 100.00 50.00 11 BGN P,Q .00 .00 300.00 200.00 12 MSB P,V 600.00 420.6564 120.00 70.00 13 BAB P,Q .00 .00 100.00 50.00 14 KUT P,Q .00 .00 100.00 60.00 15 KDS P,Q .00 .00 200.00 100.00 16 NAS P,V 650.00 - 69.1434 100.00 54.00 17 KAZ P,Q .00 .00 350.00 200.00 18 HRT P,V 380.00 35.9855 38.00 22.00 19 QRN P,Q .00 .00 70.00 30.00 Total 3400.592 463.8716 3363 2056 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 -8 -6 -4 -2 0 2 4 6 8 10 Rotor Angle in degree for gen. NSR4 Time[sec] mid 3-4 fault(mod) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 0 2 4 6 8 10 12 14 16 18 Rotor Angle in degree for gen. HAD4 Time[sec] mid 3-4 fault(mod) Al-Qadisiya Journal For Engineering Sciences Vol. 2 No. ٢ Year 2009 ٤٨٥ Appendix B: INSG System Line Data From To R (P.U) X (P.U) B (P.U) BAJ4 SDM4 0.00542 0.0487 1.4384 MOS4 SDM4 0.00143 0.0124 0.36439 MOS4 BAJ4 0.00399 0.03624 1.074 BAJ4 HAD4 0.00364 0.03024 0.8676 QAM4 HAD4 0.0035 0.03 0.7413 BGE4 BQB4 0.00076 0.00689 0.2043 BAJ4 KRK4 0.00182 0.01654 0.49031 BAJ4 BGW4-2 0.0055 0.05004 1.4826 BAJ4 BGW4-1 0.00483 0.04393 1.3017 HAD4 BGW4 0.00483 0.04393 1.3017 BGW4 BGN4 0.00093 0.00847 0.25099 BGN4 BGE4 0.00029 0.00265 0.0788 KRK4 BGE4 0.00481 0.04373 1.29581 BGE4 BGS4 0.00105 0.00955 0.28309 BGW4 BGS4 0.00144 0.0131 0.38816 BGS4 MSB4-1 0.00121 0.0102 0.30944 BGS4 MSB4-2 0.00121 0.0102 0.30944 BAB4 MSB4-1 0.00077 0.00648 0.19666 BAB4 MSB4-2 0.00077 0.00648 0.19666 BGS4 KUT4 0.00245 0.02236 0.6625 BGS4 KDS4 0.00292 0.02659 0.788 KDS4 NSR4 0.00383 0.03486 1.03314 KAZ4 NSR4 0.00439 0.03999 1.1849 KUT4 NSR4 0.00433 0.0394 1.1674 KAZ4 HRT4 0.00119 0.01083 0.32104 QRN4 HRT4 0.0013 0.01182 0.35022 QRN4 KUT4 0.00628 0.05713 1.6927 Appendix C: Optimum Power Generation according to system data load(Samir2007) Generation bus name Optimum Generation[Mw] Baiji 571 Sad Al-Mosul 250 Haditha 350 Mussayab 1000 Nasiriya 500 Hartha 400