Comparison of calculation result of 3 bus and 5 bus equivalent system

Tp HCM, September, 2020 1.PURPOSE THEORETICAL BASIS CALCULATION MODEL 4.CALCULATION RESULT COMMENTS ON THE CALCULATION RESULTS PURPOSE PURPOSE • Check for the difference in calculation with bus and bus equivalent system when calculating transient problems (TRV, MOV ) => From there, it is clear that the need to calculate transient problems with a large system in order to increase the reliability and accuracy of the results THEORETICAL BASIS Theoretical basis 2.1 Thevenin's theorem • Thevenin's theorem allows to replace a complex circuit with a simple circuit consisting of only one source and one resistor Theoretical basis 2.2 The purpose of Thevenin’s theorem Using Thevenin's theorem is especially advantageous when: • Focus on a specific part of a circuit The rest of the circuit can be replaced with a simple Thevenin equivalent circuit • Using the Thevenin equivalent avoids having to analyze complex circuits Theoretical basis 2.1 Thevenin’s theorem limitations • Thevenin's theorem does not apply to circuits containing nonlinear elements • Circuit equivalence according to Thevenin's theorem cannot be equivalent in terms of electromagnetic induction between components in the power system Theoretical basis 2.1 Limitations when using Thevenin’s equivalent • For transient problems, the Thevenin’s equivalent model can not be applied Because the wave re-reflection (standing wave) will occurs due to the large system equivalence to the smaller system The larger the simulation system, the smaller the amplitude of the reflected wave becomes n=2 bus n=5 bus n=4 bus n=3 bus n=6 bus Standing waves based on simulation system Theoretical basis 2.1 Limitations when using Thevenin’s equivalent • Volt-Ampe characteristics when calculating with circuits with nonlinear elements before and after Thevenin equivalent 10 Calculation model 3.3 Calculation fault points • Calculation of absorbed energy level of MOV with fault points 1,2,3 on the Doc Soi, Pleiku and Quang Trach Zth Quảng Trạch 43Ω 43Ω 500.4km 30.5Ω Zth 210km Zth Pleiku2 Dốc Sỏi 17 CALCULATION RESULT 18 Calculation Result 4.1 Comparison of TRV calculation result Fault at point 2.1 2.02 1.95 TRV(pu) 1.9 1.95 1.81 1.8 1.98 1.84 1.67 1.7 1.6 1.5 1.4 1.34 1.3 1.2 phase short circuit-CB Doc Soi phase short circuit-CB phase short circuit-CB Doc Soi Pleiku Bus system Bus system phase short circuit-CB Pleiku 19 Calculation Result 4.1 Comparison of TRV calculation result Fault at point 2.6 2.38 2.4 TRV(pu) 2.2 2.48 2.12 1.98 1.87 1.94 1.8 1.6 1.4 1.27 1.2 1.07 phase short circuit-CB Doc Soi phase short circuit-CB Doc Soi Bus system phase short circuit-CB Pleiku phase short circuit-CB Pleiku Bus system 20 Calculation Result 4.2 Comparison of RRRV calculation result Fault at point 0.6 0.5 0.547 0.521 0.472 0.407 RRRV(kV/µs) 0.4 0.363 0.3 0.2 0.1 0.168 0.106 0.105 phase short circuit-CB Doc phase short circuit-CB Doc phase short circuit-CB Soi Soi Pleiku Bus system Bus system phase short circuit-CB Pleiku 21 Calculation Result 4.2 Comparison of RRRV calculation result Fault at point 0.9 0.796 0.8 0.7 0.722 0.626 RRRV(kV/µs) 0.6 0.5 0.4 0.3 0.2 0.336 0.213 0.087 0.092 0.1 phase short circuit-CB Doc phase short circuit-CB Doc Soi Soi Bus system phase short circuit-CB Pleiku 0.076 phase short circuit-CB Pleiku Bus system 22 Calculation Result 4.3 Comparison of MOV calculation result phase short-circuit at Quảng Trạch 60 50 48.84 47.15 MOV(MJ) 40 30 20 12.86 9.77 10 1.17 43 Ohm Quang Trach Capacitor 43 Ohm Doc Soi Capacitor Bus system 30.5 Ohm Doc Soi Capacitor Bus system 23 Calculation Result 4.3 Comparison of MOV calculation result phase short-circuit at Quảng Trạch 140 132.18 126.55 120 MOV(MJ) 100 80 60 40 23.03 14.19 20 2.25 43 Ohm Quang Trach Capacitor 43 Ohm Doc Soi Capacitor Bus system 30.5 Ohm Doc Soi Capacitor Bus system 24 Calculation Result 4.3 Comparison of MOV calculation result phase short-circuit at Dốc Sỏi 50 45 43.19 41.83 39.49 40 MOV(MJ) 35 30 25 20.39 20 15 10 3.96 3.09 Tụ 43 Ohm Quảng Trạch Tụ 43 Ohm Dốc Sỏi Hệ thống nút Tụ 30.5 Ohm Dốc Sỏi Hệ thống nút 25 Calculation Result 4.3 Comparison of MOV calculation result phase short-circuit at Pleiku 70 58.29 60 MOV(MJ) 50 40 30 26.75 23.76 20.17 20 10 0 43 Ohm Quang Trach Capacitor 43 Ohm Doc Soi Capacitor Bus system 30.5 Ohm Doc Soi Capacitor Bus system 26 Calculation Result 4.3 Comparison of MOV calculation result phase short-circuit at Pleiku 160 147.13 140 MOV(MJ) 120 100 98.84 86.35 80 60 49 40 20 0 43 Ohm Quang Trach Capacitor 43 Ohm Doc Soi Capacitor Bus system 30.5 Ohm Doc Soi Capacitor Bus system 27 COMMENTS ON THE CALCULATION RESULTS 28 COMMENTS ON THE CALCULATION RESULTS From the calculation results we have the following comments • The difference in the TRV, RRRV calculation results between the equivalent system of bus and bus is about 30% • The difference in the MOV calculation results between bus and bus equivalent systems is very large (about 100%) → The wave-related transient problems (MOV computation) give very different results when the system equivalents are and bus Similar to the results of TRV calculation, RRRV also has a relative difference when calculating with the equivalent system of bus and bus 29 REFERENCES DOCUMENT • W Richter, "Applications of Thevenin's theorem," in Electrical Engineering, vol 64, no 3, pp 103-105, March 1945, doi: 10.1109/IEEE.1945.6440897 • A W Love, "Comment on "Limitations of the Thevenin and Norton equivalent circuits for a receiving antenna"," in IEEE Antennas and Propagation Magazine, vol 45, no 4, pp 98-99, Aug 2003, doi: 10.1109/MAP.2003.1241317 • Transient Analysis of Power Systems: Solution Techniques, Tools and Applications, First Edition Edited by Juan A Martinez-Velasco Annex B - Dynamic System Equivalents • https://en.wikipedia.org/wiki/Th%C3%A9venin%27s_theorem 30 EVNPECC2 ... Dốc Sỏi 50 45 43. 19 41. 83 39.49 40 MOV(MJ) 35 30 25 20 .39 20 15 10 3. 96 3. 09 Tụ 43 Ohm Quảng Trạch Tụ 43 Ohm Dốc Sỏi Hệ thống nút Tụ 30 .5 Ohm Dốc Sỏi Hệ thống nút 25 Calculation Result 4 .3 Comparison. .. 60 40 23. 03 14.19 20 2. 25 43 Ohm Quang Trach Capacitor 43 Ohm Doc Soi Capacitor Bus system 30 .5 Ohm Doc Soi Capacitor Bus system 24 Calculation Result 4 .3 Comparison of MOV calculation result. .. Soi Capacitor Bus system 30 .5 Ohm Doc Soi Capacitor Bus system 23 Calculation Result 4 .3 Comparison of MOV calculation result phase short-circuit at Quảng Trạch 140 132 .18 126 .55 120 MOV(MJ)