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How to Improve Power Factor, Voltage Regulation and to Reduce Harmonic Distortion of an Industrial Plant, using a Power System Simulator Santiago Barcón, Ignacio Suárez, and Luis Flamenco Abstract—The present work shows a real case of an industrial plant in México and the solution of problems in the electric system caused by the damage of a static var compensator. With help of a power system simulation we could evaluate several alternatives of solution and determine which is better from the technical and economic point of view to be applied. The objective was to improve the conditions of electric system through a low cost solution and quick application. When the EBT turned on, the voltage of lamination bus is 12.68 kV with a V_THD of 2.9%, while with the EBT turned off the voltage is 13.51 kV with a V_THD of 1.5%. Index terms-Electric variables measurement. Harmonic distortion. Power system simulation. Static var compensator. Simulation software. I. INTRODUCTION In Mexico there are only two utilities, both companies are property of the government. Since November 1991 they had a policy of penalizing to the users with a lower power factor than 0.90 and the users with a PF upper than 0.90 they received a rebate up to 2.5% in their monthly electrical billing. At this time there are not a penalizing for high harmonic distortion on the PCC, however in a few years is too possible will exist a regulation to this respect. With the damage of a static var compensator of a steel mill in Mexico, several problems arise in the electric system: low power factor less than the utility recommendations on PCC, poor voltage regulation, damage at the electronic equipment and the high probabilities of harmonic resonance that meant a risk condition to the plant. Due the time to deliver a new static var compensator, the company decided to look for other solutions to improve the conditions of electric system, with the purpose of not altering the normal production. The alternative of improvement should be of low cost and quick application. The plant has two productive areas: lamination and steel mill in the last there are two electric arc furnaces (the shaft and the EBT). In the figure 1, is included an one line diagram simplified. The most important equipment due peak of load is the EBT furnace, and depending of their operation the electric system has several behaviors, so for the present analysis considers two general situations: the EBT furnace turned on and another with the EBT turned off. Fig. 1. One line diagram simplified. The most affected area for the loss of static var compensator was the lamination, because here is located the mayor quantity of the electronic equipments, so all the efforts had to be focused to solve the problems in the lamination bus. The lamination plant is constituted by two transformers of 30 MVA working with the close link in 13.2 kV, from this bus are fed 11 circuits that supply to several loads in which are included: DC motor drives, AC motor drives, induction motors, illumination and two capacitors banks. There are two conditions to operation of lamination plant: normal load (20.13 MW with a PF of 0.904) and low load (11.04 MW with a PP of 0.996). II. METHODOLOGY In order to determine the solution of electric system it was necessary: A. To carry out electric variables measurement for each one of conditions of plant. B. To confirm the name plates data of the equipments in the electric system. C. Modeling the electric system in the simulation software. D. To obtain and evaluated the solution under the several conditions. E. Final results. A. Electric variables measurement. Electric variables measurement were carry out at each one of feeders of plant with three power quality analyzers, with the purpose to detect the feeders with the major harmonic distortion and mainly to determinate the behavior of load for each one of the operation conditions. In the next table the measurement summary are shown, and is included a evaluation of IEEE 519-92 [1]-[2] for current: Feeder kW PF I_THD (%) IEEE 519-92 Evaluation GR1-2 GR1-4 GR1-5 GR1-8 GR1-9 GR1-11 GR1-12 GR1-14 GR1-15 GR1-16 GR1-17 700 480 10,799 550 250 860 1,739 2,500 1,294 641 273 0.960 0.800 0.733 0.960 0.800 0.733 0.770 0.660 0.610 0.730 0.74 15.50 4.90 4.30 31.00 4.20 2.10 3.80 22.30 3.60 0.80 0.80 Outside Inside Inside Outside Inside Inside Inside Outside Inside Inside Inside This section consisted in to verify the name plates data of equipments that were considered in the study, from transformers until cables size and longitude of lamination plant. C. Modeling the electric system in the simulation software. With the electric measurements and the information of system was proceeded to modeling the loads, the transformers, the cables, etc. in the simulation software. D. To obtain and evaluated the solution under the several conditions. Once modeling the electric system, it was carry out simulations that includes from the original situation until to obtain the alternative solution. Next are shown some of the results obtained in the simulation software for the original condition, with the two capacitors banks and EBT furnace operating. This condition was for the normal load at lamination plant. LAMINATI ON PLANT Table 1. Summary of electrical variables measurement. 229. 08 k V V _THD 0. 4% At 13.2 kV bus are connected a capacitor bank of 9600 kVAR to 16.64 kV, while in the circuit GR1-8 exist another capacitor bank of 600 kVAR to 16.64 kV, so in this feeder the I_THD is high. Bus 230 k V 10,054 k W 4,439 k V AR TR1 10,054 k W 4,428 k V AR TR2 30 M VA 230/13. 2 k V 9. 38% I_THD 5. 4% Next are shown the signal and harmonics for current of the GR1-14 feeder. E vent waveform/detail 5,573 k V AR I_THD 24. 1% Eve nt w ave for m/detail Amps 2 00 1 50 I_THD 5. 4% 12. 68 k V B us 13. 2 k V %of FND 25 CapLam 9,600 k V AR GR1-8 Cap LA 15 2,486 k W 928 k V AR 12. 68 k V V _THD 2. 9% 348 k V AR I _THD 31% 20 1 00 30 M VA 230/13. 2 k V 9. 35% 12. 68 k V V _THD 2. 9% 600 k V AR 50 10 0 5 Fig. 3. Original condition one line diagram results. -50 -1 0 0 -1 5 0 04: 34: 11 .0 00 04: 34: 11 .0 05 04: 34: 11 .0 10 CHA Amps 04: 34: 11 .0 15 Timed event occurre d at 08/1 1/00 04:3 4:11.000 -2 0 0 04: 34: 11 .0 20 0 Thd H05 H10 H15 CHA Am ps H20 H25 Total RMS: 114.27 Amps DC Level : 10.15 Amps Fundamental(H1) RMS: 111.05 Amps Total Harmonic Distortion ( H02-H50) : 22.37 % of FND Even contribution ( H02-H50) : 0.27 % of FND Odd contribution ( H03-H49) : 22.37 % of FND The results for the original condition can be summarized in: Timed event occurred at 11/08/00 04:34:11.000 1. Fig. 2. Signal and harmonics measurement example. In these graphs can be observed how the fifth harmonic is outside of the recommendations and also we have seventh and eleventh with important values. 2. 3. On the other hand, the V_THD at 13.2 kV bus is normally inside of the recommendation the value oscillate between 1.6% to 2.9%, depending if the EBT turned on or turned off. In general could mentioned that in the secondary of transformers T1 y T2 of lamination plant is fulfilled the recommendations of the IEEE 519-92. B. To confirm the name plates data of the equipments in the electric system. 4. The total power factor of the plant was 0.904, this value is on the limit of power supply recommendations. The voltage at 13.2 kV bus, was 96.1% to the nominal voltage. The V_THD at 13.2 kV bus, was 2.9% this value meet the IEEE 519-92 recommendations. The most important harmonics were the 7th and the 11th with 2.3% and 1.3% respectively of the fundamental voltage. The capacitors banks show high THD of current, however because they are designed to 130% up to the nominal voltage do not present problems. In the figure 4, are shown the signal and harmonics for voltage at 13.2 kV bus. In so far as, the figure 5 is shown the impedance of system vs frequency at 13.2 kV bus. Plot1 - Distortion Waveform Plot1 - Distortion Spectrum 400 350 10000 Case 3 Furnace EBT ON Cap Banks OFF Lamination (normal) Case 4 Furnace EBT OFF Cap Banks ON Lamination (low) 20,142 0.785 12.455 94.35 2.50 ------- 11,045 +0.996 13.826 104.74 2.10 14.00 300 5000 Table 2. Summary results for original condition. Bus Distortion Voltage Spectrum (Volts) Bus D is tortion Voltage WaveForm (Volts ) 250 200 0 The sign (+) indicates that the power factor is capacitive. 150 -5000 100 -10000 50 0 0 50 100 150 200 250 Time (1 Cycle) or 0-360 degrees 300 0 350 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Harmonic Order Fig. 4. Signal and harmonics for 13.2 kV bus. Plot1 - Scan Magnitude 17.5 In the last table can be observed when the capacitors banks are off the harmonics go down, but affect the power factor and the voltage regulation, on the other hand when the capacitors banks turned on the power factor is improved and also the voltage at 13.2 kV bus is better, however the harmonics goes up and exist a risk condition due possible harmonic resonance near to 7th (cases 1, 2 y 4). 15.0 After studying several solutions alternatives, was concluded that the present the more advantages due low cost and quick application consisted: Bus ScanMagnitude (pu) 12.5 10.0 7.5 5.0 1. 2.5 0.0 0 5 10 15 20 25 30 Harmonic Order 35 40 45 50 2. Fig. 5. Impedance vs frequency at 13.2 kV bus. 3. In the last curve can be observed the parallel resonance at 8th harmonic and is important to mention that this represent a risk condition for the plant, because is near to the 7th harmonic. The signal and harmonics for current of capacitor bank 9600 kVAR are shown in the next graph. Plot1 - Distortion Waveform 55 50 200 45 40 Branch Distortion Current Spectrum (Amps) 100 Branch Distortion Current Waveform (Am ps) The detuned filter was used in the past, to improved the total power factor of plant before the construction of EBT furnace and their harmonic filters, after when this area was turned on the detuned filter was disconnect and some of their components were used in other sections. The results obtained in the simulation software after the application of the recommendations are show in the next one line diagram. Plot1 - Distortion Spectrum 60 300 Rehabilitate and install the detuned filter of 12 MVAR to 16.64 kV at 13.2 kV bus, this filter was off operation. To disconnect both capacitors banks of 9600 kVAR and the 600 kVAR. Change the actual tap position of transformers T1 and T2, to increase the voltage at secondary in 2.5%. 0 -100 -200 -300 35 LAMINATI ON PLANT 30 25 50 100 150 200 250 Time (1 Cycle) or 0-360 degrees 300 15 10 10,053 k W 3,527 k V AR 5 0 350 1 2 3 4 5 6 7 8 9 TR1 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Harmonic Order Fig. 6. Signal and harmonics for 9600 kVAR Applying the same procedure of analysis, several conditions of electric system where studied, in the next table are show the summary of results. Case 1 Furnace EBT ON Cap Banks ON Lamination (normal) Case 2 Furnace EBT OFF Cap Banks ON Lamination (normal) kW PF kV (%Vnom) 20129 0.904 12.679 20,122 0.921 13.513 10,053 k W 3,517 k V AR TR2 30 M VA 230/13. 2 k V 9. 38% I_THD 2. 0% In these graph could be observed that the most important harmonics are the 7th, 11th and the 13th with 16.2%, 14.6% and 8.9% respectively of the fundamental current. Original Situation Bus 230 k V 20 0 0 228. 26 k V V _THD 0. 2% 96.05 V_THD (%) 2.90 I_THD(%) Cap. Bank 24.0 102.37 2.50 21.0 B us 13. 2 k V I_THD 2. 0% 12. 95 k V 2,486 k W 36.29 k V AR 12. 95 k V 7,705 k V AR I_THD 3. 22% V _THD 0. 5% FLTR-1 30 M VA 230/13. 2 k V 9. 35% 12 M V AR Fig. 7. Future condition one line diagram results. V _THD 1. 6% Plot1 - Distortion Waveform The results of future condition can be summarized in: 9 2. 3. 4. In the next figure, are shown the signal and harmonics for voltage at 13.2 kV bus. 8 200 7 100 6 Branch Distortion Current Spectrum (Amps) The power factor of the plant was 0.935, this value fulfill with the power supply recommendations. The voltage at 13.2 kV bus, was 98.13% at nominal voltage. The V_THD at 13.2 kV bus, was 1.6% this value fulfill the IEEE 519-92 recommendations. The most important harmonics were the 11th and the 13th with 1.02% and 0.09% respectively of the fundamental voltage. The detuned filter show a low THD of current 3.2%. Branch Dis tortion Current Waveform (Am ps ) 1. 0 -100 -200 -300 175 150 10000 125 5000 100 Bus Distortion Voltage Spectrum (Volts) Bus D is tortion Voltage WaveForm (Volts ) Plot1 - Distortion Spectrum 0 -5000 -10000 75 50 25 0 0 50 100 150 200 250 Time (1 Cycle) or 0-360 degrees 300 0 350 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Harmonic Order Fig. 8. Signal and harmonics for 13.2 kV bus (future). In the figure 9, are shown the impedance of system vs frequency at 13.2 kV bus. 5 4 3 2 1 0 0 50 100 150 200 250 Time (1 Cycle) or 0-360 degrees 300 350 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Harmonic Order Fig. 10. Signal and harmonics for detuned filter. The solution was studied under the several conditions of operations and the results were summarized: Future Situation Plot1 - Distortion Waveform Plot1 - Distortion Spectrum 10 300 Case 5 EBT Furnace on Detuned Filter on Lamination (normal) Case 6 EBT Furnace off Detuned Filter on Lamination (normal) Case 7 EBT Furnace off Detuned Filter on Lamination (low) Case 8 (worst) EBT Furnace on Detuned Filter on Lamination (normal) Worst harmonic condition. kW FP kV (%Vnom) V_THD(%) 20126 0.935 12.953 98.13 1.60 I_THD(%) Filter 3.20 20120 0.953 13.818 104.68 1.4 2.80 11045 +0.961 14.19 107.50 0.80 ------- 20126 0.934 12.916 97.85 1.60 3.90 Table 3. Summary results for future condition. The sign (+) indicates that the power factor is capacitive. Plot1 - Scan Magnitude 10 The Case 8 considers the worst harmonic condition, because here includes another source injecting harmonics from the PCC that correspond to electric arc furnace in the melting stage. 9 8 7 Bus Scan Magnitude (pu) 6 5 4 E. 3 2 Final results. 1 0 0 5 10 15 20 25 30 Harmonic Order 35 40 45 50 Comparing the results obtained in the cases 1 and 5 we have: Fig. 9. Impedance vs frequency at 13.2 kV bus (future). In the last curve can be observed like near of 4th harmonic the impedance of system was reduce due the operation of detuned filter and later the trend is directly proportional to the frequency. The signal and harmonics for current of detuned filter are shown in the figure 10. In these graph can be observed that the most important harmonics are the 5th, 11th and 13th with 1.93%, 1.81% and 1.35% respectively of the fundamental current Power Factor V_THD Voltage at 13.2 kV Bus I_THD at Capacitor Bank or Detuned Filter Case 1 0.904 2.90 12.679 kV (96.05 % Vnom) 24% Case 5 0.935 1.60 12.953 kV (98.13% Vnom) 3.2% Table 4. Results comparison. Whit the application of this recommendation a better power factor was obtained, decreased the V_THD almost in half, improvement of the voltage regulation at 13.2 kV bus in 300 volts and mainly the possibility of a harmonic resonance disappear. III. CONCLUSIONS. The present work illustrate one of the multiples applications of power system simulator to solve real problems at industrial plants. Is important to remember that the possible solutions of power system was selected the alternative of low cost and the quick application, just a temporal solution. Finally, in this specific case was analyzed like an application of detuned filter could be a very good solution to power quality problems, such voltage regulation and harmonic reduction. IV. REFERENCES. [1] IEEE Standard 519-92, “Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems”, 1992. [2] IEEE Harmonics Working Group, “Guide for Applying Harmonics Limits on Power Systems”, May 1996. Santiago Barcón was born in Mexico City in 1957. He is electrical engineer from the Universidad Iberoamericana, he received the master degree in BA from Instituto Tecnológico de Estudios Superiores de Monterrey. He has worked in several companies attending from electrical maintenance areas up to sales and production management, among them Vitro and ABB. Presently, he is partner and president of Inelap,* S.A. de C.V. manufacturer low and high voltage capacitor for power factor correction, harmonic filters and protection panels. Inelap is an ISO 9001 facility. His research interests include capacitor banks, harmonics and power quality. He participated in the Power Quality 93, 95 and 97 and many conferences in Mexico and Central and South America. He is member of IEEE. Ignacio Suárez was born in México City. He is electrical engineer from Universidad Nacional Autonoma de Mexico, his experience is more than 15 year in the electric area, he has worked in many different companies where he has participated in design engineering, equipment installation, training, planning, commercial and administrative functions. At the moment he is engineering manager in Inelap,* S.A. de C.V., where his participation it obtained the ISO-9001 certification. He has participated in many conferences in Mexico, in 2000 he was speaker in the Power System World in USA. Luis M. Flamenco was born in Mexico City, in 1967. He is electrical engineer from the Universidad Nacional Autónoma de Mexico. Since 1991 he has worked for different companies carry out studies including: short circuits and protection and coordination, low flow and harmonics analysis. Actually, he is manager of power quality department at Inelap,* S.A. de C.V. He has participated two times in the Power System World in USA in 1998 and 2001. *Arteche acquired Inelap in 2005