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Power factor improvement Houshmand, Nazanin May 13, 2013

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UBC Social Ecological Economic Development Studies (SEEDS) Student Report       Power Factor Improvement Nazanin Houshmand  University of British Columbia EECE 496 May 13, 2013           Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report”.    THE UNIVERSITY OF BRITISH COLUMBIA Department of Electrical and Computer Engineering   Power Factor Improvement  By: Nazanin Houshmand Student number:    Supervisor: Dr. Andre Ivanov and Dr. Paul Lusina ii  ABSTRACT This project investigates power factor improving equipment for the following buildings on UBC campus: Life Science, Biology West, Chemistry Physics, Forest Science and Michael Smith. My objective throughout this project was to write a Microsoft Excel program that would be able to calculate the capacitor values needed to improve the power factor, and increase the life span of the transformer due to the addition of the equipment. Additionally, the program enables users to calculate the amount of yearly savings, based on the installation of the capacitors and the savings resulting by the reduction of greenhouse gas emissions, given the real power as well as the power factor. This report will discuss the different aspects of the project, such as the equipment and methodology, and the calculations and results. In the end, I was able to complete my goal of creating a Microsoft Excel file that will calculate all the necessary information for future projects as well as recommending corrective equipment for each building. The Microsoft Excel program can easily be extended to include calculations of value of money and the possible repair cost.iii  TABLE OF CONTENTS Abstract............................................................................................................................................ ii List of Tables……........................................................................................................................... iv List of Figures...................................................................................................................................v List of Equations..............................................................................................................................vi Glossary...........................................................................................................................................vii 1.0 Introduction.......................................................................................................................... 1 2.0 Equipment and methodology.................................................................................................3 3.0 Designs and Experiments......................................................................................................4 3.1 Harmonics...........................................................................................................4 3.2 Capacitor Location..............................................................................................5 3.3 Financial Savings................................................................................................6 3.4 Equipment Life Cycle Impact.............................................................................7 4.0 Results.................................................................................................................................10 4.1 Closest capacitor...............................................................................................10 4.2 Filter and breakers.............................................................................................11 4.3 Savings..............................................................................................................12 4.4 Break Even Point...............................................................................................13 4.5 Life Improvement..............................................................................................13 5.0 Conclusion...........................................................................................................................15 References......................................................................................................................................16 Appendix........................................................................................................................................17iv  LIST OF TABLES Table 1: Summary of advantages/disadvantages of different combination of capacitors….............5 Table 2: BC hydro electrical charges................................................................................................7         v  LIST OF FIGURES Figure 1: Capacitor location on motor circuit...................................................................................6 Figure 2: Loss characteristics for electrical core-steel materials over a range of magnetic induction............................................................................................................................................8 Figure 3: Closest Capacitor Value...................................................................................................10 Figure 4:Switched harmonic filter and breaker ($).........................................................................11 Figure 5: Yearly savings ($) of addition of capacitors....................................................................12 Figure 6: Breakeven point in number of months.............................................................................13 Figure 6: Life of the transformer after the addition of the capacitors.............................................14    vi  List of Equations Equation 1: Relationship between Apparent power and power factor…………………….……….4 Equation 2: Harmonics equation………………………………………………………….………..5 Equation 3: Power rating ratio……………………………………………………………..……….8 Equation 4: Equation known as per unit life …………………………………………….……...…9       vii  GLOSSARY Microsoft office Excel Microsoft program used usually for accounting to calculate formulas for large data Real Power The power that is used to do work on the load in units of Watts. Reactive Power Power merely absorbed and returned in load due to its reactive prosperities in units of VAR Apparent Power The power supplied to the system in units of VA Power factor The ratio of the real power flowing through the load to the apparent power in the circuit GHG  Green House Gas emissions are any of the atmospheric gases that contribute to the greenhouse effect by absorbing infrared radiation produced by solar warming of the Earth's surface.  They include carbon dioxide (CO2), methane (CH4), nitrous oxide (NO2), and water vapor.     1  1.0 INTRODUCTION This project investigates the possibility of saving both energy and capital by adding corrective capacitors. Furthermore, this project has all the calculations formulated so that it can be easily accessed for future projects, and generate the required information by only changing the initial data. My objective during this project is to evaluate possible equipment that can be used to reduce reactive power usage by improving power factor, while being cost efficient. In order to discover the installation cost, I used Microsoft Excel to calculate the capacitor value needed to improve the power factor to 90%, 95%, and 100%. I then found the breakeven point by means of the total electrical and GHG emission savings.  BC Hydro charges UBC for the amount of reactive power used by the transformers located at each building .The electricity bill can be reduced by decreasing the reactive power used by the transformers; this is the direct result of the transformer’s power factor improvement. Motor productivity and life span of the transformers will also increase due to the addition of capacitors to the circuit and the raised voltage level. Additionally, this project will help UBC’s sustainability team in accomplishing their goal of reducing campus’s greenhouse gas (GHG) energy emissions. This project involves great knowledge of Microsoft Excel as well as energy flow in the system. I had to learn various functions in Microsoft Excel to ensure the calculations can be easily used for future projects. I also had to learn about power ratings and per unit life in order to be able to calculate the life expectancy improvement of the transformers from the addition of the bulk of 2  capacitors. I also learned about the importance of harmonics in selecting capacitor types for individual buildings. I was able to accomplish all my objectives including calculating capacitor value, corrective equipment analysis, and financial gain from the installation of such equipment. Furthermore, I investigated the life expectancy enhancement using the thermal temperature reduction due to the increase in power factor. Given the short period of time, I was not able to account for the change in value of money and increase in the electricity charges that may occur in the future. However with the knowledge of net future value, and net present value, it can be easily formulated into Microsoft Excel during future projects. This report divides into the following primary sections: Equipment and Methodology, Designs and experiments, Results, and Conclusion.   3  2.0 EQUIPMENT AND METHODOLOGY  Upon discussing the purpose and objective of the project with Dr. Paul Lusina, we decided to use Microsoft Excel for all the calculations needed throughout this project. The decision was mainly due to Microsoft Excel’s calculation flexibility for large amounts of data as well as the program being future user friendly due to formulated cell sheets. I approached this project with the idea of comparing the present transformer usages to the values of the ones found after the addition of capacitors. During the term, Dr. Lusina and I have had weekly meetings to discuss the essential information needed to select a capacitor, as well as to estimate the total annual savings due to the addition of the equipment. In order to find the capacitor values and the savings as a result of the addition of capacitors we have concluded that the following information is necessary: active power, reactive power, apparent power, and present power factor, coldest and hottest temperature of the system, thermal resistance, the core material’s dimension, and electricity charges. Given that two of the buildings in this project have more than one transformer, life science having three, and forest science having two transformers, it would be difficult to show all the information on one page. In order to make the comparison easier, each transformer has its individual work sheet, one with the information regarding capacitor values and life expectancy, and another for savings.     4  3.0 DESIGNS AND EXPERIMENTS In order to attain the capacitor value, I first calculated the existing apparent power used by the systems via the real power and power factor measurements found from UBC Ion website.[Appendix 1] The following formula illustrates how the calculations were computed. [1]                                       Equation 1: Relationship between Apparent power and power factor [1] I then used the table of desired power factors in percentage to find the ratio multiplier for capacity; I used desired power factor of 90%, 95% and 100% in comparison to the original power factor. [Appendix 2] Multiplying the ratio found using the desired power factor table by the real power of the system, I was able to calculate the value of a capacitor in kVAR Since the exact capacitor value for the correction is not always commercially available, I investigated the installation charges for the closest value of capacitance to the average of the calculated values over two days of measured data. 3.1 Harmonics Another factor that was taken into account while choosing the appropriate capacitor was the presence of third harmonics. Due to the interaction of the capacitor with the service transformer, harmonic voltages and currents are significantly magnified which is referred to as harmonic resonance. By adding on to the existing kVAR, we are increasing the likelihood of amplifying the harmonics. It is important to avoid having system harmonics, because it can result in blown fuses or fuses not working properly, as well as reduction in motor life span. The harmonics of the system was found using the formula shown on the next page. The circuit resonance will increase 5  enormously if the h calculated is close to the major harmonics created by the nonlinear device i.e. 1, 3, 5, etc.[2]  Equation 2: Harmonics equation [2]  3.2 Capacitor Location It is not only important what value of capacitor is used, but also the type and location of installation are just as important. Table 2 indicates the advantages and disadvantages of different combinations of capacitor methods. During the project, I chose to compare the most cost efficient methods i.e. fixed banks and switched banks. [3]  Table 1: Summary of advantages/disadvantages of different combinations of capacitors [3] There are four different location options for the installation of the capacitors. The four options that are shown on figure 1: directly at the single speed induction motor terminals (on the secondary of the overload relay), between the contactor and the overload relay, location A, between the upstream circuit breaker and the contactor, location B, and at the main distribution bus, location C. However the first two locations mentioned would only provide the option of installing individual capacitors. The individual capacitors are an efficient method for power 6  factor correction; however a high installation and maintenance cost is associated with them. Therefore, making the option of installation at either location, whether that be directly at the single speed induction motor terminals, or between the contactor and the overload relay, seem unreasonable. Additionally, having the bank of capacitors at the main distribution line, will result in possibility of overcorrection under lightly loaded conditions as well as a requirement for separate disconnect switch, and over current protection method. Concluding, the best location for the installation of the corrective equipment would be between the upstream circuit breaker and the contactor. The only disadvantage for the selected location of installation is the possibility of overcorrection occurring if all motors are not running. [4]  Figure 1: Capacitor location on motor circuit [4] 3.3Financial Savings To explore the total savings as a result of the addition of the new equipment to the circuit, I had to inspect the original electrical charges of the system. UBC’s Ion system indicates the measured data in 15 minutes intervals. After finding the kVAR of the system and integrating it over 15 minutes for the month of February, I was able to calculate the month’s electrical charges using 7  the information given in table 2. The electrical charge is the multiplication of the total integration of kVAR of the system by the energy charges, added to the multiplication of the  peak value of the integration of kVAR by the demand charges. The rate rider and tax is then added to the charges from the previous step.  Electric Rate Schedule Charges Energy ($/kWh) $0.03814 Demand ($/kVA, monthly) $6.507 Applicable Taxes (7.40 % for PST & ICE fund levy + 1.65% for GST) 9.05% Rate Rider 5.20% Table 2: BC Hydro electrical charges Using the new kVAR due to the new power factor, the electrical charges for the new system can be easily calculated. UBC is also responsible for the Green House Gas emission of electricity which has the electric rate of $625/GWh. By calculating the difference of the total bill for the original system and the improved system, and adding the GHG savings enabled me to estimate the total monthly and yearly savings. Knowing the installation costs, the breakeven point can be projected to be the installation cost divided by the total daily savings. 3.4 Equipment Life Cycle Impact In addition to the corrective equipment value and the financial savings as a result of the installation of the equipment, I also investigated the life expectancy improvement of the transformers. The most important calculation in finding the improvement of the life of the transformer is the calculation of the hottest temperature of the system after the addition of the capacitors. To accomplish the goal of finding the hottest temperature, I took advantage of the formula for the power rating of the system, which is the maximum power used within the system. 8  The amount of heat that can be dissipated by the transformer, PD,max, is directly proportional to the amount of losses within the system; the losses of the system is simply efficiency subtracted from one. Efficiency of the system is the ratio of output energy to input energy, or the output energy plus the losses of the system. To find the losses of the system I used figure 2. The core material of the transformers used at the buildings in question are 0.3mm and are constructed from high quality, cold rolled, grain orientated, stress relieved silicon steel laminations, insulated on one side and working at a flux density not exceeding 1.73 Tesla. Therefore, the power loss in watts/kg is about 1 W/Kg and multiplying this value with the transformer’s weight will result in total losses of 3800 watts. [5]  Figure 2: Loss characteristics for electrical core-steel materials over a range of magnetic induction [5] Knowing the maximum safe operating temperature, TDmax, and the ambient temperature, TA, to be 165 and 40 respectively, and having PD,max already calculated using the following information, the thermal resistance, ӨDA, of the system can be found in units of m2K/W.[6]  Equation 3: Power rating ratio 9  The maximum temperature after the addition of the corrective capacitor was determined using the thermal resistance, and the new efficiency of the system. The life cycle of the current transformers can be assumed to be 40 years at 50% loading (ideal situation) and 25 years at 80% loading. By using per unit life formula, using the new hottest temperature calculated, ӨH , and having constant B to be 1500, I was able to determine constant A and consequently the improvement to the life span using the new hottest temperature of the system.  Equation 4: Equation known as per unit life    15  5.0 CONCLUSION This report investigated the possibility of power factor improvements for the following five UBC buildings: Life Science, Biology West, Chemistry Physics, Forest Science and Michael Smith. I was able to inspect the capacitor installations, the capital savings, and the life expectancy improvements as a result of the installation of the capacitors. By using Microsoft Excel sheets, I was also able to formulate my calculation so that the program will be able to run for different initial values. Analyzing various options for power improvement equipment, I recommend using switched harmonic filters and breakers. This particular breaker will ensure that overcorrection of the power factor as well as harmonic resonance, which can be damaging to the transformer, is avoided. Furthermore, depending on the initial investment, I highly recommend improving to power factor of 100%. Although the installation of the capacitance of the 100% power factor is costly, the savings exceed the cost enormously. With breakeven points of less than three months, it is apparent that the return on investment starts shortly after the installation. The maintenance costs for the power factor equipment and the preventative maintenance costs from the reduction temperature are not included in this project. With over 60 institutional buildings on campus, initiating a power improvement plan will save UBC more than $7,000,000 within the first year, assuming that the other buildings will only save as much as Forest Science 2 . For future projects, I would recommend investigating the savings the installation of capacitors will have if it was done for all the buildings on campus, while taking into account the net present value.  16  REFERENCE [1]”UBC Sustainability remote metering site”, cited winter 2013, available from World Wide  Web: <http://utilsub.lbs.ubc.ca/ion/> [2]Brahm Segal, “Costs and benefits of harmonic current and power factor reduction for  variable speed drives in an industrial facility”, Power Correction Systems, Inc., August 28, 2000[cited March 2013], available from World Wide Web: < www.activeharmonicfilters.com/Tutorial/pcs-tutorial.doc>  [3] “Power factor Capacitors and harmonic filters”,EATON, September 2011[cited on March 2013], available from World Wide Web: <http://eaton.com/consultants> [4]”Application of power factor correction capacitors”,Teknatool international corp.,2012[cited on  March 2013], available from World Wide Web: <http://www.teknatool.com/products/Lathes/DVR/downloads/How%20Power%20Factor%20corection%20works.pdf> [5]Leo L. Grigsby,” Electric power transformer engineering”, CRC Press LLC,2004 [cited on  March 2013],available from World Wide Web: <http://www.uncp.edu.pe/newfacultades/ingenieriasarqui/newelectrica/phocadownload/descargas/E%20BOOK%20Electric%20Power%20Transformer%20Engineering.pdf> [6] “Power rating”,Wikipedia,Feb 2013[cited on March 2013], available form World Wide Web:  <http://en.wikipedia.org/wiki/Power rating>17  APPENDIX [1] Phasor diagram showing the relationship between apparent power, reactive power, and real(true) power    18  [2]Table of desired power factor[5]  19      

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