[Use 10-12 Point Font] [Font Times New Roman] [Thesis/Project Collaborative (same department) Title Page] THE ELECTRICAL TRANSMISSION SYSTEM OF A 345KV WITH 170 MILES MODEL A Project Presented to the faculty of the Department of Electrical and Electronic Engineering California State University, Sacramento Submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in Electrical and Electronic Engineering by Farshad Tavatli Babak Kaviani Joupari SPRING 2013 Sample Copyright page [l] © 2013[Year of graduation] Farshad Tavatli Babak Kaviani Joupari ALL RIGHTS RESERVED [Thesis/Project Approval Page] ii THE ELECTRICAL TRANSMISSION SYSTEM OF A 345KV WITH 170 MILES MODEL A Project by Farshad Tavatli Babak Kaviani Joupari Approved by: __________________________________, Committee Chair Turan Gönen, Ph.D. __________________________________, Second Reader Salah Yousif, Ph.D. ____________________________ Date [Thesis/Project Format Approval Page] iii Student: Farshad Tavatli Babak Kaviani Joupari I certify that these students have met the requirements for format contained in the University format manual, and that this project is suitable for shelving in the Library and credit is to be awarded for the project. __________________________, Graduate Coordinator B. Preetham. Kumar, Ph.D. r Department of Electrical and Electronic Engineering iv ___________________ Date Abstract of THE ELECTRICAL TRANSMISSION SYSTEM OF A 345KV WITH 170 MILES MODEL by Farshad Tavatli Babak Kaviani Joupari A reliable and efficient transmission system benefits not only the power utility companies, but the consumer as well. This report provides clarification to concepts and calculations in the analysis of an electrical transmission system involving a 345KV with 170 miles of distance. The project will analyze the efficiency, voltage regulation, power quality, power losses by comparing different sizes of cables. A fundamental part of achieving a reliable transmission system is by considering all necessary factors such as; careful design and complicated calculations “with help of MATLAB”. Different compensator devices will be discussed and used in no load and full load situations in this report in order to design an efficient transmission circuit. _______________________, Committee Chair Turan Gönen, Ph.D. _______________________ Date v DEDICATION [Optional] I dedicate this work to my parents and a great instructor “DR Gonen”. vi [This Table of Contents covers many possible headings. Pages are optional. Use only the headings t TABLE OF CONTENTS Page Dedication .................................................................................................................... vi List of Tables .................................................................................................................x List of Figures .............................................................................................................. xi Chapter 1. INTRODUCTION ...................................................................................................1 2. LITERATURE SURVEY ........................................................................................2 2.1. Introduction ....................................................................................................2 2.2. Line Routing ..................................................................................................4 2.3. Ground Clearance ..........................................................................................4 2.4. Separation Between Conductors ....................................................................6 2.5. Insulation and Insulators ................................................................................6 2.6. Tower Structure .............................................................................................7 2.7. Sag and Tension .............................................................................................9 2.8. Thermal Ampacity .......................................................................................10 2.9. Line Parameters ...........................................................................................10 2.10. Inductance ..................................................................................................11 2.11. Capacitance ................................................................................................11 2.12. Transposition with Ground Wire ...............................................................12 vii 2.13. Long Line Model .......................................................................................12 2.14. Line Compensation ....................................................................................13 3. MATHEMATICAL MODEL ................................................................................14 3.1. Thermal Ampacity rating ....................................................................14 3.2. Series Impedance and shunt Admittance ............................................14 3.2.1. Series Impedance .................................................................................15 3.2.1a Self and Mutual Impedances with effects of Ground Wire.............17 3.2.2 Shunt Admittance..............................................................................23 3.3. Long Line Model .................................................................................29 3.4. ABCD Constants .................................................................................32 3.5. Voltage Regulation, Power Loss and Efficiency ................................32 3.6. Line Compensation .............................................................................33 3.6.1 Full Load Compensation ...................................................................34 3.6.2 No Load Compensation ....................................................................35 4. APPLICATION OF THE MATHEMATICAL MODEL ......................................39 4.1. Introduction ..........................................................................................39 4.2. Thermal Ampacity Rating...................................................................41 4.3. Line Characteristics and ABCD Constants ..........................................42 4.3.1 Series Impedance ..............................................................................43 4.3.2 Shunt Admittance..............................................................................46 4.3.3 ABCD Constants ...............................................................................50 viii 4.4. Uncompensated Line ...........................................................................51 4.4.1 Full Load ...........................................................................................52 4.4.2 No Load ............................................................................................53 4.4.3 Voltage Regulation, Power Loss and Efficiency ..............................53 4.4.4 MATLAB ..........................................................................................54 4.5. Compensation ......................................................................................55 4.5.1 Full Load Compensation ...................................................................55 4.5.2 No Load Compensation ....................................................................56 5. SUMMARY ...........................................................................................................60 Appendix A. Overhead Ground Wire Characteristics .................................................62 Appendix B. ACRS Table............................................................................................64 Appendix C. Wire Compensation of Uncompensated Line data .................................65 Appendix D. MATLAB Code of Uncompensated Line ..............................................67 Appendix E. MATLAB Code, Full Load Compensation ............................................71 Appendix F. MATLAB Code, No Load Compensation ..............................................76 Bibliography ................................................................................................................79 ix LIST OF TABLES Tables Page 1. Table 2.1 Vertical Clearance of Conductors ....................................................... 5 2. Table 4.1 MATLAB VS Theoretical Comparison for 1/0 ACSR .................... 54 x LIST OF FIGURES Figures Page 1. Figure 2.1 Suspension Type Insulators, 345 KV Tower Structures ................... 8 2. Figure 2.2 Pole Type, 345 KV Tower Structures ............................................... 9 3. Figure 3.1 Carson’s Return Theory ................................................................. 16 4. Figure 3.2 Effects of the Ground Wire ............................................................. 19 5. Figure 3.3 Sectioning of Completely Transposed line...................................... 19 6. Figure 3.4 Image Method .................................................................................. 24 7. Figure 3.5 Model of a Long Transmission Line ............................................... 30 8. Figure 3.6 Series Compensation of a Long Line .............................................. 35 9. Figure 3.7 No Load Compensation with a Shunt Reactor ................................ 36 10. Figure 4.1 Tower configuration ........................................................................ 40 11. Figure 4.2 Series Capacitor Compensation ....................................................... 56 12. Figure 4.3 Shunt Reactor Compensation .......................................................... 57 xi 1 Chapter 1 INTRODUCTION The purpose of this project is to find a means of choosing a line based on its voltage regulation, power loss, and efficiency. A voltage regulation between 3% and 5% will be ideal, while minimizing power loss and maximizing efficiency. Since ACSR (Aluminum Conductor cable Steel Reinforced) conductors are widespread used for transmission line design, therefore in this project we will be using ACSR as well. A line will be selected in the beginning just to show the hand calculations then MATLAB will be used to execute the same calculations but for different line sizes. A static receiving end load with a lagging power factor will be analyzed for a 170 miles long line at 345kv. An overhead ground wire will be used for lightning protection and will be taken into consideration when computing the long line parameters. The tower configuration to be used will be arbitrarily selected as well as the overhead ground wire type. The computational method is the most significant portion of this analysis; therefore all structural and mechanical aspects will be ignored. From this analysis the data can then be used for an economic analysis which would involve line initial cost, construction, maintenance, operation, efficiency, compensation Vars, and reliability.[1] Equation Chapter (Next) Section 1 Equation Chapter (Next) Section 1 2 Chapter 2 LITERATURE SURVEY 2.1 INTRODUCTION Designing Transmission lines is definitely not a simple task. There are so many considerations that have to be factored in to make an efficient and worth building transmission line. In addition, there are certain regulations that have to be met for the safety and wellbeing not just for the people but also for the environment. Such considerations are as following; Line Routing, Cost Estimating, Station Interfacing, Right-of Way Acquisition, Structure Design, Sag and Tension, Conductor Analysis, clearances, strengths and loading, and many more which we cannot explain all of them in this research. On top of all regulations also have to be considered from the National Electric Code (NEC) and the National Electric Safety Code (NESC). The noticeable difference between the two is that the NESC is not intended as a design specification or an instruction manual. The NEC covers the proper installation guidelines of electric conductors on buildings or structures that need to be considered to protect the people and property from hazards that occur from the usage of electricity in building and structures. The NESC addresses the practical safety and the basic provisions that are considered essential for the safety of the workers and the public. [2] Transmission lines were not always generated by alternating current (AC). In fact, Direct Current (DC) was first used as generation in 1882. However, it was quickly found 3 inefficient because voltage could not be increased for a long distance. The classes of loads are variable so it required different voltages and would result in different generators and circuits. Nikola Tesla proposed the use of alternating current which allowed efficient generation. With the use of rotary converters, an electrical machine used to convert one form of electrical power to another, networks connecting different generating plants with loads having different frequencies could be connected. Also, AC could be converted to DC with the use of rotary converter to be served to the loads that required DC. By permitting multiple interconnections between several generating plants, electricity production was more efficient resulting in the decrease in cost. Reliability immensely improved and also resulted in lower production cost. [2] AC Power can be transported by two ways. One is overhead transmission and the other is underground transmission. In overhead transmission, the electrical conductors are not covered by insulation. The conductors that are used are mainly Aluminum Conductor Steel Reinforced (ACSR). They are used as bare overhead transmission cable or primary and secondary distribution cable. The underground transmission is mainly used in densely congested areas and also where there are natural obstacles that do not permit the use of overhead transmission. The use of underground transmission is a more expensive option, actually about two to four times the cost of an overhead line. 4 2.2 LINE ROUTING One major consideration that has to be taken into account for transmission line design is the route of the lines. Where will these lines carrying so much voltage go? Selecting a route may not be an easy task. There are many considerations that need to be thought taken. For instance, there are physical (highways, railroads, other transmission lines), biological (wetlands, wildlife, woodlands), or other (federal, state controlled lands). Not only do these locations have to be examined, the cost of clearing, ease of maintaining, and the effect of the line may have on the environment. After the route has been selected, the surveyors conduct a field examination and prepare a universal drawing for the whole route. Also, there are many permits and authorizations that need to be obtained. For instance, federal permits or licenses are required, the use of private property, permit from state/county/city, permission of utility. There are others that need to be obtained but for the limited space of this report, they shall not be listed. [1] 2.3 GROUND CLEARANCE This is where the NESC come into play. There has to be enough clearances under the line so it will not pose any danger to anything underneath the line. Such clearances to consider are clearances over water surface, ground, roadways, or rails. The NESC specifies all of these under different types of nominal line voltages. For example, for a 230 KV line, there has to be at least 32.9 ft of clearance for track rails, 24.9 ft for roads and streets, and 20.9 for spaces and ways for accessible to pedestrians only. Not only is there vertical clearance, there is also horizontal clearance in order to provide more 5 cushion of safety. Often the conductors that are displaced by wind are given more clearance than those that are at rest. Some horizontal clearances may include traffic signal support or structure, buildings, or bridges. Again, all of these rules come from the NESC. In Table 2.1, a table from RUS Bulletin 1724E-200: Rural Utilities Service, U.S. Department of Agriculture is provided to give a sense of the clearances for different kinds roadways, rails, or water surfaces. [2] Table 2.1 Vertical Clearance of Conductors 6 2.4 SEPARATION BETWEEN CONDUCTORS Conductors are always assumed to move. On that note, there should always be a minimum separation between each phase of the conductors. If insulators are free to swing, that means the conductors are also going to swing since the conductor hangs from the insulator. The separation between the lines will depend on the spans and sags of the lines as well as how structures match up with another. The standard separation value should be on a worst case analysis. Galloping or “dancing” occurs where the conductors move with very high amplitudes. This is bad because it can cause contact between phase conductors or the overhead ground wire, which will cause a major electrical outage. Also, the conductor themselves may break due to the intense stress, or maybe the structure or towers themselves may have possible damage. Galloping is caused by stable wind blowing over the conductors covered by a layer of ice deposited from the freezing rain. There are measures to take to reduce the possible contact between the conductor phases that are caused by galloping. For instance, shorter spans, which are the distance from one tower to another, or increased, phase separation between the conductors. [1] 2.5 INSULATION AND INSULATORS Insulators are objects that have to be considered when designing transmission lines. An object made of a material like glass, porcelain or composite polymer that is a poor conductor of electricity. All of the materials for insulators are handled with epoxy resins, which acts like reinforcement glue for the materials of the insulators. Insulators are used 7 to attach conductors to the transmission structure and to prevent a short circuit from happening between the conductor and the structure. For this design suspension type insulators will be used, since they are used for very high voltage systems is not a practical or safe to use other types of insulators. Suspension type insulators are usually made of porcelain that can be stacked in a string and hangs from a cross arm on a tower or pole that supports the line conductor. Fig 2.2 illustrates suspension type insulators hanging from a steel lattice tower. There are also pin-typed insulators to secure the conductor to the insulator. Another type of insulator is the strain insulator. These types of insulators are used on when the line is dead-ended. It provides adequate mechanical strength to counterbalance the forces due to the tension of the conductors and as well as provide insulation. [1][3] 2.6 TOWER STRUCTURE The type of towers that needs to be used for such transmission lines has to be well thought of. It has to be just right to meet the requirements of the project. For example, the height has to be tall enough so it provides that ground clearance that was mentioned earlier. The towers have to be mechanically strong enough to withstand the weight of the insulators, the tension of the conductors, or the other possible hazards that may arise from nature such as a hurricane if installed in the east coast line. For this project a 345 KV line will be used. A typical structure for this line can be a single pole tower or an H-frame type tower. Fig 2.3 shows a typical representation of a pole tower and H-Frame. 8 Figure 2.1 Suspension Type Insulators, 345 KV Tower Structure 9 Figure 2.2 Pole Type, 345 KV Tower Structure Another type of tower structure is the steel lattice tower. These towers are for extra high voltages. [1] [3] 2.7 SAG AND TENSION In transmission lines, the behaviors of the hanging conductors are a key variable for the design. For instance, some factors that will contribute to the sag are the temperature of the environment, temperature of the conductor itself, the current running through the line, and the weight of the conductor. These are just the simple factors that will depend on 10 how much the line will sag at each span (distance between each tower). In addition, all have to be met within the desired NESC regulations. Tension is correlated with the sag. Tension should not be too high or too low because that will also contribute to the sag. Having a higher tension will increase the sag and vice versa. 2.8 THERMAL AMPACITY Transmission lines have the capability of transmitting power, which is limited to the thermal loading and stability limits. The temperature of the conductor reflects the thermal loading limit of the line and the real power loss of the line is increased as the temperature of the conductors rise. The thermal limit is specified to be at 75% of the current carrying capacity given for a conductor at a temperature of 50° Celsius. This temperature of 50° Celsius is based on a 25° Celsius air temperature with a 25° Celsius rise in conductor temperature. In order to find the current carrying capacity, the power of the line and the rated phase voltage of the selected line should be known. [3] 2.9 LINE PARAMETERS In modeling a transmission line, the resistance, inductance and capacitance of the line must be taken into consideration. These parameters will be used to find the series impedance and shunt admittance of the line which will then be used to find the ABCD constants that will relate the sending and receiving end of the line. 11 2.10 INDUCTANCE The inductance of a conductor is caused by the current being carried by the conductor and the magnetic field around the conductor. As the current changes, the flux changes and a voltage is induced in the circuit. There is also inductance inside a conductor. For this design, the skin effect, which is the tendency of the alternating current to dispense itself into the surface of the conductor making the current greater at the surface than the center, will be neglected and assume that there is uniform current density throughout the conductor cross section. The total inductance of the line will be the sum of the internal and external flux linkages of the conductor. 2.11 CAPACITANCE The capacitance of a transmission line is determined by the potential differences between the conductors. The capacitance is a ratio of the charge of the conductor to the potential difference of the conductor. The bigger the potential difference between the conductors will result in smaller capacitance of the line and it is conversely the same if the potential difference was very small. In contrast with the inductor, capacitance is associated with electric field. The charge on a conductor increases the electric field with radial flux lines. Overall the total capacitance of the line in a three phase system is the sum of the self and mutual capacitances. 12 2.12 TRANSPOSITION WITH GROUND WIRE The transposition of a line allows for a line to have approximately equal parameters. This allows for the line to be modeled by one single phase to neutral line, with the addition of an Overhead Ground Wire. Since all three phases occupy the same position for the same amount of time, 2.13 LONG LINE MODEL For a long transmission line the magnitude of the voltage over the entire line is not constant. For relatively small loads or an open circuit condition, the voltage increases from the sending end to the receiving end. For larger loads or the short circuit condition, the voltage decreases depending on the amount of load. These increases and decreases in the line voltage are unwanted. A decrease in voltage means an increase in current. This would increase the power losses in the line and decrease the lines loading capability. For the open circuit or small load situation, an increase in voltage would cause the line to be more prone to arcing. There are many ways of compensating a line. In this report, full load and no load compensation will be our primary focus. The open circuit situation has its voltage compensated with a single shunt reactor applied at the receiving end. For the full load situation, compensation is achieved with the placement of a series capacitor in the middle of the transmission line. Again, the idea is to understand how the line can be compensated for the worst case scenarios up to but not including the thermal ampacity of the line. 13 2.14 LINE COMPENSATION For a long transmission line the magnitude of the voltage over the entire line is not constant. For relatively small loads or an open circuit condition, the voltage increases from the sending end to the receiving end. For larger loads or the short circuit condition, the voltage decreases depending on the amount of load. These increases and decreases in the line voltage are unwanted. A decrease in voltage means an increase in current. This would increase the power losses in the line and decrease the lines loading capability. For the open circuit or small load situation, an increase in voltage would cause the line to be more prone to arcing. There are many ways of compensating a line. In this report, full load and no load compensation will be our primary focus. The open circuit situation has its voltage compensated with a single shunt reactor applied at the receiving end. For the full load situation, compensation is achieved with the placement of a series capacitor in the middle of the transmission line. Again, the idea is to understand how the line can be compensated for the worst case scenarios up to but not including the thermal ampacity of the line. 14 Chapter 3 MATHEMATICAL MODEL 3.1 THERMAL AMPACITY RATING The first step in our search is to figure out which lines meet the thermal ampacity rating. This ampacity is given in Appendix A, which is 75% of the current carrying capacity of the line given for a conductor temperature of 50° Celsius. From the equation for three phase apparent power with the receiving end voltage at 345kV, IR = SR(3Φ) 3VR(L-L) = 200 MVA =334.7 Amps 3×345 KV (3-1) 3.2 SERIES IMPEDANCE AND SHUNT ADMITTANCE Next, the series impedance and shunt admittance of the line will be found. These parameters will then be used to model the line. The calculations will take the effects of the earth into consideration and the effect of the overhead ground wire. This will greatly increase the amount of calculations for the compensation of the line. 15 3.2.1 SERIES IMPEDANCE Series impedance exists on a line due to inductance and resistance. The current through any conductor develops a magnetic field of proportional magnitude. The energy is then stored in the magnetic field, and there is opposition to change in currents, meaning the current through the inductors cannot change rapidly. Each conductor in a three phase system develops a magnetic field as it carries charging currents for the capacitance between the wires. Since there is always a return current path present, the magnetic field created by a changing magnetic field current in the circuit itself induces a voltage in the same circuit. Since the system is three phase, there will be induced voltage on a line from a current adjacent to another line. From Carson’s Earth Return Theory, there flows a current through a given conductor "a" above the earth and another given conductor "d" in the earth. By using Carson’s line formula, [5] VA =(z A +z DD 2z AD )IA V/unit length. (3-2) Also knowing that, z AA =(z A +z DD 2z AD ) (3-3) The self-impedance of conductor a can be established, by using Newman’s formula z AA =rA + jωL. (3-4) z AA =rA + jωkln 2s Ω/unit length DSA (3-5) 16 “s” is the length of the line. For a 3 phase line, there would be conductors a, b, and c above the earth. The mutual and self-impedance can be found in a similar way from the single conductor. Figure 3.1 Carson’s Return Theory Self Impedance z AA =(rA + rD ) + jωkln De Ω/unit length Ds z BB =(rB + rD ) + jωkln De Ω/unit length Ds z CC =(rC + rD ) + jωkln De Ω/unit length Ds z WW =(rW + rD ) + jωkln De Ω/unit length Dsw (3-6) 17 Mutual Impedance z AB = z BA = rD + jωkln De Ω/unit length D AB z BC = z CB = rD + jωkln De Ω/unit length D BC z CA =z AC = rD + jωkln De Ω/unit length DCA z AW = z WA = rD + jωkln De Ω/unit length D AW z BW = z WB = rD + jωkln De Ω/unit length D BW z CW =z WC =rD +jωkln De Ω/unit length DCW (3-7) 3.2.1a SELF AND MUTUAL IMPEDANCES WITH EFFECTS OF GROUND WIRE The self and mutual impedances are a result of the self and mutual inductance. The impedance is the sum of the inductance and the resistance. A ground wire “W” will be added to our 3 phase system. 18 where: ω= 2πf @ f = 60 hz k= 0.3219x10-3 mile De = 2160 ρ = 2790 ft. @ ρ=100 Ω×m for Avg. soil f DS , DSW = GMR of each conductor D AB , D BC , DCA , D AW , D BW & DCW = distance between conductors rD = 1.588x10-3f Ω/mile rA = rB = rC = resistance of lines Ω/mile rW = resistance of ground wire Ω/mile For a three phase line with 1 Overhead Ground Wire, the V=IZ equation becomes, VA z AA V z B = BA VC z CA VW =0 z WA z AB z AC z BB z CB z WB z BC z CC z WC z AW I A z BW I B Volts × mile z CW IC z WW I W (3-8) 19 Figure 3.2 Effects of the Ground Wire Figure 3.3 Sectioning of Completely Transposed line 20 Since our line is completely transposed, the line can be broken up into three equal sections as in figure 3.3. Positions 1, 2, and 3 will show the transposing of the line for the different sections If the impedances of the line are broken up into the different transposed sections S1, S2, and S3, as shown above, they can be written as, Evaluating the impedances separately, the impedance matrices with respect to the different positions become, Z11 Z ZS1 = 21 Z31 Z W1 Z22 Z ZS2 = 32 Z12 Z W2 Z33 Z ZS3 = 13 Z23 Z W3 Z12 Z13 Z22 Z23 Z32 Z33 Z W2 Z W3 Z23 Z33 Z21 Z31 Z13 Z11 Z W3 Z W1 Z31 Z32 Z11 Z12 Z21 Z22 Z W1 Z W2 Z1W Z2W Z3W Z WW Z2W Z3W Z1W Z WW Z3W Z1W Z2W Z WW Using kron’s reduction for the different sections of the line to only include the phase voltages, 21 Z11 ZS1'= Z21 Z31 Z12 Z22 Z32 Z13 Z1W 1 Z23 Z2W Z W1 Z Z33 Z3W WW Z W2 Z W3 Z1W Z W1 Z Z Z Z ) (Z12 1W W2 ) (Z13 1W W3 ) (Z11 ZWW ZWW ZWW Z Z Z Z Z Z = (Z21 2W W1 ) (Z22 2W W2 ) (Z23 2W W3 ) ZWW Z WW Z WW Z Z Z Z Z Z (Z31 3W W1 ) (Z32 3W W2 ) (Z33 3W W3 ) ZWW ZWW ZWW Z22 ZS2 '= Z32 Z12 Z23 Z33 Z13 Z21 Z2W 1 Z31 Z3W Z W2 Z WW Z11 Z1W Z W3 Z W1 Z2W Z W2 Z Z Z Z ) (Z23 2W W3 ) (Z21 2W W1 ) (Z22 Z WW Z WW Z WW Z Z Z Z Z Z = (Z32 3W W2 ) (Z33 3W W3 ) (Z31 3W W1 ) Z WW Z WW Z WW Z Z Z Z Z Z (Z12 1W W2 ) (Z13 1W W3 ) (Z11 1W W1 ) Z WW Z WW ZWW Z33 ZS3'= Z13 Z23 Z31 Z11 Z21 Z32 Z3W 1 Z12 Z1W Z W3 ZWW Z22 Z2W Z W1 (3-9) (3-10) Z W2 Z3W Z W3 Z Z Z Z ) (Z31 3W W1 ) (Z32 3W W2 ) (Z33 Z WW Z WW Z WW Z Z Z Z Z Z = (Z13 1W W3 ) (Z11 1W W1 ) (Z12 1W W2 ) Z WW Z WW Z WW Z Z Z Z Z Z (Z23 2W W3 ) (Z21 2W W1 ) (Z22 2W W2 ) Z WW ZWW ZWW (3-11) 22 From, 1 ZABC = (ZS1 +ZS2 +ZS3 ) 3 Since the line is completely transposed the diagonal terms of the impedance matrix are equal. Similarly, the off diagonal elements will be equal to each other, and both can be represented as, ZS = Z Z Z Z 1 1 Z Z Z11 +Z22 +Z33 1W W1 + 2W W2 + 3W W3 3 3 ZWW ZWW ZWW ZM = Z Z Z Z 1 1 Z Z Z12 +Z23 +Z31 1W W2 + 2W W3 + 3W W1 3 3 ZWW ZWW ZWW (3-12) Now the impedance matrix of the line can be written as, ZS ZABC = ZM ZM ZM ZS ZM ZM zS ZM = z M ZS z M zM zS zM zM z M ×total length of line zS (3-13) Now that the impedance matrix of the line is found, a single phase must be represented to continue our analysis. VA ZS V = Z B M VC ZM ZM ZS ZM ZM I A ZM IB ZS IC (3-14) Writing the phase currents of phases B and C in terms of the current in phase A we have, IB = (1120°)IA = aIA IC = (1240°)IA = a 2 IA (3-15) 23 VA ZS V = Z B M VC ZM ZM ZS ZM ZM I A ZM aI A ZS a 2 I A (3-16) Using only phase A to represent the series impedance of the line, V=I A ZS +aI A ZM +a 2 I A ZM =I A ZS + a+a 2 ZM =I A ZS -ZM (3-17) Therefore, the series impedance of the line can be found as, Z=ZS ZM Z Z Z Z 1 Z Z Z Z 1 Z Z 1 Z Z =Z11 1W W1 + 2W W2 + 3W W3 Z12 +Z23 +Z31 1W W2 + 2W W3 + 3W W1 3 ZWW ZWW ZWW 3 3 ZWW ZWW ZWW (3-18) 3.2.2 SHUNT ADMITTANCE The shunt admittance of a line is of the form Y = g +jωC. Where g is the conductance of the line and is considered negligible. Therefore Y = jωC. For a 3 phase line, the capacitance is found first by its potential coefficients where, V q Pq volts C and P C 1 unit length Farad 24 In addition to that, the capacitance of the 3 phase line can also be found by using the image method. This entails that the earth affects the capacitance of a transmission line because its presence alters the line’s electric field. The presence of the earth’s surface forces the electric field of the charged conductors to conform. Figure 3.5 below is a representation of the method of images that is utilized in this analysis. Variables for Shunt Admittance calculations [5] q charge c capacitance RA RB RC RW radius of conductor H A H B H C HW distance between conductor and it's image H AB distance between conductor A and conductor B's image DAB distance between conductor A and conductor B Figure 3.4 Image Method 25 With this in place, it is desired to obtain the voltages of all the conductors to ground but first consider that, 1 VA VAA' 2 1 VB VBB' 2 1 VC VCC ' 2 Then, the voltages can be determined by, 1 VA VAA' 2 H AC H AW HA H AB q A ln r qB ln D qC ln D qW ln D 1 A AB AC AW D D r D 4 q A ln A qB ln AB qC ln AC qW ln AW HA H AB H AC H AW (3-19) Then, now by combining the terms, VA H H HA H 1 qB ln AB qC ln AC qW ln AW q A ln 2 rA DAB DAC DAW H H H AB H 1 qB ln B qC ln BC qW ln BW q A ln 2 DAB rB DBC DBW H AC H H H 1 VC qB ln BC qC ln C qW ln CW q A ln 2 DAC DBC rC DCW VB VW H AW H H H 1 qB ln BW qC ln CW qW ln W q A ln 2 DAW DWB DCW rW (3-20) Continuing the process to find the capacitance, these voltages must be related to the potential coefficients by, V Pq 26 Then, the potential coefficient are calculated by, Pii Pij 1 2 1 2 ln ln H i 1 F m Self Potential Coefficient ri H ij Dij F 1m Mutual Potential Coefficient Here, the i and j subscripts can represent phases a, b and c. Epsilon, , is the permeability of air and its value is . Applying that value in for the potential coefficients, The 1 2 term becomes 18 109 F1m Then converting this number from meters to mile calls for, 18 109 F1m 11.185 F1mile m 1609 mile Using this to in the following to find the self-potential coefficients of the line with the OHGW results in, p AA =11.185ln HA MF-1mile RA p BB =11.185ln HB MF-1mile RB pCC =11.185ln HC MF-1mile RC p WW =11.185ln HW MF-1mile RW 27 Then the mutual potential coefficients between the phase conductors are, p AB =p BA =11.185ln H AB MF-1mile D AB p BC =pCB =11.185ln H BC MF-1mile D BC pCA =p AC =11.185ln H CA MF-1mile DCA Also the mutual charge coefficients between the OHGW and phases, p AW =p WA =11.185ln H AW MF-1mile D AW p BW =p WB =11.185ln H BW MF-1mile D BW pCW =p WC =11.185ln H CW MF-1mile DCW The line can then be represented by its potential coefficients with the overhead ground wire. VA p AA V p B = BA VC pCA VW =0 p WA p AB p AC p BB pCB p WB pBC pCC p WC p AW q A pBW q B pCW q C p WW q W (3-21) However, just like the series impedance, the phase values are only needed. Therefore by Kron’s reduction, p AW pW A p AA pW W V A V p p BW pW A B BA pW W VC pCW pW A pCA pW W p p p AB AW W B pW W p p p BB BW W B pW W pCW pW B pCB pW W p p p AC AW W C pW W q A p p p BC BW W C q B pW W q pCW pW C C pCC pW W (3-22) 28 Converting the charge coefficients to capacitances, CAA C=P = CBA CCA -1 CAB CBB CCB CAC CBC CCC The capacitances to ground for the different phases are, CAG = CAA CAB CAC CBG = CBBCAB CBC CCG = CCC CAC CBC (3-23) Since the line is transposed, the capacitance to ground in each phase is the average of the capacitance to ground of the three phases, CG = 1 CAG CBG CCG 3 Now to find the capacitance to neutral, the mutual capacitances of the line has to be calculated. Since the mutual capacitances are delta connected, they must be converted to wye, Cmutual (1/ 3)(C AB CBC CCA ) CY 3 Cmutual And the capacitance to neutral, C CG CY Therfore, Shunt Admittance, Y=jωC 29 3.3 LONG LINE MODEL Since the lines are so long (150 mi or more), it is not an accurate way to calculate for the voltage and currents assuming the parameters to be lumped. Various points should be considered anywhere along the line to fully have the most precise values that are being desired. Figure 3.6 is used to find the equations for the voltage and current equations. From Kirchoff’s voltage and current law, Voltage and current can be expressed with relation between sending and receiving as: V(x+Δx)=V(x) + zΔxI(x) V(x+Δx) V(x) =zI(x) Δx (1) (3-24) I(x+Δx)=I(x)+yΔxV(x+Δx) I(x+Δx)-I(x) =yV(x+Δx) Δx (2) Taking the limit as x 0 of eqn. (1) and (2), dV(x) V(x) V(x) 0 = = L'hopital=zI(x) dx Δx 0 (3) dI(x) I(x) I(x) 0 = = L'hopital=yV(x) dx Δx 0 (4) d 2 V(x) dI(x) =z dx 2 dx (5) 30 Figure 3.5 Model of a Long Transmission Line Differentiating eqn. (3) and plugging in eqn. (5) to (4) gives (6) d 2 V(x) = zyV(x) dx 2 Let γ 2 =zy d 2 V(x) 2 γ V(x) dx 2 (6) 31 Long Line Paramenters: γ = zy =α + jβ = propogation constant where z = impedance / unit length y = admittance / unit length α = attenuation constant rad/unit length β = phase constant rad/unit length Characteristics impedance: zC = z y The voltage and current equations are the following. Therefore: V(x)=A1e γx +A 2e-γx I(x)= 1 (A1e γx A 2e-γx ) ZC Let, VR +ZC I R 2 V ZC I R A2 = R 2 A1 = e γx +e γx e γx e γx V(x)= VR +ZC IR 2 2 1 e γx e γx e γx +e γx I(x)= VR +ZC IR ZC 2 2 (7) (8) (3-25) 32 3.4 ABCD CONSTANTS From the voltage and current equations, ABCD constants were created and the voltage and currents were rewritten into a matrix form by, Rewriting eqns. (7) and (8) V(x) = coshγxVR +ZCsinhγxI R I(x) = 1 sinhγxVR +coshγxI R ZC Considering in the length of the line, x l , γ= ZY and ZC = Z Y ABCD Constants: VS A B VR I = C D I R S where: A=cosh ZY B= Z sinh ZY Y 1 sinh ZY D=cosh ZY Z Y A=D and AD-BC=1 C= 3.5 VOLTAGE REGULATION, POWER LOSS AND EFFICIENCY The voltage regulation can be found using the magnitudes of the receiving end voltages calculated for the no load and full load conditions. The percent voltage regulation is defined by the rise in voltage when full load is removed, that is given by, %Voltage Regulation= V R L-L NO LOAD VR L-L FULL LOAD VR L-L FULL LOAD ×100% (3-26) 33 For calculate of the power loss and efficiency of the line, the receiving and sending end three phase apparent powers and their respective power factors must be found for the full load condition by the following, [1] SS,3 3VSI*S MVA SR,3 3VR I*R MVA PFSECD cos ( Vs Is ) PFREC cos (VR IR ) (3-27) Therefore the power loss in the line is given as the difference between the 3 phase powers of the sending end and receiving end, PLOSS =PS,3 PR,3 MW The efficiency of the line is the ratio of the receiving end and sending end 3 phase powers, η= PR,3 PS,3 ×100% 3.6 LINE COMPENSATION Compensating for the voltage in a line allows for an improved voltage regulation. This is why the line must be compensated for its full and no load situations. 34 3.6.1 FULL LOAD COMPENSATION For the full load condition, a single capacitor was used at the middle of the line to improve the voltage regulation. Because of the complexity of the calculations for the full load condition, MATLAB iteration will be used to calculate the full load compensation vars and then the line variables. Splitting the line down the middle gives the new equation relating the sending end and receiving end of the line. VS A1 I = C S 1 B1 1 ZCAP A 2 D1 0 1 C 2 B2 VR D 2 I R (3-28) Since the line is split down the middle, the lengths of both ABCD matrices are equal. Therefore, both matrices are equal and can be represented by the same ABCD constants. VS A I = C S B 1 D 0 ZCAP A 1 C B VR D I R (3-29) This matrix will then be used in MATLAB plugging in different values for Z. 35 Figure 3.6 Series Compensation of a Long Line 3.6.2 NO LOAD COMPENSATION When compensating a transmission line for the no load condition, the situation calls for an inductive compensation using a shunt reactor. To keep the analysis short, a single inductive reactor was used at the receiving end of the line. From the equation of the line relating the sending end and the receiving end the first equation is found. VS A B VR I = C D I R S Vs=AVR +BIR Relating the shunt reactance to the voltage and current at the receiving end then substituting into the previous equation we have, 36 IR = VR jX Lsh Vs=AVR +B VR jX Lsh (3-30) Solving for the reactance, jX Lsh = BVR BVR = VS -AVR VS δ-AVR (3-31) where δ is the angle of VS Figure 3.7 No Load Compensation with a Shunt Reactor Setting the receiving end voltage as the reference, the only other variable other than the reactance is the angle of the sending end voltage. Since the compensation of the line is purely reactive, the real power at the receiving end is zero. From the ABCD constants of the line we solve for the receiving end current. 37 VS =AVR +BI R VS AVR B changing into its phasor notation, IR = (3-32) IR = IR = VS δ A θ A VR 0 B θ B VS B δ θ B A VR B θ A θ B From the equation of three phase power the current is substituted, SR,3 =3VR I*R * V A VR SR,3 =3 VR 0 S δ θ B θ A θ B B B ° SR,3 = 3 VR VS B θ B δ 3 A VR B (3-33) 2 θ B θ A Now only the real power equation is needed to find the angle of the sending end voltage, 38 Therfore, PR,3 =0 PR,3 = 3 VR VS B 3 VR VS B cos θ B δ cos θ B δ = 3 A VR 3 A VR B 2 B 2 cos θ B θ A =0 (3-34) cos θ B θ A Solving for the sending end voltage angle, A VR δ=θ B cos -1 cos θ B θ A (3-35) V S Now the two equations can be put together and the shunt inductive reactance can be found by, jX Lsh = BVR A VR VS θ B cos-1 cos θ B θ A AVR VS Ohms (3-36) Also the shunt reactor to be installed must have a Mvar rating that corresponds to the reactance found where, 3 VR 2 Q = var 3 X Lsh 39 Chapter 4 APPLICATION OF THE MATHEMATICAL MODEL 4.1 INTRODUCTION A load of 200MVA at a lagging power factor of 0.95 will be located 170 miles out from the point of origin. A 7 No. 8 Alumoweld Overhead Ground Wire for protection and an earth resistivity of 100 Ohm meters will be used. Also, a minimum line size of 1/0 ACSR will be understood for structural limitations. Assuming the pre-design specifications call for a 345kV transposed line, a comparison of the different lines will be made for their no and full load scenarios. These comparisons will be done based on their uncompensated & compensated values. In the case of the uncompensated line values, the voltage rise for the no load situation and the voltage drop for the full load situation will be calculated by hand. For the analysis, many assumptions were made. For one, the tower configuration of the line was randomly chosen based on a standard 345kV tower design. The height of the lowest conductor was set to 53.83 feet at the towers. Two, the load was assumed to be a worst case scenario and future growth was already considered. Three, all the mechanical and structural considerations were not considered in the calculations. Other than the minimum line size of 1/0 ACSR all else will be neglected. And four, different line types will be compared from among the different sizes of ACSR conductors. Other types of conductors will be omitted from our analysis. 40 Figure 4.1 Tower configuration In preparation of the analysis, first the thermal ampacities must be compared to the estimated ampacity found for the receiving end voltage at 345 kV and load at 200MVA. Then the lines that meet or exceed the ampacity rating at 345kV will be compared by directly connecting their sending end to a 345kV source and comparing their no load and full load values. From these values, voltage regulation and efficiency will be found for all the lines in the appropriate range. 41 For the application, only the two extremes of the spectrum will be analyzed and compensated. There are many ways of compensating a line, but the very basic methodology will be used. The receiving end voltage will be compensated to a 100% for both situations which sets the magnitudes of the receiving and sending end voltage equal to each other. For the open circuit situation, a single shunt reactor will be used at the receiving end of the line to compensate for the voltage. For the full load situation, a series capacitor compensation will be used midway of the transmission line. A MATLAB program will be used to verify the hand calculations that will be done and it will also, instantly calculate the same parameters obtained from the hand calculations but for all other lines in the range. 4.2 THERMAL AMPACITY RATING The first step in our search is to figure out which lines meet the thermal ampacity rating. From the equation for three phase apparent power with the receiving end voltage at 345kV, IR = SR(3 ) 3VR(L-L) 200MVA = =334.69 Amps 3×345kV (2.1) From the ACSR table in appendix B, our current of 334.696 Amps could be handled by a #1 AWG. But since we are limited to 1/0, we will start our analysis from there. 42 4.3 LINE CHARACTERISTICS AND ABCD CONSTANTS The next step in our analysis is to model the line. Figure 4.1 shows the tower configuration of our line where the distance from the ground to the lowest conductor is at 53.83 feet. In considering the effects of ground on the line impedance the earth condition is of “average damp earth” with a resistivity of 100 Ohm meters. For our long line, the series impedance and shunt admittance per unit length must be found first before calculating the ABCD constants of the line. The effects of the earth will be taken into consideration and the overhead ground wire. The GMD’s between the conductors and their images are first found. GMD Between conductors DAB DAB 11.52 182 21.36 Feet D BC DCB 11.52 182 21.36 Feet DCA DAC 23 Feet D AW DWA 92 23.52 25.1645 Feet D BW DWB 92 452 45.8912 Feet DCW DCW 92 56.52 57.2123Feet GMD Between conductors & their images H A 2 76.83 153.66 Feet H B 2 65.03 130.06 Feet HC 2 53.83 107.66 Feet HW 2 110.03 220.06 Feet 43 GMD Between conductors & images of other conductors H AB H BA 182 76.83 65.03 142.997 FeeT 2 H BC H CB 182 65.03 53.83 120.215 Feet 2 H CA H AC (76.83 53.83) 130.66 Feet H AW HWA 92 110.03 76.83 187.077 Feet 2 H BW HWB 92 110.03 65.03 175.291 Feet 2 H CW HWC 92 103.03 53.83 164.107 Feet 2 4.3.1 SERIES IMPEDANCE For a 60Hz line, with a return earth condition for “average damp earth”, rD earth resist ance 1.588 10 3 (60 Hz ) 0.09528 and DE 2160 f mile 2788.55 feet Using appendix B for a 1/0 ACSR conductor, the resistances per phase conductor, rA rB rC r 1.12 and their self GMR' s mile DSA DSB DSC DS 0.00446 feet For the 7 No. 8 Alumoweld Overhead ground wire, The self & mutual impedances are than calculated as, rW 2.44 /mile D SW 0.002085 Feet Self GMR D AW DWA 92 23.52 25.1645 Feet D BW DWB 92 452 45.8912 Feet DCW DWC 92 56.52 57.2123 Feet 44 D where Z S self impedance (r rD ) j 0.12134 ln E DS 2788.55 (1.12 0.09528) j 0.12134 ln 0.00446 1.2153 j1.6194 mile and Z ABC D Z M mutual impedance rD j 0.12134 ln E DEQ 2788.55 0.09528 j 0.12134 ln 21.8932 0.09528 j 0.5881 mile 1.2153 j1.6194 0.09528 j 0.5881 0.09528 j 0.5881 0.09528 j 0.5881 1.2153 j1.6194 0.09528 j 0.5881 0.09528 j 0.5881 0.09528 j 0.5881 1.2153 j1.6194 Now the self and mutual impedances for the ground wire, 2788.55 Z SW self impedance (2.44 0.09528) j 0.12134 ln 0.002085 2.5353 j1.7117 2788.55 Z AW ZWA mutual impedance (0.09528) j 0.12134 ln 25.1645 0.09528 j 0.57125 mile 2788.55 Z BW ZWB mutual impedance (0.09528) j 0.12134 ln 45.8912 0.09528 j 0.49834 mile 2788.55 Z CW ZWC mutual impedance (0.09528) j 0.12134 ln 57.2123 0.09528 j 0.47159 mile 45 Kron’s reduction will be used to find the new self and mutual impedances (zs’ & zm’) in order to determine the series impedance of the line with the ground wire, z z z z 1 1 z z z AA zBB zCC AW WA BW WB CW WC 3 3 zWW zWW zWW zs ' z AA zBB zCC , z AW zWA , zBW zWB , zCW zWC 1 z AW 2 zBW 2 zCW 2 zs z AA 3 zWW zWW zWW ' 1 0.09528 j 0.57125 0.09528 j 0.49834 0.09528 j 0.47159 zs 1.2153 j1.6194 3 2.5353 j1.7117 2.5353 j1.7117 2.5353 j1.7117 zs ' 1.280 j1.533 /mile 2 ' zm ' 2 2 z z z z 1 1 z z z AB zBC zCA AW WA BW WB CW WC 3 3 zWW zWW zWW z AB zBC zCA & z AW zWA , z BW zWB , zCW zWC 1 z 2 z 2 z 2 zm ' z AB AW BW CW 3 zWW zWW zWW 2 2 2 1 0.09528 j 0.6289 0.09528 j 0.5535 0.09528 j 0.5074 ' zm 0.09528 j 0.582 3 2.5353 j1.7117 2.5353 j1.7117 2.5353 j1.7117 zm ' 0.160 j 0.496 /mile Z s ' zs ' l Z s ' 1.280 j1.533 170 Z s ' 217.6 j 260.61 Z s ' 339.5150.14 Z m ' zm ' l Z m ' 0.160 j 0.496 170 Z m ' 27.2 j84.32 Z m ' 88.59972.12 46 Z series Z s ' Z m ' Z series 217.6 j 260.61 27.2 j84.32 Z series 190.4 j176.29 Z series 259.48142.80 4.3.2 SHUNT ADMITANCE The shunt admittance will be found by the image method. Figure 4.1 shows the configuration of the line with the overhead ground wire being at the top of the tower 14 feet above the highest phase conductor. The self-potential coefficients of the line with the OHGW are, 153.66 MF 1mile 0.016583 102.165 MF 1mile p AA 11.185ln p AA 130.06 MF 1mile 0.016583 1 100.3MF mile pBB 11.185ln pBB 107.66 MF 1mile 0.016583 98.1859 MF 1mile pCC 11.185ln pCC 220.06 MF 1mile 0.016042 106.553 MF 1mile pWW 11.185ln pWW The mutual potential coefficients between the phase conductors are, 47 142.997 MF 1mile 21.36 21.2661 MF 1mile p AB pBA 11.185ln p AB pBA 120.215 MF 1mile 21.36 19.325 MF 1mile pBC pCB 11.185ln pBC pCB 130.66 MF 1mile 23 19.4295 MF 1mile pCA p AC 11.185ln pCA p AC The mutual potential coefficients between the OHGW and phases, 187.077 MF 1mile 25.1645 22.4381 MF 1mile p AW pWA 11.185ln p AW pWA 175.291 MF 1mile 45.8912 14.9898 MF 1mile pBW pWB 11.185ln pBW pWB 164.107 MF 1mile 57.2123 11.7862 MF 1mile , pCW pWC 11.185ln pCW pWC 48 PAB ' PBA' PAB PAW PWB PWW 22.438114.9898 106.553 1 18.1095 MF mile PAB ' PBA' 21.2661 PAB ' PBA' PAC ' PCA' PAC PAW PWC PWW 22.438111.7862 106.553 1 16.9475 MF mile PAC ' PCA' 19.4295 PAC ' PCA' PBC ' PCB ' PBC PBW PWC PWW 14.9898 11.7862 106.553 1 17.6669 MF mile PBC ' PCB ' 19.325 PBC ' PCB ' From Kron’s Reduction PAA' PAA PAW PWA PWW PAW PWA & PBW = PWB & PCW PWC PAA' PAA PAW 2 P 2 P 2 & PBB ' PBB BW & PCC ' PCC CW PWW PWW PWW 22.43812 106.553 97.4399 MF 1mile PAA' 102.165 PAA' 14.98982 106.553 98.1912 MF 1mile PBB ' 100.3 PBB ' 11.7862 2 106.553 96.8822 MF 1mile PCC ' 98.1859 PCC ' 49 Converting the charge coefficients to capacitances PABC ' 97.4399 18.1095 16.9475 18.1095 98.1912 17.6669 MF 1mile 16.9475 17.6669 96.8822 c P' c ABC 1 10.858 1.717 1.586 1.717 10.801 1.669 nF mile 1.586 1.669 10.904 c AG c AA - c AB - c AC 10.858 - -1.717 -1.586 c AG 14.161 nF mile cBG cBB - c AB - cBC 10.801- -1.717 -1.669 cBG 14.187 nF mile cCG cCC - c AC - cBC 10.904 - -1.586 -1.669 cCG 14.159 nF mile 1 1 cAG cBG cCG 14.161 14.187 14.159 3 3 cG 14.169 nF mile cG cmutual 1 3 c AB cBC cCA 1 3 1.717 1.669 1.586 1.6573 nF c 3cmutual cG 4.972 14.169 9.197 nF mile mile 50 Finally the shunt admittance of the line is given as, y jc j (2 ) 60 (9.197 109 ) j 3.467 6 mile 4 Y j 3.467 10 170 j 5.8939 10 4.3.3 ABCD CONSTANTS After calculating the series impedance and shunt admittance from the previous sections, those quantities will now be used to determine the ABCD constants for the line. As calculated previously, Z 190.4 j176.29 Y j 5.8939 104 Using the series impedance and shunt admittance for the 170 mile long line, A cosh YZ cosh j5.8939 10 190.4 j176.29 4 A 0.9480 j 0.0550 0.916.52 B Z 190.4 j176.29 sinh YZ sinh Y j 5.8939 104 j5.8939 10 190.4 j176.29 4 B 183.49 j176.75 254.77343.9 C Y j 5.8939 104 sinh YZ sinh Z 190.4 j176.29 j5.8939 10 190.4 j176.29 C 1.0889 105 j5.7918 10 4 5.79 10 4 91.1 D A 0.9480 j 0.0550 0.916.52 4 51 Therefore, the line can be represented in terms of its ABCD constants with the following equation: VS A B VR I C D I R S In rectangular form, 0.9480 j 0.0550 VS I 1.0889 105 j 5.7918 104 S 183.49 j176.75 VR 0.9480 j 0.0550 I R In polar form, VS 0.916.52 I 4 S 5.79 10 91.1 254.77343.9 VR 0.916.52 I R This solution will be used in the upcoming sections to calculate the uncompensated and compensated line parameters such as voltage regulation, power loss, and efficiency. However, for the full load compensation, the ABCD constant matrix will not be used because of the series capacitor installed at the center of the line. A new ABCD constant matrix will have to be found. 4.4 UNCOMPENSATED LINE For the uncompensated line, the voltage regulation, efficiency and power loss was found using the 1/0 ACSR conductor to show the hand calculations [6]. For voltage regulation, the no load and full load values will be found by setting the receiving end as the reference and calculations will only be done for the full load situation. The calculations will be followed by a MATLAB program that will calculate the same values for all the lines within our range. 52 4.4.1 FULL LOAD For the full load condition, the receiving end voltage was fixed to 230kV with an associated angle of 0°. Using the specified apparent power at the receiving end given in section 4.1, all other values were found. From, VRLL FULL LOAD 3450 kV S R ,3 3VR I R* IR S R ,3 * 3VR * 200 cos 1 0.95 MVA 345kV 3 3 334.696 18.19 A Now the sending end values can be calculated using the ABCD matrix of the line. VS 0.916.52 I 4 S 5.79 10 91.1 345000 254.77343.9 3 0.916.52 334.696 18.19 VS 26328912.6311 V I 300.89410.2805 A S VSLL 3 VS 456030 kV 53 4.4.2 NO LOAD For the no load condition, the sending end voltage calculated above was used to determine the no load receiving end voltage. VS A B VR I C D I R S and IR 0 VR VS A Plugging in the values for the 1/0 ACSR line, VR NO LOAD 263.28912.6311 2893296.1111V 0.916.52 and the line to line voltage, VRLL NO LOAD 3 2893296.1111 5011336.1111 kV 4.4.3 VOLTAGE REGULATION, POWER LOSS AND EFFICIENCY Now the voltage regulation can be found using the receiving end voltages calculated for the no load and full load conditions. %Voltage Regulation V RL L NO LOAD %Voltage Regulation 45.26% VRLL FULL LOAD VRLL FULL LOAD 100% 501.133kV 345kV 100% 345kV 54 To calculate the power loss and efficiency of the line the receiving end three phase powers are found for the full load condition. S S ,3 3VS I S* 3 26328912.6311 300.894 10.2805 237.466 j 9.748 MVA cos 12.6311 10.2805 0.9991 PFSEND cos VS I S S R ,3 190 j 62.45 MVA Therefore the power loss in the line, PLOSS PS ,3 PR ,3 237.466 190 47.466 MW And the efficiency of the line is, PR ,3 PS ,3 190 100% 80.01% 237.466 4.4.4 MATLAB A MATLAB code was generated for sections 4.3 and 4.4 which calculate all the voltages, currents, powers, and line constants. Appendix E,F and G, shows the table for all the ACSR lines within range. This table was made to compare voltage regulation, power loss, and efficiency of all the lines. In addition to that, it will be used to compare to the compensated values calculated in section 4.5. For the 1/0 ACSR line used in the hand calculations the values are compared to MATLAB in the table 4.2. Stranding Is (Amps) Sending End PF Vs(L-L) kV Ps (MW) Qs (Mvar) Vreg Ploss (MW) Efficiency MATLAB 1-Jun 306.97 0.998 467.59 248.47 16.68 42 58.047 76.6 THEORETICAL 1-Jun 300.89 0.99 456.03 237.47 9.748 45 47.466 80.01 Kcmil / Awg Table 4.1 MATLAB VS Theoretical comparison for 1/0 ACSR 55 4.5 COMPENSATION Now to minimize the power loss and voltage regulation and to maximize the line efficiency, the no load and full load voltages were compensated for. As with section 4.4, the calculated sending end voltage will be used to calculate the no load values. However, the full load calculations were not straight forward so MATLAB was used to generate the variables. 4.5.1 FULL LOAD COMPENSATION For the full load condition a series capacitor will be applied halfway through the line to correct for the voltage drop at the receiving end of the line. There are many different arrangements using multiple series and/or shunt capacitors, but for our analysis only one midway will be used. Since the line is divided in half, the ABCD constants must be calculated for half the distance. Therefore, the ABCD constants for the two sections must be recalculated with the line length being, l 170 85 miles 2 Y y l j 5.249 106 85 Y j 4.462 104 Z z l 1.120 j1.037 85 Z=95.195+j88.151=129.74142.80 56 Figure 4.2 Series Capacitor Compensation And the new ABCD constant matrix of the line with the series capacitor is, VS A B 1 ZCAP A B VR I C D 0 1 C D I R S Lines 1/0, 266.8kcmil, 336.4kcmil, 500.0kcmil, and 636.0 were chosen to further analyze. For these lines, there was an impedance found that minimized the sending end voltage while fixing the receiving end voltage at 230kV. Appendix D shows the values found for these lines. 4.5.2 NO LOAD COMPENSATION For the no load condition a shunt reactor will be used to correct for the voltage rise at the receiving end of the line. From the analysis done for the full load condition, a different sending end voltage magnitude was found for the different lines. This voltage will be used to calculate the receiving end voltage for the no load condition while fixing 57 the voltage regulation to 3%. Many different methods could be used to do the analysis, but to simplify the calculations further the voltage regulation was held constant. Voltage Regulation 3% 0.05 V RL L NO LOAD VRLL FULL LOAD VRLL FULL LOAD V RL L NO LOAD 345000 345000 VRLL NO LOAD 1.05 230000 362.250kV therefore VR ( NO LOAD ) 362.250 3 209.145kV Figure 4.3 Shunt Reactor Compensation This voltage will then be set as the reference and the angle for Vs will be found. Again using the magnitude of the sending end voltage calculated for the 1/0 line to show illustrate the procedure, VR 209.1450 kV VS 275.452kV 58 Therefore the power angle of the sending end voltage is, A VR δ=θ B -cos -1 cos θ B -θ A V S 0.91 209145 43.9 cos 1 275452 cos 43.9-6.52 12.7986 The shunt reactance is found by, jX Shunt jX Shunt BVR VS AVR 254.77343.9 209145 275452 12.7986 0.916.52 209145 jX Shunt j 464.649 The Reactive Power is calculated as so, QR ,3 3 VR 2 X Shunt 3 209.145kV 2 464.649 QR ,3 282.417 MVar A three phase shunt reactor rating of up to 282.417 Mvar would be needed to compensate the line for a 5% voltage regulation. This means the voltage between the magnitudes of the sending end and receiving end will be equal, but it does not mean that the voltage is constant throughout the line. In fact the voltage rises from the sending end to approximately the midway point of the line, and then it begins to decline as it approaches the receiving end. The rise in the voltage is due to the capacitance of the line therefore, 59 the reactor is used increase the current and the impedance of the line which in turn decreases the voltage. 60 Chapter 5 SUMMARY The basis of our analysis was to determine a method of selecting a line based on its electrical characteristics. These electrical characteristics include but are not limited to power loss, efficiency, and voltage regulation. However, those three characteristics are the focus of our analysis. This investigation was made by fixing the full load apparent power and receiving end voltage to 200MVA at 0.95 lagging power factor and 345kV respectively. Other parameters that remained constant throughout the analysis were the tower configuration, line length, and overhead ground wire type. This enabled us keep the mathematical model as simple as possible without leaving anything out. Once the lines were modeled, a table was generated for the uncompensated condition to show the difference in line characteristics as size varies from 1/0 up to 1590kcmil. Then out of the table, 5 different lines were selected to further investigate its electrical properties. In solving for the uncompensated condition the full load receiving end voltage was fixed to 345kV. Then the full load sending end voltage was applied to the no load condition to calculate the no load receiving end voltage. The analysis showed that for the no load condition, the voltage drastically increases and for full load condition it decreases. Also, by varying the line sizes from 1/0 to 1590.0kcmil, as the line size goes up, the full load sending end voltage goes down while power loss, efficiency, and voltage regulation improve. Compensating for the voltage of a transmission line increases its voltage capability. It also allows for a line to stay within a specified range which is determined by the tower 61 configuration, insulator other hardware ratings. In the compensation section in our analysis, five different lines were selected to further analyze. These lines were the 1/0, 266.8kcmil 6/7 strand, 336.4kcmil 26/7 strand, 500.0kcmil 30/7 strand, and 636.0kcmil 26/7 strand ACSR conductors. A comparison was first done between the uncompensated and compensated values found for the different lines. Then a comparison was done between the 5 lines for the compensated condition. Now that a basis has been established, the electrical characteristics can then be used to perform an economic analysis to determine which line to choose. Power loss, power supplied, and Mvar corrected would be converted to its dollar value and compared between the different wires and the most economical line will be chosen. 62 Appendix A OVERHEAD GROUND WIRE CHARACTERISTICS A.1 ACSR CHARACTERISTICS 63 A.2 ACSR PHYSICAL AND ELECTRICAL CHARACTERISTICS 64 Appendix B ACSR TABLE 65 Appendix C WIRE COMPENSATION OF UNCOMPENSATED LINE DATA MATLAB PRINTOUT Comparison of ACSR conductors from 1/0 to 1590.0 kcmil for Vr=345kV Sr=200MVA, PF=0.95 lagging, Uncompensated Line 66 67 Appendix D MATLAB CODE OF UNCOMPENSATED LINE % ACSR Table from 1/0 to 1,590kcmil table B.8 % GMR/feet Diameter/inch Resistance table=[ 0.00394 0.198 3.98 0.00416 0.223 3.18 0.00452 0.257 2.55 0.00401 0.250 2.57 0.00403 0.281 2.07 0.00504 0.325 1.65 0.00418 0.316 1.69 0.00418 0.355 1.38 0.00446 0.398 1.12 0.00510 0.447 0.895 0.00600 0.502 0.723 0.00814 0.563 0.592 0.00684 0.633 0.552 0.02170 0.642 0.385 0.02410 0.700 0.342 0.02300 0.680 0.342 0.02550 0.741 0.306 0.02440 0.721 0.306 0.02780 0.806 0.259 0.02650 0.783 0.259 0.03040 0.883 0.216 0.02900 0.858 0.216 0.03110 0.904 0.206 0.03280 0.953 0.1859 0.03130 0.927 0.1859 0.03270 0.966 0.1720 0.03210 0.953 0.1775 0.03510 1.019 0.1618 0.03350 0.990 0.1618 0.03290 0.977 0.1688 0.03370 1.000 0.1601 0.03720 1.081 0.1442 0.03550 1.051 0.1442 0.03490 1.036 0.1482 0.03930 1.140 0.1288 0.03750 1.108 0.1288 0.03680 1.093 0.1378 0.03860 1.146 0.1228 0.03910 1.162 0.1185 0.04030 1.196 0.1128 68 0.04200 1.246 0.1035 0.04350 1.293 0.0969 0.04500 1.338 0.0906 0.04650 1.382 0.0851 0.04790 1.424 0.0803 0.04930 1.465 0.0760 0.05070 1.506 0.0720 0.05200 1.545 0.0684 ]; %CONSTANTS FOR ALL LINES Length = 170; %miles Srmag = 200; %in MVA PFrec = 0.95; %receiving end power factor rd = 0.09528; %earth resistance ohms per mile De = 2788.55; %in feet %%% OHGW %%% rw = 2.44; %ohms per mile Dsw = 0.002085; %GMR feet radiusw = 0.016042; %feeT %%% Distances %%% Dab = sqrt(11.5^2+18^2); Dbc = sqrt(11.5^2+18^2); Dca = 23; Daw = sqrt(9^2+23.5^2); Dbw = sqrt(9^2+45^2); Dcw = sqrt(9^2+56.5^2); Deq = (Dab*Dbc*Dca)^(1/3); Ha = 2*76.83; Hb = 2*65.03; Hc = 2*53.83; Hw = 2*110.03; Hab = sqrt(18^2+(76.83+65.03)^2); Hbc = sqrt(18^2+(65.03+53.83)^2); Hca = 76.83+53.83; Haw = sqrt(9^2+(110.03+76.83)^2); Hbw = sqrt(9^2+(110.03+65.03)^2); Hcw = sqrt(9^2+(110.03+53.83)^2); fprintf(' Is reactive(Mvar) PF Vreg Vs(L-L) Ploss power(MW) Efficiency \n'); n=1; for row=1:n Ds =table(row,1); diameter =table(row,2)/12; r =table(row,3); radius = diameter/2; %put in feet 69 %%%%%%% Calculating Z and Y %%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%% series impedance %%% zaa = r+rd+j*0.12134*log(De/Ds); zbb = zaa; zcc = zaa; zww = rw+rd+j*0.12134*log(De/Dsw); zab = rd+j*0.12134*log(De/Deq); zbc = rd+j*0.12134*log(De/Deq); zca = rd+j*0.12134*log(De/Deq); zaw = rd+j*0.12134*log(De/Daw); zbw = rd+j*0.12134*log(De/Dbw); zcw = rd+j*0.12134*log(De/Dcw); Zs = (1/3)*(zaa+zbb+zcc)-(1/3)*((zaw*zaw+zbw*zbw+zcw*zcw)/zww); Zm = (1/3)*(zab+zbc+zca)-(1/3)*((zaw*zaw+zbw*zbw+zcw*zcw)/zww); z =Zs-Zm; paa = 11.185*log(Ha/radius); %%mile/MF pbb = 11.185*log(Hb/radius); pcc = 11.185*log(Hc/radius); pww = 11.185*log(Hw/radiusw); pab = 11.185*log(Hab/Dab); pbc = 11.185*log(Hbc/Dbc); pca = 11.185*log(Hca/Dca); paw = 11.185*log(Haw/Daw); pbw = 11.185*log(Hbw/Dbw); pcw = 11.185*log(Hcw/Dcw); potential = [ (paa-(paw*paw)/pww) (pab-(paw*pbw)/pww) (pca(pcw*paw)/pww) ; (pab-(paw*pbw)/pww) (pbb-(pbw*pbw)/pww) (pbc-(pbw*pcw)/pww) (pca-(pcw*paw)/pww) (pbc-(pbw*pcw)/pww) (pcc(pcw*pcw)/pww)]*1000000; capacitan = inv(potential); %% F/mile Ca = capacitan(1,1)-capacitan(1,2)-capacitan(1,3); Cb = capacitan(2,2)-capacitan(2,1)-capacitan(2,3); Cc = capacitan(3,3)-capacitan(3,2)-capacitan(3,1); Cmutual=(1/3)*(capacitan(1,2)+capacitan(2,3)+capacitan(3,1)); Cap = (1/3)*(Ca + Cb + Cc)+(3*Cmutual); y = j*2*pi*60*Cap; %%%% In ohms/mile %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Z = z * Length; Y = y * Length; %calculating ABCD constants Zc = sqrt(Z/Y); A = cosh(sqrt(Z*Y)); B = Zc*sinh(sqrt(Z*Y)); C = (1/Zc)*sinh(sqrt(Z*Y)); D = A; ABCD = [A B;C D]; 70 %%%%%% FULL LOAD VALUES %%%%% Vr_full = (345000 + j*0)/sqrt(3); angleS = acos(PFrec); Sr_3ph = 200000000*cos(angleS)+j*200000000*sin(angleS); Ir_full = conj(Sr_3ph)/(3*Vr_full); VsIs_full = ABCD*[Vr_full ; Ir_full]; Vs_full = VsIs_full(1); Is_full = VsIs_full(2); %%%%%%% NO LOAD VALUES %%%%%% Ir_noload = 0; Vr_noload = Vs_full/A; %%%%%%% POWER CALCULATIONS %%%%%% Ss = 3*Vs_full*conj(Is_full); Sr = 3*Vr_full*conj(Ir_full); PFsend = cos(angle(Vs_full)-angle(Is_full)); %%%%%% VOLTAGE REGULATION %%%%% V_reg = (Vr_noload - Vr_full)/Vr_full; Ploss = real(Ss) - real(Sr); Efficiency = real(Sr)/real(Ss); fprintf('%6.3f ', abs(Is_full)) %Amps Sending end current fprintf('%4.3f ', PFsend) %Sending end PF fprintf('%6.3f ', sqrt(3)*abs(Vs_full)/1000) %kV Sending end line to line volatge fprintf('%6.3f ', real(Ss)/1000000) %Sending end power in watts fprintf('%6.3f ', imag(Ss)/1000000) %Sending end reactive power fprintf('%6.3f ', V_reg) %Voltage regulation fprintf('%6.3f ', Ploss/1000000) %Power Loss fprintf('%6.3f \n', Efficiency) %Efficiency end 71 Appendix E MATLAB CODE, FULL LOAD COMPENSATION % ACSR Table from 1/0 to 1,590kcmil table B.8 % GMR/feet Diameter/inch Resistance table=[ 0.00394 0.00416 0.00452 0.00401 0.00403 0.00504 0.00418 0.00418 0.00446 0.00510 0.00600 0.00814 0.00684 0.02170 0.02410 0.02300 0.02550 0.02440 0.02780 0.02650 0.03040 0.02900 0.03110 0.03280 0.03130 0.03270 0.03210 0.03510 0.03350 0.03290 0.03370 0.03720 0.03550 0.03490 0.03930 0.03750 0.03680 0.198 0.223 0.257 0.250 0.281 0.325 0.316 0.355 0.398 0.447 0.502 0.563 0.633 0.642 0.700 0.680 0.741 0.721 0.806 0.783 0.883 0.858 0.904 0.953 0.927 0.966 0.953 1.019 0.990 0.977 1.000 1.081 1.051 1.036 1.140 1.108 1.093 3.98 3.18 2.55 2.57 2.07 1.65 1.69 1.38 1.12 0.895 0.723 0.592 0.552 0.385 0.342 0.342 0.306 0.306 0.259 0.259 0.216 0.216 0.206 0.1859 0.1859 0.1720 0.1775 0.1618 0.1618 0.1688 0.1601 0.1442 0.1442 0.1482 0.1288 0.1288 0.1378 72 0.03860 0.03910 0.04030 0.04200 0.04350 0.04500 0.04650 0.04790 0.04930 0.05070 0.05200 ]; 1.146 1.162 1.196 1.246 1.293 1.338 1.382 1.424 1.465 1.506 1.545 0.1228 0.1185 0.1128 0.1035 0.0969 0.0906 0.0851 0.0803 0.0760 0.0720 0.0684 %CONSTANTS FOR ALL LINES Length = 170/2; Srmag = 200; PFrec = 0.95; rd = 0.09528; De = 2788.55; %miles %in MVA %receiving end power factor %earth resistance ohms per mile %in feet %%% OHGW %%% rw = 2.44; %ohms per mile Dsw = 0.002085; %GMR feet radiusw = 0.016042; %feet %%% Distances %%% Dab Dbc Dca Daw Dbw Dcw = = = = = = sqrt(11.5^2+18^2); sqrt(11.5^2+18^2); 23; sqrt(9^2+23.5^2); sqrt(9^2+45^2); sqrt(9^2+56.5^2); Deq = (Dab*Dbc*Dca)^(1/3); Ha Hb Hc Hw = = = = 2*76.83; 2*65.03; 2*53.83; 2*110.03; 73 Hab Hbc Hca Haw Hbw Hcw = = = = = = sqrt(18^2+(76.83+65.03)^2); sqrt(18^2+(65.03+53.83)^2); 76.83+53.83; sqrt(9^2+(110.03+76.83)^2); sqrt(9^2+(110.03+65.03)^2); sqrt(9^2+(110.03+53.83)^2); fprintf(' Is reactive(Mvar) # Ploss PF Vs(L-L) Efficiency \n'); power(MW) n=20; for row=20:n Ds =table(row,1); diameter =table(row,2)/12; r =table(row,3); radius = diameter/2; %%%%%%% Calculating Z and Y %put in feet %%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%% series impedance %%% zaa zbb zcc zww = = = = r+rd+j*0.12134*log(De/Ds); zaa; zaa; rw+rd+j*0.12134*log(De/Dsw); zab = rd+j*0.12134*log(De/Dab); zbc = rd+j*0.12134*log(De/Dbc); zca = rd+j*0.12134*log(De/Dca); zaw = rd+j*0.12134*log(De/Daw); zbw = rd+j*0.12134*log(De/Dbw); zcw = rd+j*0.12134*log(De/Dcw); Zs Zm = (1/3)*(zaa+zbb+zcc)-(1/3)*((zaw*zaw+zbw*zbw+zcw*zcw)/zww); = (1/3)*(zab+zbc+zca)-(1/3)*((zaw*zbw+zbw*zcw+zca*zaw)/zww); z =Zs-Zm; %%% shunt admittance variables %%% 74 paa pbb pcc pww = = = = 11.185*log(Ha/radius); 11.185*log(Hb/radius); 11.185*log(Hc/radius); 11.185*log(Hw/radiusw); %%mile/MF pab = 11.185*log(Hab/Dab); pbc = 11.185*log(Hbc/Dbc); pca = 11.185*log(Hca/Dca); paw = 11.185*log(Haw/Daw); pbw = 11.185*log(Hbw/Dbw); pcw = 11.185*log(Hcw/Dcw); potential = [ (paa-(paw*paw)/pww) (pab-(paw*pbw)/pww) (pca(pcw*paw)/pww) ; (pab-(paw*pbw)/pww) (pbb-(pbw*pbw)/pww) (pbc-(pbw*pcw)/pww) ; (pca-(pcw*paw)/pww) (pbc-(pbw*pcw)/pww) (pcc(pcw*pcw)/pww)]*1000000; capacitan = inv(potential); %% F/mile Ca = capacitan(1,1)-capacitan(1,2)-capacitan(1,3); Cb = capacitan(2,2)-capacitan(2,1)-capacitan(2,3); Cc = capacitan(3,3)-capacitan(3,2)-capacitan(3,1); Cap = (1/3)*(Ca + Cb + Cc); y = j*2*pi*60*Cap; %%%% In ohms/mile %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Z = z * Length; Y = y * Length; %calculating ABCD constants Zc = sqrt(Z/Y); A = cosh(sqrt(Z*Y)); B = Zc*sinh(sqrt(Z*Y)); C = (1/Zc)*sinh(sqrt(Z*Y)); D = A; ABCD = [A k=0; B;C D]; for Z_cap = 84:84 75 ABCD_new = ABCD*[1 -j*Z_cap ;0 1]*ABCD; %%%%%% FULL LOAD VALUES %%%%% Vr_full = angleS = Sr_3ph = (345000 + j*0)/sqrt(3); acos(PFrec); 200000000*cos(angleS)+j*200000000*sin(angleS); Ir_full = conj(Sr_3ph)/(3*Vr_full); VsIs_full = ABCD_new*[Vr_full ; Ir_full]; Vs_full = Is_full = VsIs_full(1); VsIs_full(2); %%%%%%% POWER CALCULATIONS %%%%%% Ss = 3*Vs_full*conj(Is_full); Sr = 3*Vr_full*conj(Ir_full); PFsend = cos(angle(Vs_full)-angle(Is_full)); Ploss = real(Ss) - real(Sr); Efficiency = real(Sr)/real(Ss); fprintf('%6.3f %d ', abs(Is_full),k) %Amps Sending end current fprintf('%4.3f ', PFsend) %Sending end PF fprintf('%8.5f ', sqrt(3)*abs(Vs_full)/1000) %kV Sending end line to line volatge fprintf('%6.3f ', real(Ss)/1000000) %Sending end power in watts fprintf('%6.3f ', imag(Ss)/1000000) %Sending end reactive power fprintf('%6.3f ', Ploss/1000000) %Power loss fprintf('%6.3f ', Efficiency) %Efficiency fprintf('%8.8f \n', 1/(Z_cap*2*pi*60)) %capacitance k=k+1; end end 76 Appendix F MATLAB Code, No load compensation % GMR/feet table=[ 0.00446 ]; Diameter/inch 0.398 1.12 Resistance 275452 %CONSTANTS FOR ALL LINES Length = 170; %miles Vrmag = 1.03*345000/sqrt(3); %for 3% voltage regulation rd = 0.09528; %earth resistance ohms per mile De = 2788.55; %in feet %%% OHGW %%% rw = 2.44; %ohms per mile Dsw = 0.002085; %GMR feet radiusw = 0.016042; %feet %%% Distances %%% Dab = sqrt(11.5^2+18^2); Dbc = sqrt(11.5^2+18^2); Dca = 23; Daw = sqrt(9^2+23.5^2); Dbw = sqrt(9^2+45^2); Dcw = sqrt(9^2+56.5^2); Deq = (Dab*Dbc*Dca)^(1/3); Ha = 2*76.83; Hb = 2*65.03; Hc = 2*53.83; Hw = 2*110.03; Hab = sqrt(18^2+(76.83+65.03)^2); Hbc = sqrt(18^2+(65.03+53.83)^2); Hca = 76.83+53.83; Haw = sqrt(9^2+(110.03+76.83)^2); Hbw = sqrt(9^2+(110.03+65.03)^2); Hcw = sqrt(9^2+(110.03+53.83)^2); fprintf('Xshunt Is Vs(L-N) n=1; for row=1:n inductance Qshunt sendpower(MW) reactive(Mvar) \n'); 77 Ds diameter r Vsmag radius %%%%%%% =table(row,1); =table(row,2)/12; =table(row,3); =table(row,4); = diameter/2; Calculating Z and Y %put in feet %%%%%%%%% %%% series impedance %%% zaa zbb zcc zww = = = = r+rd+j*0.12134*log(De/Ds); zaa; zaa; rw+rd+j*0.12134*log(De/Dsw); zab = rd+j*0.12134*log(De/Dab); zbc = rd+j*0.12134*log(De/Dbc); zca = rd+j*0.12134*log(De/Dca); zaw zbw zcw Zs Zm = = = = = rd+j*0.12134*log(De/Daw); rd+j*0.12134*log(De/Dbw); rd+j*0.12134*log(De/Dcw); (1/3)*(zaa+zbb+zcc)-(1/3)*((zaw*zaw+zbw*zbw+zcw*zcw)/zww); (1/3)*(zab+zbc+zca)-(1/3)*((zaw*zbw+zbw*zcw+zca*zaw)/zww); z =Zs-Zm; %%% shunt admittance variables %%% paa pbb pcc pww = = = = 11.185*log(Ha/radius); 11.185*log(Hb/radius); 11.185*log(Hc/radius); 11.185*log(Hw/radiusw); %%mile/MF pab = 11.185*log(Hab/Dab); pbc = 11.185*log(Hbc/Dbc); pca = 11.185*log(Hca/Dca); paw = 11.185*log(Haw/Daw); pbw = 11.185*log(Hbw/Dbw); pcw = 11.185*log(Hcw/Dcw); potential = [ (paa-(paw*paw)/pww) (pab-(paw*pbw)/pww) (pca(pcw*paw)/pww) ; (pab-(paw*pbw)/pww) (pbb-(pbw*pbw)/pww) (pbc-(pbw*pcw)/pww) ; (pca-(pcw*paw)/pww) (pbc-(pbw*pcw)/pww) (pcc(pcw*pcw)/pww)]*1000000; capacitan = inv(potential); %% F/mile 78 Ca = capacitan(1,1)-capacitan(1,2)-capacitan(1,3); Cb = capacitan(2,2)-capacitan(2,1)-capacitan(2,3); Cc = capacitan(3,3)-capacitan(3,2)-capacitan(3,1); Cap = (1/3)*(Ca + Cb + Cc); y = j*2*pi*60*Cap; %%%% In ohms/mile %%%% Calculating ABCD Constants %%%%% Z = z * Length; Y = y * Length; Zc = sqrt(Z/Y); A = cosh(sqrt(Z*Y)); B = Zc*sinh(sqrt(Z*Y)); C = (1/Zc)*sinh(sqrt(Z*Y)); D = A; ABCD = [A B;C D]; %%%%% SHUNT COMPENSATION %%%%%% Vr = Vrmag + j*0; K = (abs(A)*Vrmag)/Vsmag; delta = angle(B)-acos(K*cos(angle(B)-angle(A))); Vs_calc = Vsmag*cos(delta)+j*Vsmag*sin(delta); X_shunt = B*Vr/(Vs_calc-A*Vr); %calculating the voltages and currents Ir = Vr/X_shunt; VsIs = ABCD * [Vr ; Ir]; Vs = VsIs(1); Is = VsIs(2); Ismag = abs(Is); Sr = (3*abs(Vr)^2)/conj(X_shunt); %Sending end PF,S,P,3-phasevoltage PFsend = cos(angle(Vs_full)-angle(Is_full)); Ss=3*Vs*conj(Is); Vs3ph = sqrt(3) * abs(Vs); fprintf('%6.3f ',imag(X_shunt)) %single phase shunt reactance fprintf('%6.3f ',imag(X_shunt)/(2*pi)) fprintf('%6.3f ',imag(Sr)/1000000) %3-phase power compensation fprintf('%6.3f ', Ismag) %Amps Sending end current fprintf('%6.3f ', sqrt(3)*Vs/1000) %kV Sending end line to line voltage fprintf('%6.3f ', real(Ss)/1000000) %3-phase Sending end power fprintf('%6.3f ', imag(Ss)/1000000) %3-phase Sending end reactive power fprintf('%6.3f ', Ploss/1000000) %Power loss fprintf('%6.3f ', Efficiency) %Efficiency fprintf('%4.3f \n', PFsend) end 79 BIBLIOGRAPHY [1] Gonen, T. 2009.Electrical power transmission system engineering analysis and design, 2nd ed. Florida: CRC Press. [2] Gonen, T. 1986.Electrical power distribution system engineering. New York: McGraw-Hill. [3] Sadaat, H. 2002.Power system analysis, 2nded. New York: McGraw-Hill. [4] Granger, J. J. and W. D. Stevenson.1994. Power system analysis. New York: McGraw-Hill. [5] SMUD. 1995. UG/OH Conductor sequence impedance study. [6] Gonen, T. 1988. Modern power system analysis. New York: McGraw-Hill.