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  • 1 Protective Device Coordination Hector J. Rivera, Member, IEE they must be very reliable. Abstract-- Power Protection is one of the most important fields In much the same way as the early computers of the in Power Electrical Engineering. Through time many software’s 1950s and 1960s were a precursor to the computational has been created to analyze electrical designs. Our project capabilities of today’s computers. Specialized hardwire consist of prepare a user guide easy to understand of how to use systems were developed for locally monitoring the operation an existing power protection analysis program calling ETAP. This user guide must include how to create a one-line diagram, of power plants and for remotely monitoring and controlling how to configure power system devises, and an explanation of the switches in transmission substation. The Remote Terminal right way to perform a short and fault analysis. Finally, we Units of these early monitoring systems were implemented prepare an advance user guide with detailed explanations of with relay logic, while the master station consisted primarily special features and technical concept of ETAP program. Also, of large banks of annunciator panels with red and green light as a requirement of our project, we analyzed a case study of indication the state of the points being monitored with flashing power system and perform the protective device coordination of it. light indication a change in state or an alarm condition. The impact of computers has nowhere been more Index Terms—ETAP, fault analysis, protection devices, revolutionary than in electrical engineering. The design, protective device coordination. analysis and operation of electrical and electronic systems has become completely dominated by computers, a transformation I. INTRODUCTION that has been motivated by the natural ease of interface between computers and electrical systems, and the promise of E lectricity has been a subject of scientific interest since at least the early 17th century. Probably the first electrical engineer was William Gilbert who designed the versorium: a spectacular improvements in speed and efficiency. Our project consists of develop a protective device device that detected the presence of statically charged objects. coordination using a graphical software program to add He was also the first to draw a clear distinction between features and flexibility in the area of electrical system magnetism and static electricity and is credited with protection. Also, this graphical software program it’s going to establishing the term electricity. However it was not until the be using for all kind of element that used these. We will select 19th century that research into the subject started to intensify. the software program, analyze all types of element protection Notable developments in this century include the work of that are utilizing in electrical systems, and simulate the Georg Ohm, who in 1827 quantified the relationship between program using various management studies. the electric current and potential difference in a conductor, Michael Faraday, the discoverer of electromagnetic induction II. TOPICS COVERED in 1831, and James Clerk Maxwell, who in 1873 published a Trough this capstone project we covered a lot of electrical unified theory of electricity and magnetism in his treatise on power engineering topics. Some of these are summarized Electricity and Magnetism. They are the fathers of electrical below. engineering and the electric systems. Today, power system protection is that part of electrical A. Relay Hardware power engineering that deals with protecting the electrical The relay hardware for electronic relays consists of both power system from faults by isolating the faulted part from the analog and digital devices. The input signals are analog and rest of the network. require, at very minimum, a conversion to digital form. Any electric power system involves a large amount of Therefore, the relays design is often a mixture of analog auxiliary equipment for the protection of generators, electronic devices and digital hardware. The relays may also transformers, and the transmission lines. Circuit breakers are contain transformers or other components that are also found employed to protect all elements of a power system from short in electromagnetic and electromechanical protective devices. circuits and overloads, and for normal switching operations. Induction relays are available in many variations to provide The principle of a protection scheme is to keep the power accurate pickup and time-current responses for a wide range of system stable by isolating only the components that are under simple or complex system conditions. Induction relays are fault, even as leaving as much of the network as possible still basically induction motors. The moving element, or rotor, is in operation. Thus, protection schemes must apply a very usually a metal disk, although it sometimes may be a metal pragmatic and pessimistic approach to clearing system faults. cylinder or cup. Electronic relays require less power to operate For this reason, the technology and philosophies utilized in than their mechanical equivalents, producing a smaller load protection schemes are often old and well-established because burden on the CT’s and PT’s that supply them. The most frequently used relay is the over current relay, combining both instantaneous and inverse-time tripping functions.
  • 2 B. Protective Devices Bayamón Waste Water Treatment Plant. This information The protective system device usually consists of several will be the data base for the short circuit study. elements that are arranged to test the system condition, make B. Diagram decision regarding the normally of observed variables, and We were required to perform an analysis for choose take action as required. Over current time unit have necessary equipment to protect electric power system o characteristics such that its operation time vary inversely with Bayamón Waste Water Treatment Plant. After analizing the the current flow in the relay. These characteristics are system, we decided to use following coordination equation; available generally in three types of curves, Inverse, Very t2 = 1.3t1 +15. Using it, we set next coordination level Inverse, and Extremely Inverse. between 23 to 25 cycles. Other protective device is fuses. Fuses are designed for Fig.1 shows the original oneline diagram given to us many different applications and with variety of characteristics with the objective of perform the protective device to meet the requirements both routine and special situations. coordination. It does not include any protective device. Fuses have different curves to realize these requirements. The minimum melting curve is an average melting time measured in low voltage test where arcing does not occur. Other curve is total clearing curve should be used in coordinating against the minimum melting characteristics of a larger fuse, located toward the power source. Distribution fuses links are given voltage ratings of 7.2, 14.4, and 17 KV nominal, or 7.8, 15, and 18 KV maximum for use in open-link cutouts. C. ETAP Program ETAP seamlessly integrates the analysis of power control circuits within one electrical analysis program. The control system diagram simulates the sequence of the operation control devices such as solenoids, relays, controlled contacts multi-sequence contacts and actuators including inrush conditions. The control system diagram has the capability of determine pick-up and dropout voltage, losses and current Fig. 1. Original Oneline Diagram of Bayamón WWTP flows at any time instance as well as overall margin and critical alerts. A large library of equipment enables engineers C. Fault Simulation to quickly model and simulate the action of relays associate Fig. 2 presents a three phase fault simulation at load 1. with the control interlocks after given time delays. This fault provokes the operation of protective devices. Operation times are showed in Fig. 3. III. BAYAMON WWTP STUDY A. Scope Develop a short circuit study for Power Transformers and relay settings for a waste water treatment plant and the protective devices associated. The Bayamón Waste Water Treatment Plant has seven large power transformers with their respective protective devices (power fuses or protective relaying) in service. The intention of this short circuit study is to verify the appropriated protective device coordination and recommended the appropriated changes if any. For this plant we will cover the relay coordination and settings for the protective device associated. The short circuit current available at Bayamón Waste Water Treatment Plant, with 38 kV connection tap, is submitted by Puerto Rico Electric Authority (PREPA). Three phase short circuit current is 20,000 A and 11,547 A Fig. 2. Fault Simulation at Load 1 of BWWTP for phase to ground. The ETAP Power Simulation computer program, version 5.5 from Operation Technology, Inc was used for all the short circuit studies and simulations. The following tables detail information available for the electrical equipment from the electrical drawings for
  • 3 Line to ground Fault Operating Short Localization Voltage Circuit Operation Protection Devices Time (Cycles) Fault (kV) Current Fuse 1/5 Fuse 2/6 Fuse 3/4/7/8 Fuse 9 Relay(50) Relay(51) T1, T4 Primary 38 0A -------- -------- -------- -------- -------- -------- T1, T4 4.16 0A -------- -------- -------- -------- -------- -------- Secondary Bus1, Bus 6 4.16 10,730 A -------- -------- -------- -------- 0 23.10 Bus2 , Bus 3 4.16 10,180 A -------- 1.62 -------- -------- 0 23.10 T2 , T3, T5 , T6 4.16 10,180 A -------- 1.62 5.7 -------- -------- 23.10 Primary T2 , T3, T5 , T6 0.48 41,060 A -------- -------- 48.78 -------- -------- -------- Secondary T7 Primary 4.16 10,730 A -------- -------- -------- -------- 0 23.10 T7 Secondary 0.48 6,850 A -------- -------- -------- 14.34 -------- -------- Fig. 5. Line to Ground Fault Results Fig. 3. Sequence of Operations Events at Load 1 The figure above shows line to ground fault at different areas of system. This kind of fault change operation time of A fault at transformer 2 or 3 has a protection in devices. However, protective device coordination still secondary side. Fuse 3 will operates like a back up with 25 working the same. All points reach coordination criteria of cycles of different between primary protections. If fuse 3 23 to 25 cycles between coordination levels. Results was does not operate, fuse 2 will operate with 25 cycles different verified with manual calculations and using ETAP software. between the fuse 3. Bayamon WWTP has two emergency backup generators A Three Phase Fault is happened in the secondary side of in case of PREPA faults. For that reason we perform a short the transformer 7 (BTS-12). The transformer capacity is circuit simulation of this power system using generators. 0.15 MVA and the connection is Delta-Wye. The Our results are displayed below (Fig. 6 and 7). impedance viewed at this point is by the utility, two Three Phase Fault transformers and lines. The short circuit current is 6,687A. Operated When the Line to Ground Fault occur the zero sequence Localization Voltage Short Circuit Operation Protection Devices Time (Cycles) Fault Current impedance is open by the primary side of the transformer 7 (kV) Fuse Fuse Fuse Fuse 9 Relay G(50) RelayG(51) (BTS-12). The short circuit current at the secondary side of 1/5 2/6 3/4/7/8 the transformer is 6,855A. Bus1, Bus 6 4.16 258,532.1 A -------- -------- -------- 0 0 17.91 As the same way, we simulate faults trough all system. Bus2 , Bus 3 4.16 112,864.33 A -------- 0 -------- -------- -------- 18.06 T2 , T3, T5, T6 Results are showed at Fig. 4. Secondary 0.48 56,673.16 A -------- 0.78 5.4 -------- -------- 65.58 T7 Secondary 0.48 7,193.37 A -------- -------- -------- 1.8 -------- -------- Three Phase Fault Localization Operating Short Fig. 6. Three Phase Fault Results Using Generators Voltage Circuit Operation Protection Devices Time (Cycles) Fault (kV) Current Fuse1/5 Fuse2/6 Fuse3/4/7/8 Fuse9 Relay(50) Relay(51) Line to ground Fault T1, T4 Primary 38 20,000A 1.44 -------- -------- -------- -------- -------- T1, T4 4.16 10,504 A 44.70 -------- -------- -------- -------- -------- Localization Operated Short Circuit Secondary Fault Voltage Current Operation Protection Devices Time (Cycles) Bus1, Bus 6 4.16 10,500 A 44.82 -------- -------- -------- 0 19.5 (kV) Bus 2, Bus 3 4.16 9,950 A 49.62 1.62 -------- -------- -------- 23.64 Fuse 1/5 Fuse 2/6 Fuse Fuse 9 Relay(50) Relay(51) T2, T 3 , T5 , T6 3/4/7/8 4.16 9,950 A -------- 1.62 5.88 -------- -------- 23.64 336,678,51 A -------- -------- -------- 0 0 18.0 Primary Bus 1, Bus 6 4.16 T2, T 3 , T5 , T6 0.48 35,440 A -------- 50.4 23.76 -------- -------- 75.78 Secondary 140,244.95 A -------- 0 -------- -------- -------- 18.0 Bus2 , Bus 3 4.16 T7 Primary 4.16 9,950 A 49.62 1.62 -------- -------- -------- 23.64 T2 , T3, T5, T6 57,815.87 A -------- 33.6 5.58 -------- -------- 33.6 T7 Secondary 0.48 6,690 A -------- -------- -------- 7.98 -------- -------- 0.48 Secondary T7 Secondary 7,164.46 A -------- -------- -------- 1.8 -------- -------- 0.48 Fig. 4. Three Phase Fault Results We realized a three phase fault through BWWTP power Fig. 7. Line to Ground Fault Results Using Generators system using PREPA connection. Our evaluation criteria to all faults were 23 to 25 cycles of difference between When Bayamón WWTP is working with generators is coordination levels. Figure 4.60 shows the short circuits possible that faults could happen. For that reason we made magnitudes at the points analyzed. It also includes protective device coordination for BWWTP using operation time for each equipment. generators. For a three phase fault at generators the We also perform short circuit simulation of phase to overcurrent relay operates. If a fault occurs in system far ground fault. All results are present at Fig. 5. from generators, protective devices work faster than when using utility. It reduces time between coordination devices. Coordination results are showing in table below.
  • 4 IV. RESULTS Power Fuses Selection Power Transformers T1, T2, T3, T4, T5, T6 and T7. The Power Fuse Time Coordination show the analysis for the short circuit simulations at the utility side and the power plant side for the T1, T2, T3, T4, T5, T6 and T7. The fuse coordination complies with time (12-30cycles) permitted by each coordination. The following table (Fig. 8) shows the power fuse summary for the transformers. # Power Transformer Recommended Power Fuse Curve 1 T1 38/4.16 SMD-2C-100E Slow Speed 2 T2 4.16/0.48 SMU-40-300E Slow Speed 3 T3 4.16/0.48 SMU-40-300E Slow Speed 4 T4 38/4.16 SMD-2C-100E Slow Speed 5 T5 4.16/0.48 SMU-40-300E Slow Speed 6 T6 4.16/0.48 SMU-40-300E Slow Speed 7 T7 4.16/0.48 SMU-40-30E STD Speed 8 Main Feeder Fault Fiter-600 Time-delayed Fig. 8. Recommendations to Fuse Protection V. REFERENCES [1] J. F. Fuller, E. F. Fuchs, and K. J. Roesler, "Influence of harmonics on power distribution system protection," IEEE Trans. Power Delivery, vol. 3, pp. 549-557, Apr. 1988. [2] E. H. Miller, "A note on reflector arrays," IEEE Trans. Antennas Propagat., to be published. [3] R. J. Vidmar. (1992, Aug.). On the use of atmospheric plasmas as electromagnetic reflectors. IEEE Trans. Plasma Sci. [Online]. 21(3), pp. 876-880. Available: http://www.halcyon.com/pub/journals/21ps03- vidmar [4] E. Clarke, Circuit Analysis of AC Power Systems, vol. I. New York: Wiley, 1950, p. 81. [5] G. O. Young, "Synthetic structure of industrial plastics," in Plastics, 2nd ed., vol. 3, J. Peters, Ed. New York: McGraw-Hill, 1964, pp. 15-64. [6] J. Jones. (1991, May 10). Networks. (2nd ed.) [Online]. Available: http://www.atm.com [7] E. E. Reber, R. L. Mitchell, and C. J. Carter, "Oxygen absorption in the Earth's atmosphere," Aerospace Corp., Los Angeles, CA, Tech. Rep. TR-0200 (4230-46)-3, Nov. 1968. [8] S. L. Talleen. (1996, Apr.). The Intranet Architecture: Managing information in the new paradigm. Amdahl Corp., Sunnyvale, CA. [Online]. Available: http://www.amdahl.com/doc/products/bsg/intra/ infra/html [9] D. Ebehard and E. Voges, "Digital single sideband detection for interferometric sensors," presented at the 2nd Int. Conf. Optical Fiber Sensors, Stuttgart, Germany, 1984. [10] Process Corp., Framingham, MA. Intranets: Internet technologies deployed behind the firewall for corporate productivity. Presented at INET96 Annu. Meeting. [Online]. Available: http://home.process.com/ Intranets/wp2.htp [11] J. L. Alqueres and J. C. Praca, "The Brazilian power system and the challenge of the Amazon transmission," in Proc. 1991 IEEE Power Engineering Society Transmission and Distribution Conf., pp. 315-320. [12] S. Hwang, "Frequency domain system identification of helicopter rotor dynamics incorporating models with time periodic coefficients," Ph.D. dissertation, Dept. Aerosp. Eng., Univ. Maryland, College Park, 1997. [13] IEEE Guide for Application of Power Apparatus Bushings, IEEE Standard C57.19.100-1995, Aug. 1995. [14] G. Brandli and M. Dick, "Alternating current fed power supply," U.S. Patent 4 084 217, Nov. 4, 1978. shed (January 1, 1993).