Journal of Reliable Power - SEL

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Introduction With this inaugural issue, SEL introduces the Journal of Reliable Power. This regularly published journal will present a series of papers with lasting value that focuses on the fundamentals of power reliability. We believe that the concepts, case studies, technologies, and issues that the Journal covers will be applicable to power engineers working for utilities, industrial and commercial facilities, government, and academia. Each issue of the Journal will focus on a broad topic area or theme. The theme of this first issue, guest-edited by SEL Senior Power Engineer Karl Zimmerman and Principal Systems Engineer Bogdan Kasztenny, with the combined technical expertise of many SEL authors, is line distance protection, where SEL got its start. Future themes will include the application of digital communications in protection and control, distribution automation and protection (“smart grid”), communications for critical infrastructure, synchronous measurement and control, and advances in protection methods. The second issue, edited by SEL Senior Automation System Engineer Tim Tibbals, will focus on communications and protocols. We welcome your suggestions for topics as well. Several outstanding publications in the electric power industry today communicate important ideas, applications, successes, and trends through news articles, editorials, and success stories. Our goal is to complement these publications by sharing in-depth, conference-length papers in a journal format. The Journal is forward-looking. When we include an older paper, it will be a foundational classic, with concepts that are still applicable today. In many cases, these older papers will teach us new things as we read and apply them; the power system and the work we do have changed in ways that none of us could have anticipated. We hope that you find this first collection of papers centered around line protection relevant to you and the work you do to make electric power safer, more reliable, and more economical. *** Microprocessor-based relay technology became possible more than 25 years ago, owing to a perfect combination of available, suitable microprocessors and advancements in industrial electronics more generally; the opportunity to provide new functions far beyond what was possible within the electromechanical and static technologies; remarkable size and cost reductions; and the imagination, skills, and perseverance of early inventors in this new field. Early designs, although limited by available processing power, integrated a wealth of new functions, ranging from sequential events recording and fault location to metering, multiple settings groups, and communications. Once digital relays proved reliable in the eyes of the power system protection community, and as the dramatic cost reduction compared to previous technologies became evident, the digital relay revolution only accelerated. It became increasingly obvious that analog technology, in addition to being more expensive, could not provide new functions, self-monitoring, reliability, innovative operating principles, and other facets of protection performance made possible through microprocessor-based technology. Early microprocessor-based protective relays brought innovation in line protection principles as well as digital implementation of the existing art of distance protection. Constrained by the available processing power and facing the disadvantage of a nonzero processing latency, designers strived for increased response time of their algorithms while optimizing the computational power required. Applying the cosine filter and shaping distance characteristics via “m calculations” are good examples of smart design that delivered good performance under the limitations of early microprocessor-based relay platforms. “Distance Relay Element Design,” written in 1993 and included in this issue of the Journal, is a foundational paper for SEL microprocessor-based distance protection. One cannot overlook the role that fault location played in the industry’s adoption of the new technology. This useful and “safer”—compared with the full protection package—function opened the door for new technology (SEL-21 and SEL-121 Distance Relay and Fault Locator products). In the 1980s, early applications of relays working as fault locators demonstrated hardware and software reliability and delivered solid, useful, and verifiable information to early adopters. “Impedance-Based Fault Location Experience” summarizes the almost 25 years of advancements in fault location at the time it was written in 2004. 2 | Journal of Reliable Power
Capable of running protection calculations with latencies low enough for line protection, microprocessor-based relays allowed designers to take full advantage of the flexibility of digital implementations. Building protection elements by calculating signature signals and freely applying comparators, logic, and timers, designers were no longer constrained by analog means; they could truly innovate by going back to first principles and using these principles to devise new and powerful protection elements. Positivesequence voltage memory to maintain distance element security during close-in faults, advancements in digital filtering, a negative-sequence impedance ground directional element, load-encroachment logic, and fault identification selection logic are among the many innovations introduced in the early 1990s as part of the SEL-321 Relay. Ability to communicate was an inherent advantage of microprocessor-based relays from the very beginning. Communication started with users accessing and manipulating settings, records, and online measurements but quickly progressed into serving data to SCADA systems and peer-to-peer devices. Invention of Mirrored Bits ® communications—fast, reliable, and dependable protection-grade communications—opened a new chapter of digital teleprotection signaling for line protection. (See “Digital Communications for Power System Protection: Security, Availability, and Speed” in this issue.) The last decade brought considerable advances in distance protection. Higher sampling rates and increased processing power opened the door to sophisticated protection principles and enhancements. Improvements in security and speed of distance protection have been achieved through a combination of CVT transient detection under high SIR conditions and usage of incremental quantities while applying optimized, faster, short-window filters. Fault type identification logic now performs better under weak infeed conditions. Adaptive polarizing algorithms maintain the best possible choice of polarization while releasing the user from making tradeoffs and running detailed engineering studies to aid setting selection. Protection issues related to series compensation of transmission lines have been addressed as well. Frequency tracking of modern relays allows applications under stressed system conditions when frequency excursions and rate of change of frequency jeopardize some traditional concepts, such as memory polarization. “Transmission Line Protection System for Increasing Power System Requirements” gives an excellent overview of these advancements. The SEL-421 Protection, Automation, and Control System, developed in 2001, incorporates all of these enhancements while including a truly impressive set of functions that complement its core protection functionality. Examples are high-resolution digital fault recording, sequential events recording, and synchrophasor measurements, all with submicrosecond accuracy, a wealth of both peer-to-peer and SCADA communications protocols, metering functions, advanced programmable protection and automation logic, two CT sets of inputs for dualbreaker line terminals with associated protection, and automation functions. These are functions that we all take for granted today. Looking back, the ability to provide data for postevent analysis turned out to be one of the major benefits of microprocessor-based relays. “Lessons Learned Analyzing Transmission Line Faults” provides an overview of how data produced by modern relays aid troubleshooting and improve our understanding of the power system. Innovations in line protection are ongoing. Examples include improved power swing detection based on the rate of change of the swing center voltage and better resistive coverage of distance functions through an adaptive quadrilateral characteristic. (See “Adaptive Phase and Ground Quadrilateral Distance Elements” in this issue.) The journey that started a quarter of a century ago continues. Today, we use precise timing to align and timetag measurements. We use high-speed communications to share data in real time to improve protection and automation functions. And, we use more powerful processors to efficiently run increasingly more sophisticated algorithms. The opportunity that technology created 25 years ago is still here. It is only the laws of physics and our own imaginations that bound us today. If you have comments or suggestions, please e-mail journal@selinc.com or share your thoughts with our editors by phone at +1.509.332.1890. Introduction | 3
Page 1 and 2: $12.00 Journal of Reliable Power Vo
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Page 7 and 8: Both P and Q are two-input phase an
Page 9 and 10: TABLE 1: MHO ELEMENT POLARIZING CHO
Page 11 and 12: For an Aφ-ground fault on the syst
Page 13 and 14: The most onerous 3φ fault is one w
Page 15 and 16: If the angle is near +120°, then t
Page 17 and 18: Impedance-Based Fault Location Expe
Page 19 and 20: A. Simple Reactance Method From Fig
Page 21 and 22: Figure 9 shows a screen capture of
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Page 25 and 26: IX. LAB TEST SETUP Several line fau
Page 27 and 28: APPENDIX The following are the rela
Page 29 and 30: The following shows the analog math
Page 31 and 32: Digital Communications for Power Sy
Page 33 and 34: increasing security by a factor of
Page 35 and 36: The receiver amplifier is the major
Page 37 and 38: Noise from faults or other sources
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Page 41 and 42: 15. A POTT scheme implemented over
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Page 45 and 46: One-Cycle Directional Element Figur
Page 47 and 48: element misoperation. Shunt reactor
Page 49 and 50: • SW2 is in Position 1 when there
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Page 53 and 54: IX. BIOGRAPHIES Armando Guzmán, P.
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2 II. COMMON ZONE TIMING In June 20
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4 ment 67N2 after a 1-cycle carrier
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6 VI. ZONE 1 OVERREACH DUE TO CVT I
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8 1_VA 1_VB 1_VC 2_VA 2_VB 2_VC 3_V
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10 The phasors during the fault are
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12 The prefault data from the backu
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1 Adaptive Phase and Ground Quadril
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3 C. Short Line Applications A shor
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5 II. QUADRILATERAL DISTANCE ELEMEN
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7 For the purpose of implementing t
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9 The three-phase fault detection e
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11 Zone 1 distance elements should
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13 Fig. 24 shows the apparent resis
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15 B. Adaptive Resistance Element F
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17 Fig. 34 and Fig. 35 illustrate t
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Line Protection Bibliography Issue
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Hou, Daqing, and Jeff Roberts. “C
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©2010 Schweitzer Engineering Labor
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