Showing papers on "Power-system protection published in 1992"
TL;DR: In this paper, the possibility of nonoperation of second-harmonic restraint differential protection in the case of internal faults of power transformers was studied and modified schemes for improved operation for internal faults were presented.
Abstract: The possibility of nonoperation of second-harmonic restraint differential protection in the case of internal faults of power transformers was studied. The smaller the setting for harmonic restraint, the longer will likely be the time delay in the operation of the relay. To study this aspect, various internal faults and inrush conditions were tested on a physical model of a three-phase transformer in the laboratory. The data were analyzed by different protection algorithms. Based on the results of these studies, modified schemes for improved operation for internal faults are presented. >
162 citations
TL;DR: In this article, improved models for current transformers (CT), potential transformers, and capacitive voltage transformers were presented for a relay software library based on the nonlinear power curve formulation of J.R. Lucas (1988).
Abstract: Improved models for current transformers (CT), potential transformers, and capacitive voltage transformers (CVT) for a relay software library are presented. The magnetizing characteristic in each of these transformers is based on the nonlinear power curve formulation of J.R. Lucas (1988). The flux-current loops of the transformer core are self-generated rather than predetermined or based on look-up tables. The results presented show that the models developed for the transformers behave as expected, and agree with reported field investigations. Models for the CT and CVT give acceptable results, including those under remanent conditions and ferroresonant conditions. These models are thus necessary components for relay studies carried out with electromagnetic transient programs whether offline or in real time. >
113 citations
TL;DR: A Markov model extends and improves previous models for determining the unreadiness probability and unavailability of a protective system, such as those found on electric-power transmission and distribution systems, and can be computed based on typical system-transition rates.
Abstract: A Markov model extends and improves previous models for determining the unreadiness probability and unavailability of a protective system, such as those found on electric-power transmission and distribution systems. Improved definitions of unreadiness probability and other relevant measures are proposed, based on a new Markov model of the system. This new model provides a more direct and physically important definition of unreadiness, and can be computed based on typical system-transition rates. Using this model, it is possible to estimate the optimal value of the protection inspection interval, viz, the time between inspections of the protective system. The model accounts for the operation of backup protection, the removal of protection for inspection, the occurrence of common-cause failures, and the usual clearing of faults. >
100 citations
TL;DR: The functional dependency approach is seen to be more flexible and more powerful than the graph theoretic schemes, and holds out much promise for the development of efficient computer-aided design tools for the protection engineer.
Abstract: The concept of functional dependency is applied to the problem of relay coordination in protection systems. An algorithm is developed for the identification of a minimal break point set (BPS) of relays of a protection topology. This algorithm is an improvement over existing algorithms in that it identifies a minimal BPS within a time period that is a polynomial function of the number of relays, while the earlier algorithms had exponential time behavior. In the case of large protection schemes, the saving in computation costs is considerable. An algorithm is developed for the selection of a relative sequence matrix; this algorithm also has polynomial time complexity. The functional dependency approach is seen to be more flexible and more powerful than the graph theoretic schemes, and holds out much promise for the development of efficient computer-aided design tools for the protection engineer. >
97 citations
TL;DR: In this article, a microprocessor-based high-speed relay that correctly detects transformer winding faults is presented, instead of relying on the presence of harmonics to identify magnetizing inrush, it uses a nonlinear model of the transformer to determine the state of its health.
Abstract: The authors present the design, implementation and testing of a microprocessor-based high-speed relay that correctly detects transformer winding faults. Instead of relying on the presence of harmonics to identify magnetizing inrush, it uses a nonlinear model of the transformer to determine the state of its health. One version of the relay is suitable for protecting single-phase transformers, whereas another version is for protecting three-phase transformers. A three-phase delta-wye 15 kVA transformer was used to test the relay for a variety of operating conditions. The results show that the relay performs well. >
86 citations
Book•
31 Dec 1992
TL;DR: In this paper, the authors present an overview of the application of current-differential protection schemes to transformers and their application to overhead lines and cables, as well as the protection of overhead transmission and distribution lines.
Abstract: Part 1 Fuses: historical background basic requirements fuse types and constructions the behaviour of cartridge fuselinks the construction of cartridge fuses semi-enclosed fuses expulsion fuses liquid fuses the applications of fuses the future. Part 2 Current transformers: historical background conventional current transformers linear couplers current transformers with air-gapped cores non-conventional current transducers specifications and testing the future. Part 3 Voltage transformers: historical background electromagnetic voltage transformers capacitor-voltage transformers recent developments specifications and testing the future. Part 4 Overcurrent and earth-fault protection: historical background relay connections and operation electronic relays applications of overcurent, earth-fault and directional relays the application of directional current-operated relays current and voltage transformers standard specifications the future. Part 5 Current-differential protective schemes: historical background factors affecting current-differential schemes the use of biasing features implementation of schemes. Part 6 The protection of transformers: historical background the construction and behaviour of transformers the application of protective schemes and devices to power transformers with two or more windings per phase the protection of earthing transformers auto transformers and their protection the future. Part 7 The protection of rotating machines: historical background protective devices and schemes the protection of motors the protection of alternators the future. Part 8 The protection of busbars: historical background busbars sectionalization faults on or near busbars positioning of current transformers and incorrectly protected zones protective arrangements for busbars relays used in current-differential schemes manual and automatic testing the future. Part 9 The protection of overhead lines and cables by current-differential schemes: historical background cables and overhead transmission and distribution lines the application of current-differential protective schemes the application of current-differential schemes to multi-ended circuits the application of current-differential schemes to lines and cables terminated with transformers the future.
83 citations
TL;DR: In this paper, the authors describe a method simulating, on a substantial power system, the events leading to system voltage instability and collapse, and show the effectiveness of a protection arrangement, functioning during the first postdisturbance period, with well-timed measures concentrated only in the region most affected by the disturbance.
Abstract: The authors describe a method simulating, on a substantial power system, the events leading to system voltage instability and collapse. Simulations on a 92-bus network were used to study the consequences of losing five lines simultaneously. With no countermeasures, the disturbance caused system voltage instability which culminated in its collapse. Following the same disturbance, a series of specific countermeasures was simulated. This arrangement of measures was able to restore the grid to a secure operating state, even with the five lines still out of service. The simulation studies show the effectiveness of a protection arrangement, functioning during the first postdisturbance period, with well-timed measures concentrated only in the region most affected by the disturbance. By limiting the application of measures only to this area, it also prevents any effects of the disturbance from spreading to the remainder of the power grid. >
63 citations
TL;DR: The authors establish the relevance of PetriNet modeling to protection studies and illustrate how the different Petri net models capture the information that is of importance to both qualitative and quantitative evaluation of protection schemes.
Abstract: The authors establish the relevance of Petri net modeling to protection studies. They illustrate how the different Petri net models capture the information that is of importance to both qualitative and quantitative evaluation of protection schemes. The marked Petri nets allow one to evaluate the qualitative performance measures of conservativeness, safeness, and properness. Time Petri nets are able to represent the timing parameters of protection schemes, and serve as a tool for the establishment of relationships between these parameters, in order that the coordination between primary and backup protection is ensured. An alternative means of representing timing information is the timed Petri net, which is useful in the computation of the cycle times of the operational cycles of protection schemes. Stochastic Petri nets adequately represent the stochastic nature of protection. Their advantage over simulation techniques as a means of computing the mean sojourn time and the steady-state probability of occupancy of each state of the protection scheme is demonstrated. >
59 citations
TL;DR: A novel digital relaying technique for parallel transmission lines is presented and the idea of the protection algorithm is based on the comparison of the average current of corresponding phases.
Abstract: A novel digital relaying technique for parallel transmission lines is presented. Only one relay at each end of the two lines is used. The idea of the protection algorithm is based on the comparison of the average current of corresponding phases. The technique is simple and avoids many problems of parallel lines. Simulation studies show that the trip signal is generated about 5 ms after the inception of the fault. The stability of the relay under different operating conditions is also examined. >
51 citations
TL;DR: In this paper, the applicability of memory-polarized distance relay mho elements to the protection of MOV (metal oxide varistor) protected series-compensated lines is shown.
Abstract: It is shown that the applicability of memory-polarized distance relay mho elements to the protection of MOV (metal oxide varistor) protected series-compensated lines is dependent on the system configuration, line loading, the location of the potential source, and the magnitude of memory polarization. For a configuration with compensation at one end of a line, the results indicate certain advantages in using the potential from the line side of the capacitor, and the use of a relatively large magnitude of memory polarization. The presence of a conducting MOV enhances the performance of the mho element both in terms of security on reverse faults and dependability on forward faults. The results obtained pertain to the proposed application in the Ontario Hydro system of a relatively large amount of compensation at one terminal in each circuit of a double-circuit line. >
50 citations
TL;DR: A practical expert system which estimates the fault section in an electric power system by inferring dynamically the protective coordination of the protective relays by using numerical figures corresponding to the protection zone and time setting is described.
Abstract: The authors describe a practical expert system which estimates the fault section in an electric power system by inferring dynamically the protective coordination of the protective relays. The expert system represents the characteristics of protective relays by using numerical figures corresponding to the protection zone and time setting. This method provides high maintainability of the system, and also allows the system to display inference processes in a user friendly manner. The expert system described will be used at three new control centers of Shikoku Electric Power Co., Inc., in 1991. >
TL;DR: The main and backup electric power system for the Boeing 777 is comprised of two independent electrical systems, the main and the backup as discussed by the authors, and the main electric system includes two engine-driven integrated drive generators, a generator driven by the auxiliary power unit, three generator control units, and a bus power control unit.
Abstract: The electric power system for the Boeing 777 is comprised of two independent electrical systems, the main and the backup. The main electric system includes two engine-driven integrated drive generators, a generator driven by the auxiliary power unit, three generator control units, and a bus power control unit. The backup electric system includes two engine-drive generators and one integrated converter/control unit to provide the redundancy of electrical sources equivalent to a three-engine airplane. Automation of the system is achieved by the use of state-of-the-art, microprocessor-based control units that perform system control, protection, and built-in-test functions. Each control unit has redundant two-way communication through an ARINC 629 communication bus that requires significantly fewer discrete wires than similar systems, allowing considerable reduction of the interface circuits and reduction in weight. >
TL;DR: In this article, the authors describe the relaying concepts of charge comparison and propose a new transmission line protection system called charge comparison, which is suitable for the protection of two or three-terminal AC transmission lines, of all lengths and voltage levels.
Abstract: The authors describe the relaying concepts of charge comparison. Charge comparison is a new transmission line protection system. It is a form of current differential relaying. Charge comparison largely resolves the traditional problems of current differential relaying of transmission lines, which are that protection is lost if a channel fails, a large channel capacity is required, and precise channel delay compensation is required. This technique is suitable for the protection of two- or three-terminal AC transmission lines, of all lengths and voltage levels, with or without series of shunt compensation, with three-hole or single-pole tripping. >
TL;DR: In this article, the protection and control requirements needed for a 115 kV line after it was reconfigured to operate as a single-circuit six-phase line as part of a high-phase-order demonstration project are discussed.
Abstract: The protection and control requirements needed for a 115 kV line after it was reconfigured to operate as a single-circuit six-phase line as part of a high-phase-order demonstration project are discussed. Addressed are the required modification and/or additions needed for the existing protection and control equipment. The criteria selected for the protection of the transmission line are described, including the transformers required for six-phase reconfiguration. The commercially available digital protection systems applicable to the protection of the line and their limitations are reviewed. Requirements for protection and control panels, their location for optimal wiring, and facilities to perform tests and measurements are also covered. >
29 Jun 1992
TL;DR: A mathematical model based on space-vector theory is used to analyze inverter-fed induction motors faults and finds an asymmetry in the supply voltages, in the current values, and in the spatial field distribution.
Abstract: A mathematical model based on space-vector theory is used to analyze inverter-fed induction motors faults. Inverter supply faults like an open phase fault, the failure of a transistor to switch on, the delay in a branch command, or the stand of the branch command are analyzed. These events introduce an asymmetry in the supply voltages, in the current values, and in the spatial field distribution. A detailed investigation of typical inverter supply failures is presented and discussed in order to identify remedial strategies. >
TL;DR: Three distinct types of UHS relaying realization in distance protection via advanced-generation digital signal processing, possible with cheap and readily available VLSI chips, are considered.
Abstract: UHS (ultra high speed) refers to operating times of less than 5 ms on 50 Hz power systems. Three distinct types of UHS relaying realization in distance protection via advanced-generation digital signal processing, possible with cheap and readily available VLSI chips, are considered. Type I is the correlator detector: Type II and III are the spectrum and cepstrum analyzers, respectively. The performance of these detectors is evaluated with respect to varying system configurations that complicate the post fault signals. Microprocessor implementation of these techniques show that 5 ms limit is achieved in Type I and II detectors, whereas the Type III detector can operate in 3 ms. >
TL;DR: In this article, a typical application procedure for a coordinated load shedding scheme using both frequency trend relays and normal discrete underfrequency relays is described, and the strategy for islanding such industrial power systems from the grid during grid disturbances is described.
Abstract: A typical application procedure for a coordinated load shedding scheme using both frequency trend relays and normal discrete underfrequency relays is described. By using such a combination of relays it is possible to develop comprehensive protection against frequency disturbances, both sudden and gradual. It is emphasized that in a system where the causes of frequency disturbances are quite varied and complex, a fully automatic scheme may not be the ideal solution and manual load shedding as a backup may be necessary. A typical procedure for a captive power plant system operating in parallel with the grid is described as applicable to a continuous process plant industry. The strategy for islanding such industrial power systems from the grid during grid disturbances is described. >
TL;DR: In this article, the basic concepts of a digital approach to the communications requirements of a new transmission line protection scheme were presented, where the authors compared local and remote quantities of charge, using a bidirectional communications channel.
Abstract: The authors present the basic concepts of a digital approach to the communications requirements of a new transmission line protection scheme. Charge comparison is a new transmission line protection system. It compares local and remote quantities of charge, using a bidirectional communications channel. Charge comparison is a form of current differential relaying. Traditional current differential relaying schemes have three critical communications-related problems: protection is lost if the channel fails, a large channel capacity is required, and precise channel delay compensation is required. In large measure, charge comparison overcomes these three communications-related problems. >
TL;DR: In this paper, a three-zone quadrilateral distance relay for the protection of EHV/UHV transmission lines is proposed based on the Fourier transform method of extracting the fundamental components of voltage and current signals from nonsinusoidal post fault signals.
Abstract: The development of a three-zone quadrilateral distance relay for the protection of EHV/UHV transmission lines is discussed. The proposed scheme is based on the Fourier transform method of extracting the fundamental components of voltage and current signals from nonsinusoidal post fault signals. The determination of the quadrilateral characteristic is completed through software. The relay is successfully tested for a number of different three-step quadrilateral characteristics. It is shown that any quadrilateral characteristic can be obtained. Recommendations are made on using 16 bit microprocessors to reduce the operating time and for better accuracy. >
20 Sep 1992
TL;DR: A unified approach to automatic pattern generation for diagnosis of board-level wiring defects between modules both with and without boundary scan is introduced and the number of patterns for complete diagnosis compares favorably with patterns required for first detection of single stuck-at faults only.
Abstract: This paper introduces a unified approach to automatic pattern generation for diagnosis of board-level wiring defects between modules both with and without boundary scan. The fault model for wiring defects includes bridging faults, stuck-at faults and open faults. We show that complete diagnosis of 1/0 faults can be achieved by considering single faults only rather than fault pairs and we have modified a traditional sptem that supports single stuck fault test generation to also perform pattern generation for complete diagnosis. Rather than building a fault dictionary from detection patterns, we introduce distinguishing functions, a fault diagnosis tree and heuristics to resolve signatures of faults so that they become unique or are proven equivalent. Experimental results with large benchmark circuits show that complete diagnosis for stuck-at as well as bridging I/O faults is possible. The number of patterns for complete diagnosis compares favorably with patterns required for first detection of single stuck-at faults only.
18 May 1992
TL;DR: In this paper, real-time solid-state power controllers (SSPC) are used in the design of the electrical load management center (ELMC), which can achieve the overall system flexibility needed for next-generation complex platforms.
Abstract: Real-time solid-state power controllers (SSPCs) are used in the design of the electrical load management center (ELMC). ELMCs which are either centrally or remotely located can achieve the overall system flexibility needed for next-generation complex platforms. The electrical and mechanical features of the SSPC series are discussed, together with military screening, mechanical specifications, and other product options. Power MOSFET circuitry plays a significant role in the direct digital control SSPCs which are described. >
TL;DR: The practical of two of CAPE's modules, Coordination Graphics and Short Circuit, for readily identifying and correcting miscoordinations is discussed and realistic examples illustrate the detection of miscoordination.
Abstract: A coordinated set of data management and analysis programs, already in use at several major utilities in the USA, is presented. The programs are known as the computer-aided protection engineering (CAPE) system. CAPE consists of an integrated set of ten data management and analysis programs designed to assist protection engineers with their day-to-day activities of selecting, setting, and coordinating protective relays. Underlying all the CAPE programs is a comprehensive (and general-purpose) relational database of both system and protective service data. The practical of two of CAPE's modules, Coordination Graphics and Short Circuit, for readily identifying and correcting miscoordinations is discussed. Both distance and overcurrent protective devices are treated. Realistic examples illustrate the detection of miscoordination. Corrective actions are taken using graphical manipulations (curve dragging) and direct specification of taps, test points, or desired reach. >
07 Jun 1992
TL;DR: In this article, the authors proposed an optimized surge attenuating cable (SAC) for surge protection of inductive devices and to distribution system cabling, which can protect rotating machines and transformers from damage induced by short risetime transients generated by switching devices and lightning.
Abstract: A novel functionality can be added to solid dielectric power cable by optimizing semiconductor shield properties for attenuation of high frequencies propagating down the cable. A cable optimized for high frequency attenuation can protect inductive devices, such as rotating machines and transformers, from damage induced by short risetime transients generated by switching devices and lightning. The use of an optimized surge attenuating cable (SAC) for this purpose effects protection in a manner which is economic and has no negative implications for system reliability. SAC concepts and attenuation characteristics are discussed. SAC applications to surge protection of inductive devices and to distribution system cabling are considered. >
TL;DR: In this article, the trajectory of the seen impedance by distance type relays during sequential disturbances was investigated using phase coordinate analysis with full machine and system representation, and a case study of seen impedance of the healthy phases during single-phase autoreclose (SPAR) following earth faults and the loss of excitation relay during simultaneous faults, an earth fault in the external system triggering another fault in generator excitation system, were investigated.
Abstract: The trajectory of the seen impedance by distance type relays during sequential disturbances was investigated. For transmission systems, distance relays are known to be the main protection. For generator protection, loss of field relays present a major element of the protection systems. These two impedance type relays are considered. A case study of the seen impedance by the healthy phases during single-phase autoreclose (SPAR) following earth faults and the seen impedance by the loss of excitation relay during simultaneous faults, an earth fault in the external system triggering another fault in the generator excitation system, were investigated using phase coordinate analysis with full machine and system representation. >
TL;DR: In this article, a digital directional relay based on compensated voltage comparison has been implemented with a 16-bit microcontroller, which can provide correct operation for various faults during different operating conditions of the protected line.
Abstract: A digital directional relay based on compensated voltage comparison has been implemented with a 16 bit microcontroller. The authors describe the digital implementation of the phase-angle comparators which make use of fundamental frequency components of the compensated voltages. A simple hybrid hardware structure and intelligent software routines have been developed to ensure high reliability. Using an adaptive sampling interval, the relay can maintain its overall performance even for faults that occur during power frequency disturbances. Dynamic tests on a 500 kV, 290 km transmission line analog model confirmed that the relay can provide correct operation for various faults during different operating conditions of the protected line. >
14 Oct 1992
TL;DR: The main functions and structure of copy protection systems, including the Iron Curtain, and recommendations for selection of the right copy protection system are given.
Abstract: Copy protection systems are a reliable way to protect programmers' rights and to stimulate market development because they prevent unauthorized software use and copying. The main functions and structure of such systems are discussed. Possible attacks and breaking of copy protection systems are considered. One of the strongest systems, called the Iron Curtain, is described. Recommendations for selection of the right copy protection system are given. >
Patent•
15 Dec 1992TL;DR: In this article, a method and a device for preventing overstabilization of longitudinal differential protections in case of internal faults on power lines, which may take place when a fault situation, which is indicated as an external fault, is in reality an internal fault.
Abstract: A method and a device for preventing overstabilization of longitudinal differential protections in case of internal faults on power lines, which may take place when a fault situation, which is indicated as an external fault, is in reality an internal fault. The invention comprises criteria which finally provide information as to whether the longitudinal differential protection is to enter into operation. The criteria comprise level and directional determination of the currents which are measured in the terminals of the power lines, checking whether these have the same direction, and so on.
18 Oct 1992
TL;DR: Two integrated microcomputer-based detection and protection schemes for distribution system faults including high-impedance faults to deal with single-line-to-ground faults of feeders on a distribution substation using delta-delta connection are described.
Abstract: The authors describe two integrated microcomputer-based detection and protection schemes for distribution system faults including high-impedance faults. The main objective of the two schemes is to deal with single-line-to-ground faults of feeders on a distribution substation using delta-delta connection. The first scheme, based on an innovative fault-detection algorithm, identifies a faulty feeder by measuring varied phase angles between phase currents and bus voltages. The second scheme, including several existing detection algorithms, incorporates an expert system for selecting an algorithm suitable for a given application based on their advantages. A simulation software package is built to simulate the implementation of the two schemes and their combination. Using the simulation package and feeder fault data, simulation tests are made to verify the feasibility of the schemes, the algorithms, and the system structures suggested. >
TL;DR: In this paper, the system relay engineer of Kansas Power & Light Gas Service has served as a guest lecturer for the course on fault analysis and protection of power systems at Kansas State University, and the benefits of such cooperation between university and industry are outlined.
Abstract: Since 1988, the system relay engineer of Kansas Power & Light Gas Service has served as a guest lecturer for the course on fault analysis and protection of power systems at Kansas State University. He meets the class five times during the semester. Two of these visits are field trips. In the other three visits he discusses power systems protection from a practicing engineer's point of view. He also discuss a practical design problem prepared for this class. The details of the course, the design project, and other activities are described. The benefits of such cooperation between university and industry are outlined. The main objectives of this course are to: make the students familiar with symmetrical components and fault analysis; make the students familiar with computer methods for fault analysis; make the students familiar with directional overcurrent, differential, distance, and pilot protection; impart practical knowledge on protection to the students; are prepare students for projection-related jobs in the utilities. >
02 Dec 1992
TL;DR: In this paper, the simulation results and the analysis of the system waveform patterns under various conditions were presented, showing that under fault conditions, the operation of the capacitor gap or varistor does not conform to any clearly defined pattern.
Abstract: The development of flexible AC transmission systems (FACTS) technology offers better opportunities to utilize existing transmission systems. One of the key FACTS devices is controllable series capacitor compensation (CSC). The authors discuss the digital simulation of CSC protection schemes. A parallel protective device is required to provide overvoltage limitation during system faults. There are two approaches adopted by utilities: one involves the combination of a traditional gap and a mechanical bypass switch; the other involves the use of varistor technology, in which the varistor is connected directly in parallel with the capacitor and provides fault overvoltage protection. With the incorporation of the components of a 500 kV series-compensated system into the Electromagnetic Transients Program (EMTP), the authors present some simulation results and the analysis of the system waveform patterns under various conditions. The studies show that under fault conditions, the operation of the capacitor gap or varistor does not conform to any clearly defined pattern.