Showing papers on "Power-system protection published in 1998"
••
TL;DR: This approach to real-time fault detection and classification in power transmission systems by using fuzzy-neuro techniques can be used as an effective tool for high speed digital relaying, as the correct detection is achieved in less than 10 ms.
Abstract: This paper presents a new approach to real-time fault detection and classification in power transmission systems by using fuzzy-neuro techniques. The integration with neural network technology enhances fuzzy logic systems on learning capabilities. The symmetrical components in combination with three line currents are utilized to detect fault types such as single line-to ground, line-to-line, double line-to-ground and three line-to-ground, and then to define the faulty line. Computer simulation results are shown in this paper and they indicate this approach can be used as an effective tool for high speed digital relaying, as the correct detection is achieved in less than 10 ms.
200 citations
••
TL;DR: In this article, a multi-channel filter unit is applied to the captured signals to extract desired bands of high frequency signals, and a comparison between the spectral energies of different bands of the filter outputs determines whether a fault is internal or external to the protected zone.
Abstract: This paper proposes a new noncommunication protection technique for transmission line protection. The technique relies on firstly the detection of fault generated high frequency current transient signals. A specially designed multi-channel filter unit is then applied to the captured signals to extract desired bands of high frequency signals. Comparison between the spectral energies of different bands of the filter outputs determines whether a fault is internal or external to the protected zone. In addition to the saving in costs through negating the need for a communication link, the technique also retains many advantages of the 'transient based protection' technology, such as insensitivity to fault type, fault position, fault path resistance and fault inception angle. It is also not affected by CT saturation, the power frequency short-circuit level at the terminating busbar or the precise configuration of the source side networks.
148 citations
••
TL;DR: In this article, a series device is described as having a certain percent RMS magnitude voltage injection capability, which can be graphically illustrated using magnitude versus duration matrices or curves.
Abstract: The growing interest in power quality has led to a variety of devices designed for mitigating power disturbances, primarily voltage sags. One class of these devices is the series device. The size of a series device (SD) is usually described as having a certain percent RMS magnitude voltage injection capability. The required RMS magnitude is usually taken from measured data or the results of a circuit model simulation. These results can be graphically illustrated using magnitude versus duration matrices or curves. Due to the one cycle averaging effect of the RMS calculation, waveshape, transients, and phase shift are not adequately described, and thus does not accurately predict the necessary injection capability required of the series device. Careful consideration must also be taken when applying a series device onto a system. The series device acts as an additional energy source on the system. The device must coordinate with other protective devices to prevent damage to other loads on the system, particularly upstream loads. The series device requires a continuous current path to insert energy, so protective devices must be arranged accordingly. However, a load upstream of the series device and downstream of the protective device creates a potential for reverse current flow through the upstream load.
138 citations
••
TL;DR: The use of an artificial neural network as a pattern classifier for a distance relay operation that utilizes the magnitudes of three phase voltage and current phasors as inputs is demonstrated.
Abstract: A distance relay for the protection of transmission lines is usually designed on the basis of fixed settings. The reach of such relays is therefore affected by the changing network conditions. The implementation of a pattern recognizer for power system diagnosis can provide great advances in the protection field. This paper demonstrates the use of an artificial neural network as a pattern classifier for a distance relay operation. The scheme utilizes the magnitudes of three phase voltage and current phasors as inputs. An improved performance with the use of an artificial neural network approach is experienced once the relay can operate correctly, keeping the reach when faced with different fault conditions as well as network configuration changes.
137 citations
••
TL;DR: In this paper, an adaptive protection scheme for advanced series compensated (ASC) transmission lines is proposed based on Kalman and adaptive Kalman filters, which utilizes the differences in the transient current signals for faults encountering and not encountering the ASC to determine fault location with respect to the ASC and the faulted phases.
Abstract: This paper presents an adaptive protection scheme for advanced series compensated (ASC) transmission lines. The scheme is based on Kalman and adaptive Kalman filters. The adaptive scheme utilizes the differences in the transient current signals for faults encountering and not encountering the ASC to determine the fault location with respect to the ASC and the faulted phases. Equations to determine the line impedance to the fault on these lines are developed. The adaptive scheme is tested for faults along and outside the protected line using EMTP simulated data.
137 citations
••
TL;DR: The authors propose a new concept, the "relay agent", to realize a cooperative power system protection system, which consists of distributed equipment combined with a communication network to cooperate in the realization of adaptive protection functions.
Abstract: The authors propose a new concept, the "relay agent", to realize a cooperative power system protection system, which consists of distributed equipment combined with a communication network to cooperate in the realization of adaptive protection functions. Relay agents move between equipment to utilize data and functions distributed over the power system. In the paper, relay agents are classified by their roles and protection functions under some typical conditions are simulated. Consideration based on the simulations indicate that the concept enables the protection system to keep an isolated zone minimum against any changes in power system conditions and to secure high reliability of the protection system with less redundant hardware. The new concept "relay agent" will provide a powerful means of advanced protection functions by combination of microprocessor technology and information communication technology.
111 citations
••
TL;DR: In this article, the authors proposed a differential backup protection for a busbar and transmission circuits connected to that busbar on an inter-station or wide-area basis, which can operate better than conventional systems with respect to operation time, section selectivity, etc.
Abstract: As power systems grow larger, it is becoming difficult to achieve reach and time coordination in backup protection when using distance relays. To cope with those problems, current differential backup protection for a busbar and transmission circuits connected to that busbar on an inter-station or wide-area basis is proposed. The proposed system can operate better than conventional systems with respect to operation time, section selectivity, etc. A system configuration is also proposed to utilize ATM transmission networks and time synchronous systems which make the construction and operation of the proposed wide-area protection system easy and flexible.
102 citations
••
15 Feb 1998
TL;DR: In this paper, the authors present the technical aspects of designing a dynamic voltage restorer to meet the stringent requirements of voltage dips mitigation with respect to the magnitude of voltage dip, fault duration, permissible line voltage deviations and response time.
Abstract: This paper presents the technical aspects of designing a dynamic voltage restorer to meet the stringent requirements of voltage dips mitigation with respect to the magnitude of voltage dip, fault duration, permissible line voltage deviations and response time. An introduction to IGCT technology based on latest transparent anode GTO (T-GTO) and gate technology is given. The performance of the DVR based on digital simulations is discussed. A description of a hardware-based real-time simulator model for the performance assessment of DVR in voltage dips mitigation is presented. The results of the real-time simulator are compared with the digital simulations. Finally, control and protection concepts for the DVR are highlighted.
93 citations
••
26 Apr 1998
TL;DR: In this paper, the authors present several mechanical and electrical methods of detecting high impedance faults in electrical distribution systems and the issues and application of this technology are discussed, as well as their issues and applications.
Abstract: The detection of high impedance faults on electrical distribution systems has been one of the most persistent and difficult problems facing the electric utility industry. Recent advances in digital technology have enabled practical solutions for the detection of a high percentage of these previously undetectable faults. This paper reviews several mechanical and electrical methods of detecting high impedance faults. The issues and application of this technology are also discussed.
88 citations
••
TL;DR: In this article, two numerical algorithms for fault location and distance protection using data from one end of a transmission line are presented, which are relatively simple and easy to be implemented in the on-line application.
Abstract: Two numerical algorithms for fault location and distance protection which use data from one end of a transmission line are presented. Both algorithms require only current signals as input data. Voltage signals are unnecessary for determining the unknown distance to the fault. The solution for the most frequent phase to ground fault is presented. The algorithms are relatively simple and easy to be implemented in the on-line application. The algorithms allow for accurate calculation of the fault location irrespective of the fault resistance and load. To illustrate the features of the new algorithms, steady-state and dynamic tests are presented.
87 citations
••
TL;DR: In this paper, the authors proposed a binary programming optimization to identify type and location of the protective devices on a distribution feeder, which uses engineering heuristics to minimize computational time.
Abstract: The fundamental goal of an electric utility is to serve its customers with a reliable and low cost power supply. This goal has led to a number of standard protection engineering practices that ensure adequate service; however, with deregulation of the utility industry and increased competitive pressures, there is a desire to further improve service reliability and reduce costs. In this vein, this work proposes a binary programming optimization to identify type and location of the protective devices on a distribution feeder. The proposed algorithm uses engineering heuristics to minimize computational time. Numerical examples highlight the proposed approach.
••
TL;DR: In this paper, the authors developed techniques to increase survivability, eliminate human mistakes, make intelligent reconfiguration decisions more quickly, reduce the manpower required to perform the functions and provide optimal electric power service through the surviving system.
Abstract: The electric power systems in today's US Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. To maintain the availability of energy to the connected loads that keep all systems and equipment operational, the electric systems utilize fuses, circuit breakers and protective relays to interrupt the smallest portion of the system under any abnormal condition. New techniques are being developed that make use of advanced monitoring and control, automated failure location and automated intelligent system reconfiguration and restoration. The goal is to increase survivability, eliminate human mistakes, make intelligent reconfiguration decisions more quickly, reduce the manpower required to perform the functions and provide optimal electric power service through the surviving system. With fewer personnel being available on ships in the future, the presence of such a system will become essential for maintaining optimal electric power service.
••
03 Mar 1998
TL;DR: In this paper, the authors present the technical aspects of designing a dynamic voltage restorer to meet the stringent requirements of voltage dips mitigation with respect to the magnitude of voltage dip, fault duration, permissible line voltage deviations and response time.
Abstract: This paper presents the technical aspects of designing a dynamic voltage restorer to meet the stringent requirements of voltage dips mitigation with respect to the magnitude of voltage dip, fault duration, permissible line voltage deviations and response time. An introduction to the IGCT technology based on latest transparent anode GTO (T-GTO) and gate technology is given. The performance of the DVR based on digital simulations is discussed. A description of a hardware based real time simulator model for performance assessment of DVR in voltage dips mitigation is presented. The results of the real time simulator are compared with the digital simulations. Finally, control and protection concepts for the DVR are highlighted.
••
18 Aug 1998TL;DR: In this paper, the authors show that sampling frequency has an influence on distance protection performance in TCSC transmission lines, and they propose an overreaching setting value for TCSC line's protection, but it has difficulty in setting the relay on the reverse directional line.
Abstract: When a fault occurs in thyristor controlled series compensation (TCSC) transmission lines, TCSC presents a very complicated impedance characteristic and exerts influence on the power system's distance relays. Under ground faults, the complex changes of sequence currents exert influences on the mho characteristic, reactance characteristic and directional characteristic and makes the protection region unstable. Longitude distance protection with an overreaching setting value may be a solution to TCSC line's protection, but it has difficulty in setting the relay on the reverse directional line to avoid misoperation. Simulation shows that sampling frequency has an influence on distance protection performance in TCSC transmission lines.
••
03 May 1998
TL;DR: In this article, the authors provide an analytical perspective on the problem and suggest that the real issue is the manner in which the neutral of the generator itself is grounded, rather than the stator ground faults.
Abstract: Industry has recently become sensitized to the problem of severe generator damage due to stator ground faults. To prevent this damage, it has been suggested that the practices employed for neutral grounding should be changed. This paper provides an analytical perspective on this problem and suggests that the real issue is the manner in which the neutral of the generator itself is grounded.
••
TL;DR: In this article, a Petri net (PN) algorithm combined with a new power system restoration approach is implemented for multiple distribution contingencies, which is performed by releasing some loads required to maintain the rest of the system in safe operation in overload cases and opening all of the switches in the out-of-service areas for fault cases, and then closing proper switches to restore the isolated areas.
Abstract: In this paper, a Petri net (PN) algorithm combined with a new power system restoration approach is implemented for multiple distribution contingencies. This approach is performed by releasing some loads required to maintain the rest of the system in safe operation in overload cases and opening all of the switches in the out-of-service areas for fault cases, and then closing proper switches to restore the isolated areas. PN switching models and the construction of PNs for multiple contingency operation are proposed to implement the restoration algorithm. Problem solving is efficiently performed by parallel-like reasoning in the PN for all the multiple events simultaneously. Heuristic rules and evaluation functions are presented for the best first search in the PN. Multiple contingencies studied in this paper include problems of feeder fault/overload/over-unbalance and main transformer fault/overload. A practical Taiwan power (Taipower) distribution system is simulated to demonstrate the effectiveness of the proposed method. It is concluded that multiple contingencies of distribution systems can be solved by the proposed method effectively.
••
TL;DR: In this paper, the authors presented some improvements of the differential equation algorithm for transmission line protection, including fault classification, new filtering, and a new algorithm for three-phase faults.
Abstract: This paper presents some improvements of the differential equation algorithm for transmission line protection. The improvements are: fault classification; new filtering; and a new algorithm for three-phase faults. Simulation results indicate a nominal operation time of 5-7 ms for three-phase faults and slightly higher for other fault types.
••
TL;DR: In this article, the authors review the state of the art in digital relaying for power transformers and discuss new approaches and future directions for power transformer protection, including the use of artificial intelligence (AI) to enhance the classical protection principles.
Abstract: High demands are imposed on power transformer protective relays. Requirements include dependability (no missing operations), security (no false trippings), and speed of operation (short fault clearing time). The operating conditions of power transformers do not make the relaying task easy. Protection of large power transformers is one of the most challenging problems in the power system relaying area. Advanced digital signal processing techniques and artificial intelligence (Al) approaches to power system protection provide the means to enhance the classical protection principles and facilitate faster, more secure, and dependable protection for power transformers. Also, it is anticipated that, in the near future, more measurements will be available to transformer relays, owing to both substation integration and novel sensors installed on power transformers. All of this will change the practice for power transformer protection. This article briefly reviews the state of the art, but is primarily devoted to discussion of new approaches and future directions in digital relaying for power transformers.
••
TL;DR: In this article, a high speed protection technique based on fault generated high frequency (HF) voltage signals is developed and applied to the protection of EHV series compensated power transmission lines.
Abstract: A new high-speed protection technique based on fault generated high frequency (HF) voltage signals is developed and applied to the protection of EHV series compensated power transmission lines. It is a nonunit protection technique as it relies totally on locally derived information, but it has the discriminative properties normally associated with unit protection schemes. The protection scheme has been designed using CAD techniques including emulation of analogue interfaces and hardware. It is shown that the new relay scheme is able to overcome many difficult protection problems encountered on such EHV power lines using conventional methods, and discriminates clearly between internal and external faults, producing a fast trip output.
••
TL;DR: System simulation studies show that the proposed approach is able to detect the direction of a fault on a transmission line rapidly and correctly and is suitable to realize a very fast transmission line directional comparison protection scheme.
Abstract: Detection of the direction of a fault on a transmission line is essential to the proper performance of a power system. It would be desirable to develop a high speed and accurate approach to determine the fault direction for different power system conditions. To classify forward and backward faults on a given line, a neural network's abilities in pattern recognition and classification could be considered as a solution. To demonstrate the applicability of this solution, neural network technique is employed and a novel Elman recurrent network is designed and trained. Details of the design procedure and the results of performance studies with the proposed network are given and analysed in the paper. System simulation studies show that the proposed approach is able to detect the direction of a fault on a transmission line rapidly and correctly. It is suitable to realize a very fast transmission line directional comparison protection scheme.
••
TL;DR: In this article, a comparative analysis of the effects of expulsion and current-limiting fuse (CLF) operations in distribution systems on power quality and power system protection is presented. But, the analysis is limited to a single distribution system.
Abstract: This paper presents a comparative analysis of the effects of expulsion and current-limiting fuse (CLF) operations in distribution systems on power quality and power system protection. This analysis included field tests of both types of fuses on a distribution system in Florida, USA. To further analyze fuse effects on the voltage dip duration and spread of the overvoltages created during the fuse operations throughout the power system, computer simulations were also performed. Unique digital fuse models were developed for use with the EMTP/ATP program. This paper shows that CLFs improve power quality by supporting power system voltage during faults, reducing the voltage dip duration, and do not affect load operation. Additionally, CLFs reduce the fault let-through I/sup 2/t.
•
01 Jun 1998
TL;DR: In this paper, the authors describe a power system with symmetric components and symmetric faults, including symmetric and unsymmetric faults. But they do not specify the transmission line parameters.
Abstract: Fundamentals. Symmetrical components. Power transformers. Transmission line parameters. Transmission lines: steady state operation. Power flows. Symmetrical faults. Unsymmetrical faults. Power system controls. Transmission lines: transient operation. Transient stability.
••
TL;DR: In this article, a new system developed by Ontario Hydro to integrate the protection, control and monitoring functions at transmission and distribution substations is described, with an emphasis on the protection functions.
Abstract: This paper describes a new system developed by Ontario Hydro to integrate the protection, control and monitoring functions at transmission and distribution substations. The implementation of each of the system functions is discussed, with an emphasis on the protection functions. The focus is on the processing of power system information at each level of the system architecture. The system has been successfully operating in Ontario Hydro's power system.
••
01 Sep 1998TL;DR: The paper reports on the next stage of decision support for the protection engineers which builds upon the diagnosis provided by the knowledge-based systems and is provided by a model-based diagnostic system which provides automatic analysis of the available fault recorder data.
Abstract: Following a power system fault, protection engineers have to analyse the protection scheme activity to ensure correct operation. To aid them in this task, data gathering systems are increasingly being fitted to power systems. However, during extreme operating conditions, the volume of data made available by these systems can be overwhelming. To help overcome this, knowledge-based systems have been developed and installed at ScottishPower's corporate headquarters to extract the relevant `information' from the supervisory control and data acquisition (SCADA) system `data'. The paper reports on the next stage of decision support for the protection engineers which builds upon the diagnosis provided by the knowledge-based systems. This enhanced support is provided by a model-based diagnostic system which provides automatic analysis of the available fault recorder data. This system utilises the most appropriate techniques employed by existing model-based diagnostic systems. A novel approach for handling tolerances associated with the operating times of protection scheme components is introduced, thus enabling modelling measurement inaccuracies to be dealt with
••
TL;DR: In this paper, the authors proposed an approach to improve the lightning protection of sensitive electronics against lightning by injecting currents into the installation or into relevant parts of the installation, so that inductive effects determined the current distribution.
Abstract: The classical lightning conductor, which must prevent fire, has to have a sufficiently small resistance. An analogous condition can be formulated for the new challenge: the protection of sensitive electronics against lightning. In this case, the so-called transfer impedance, which gives the interference voltages across a sensitive input per ampere lightning current, must be made small. The arguments for this approach are described. A theoretical description is available and practical experience has been built up over the years, also in high-voltage (HV) research and in power engineering measurements in the field. This approach was used to greatly improve the lightning protection of several installations: a marine radio station, the peripheral equipment of a nuclear power plant, and an electronic siren for a nationwide public warning system. Detailed investigations were requested by our contract partners, together with suggestions for economically acceptable improvements that could be carried out in reasonable time. Later, the correctness of the renovations had to be demonstrated. In the validation measurements, we injected currents into the installation or into relevant parts thereof. The current waveform was chosen fast enough so that inductive effects determined the current distribution. At present, lightning position and tracking system (LPATS) data on lightning strikes near the marine radio station and the nuclear power plant are available to verify the effectiveness of the protection. After our improvements no more damage was reported.
••
TL;DR: The proposed technique analyzes the radiation produced due to arcing faults using artificial neural networks and a DSP-based data acquisition system and was implemented and tested in the laboratory.
••
TL;DR: In this article, a systematic approach to the evaluation of the overall impact of the electric traction demands of a high-speed railroad (HSR) on a power system was introduced.
Abstract: This paper introduces a systematic approach to the evaluation of the overall impact of the electric traction demands of a high-speed railroad (HSR) on a power system. These large unbalanced traction loads may cause system voltage and current unbalances and, therefore, overheat rotating machines, increase system losses, interfere with neighboring communication systems, and cause protection relays and measuring instruments to malfunction. Some of these problems may significantly affect the operation of the power system and other equipment connected to it. Hence, the proposed approach is oriented toward applications in system operation analysis rather than planning analysis. On the basis of the Newton-Raphson algorithm, a three-phase powerflow program was developed. In this program, most of the component models and solution techniques are those that were developed for three-phase power-flow studies. They are applied to accurately simulate a three-phase high-voltage network supplying the traction loads. Rigorous component models, such as generator, transmission line, power transformer and traction substation models, were incorporated into this program. By combining the electric demands of traction substations along an HSR, this program can be used to evaluate the overall impact of traction loads on a power system. On the basis of the simulation results, related improvement projects can be evaluated and conducted if necessary. This approach has been successfully tested on Taiwan's power system (Taipower system), to which the power-supply system of a planned HSR will be connected in the near future.
••
18 Aug 1998
TL;DR: In this article, a few methods used in power system grounding analysis and illustrates the advantages, limitations and the applicability of these methods are presented and compared the various cases modeled in this paper include grounding networks of different sizes, grounding networks with buried metallic structures such as steel pipes, and high frequency cases.
Abstract: This paper examines a few methods used in power system grounding analysis and illustrates the advantages, limitations and the applicability of these methods. Computation results using these methods are presented and compared the various cases modeled in this paper include grounding networks of different sizes, grounding networks with buried metallic structures, such as steel pipes, and high frequency cases. The discussions and conclusions given in this paper can be used as a reference when deciding which method should be used to carry out an accurate and efficient grounding analysis.
••
TL;DR: In this paper, an EMTP-based simulator was used in conjunction with a relay test set to type-test a protection relay operating within a circulating current differential protection scheme, which was designed to replace a high power synthetic test plant that has been used for more than 30 years for type and approval testing of differential protection relays.
Abstract: This paper describes how an EMTP-based simulator can be used in conjunction with a relay test set to type-test a protection relay operating within a circulating current differential protection scheme. The combination of a simulator and a test-set is designed to replace a high power synthetic test plant that has been used for more than 30 years for type and approval testing of differential protection relays. The paper includes results that describe the operating performance of the new test system, on both internal and external faults, and these are compared with experimental results obtained from an identical set of tests on the synthetic test plant.
••
TL;DR: In this article, a technique that detects the presence of an electric arc is presented, which can be used to protect power system equipment, such as transformers, inductors, capacitors etc.
Abstract: A technique that detects the presence of an electric arc is presented in this paper. It is also shown that it is possible to determine its location in a three-dimensional space. The proposed technique can be used to protect power system equipment, such as transformers, inductors, capacitors etc. The technique was implemented and tested in the laboratory. Some test results are also included in the paper.