Showing papers on "Power-system protection published in 2002"
10 Dec 2002
TL;DR: In this paper, the feasibility of direct current for the supply of offices and commercial facilities is analyzed by analyzing a case study, i.e., the supply to the Department of Electric Power Engineering, Chalmers University of Technology, Gothenburg, Sweden.
Abstract: This paper analyzes the feasibility of direct current for the supply of offices and commercial facilities. This is done by analyzing a case study, i.e. the supply to the Department of Electric Power Engineering, Chalmers University of Technology, Gothenburg, Sweden. Voltage drop calculations have been carried out for different voltage levels. A backup system for reliable power supply is designed based on commercially available batteries. Finally, an economic evaluation of AC versus DC is performed and protection of the proposed system is briefly addressed.
451 citations
TL;DR: In this paper, the onset of voltage collapse point is calculated based on the load characteristics and simulated voltage and current phasors measurements, which are provided by a network of phasor-measurement units.
Abstract: This paper presents a concept for local monitoring of the onset of voltage collapse, protective, and emergency control in the presence of voltage-sensitive loads. The onset of voltage collapse point is calculated based on the load characteristics and simulated voltage and current phasors measurements, which are provided by a network of phasor-measurement units. If the stability margin is small and the reactive-power reserves are nearly exhausted, then controls to steer the power system away from the critical point will be activated.
350 citations
25 Jul 2002
TL;DR: In this article, the impacts of DG on system protection and coordination are discussed, particularly in cases where DG is added to a distribution feeder with existing line reclosers and fuses.
Abstract: Interconnection of distributed generation (DG) on a radial distribution system presents situations not normally encountered by the distribution engineer. The author's intent is to point out some of the more common problems and the resulting misapplication of protection schemes incurred with the installation of DG. This paper discusses the impacts of DG on system protection and coordination particularly in cases where DG is added to a distribution feeder with existing line reclosers and fuses.
197 citations
TL;DR: In this paper, a wavelet-based scheme for distinguishing between transformer inrush currents and power system fault currents is presented. But the proposed scheme proved to be reliable, accurate, and fast.
Abstract: This paper presents the development of a wavelet-based scheme, for distinguishing between transformer inrush currents and power system fault currents, which proved to provide a reliable, fast, and computationally efficient tool. The operating time of the scheme is less than half the power frequency cycle (based on a 5-kHz sampling rate). In this work, a wavelet transform concept is presented. Feature extraction and method of discrimination between transformer inrush and fault currents is derived. A 132/11-kV transformer connected to a 132-kV power system were simulated using the EMTP. The generated data were used by the MATLAB to test the performance of the technique as to its speed of response, computational burden and reliability. The proposed scheme proved to be reliable, accurate, and fast.
175 citations
TL;DR: In this paper, the impact of the static synchronous compensator (STATCOM) on the impedance-based protection relays in a power system containing a flexible alternating current transmission (FACTS) controller is investigated.
Abstract: This paper presents analytical and simulation results for investigating the operation of impedance-based protection relays in a power system containing a flexible alternating current transmission (FACTS) controller such as the static synchronous compensator (STATCOM). The analyses are based on steady-state operation for modeling the STATCOM and the protection relays. The impact of the FACTS device on protection relays is studied for normal operating conditions as well as for fault conditions under different loading levels. Results for a case study are given.
154 citations
TL;DR: In this article, a new adaptive phasor measurement unit (PMU) based protection scheme for both transposed and untransposed parallel transmission lines is proposed, which decouples the mutual coupling effects between parallel lines by means of eigenvalue/eigenvector theory.
Abstract: This paper proposes a brand-new adaptive phasor measurement unit (PMU) based protection scheme for both transposed and untransposed parallel transmission lines. The development of the scheme is based on the distributed line model and the synchronized phasor measurements at both ends of lines. By means of eigenvalue/eigenvector theory to decouple the mutual coupling effects between parallel lines, the fault detection and location indices are derived. The two proposed indices are used in coordination such that the internal and external fault events can be distinguished completely. By on-line estimation of the line parameters under the actual power system conditions, the proposed scheme will respond more accurately to power system faults. Extensive simulation results using EMTP have verified that the accuracy of the fault location achieved is up to 99.9%. The proposed protection system responds well and fast with regard to dependability and security. All the results show that the performance of the proposed detection/location indices is independent of fault types, locations, resistance, source impedance, fault inception angles, and load flows.
149 citations
TL;DR: In this paper, a wavelet-based directional protection scheme was proposed for UHV/EHV transmission line protective relay. But the wavelet singularity detection technique was not used in this paper.
Abstract: A novel wavelet-based directional protection scheme is presented in this paper. Using the theory of wavelet singularity detection as a powerful signal-processing tool, the initial arrival of the traveling wave and its sign can be identified reliably. Characteristics of the proposed directional protection algorithm are analyzed and results of simulation studies are given. The wavelet-based directional protection scheme solves several problems existing in current protective relays and is suitable for use as an ultra high speed UHV/EHV transmission line protective relay.
122 citations
TL;DR: In this article, a coordinated system protection scheme (SPS) against voltage collapse based on model predictive control and tree search is presented, which optimally coordinates dissimilar and discrete controls, such as generator, tap changer and load shedding controls, in presence of soft and hard constraints on controls as well as voltages and currents in the network.
Abstract: A coordinated system protection scheme (SPS) against voltage collapse based on model predictive control and tree search is presented. It optimally coordinates dissimilar and discrete controls, such as generator, tap changer, and load shedding controls, in presence of soft and hard constraints on controls as well as voltages and currents in the network. The response with the coordinated SPS is compared to an SPS based on local measurements using simulation of the Nordic 32 test system. In terms of the amount of load shedding required to restore voltage stability, the simulations indicate that load shedding based on local criteria is near optimal in the system studied. However, when generator controls are considered also as emergency controls, the coordinated scheme reduces the amount of required load shedding by 35% compared to the local scheme.
119 citations
TL;DR: In this article, a wide-area back-up protection and artificial intelligence techniques are employed to minimize the impact of a fault on a power network, which can prevent cascading outages in power systems.
Abstract: A strategy to prevent cascading outages in power systems is proposed in this paper. The strategy employs wide-area back-up protection and artificial intelligence techniques to minimize the impact of a fault on a network. There are two ways in which wide-area backup protection can prevent cascading trips leading to a wide spread blackout: 1) Precise location of a fault so that only the circuit breakers necessary to isolate the fault are tripped; and 2) Avoidance of unnecessary trips, due to hidden failure or overloading, by blocking the trip signals of conventional back-up protection relays. The limitations of conventional back-up protection are examined and methods of improvement are presented.
103 citations
TL;DR: In this article, a novel ultra-high-speed directional protection scheme developed using mathematical morphology (MM) was proposed to extract transient features from faultgenerated voltage and current wave signals propagating along transmission lines during a post-fault period.
Abstract: This paper presents a novel ultra-high-speed directional protection scheme developed using mathematical morphology (MM). The MM technique proposed is used to extract transient features from fault-generated voltage and current wave signals propagating along transmission lines during a post-fault period. Fault direction is determined by two composite relaying signals, which are composed of the extracted transient features. A variety of fault scenarios have been simulated to evaluate the validity of the proposed scheme.
102 citations
TL;DR: In this article, the field tests made for two 463 MVA system transformers show that tested transformers may tolerate very high dc currents for times typical to geomagnetic storms.
Abstract: The geomagnetic induced currents in a transmission network may saturate transformers and cause additional losses, a high level of harmonics, and a lack of reactive power in the grid. Malfunctioning of protection circuits is also reported in the literature. The field tests made for two 463 MVA system transformers show that tested transformers may tolerate very high dc currents for times typical to geomagnetic storms. The effects for the voltage control and voltage quality in network are also considered and results of earlier Finnish GIC risk studies are reported.
04 Jun 2002
TL;DR: In this paper, it was shown that a permanent magnet generator coupled with a PWM voltage source converter will adequately meet the LP shaft generator requirements for a future More Electric Aircraft (MEA) and satisfy the requirements for wide speed range control and fault tolerance.
Abstract: This study has shown that a permanent magnet generator coupled with a PWM voltage source converter will adequately meet the LP shaft generator requirements for a future More Electric Aircraft. It also adequately satisfies the requirements for wide speed range control and fault tolerance, although it should be noted that full fault tolerance only seems achievable with a direct drive (nongeared) generator. The direct drive machine is suitable for either oil or air cooling, the oil-cooled option being smaller and lighter, even after taking into account the additional converter and cable weight arising from its increased reactance. The geared machine offers a net weight saving of 16% (compared with oil-cooled direct drive) but its fault tolerance is limited to open circuit faults and loss of drive in the power converter only. The study has firmly established the feasibility of permanent magnet generators for the More Electric Aircraft; however further work is required, most notably the estimation of rotor stray loss and the study of power system stability and protection.
TL;DR: In this paper, an adaptive algorithm to prevent undesirable distance protection operations during voltage instability is proposed, based on mathematical logic blocks and uses the rate of change of voltage as an additional relay criteria to increase the relay security with respect to voltage instability.
Abstract: An adaptive algorithm to prevent undesirable distance protection operations during voltage instability is proposed. The algorithm is based on mathematical logic blocks and uses the rate of change of voltage as an additional relay criteria to increase the relay security with respect to voltage instability. Studies are based on simulations using two different test systems; a 15-bus system developed by the authors and the Nordic32 system. The investigation shows that undesirable zone 3 distance relay operations can be the difference between a blackout and a recovering system during voltage instability. However, simulations have shown that the adaptive algorithm may save the system from a collapse. Although the algorithm prevents mal-trips due to voltage instability, the reach of the distance relay will not be restricted.
TL;DR: In this article, the Rogowski coils are used for the design of advanced protection systems when used with new multifunction relays and fiberoptic communication, which can easily adjust to load and/or power system configuration changes.
Abstract: Innovative Rogowski coils enable the design of advanced protection systems when used with new multifunction relays and fiberoptic communication. The protection systems have faster response times to faults and can easily adjust to load and/or power system configuration changes. Since the new Rogowski coils are very accurate and do not saturate, protection levels can be set to lower fault current thresholds, reducing the stress on the protected equipment. The whole system is immune to external magnetic fields and has self-testing logic. No wiring is necessary.
TL;DR: In this paper, a Markov model is described to examine the reliability features of a protection relay, including common cause failures, temporary and permanent faults and the associated clearing times, operation of back-up protection, and relay mal-trips.
Abstract: Relaying reliability is generally separated into the two different aspects of dependability and security. The reliability of a protection relay can be improved by carrying out routine maintenance or by including built-in monitoring and self-checking facilities during the design stages. A Markov model is described in this paper which can be used to examine these features. The model also recognizes common-cause failures, temporary and permanent faults and the associated clearing times, operation of back-up protection, and relay mal-trips. Studies have been conducted to illustrate the expected reliability benefits by inclusion of monitoring and self-checking facilities within the relay.
TL;DR: A new approach for transformer differential protection that ensures security for extemal faults, inrush, and overexcitation conditions and provides dependability for internal faults is described.
Abstract: For pt.I see ibid., vol.16, p.485-91 (2001). This paper describes a new approach for transformer differential protection that ensures security for external faults, inrush, and overexcitation conditions and provides dependability for internal faults. This approach combines harmonic restraint and blocking methods with a wave-shape recognition technique. We compare in the paper the behavior of some traditional transformer protection methods to that of the new method for real cases of magnetizing inrush conditions.
07 Aug 2002
TL;DR: In this paper, the authors presented a new logic based islanding detection algorithm for distributed resources that is interconnected with distribution network that utilizes four system parameters that include the conventionally used ones of voltage magnitude, phase, and frequency and the newly proposed one of total harmonic distortion (THD) of current.
Abstract: The islanding protection for distributed resources (DR) becomes an important and emerging issue in power system protection since the distributed resources installations are rapidly increasing and most of the installed systems are interconnected with distribution network In order to avoid the negative impacts from islanding operations of DR to protection, operation, and management of distribution system, it is necessary to effectively detect the islanding operations of DR and disconnect it from distribution network rapidly Generally, it is difficult to detect islanding operation by monitoring only single system parameter This paper presents a new logic based islanding detection algorithm for distributed resources that is interconnected with distribution network The proposed islanding detection algorithm utilizes four system parameters that include the conventionally used ones of voltage magnitude, phase, and frequency and the newly proposed one in this paper of total harmonic distortion (THD) of current The method monitors changes in four parameters and detects the islanding operations by logical rules The authors verified the efficiency of the proposed method using the radial distribution network of IEEE 34 bus model
TL;DR: In this article, the authors illustrate the way a blackout can be prevented in real time through controlled segregation of a system into a number of viable islands together with generation and/or load shedding.
Abstract: The power systems operated by the utilities in developing countries suffer from a large gap between demand and generation, inadequate transmission capacity, and nonuniform location of the load centers and generating stations. Occurrences of faults in such systems, in most of the cases, end up with the worst consequences (i.e., complete blackout). This paper illustrates the way a blackout can be prevented in real time through controlled segregation of a system into a number of viable islands together with generation and/or load shedding. The nature and location of any fault that warrants such islanding can be ascertained in real time through monitoring the active-power (megawatt) flows at both ends of a number of prespecified lines. The blackout of June 20, 1998 in the Bangladesh Power Development Board system has been used as an example in the illustration. The philosophy of the proposed islanding scheme may be considered for implementation in other power systems also.
TL;DR: In this article, a generic procedure for risk-based assessment of SPS is proposed, which can help the system operator to identify the risk brought by SPS and to make SPS-related decisions.
Abstract: Summary form only given as follows. Special protection systems (SPS) have been widely used to increase the transfer capability of the network by assisting system operators in administering fast corrective actions. Compared with constructing new transmission facilities, SPS can be placed in service relatively quickly and inexpensively. However, increased reliance on SPS results in additional risks to system security. In this paper, based on existing reliability evaluation methods, a generic procedure for risk-based assessment of SPS is proposed. The procedure can help the system operator to identify the risk brought by SPS and to make SPS-related decisions. An illustrative example which uses a generator rejection scheme (GRS) for transient instability is provided.
TL;DR: In this paper, the authors present a formulation for the analysis of grounding systems embedded in stratified soils, on the basis of the boundary element method (BEM), which allows to use the highly efficient analytical integration techniques derived by the authors for grounding systems buried in uniform soils.
Abstract: The design of safe grounding systems in electrical installations is essential to assure the security of the persons, the protection of the equipment and the continuity of the power supply. In order to achieve these goals, it is necessary to compute the equivalent electrical resistance of the system and the potential distribution on the earth surface when a fault condition occurs. In this paper we present a formulation for the analysis of grounding systems embedded in stratified soils, on the basis of the boundary element method (BEM). Suitable arrangements of the final discretized equations allow us to use the highly efficient analytical integration techniques derived by the authors for grounding systems buried in uniform soils. The feasibility of this approach is demonstrated by applying the BEM formulation to the analysis of a real grounding system with a two-layer soil model.
25 Jul 2002
TL;DR: In this paper, the authors review the overvoltage issues associated with the application of distributed resources on power systems and recommend approaches for prevention of overvoltages in electric power systems.
Abstract: Distributed resources (DR) can be a source of overvoltage problems for the electric power system if care is not exercised in the design and interface of the DR equipment. Conversely, DR may be adversely impacted by overvoltage conditions that originate on distribution feeders during faults, switching events, or as a result of lightning. Use of the appropriate DR grounding, interface transformer winding, proper switching methods, anti-island protection settings, lightning surge protection, and equipment voltage withstand ratings can help reduce the chance that either the DR or the utility system will be adversely impacted by overvoltages. This paper reviews the overvoltage issues associated with the application of DR on power systems and recommends approaches for prevention of problems.
TL;DR: In this article, a procedure for fast suppression of the phenomenon of ferroresonance in coupling capacitor voltage transformers (CCVT) without major change in the CCVT design is described.
Abstract: This paper describes a procedure for fast suppression of the phenomenon of ferroresonance in coupling capacitor voltage transformers (CCVT) without major change in the CCVT design. It is shown that it is possible to adjust parameters of the secondary overvoltage protection and the filter circuit so that the ferroresonance can be cleared in a very short time interval. The study cases reported in this paper show that ferroresonance is effectively cleared within two cycles. An implementation of metal oxide varistors (MOV) as part of passive ferroresonance protection is also addressed. The Electromagnetic Transients Program (EMTP) is used for modeling transients and fine-tuning the ferroresonance suppressing circuit. The studies are conducted on the Trench TEHMP161A CCVT.
25 Jul 2002
TL;DR: In this article, a modified protection system reliability model including two major protection failure modes is established, and a nonsequential Monte Carlo simulation approach is used to implement the stochastic properties of component contingency and protection system failure.
Abstract: This paper describes power system reliability evaluation including protection system failures. A modified protection system reliability model including two major protection failure modes is established. Protection system failure is the main cause of cascading outages. The mechanism and scheme of protection system have been analyzed on their contribution to the cascading outages after a fault occurs. A nonsequential Monte Carlo simulation approach is used to implement the stochastic properties of component contingency and protection system failure. The whole procedure is verified in the WSCC-9 bus system. BIP (bus isolation probability), LOLP (loss of load probability), and newly introduced EPL (expected power loss) are calculated to demonstrate the vulnerability of a power system under cascading outages.
07 Aug 2002
TL;DR: The modification of a Voltage Instability predictor provides a path for integration of a stand-alone, local protection devices with a potential system-wide action, and takes into account the voltage characteristics of the loads.
Abstract: The growing concern about wide area power system disturbances and their impact on power systems have reinforced interest in the new generation of system protection tools. Their application depends on their reliability, which, in turn, depends on the reliability of the hardware infrastructure on which they rely. In this paper, we propose a modification of a Voltage Instability predictor, proposed some time ago. The modification provides a path for integration of a stand-alone, local protection devices with a potential system-wide action, and takes into account the voltage characteristics of the loads.
06 Oct 2002
TL;DR: In this article, the authors presented a new method to diagnose faults in a transmission system based on detecting high frequency components contained in a fault signal spectrum, which is used in the analysis in order to classify fault types and to locate fault positions.
Abstract: This paper presents a new method to diagnose faults in a transmission system This is based on detecting high frequency components contained in a fault signal spectrum The discrete wavelet transform (DWT) is used in the analysis in order to classify fault types and to locate fault positions Simulations are performed using ATP/EMTP It is found that the proposed method gives satisfactory results, and will be very useful in the development of a power system protection scheme
07 Aug 2002
TL;DR: A software model for the time domain simulation of inverse time overcurrent relays that incorporates the IEC and IEEE standard curves is described, and was developed using Fortran language under the PSCAD platform.
Abstract: This paper describes a software model for the time domain simulation of inverse time overcurrent relays. The software model incorporates the IEC and IEEE standard curves, and was developed using Fortran language under the PSCAD platform. The software model simulates the effect of current on an inverse time overcurrent relay, and can be configured to represent various custom-designed overcurrent relays. Extensive tests have shown that the software model can be used to simulate electromechanical, static analog and digital time overcurrent relays with accuracy.
TL;DR: In this paper, an expert-system-based reconfiguration methodology for load restoration in shipboard power systems is presented, which is based on the layout profile of a US surface combatant ship.
Abstract: Network reconfiguration for restoration in a military shipboard power system is a very important task that is performed in order to restore loads as a result of battle damage or system faults. This article features an expert-system-based reconfiguration methodology for load restoration in shipboard power systems. The power system considered in the present study is based on the layout profile of a US surface combatant ship. The methodology developed will determine whether the loads that lost supply are restorable. When considering loads, it gives precedence to high priority loads. It also determines if there is any violation of current constraints of any cables and voltage constraints at load nodes. If the load is restorable, as suggested by an expert system, and there is no violation of any constraints, then the load is said to be restorable and the operation sequence required in restoring that load would be given as the output. A CAD drawing of the power system and a database of the system information has been developed using a geographic information system (GIS). A software tool incorporating failure assessment and expert system restoration methodology was developed using Visual C++, Multilogic Exsys Developer, Alternate Transients Program (ATP), and Microsoft Access. Microstation has been used for GIS. Various fault cases were designed, and the developed tool was used to run them and perform expert system restoration.
TL;DR: In this paper, a novel technique for current differential pilot relay protection (CDPR) by using wavelet analysis is described, where power system CAD is used to generate current signals at both ends of a transmission line in a typical system with fault at various locations.
Abstract: This paper describes a novel technique for current differential pilot relay protection (CDPR) by using wavelet analysis. Power system CAD (PSCAD) is used to generate current signals at both ends of a transmission line in a typical system with fault at various locations. In this paper, discriminating between internal fault and external fault/change, identifying of faulted phase, and classifying fault type are achieved by using wavelet analysis. The simulation results show that this approach provides a high operating sensitivity for internal fault and remains stable for external fault/change.
25 Jul 2002
TL;DR: In this article, the authors investigated the influence of current transformer saturation on overcurrent protection when protection devices are located far from the CTs, causing their saturation during faults, and they showed that CT saturation will not significantly delay over current protection operation for most common settings.
Abstract: If current transformer (CT) characteristics are not properly selected for fault conditions, saturation will occur which can affect protection device operation. In some applications even if CTs are properly sized, it is necessary to locate protection devices far from the CTs. In these cases, the wire resistance, which adds to the CT burden, causes CT saturation at smaller currents than when located close to the protection devices. The impact of CT saturation on protection device operation is different for different protection device types and protection schemes. This paper investigates the influence of CT saturation on overcurrent protection when protection devices are located far from the CTs, causing their saturation during faults. A study was performed to verify that delayed overcurrent protection response will not cause mis-coordination with other protection devices. It is shown that CT saturation will not significantly delay overcurrent protection operation for most common settings.
TL;DR: A system for online adaptive setting and coordination of protection relays in meshed networks where the backup protection is achieved in remote form and new time characteristics for the coordination are found.
Abstract: Changes in power system operating conditions can affect both the reach point of distance relays and the coordination of distance and overcurrent relays. To improve the performance of the protection system, an adaptive scheme of relay settings is proposed. That is possible since the protection relays became digital . This paper describes a system for online adaptive setting and coordination of protection relays in meshed networks where the backup protection is achieved in remote form. After changes in the state of the network, an expert system (ES) performs the detection and proposes the correction of erroneous settings of protection zones and miscoordinations between relays at different stations; through an algorithm based on a fast determination of a nonminimal set of "break-points" (BPs) relays , new time characteristics for the coordination are found. The results of the application of the developed system to a test network of 34 nodes, 55 branches, and 110 relays are shown.