System Protection Schemes Research Articles

Design of New Load Shedding Special Protection Schemes for a Double Area Power System

Design of New Load Shedding Special Protection Schemes for a Double Area Power System

Risk Informed Design Refinement of a Power System Protection Scheme

To prevent wide-area disturbances, and enhance power system reliability, various forms of system protection scheme (SPS) have been designed and implemented by utilities. One of the main concerns in SPS deployment is to ensure that the system will fit with the reliability requirement specification in terms of dependability, and security. After major changes in system operating practices, or physical changes of the protected system, a refinement of the SPS decision process may be required. This paper uses a currently operational SPS as an example to demonstrate a refinement study. By incorporating an interval theory, a risk reduction worth importance concept, and a probabilistic risk-based index, the proposed procedure conducts parameter uncertainty analysis, identifies critical factors in the reliability model, performs risk assessments, and determines a better option for the refinement of the studied SPS decision process logic module.

Immunology

Immunology

Intelligent and Reliable Photonic Cross-Connect System Based on Overlay Model

We developed a carrier-based photonic cross-connect (PXC) system based on an optical switch, which provides wavelength-division-multiplexing transmission, generalized multiprotocol label switching, and optical-transport-network management. This system uses an overlay model in which the administrative authority between the client-network-element (NE) layer and the carrier's PXC layer is completely separated. The PXC system provides user-network interface signaling between the client NEs and the PXCs, which enables automatic optical path setting between the two client NEs through a PXC network. We considered new protection schemes for the PXC system and successfully carried out an experiment in a testbed network using one of the discussed schemes. The new concept of policy control in the control-plane management is introduced, and the feasibility of our PXC system is demonstrated. This system is promising as a prototype for a next-generation optical transport system. Furthermore, the PXC system will enable the creation of a new type of optical transport layer service, accommodate increased Internet traffic demand, and reduce network operation loads and costs for Internet service providers and carriers in the near future.

A combined adaptive network and fuzzy inference system (ANFIS) approach for overcurrent relay system

Accurate models of overcurrent (OC) relays with inverse time relay characteristics play an important role for the coordination of power system protection schemes. Conventional OC relay modelling using techniques like system identification, parameter estimation, direct data storage and software gave only approximate models. Hence, in this paper a new method for modelling OC relay characteristics curves based on a combined adaptive network and fuzzy inference system (ANFIS) is proposed. In this method, OC relay modeling is done using ANFIS for two types of OC relays (RSA20 and CRP9 with different types and various numbers of membership functions to bring out the optimal design. The simulated results are compared with the published results of analytical method and fuzzy model systems. The results obtained are quite encouraging and will be useful as an effective tool for modelling OC relays.

Overcurrent Protection on Voltage-Source-Converter-Based Multiterminal DC Distribution Systems

This paper proposes a protection scheme which utilizes modern voltage-source converters as fast-acting current-limiting circuit breakers. This paper investigates the main challenges of detecting and localizing a fault, and interrupting it as quickly as possible in a multiterminal dc system. A system protection scheme consisting of smart relays associated with converters has been developed. The protection relays monitor local quantities to detect and isolate disturbances/faults. It is shown that overcurrent-based schemes can be adopted for these relays to meet the fast response requirements. The effectiveness of the proposed protection scheme is illustrated through simulations

Institutionalizing the Electric Warship

The Navy has invested a considerable amount of resources in developing Electric Warship technology in the past twenty years. We have witnessed a number of early technology demonstrations as well as incorporation of Integrated Power System (IPS) technology into ship programs such as LHD 8, T-AKE, DD(X), and CVN 21. Although these early adopters have paved the way for establishing the practice of electric warship design, we are now at a critical point in time for institutionalizing the electric warship. A technology is institutionalized when the following activities have occurred: ▪ Establish a common architecture and interfaces. ▪ Establish a common design processes. ▪ Incorporate the architecture and design processes into design tools. ▪ Codify the practice in government or industry specifications, standards, and guides. ▪ Teach the architecture and design process as part of a typical engineering school curriculum. This article reviews the progress in electric warship technology, describes progress (including ongoing efforts) in institutionalization, and highlights critical near term shortcomings. Some of the shortcomings in design processes and tools include: ▪ Undefined (in authoritative documentation) concepts such as zonal survivability and quality of service. ▪ Obsolete requirement terms such as “sustained speed” and “endurance speed/range” ▪ Conflicting design practices for propulsion and ship service prime mover sizing. ▪ Customized system protection strategies for different classes of ships. ▪ Ambiguous methods for the sizing of zonal distribution system components. ▪ Lack of integration of IPS design algorithms into ship concept tools such as ASSET. ▪ Lack of knowledge as to how to effectively use modeling and simulation to make electric plant design decisions for each stage of ship design. Additionally, the article details progress in updating standards and specifications, such as the Naval Vessel Rules and DOD-STD-1399. Finally, efforts to incorporate Electric Warship design into the curriculum at [RA1] traditional Naval Architecture are described.

06/00663 Pre-processing of the optimal coordination of overcurrent relays: Karegar, H. et al. Electric Power Systems Research, 2005, 75, (2–3), 134–141.

Accurate models of overcurrent (OC) relays with inverse time relay characteristics play an important role for the coordination of power system protection schemes. Conventional OC relay modelling using techniques like system identification, parameter estimation, direct data storage and software gave only approximate models. Hence, in this paper a new method for modelling OC relay characteristics curves based on a combined adaptive network and fuzzy inference system (ANFIS) is proposed. In this method, OC relay modeling is done using ANFIS for two types of OC relays (RSA20 and CRP9 with different types and various numbers of membership functions to bring out the optimal design. The simulated results are compared with the published results of analytical method and fuzzy model systems. The results obtained are quite encouraging and will be useful as an effective tool for modelling OC relays.

SAFETY AND RELIABILITY ANALYSIS OF PROTECTION SYSTEMS FOR POWER SYSTEMS

This paper addresses the problem of risk analysis of protection systems and protection scheme of transmission grid. According to IEC 61508, a hybrid model has been developed supporting the analysis of protection systems. The use of analytic models in risk analysis of the elements of system protection scheme allows evaluating the security level associated to different protection strategies and supports the identification of specific ICT criticalities.

Wide-Area Protection and Power System Utilization

This paper describes basic principles and philosophy for wide-area protection schemes, also known as remedial action schemes (RAS) or system protection schemes (SPS). In the areas of power system automation and substation automation, there are two parallel trends in different directions: centralization and decentralization. More and more functions are moved from local and regional control centers toward the central or national control center. At the same time we also observe more and more "intelligence" and "decision-power" moving closer toward the actual power system process. We also see a great deal of functional integration, i.e., more and more functionality enclosed in the same hardware. This raises discussions concerning reliability (security and dependability). The main targets for this paper is therefore to: 1) sort out the terminology used in this area; 2) describe different application areas and related requirements; 3) illustrate different design principles-"top-down", "bottom-up", hierarchy, flat, etc., for different applications; and 4) identify similarities and differences between classic equipment protection and system protection-concerning philosophy as well as concerning product and system design. The theme of the paper is on the use of information technology to obtain more flexibility and smartness in power-system controls.

A System Protection Scheme Concept to Counter Interarea Oscillations

This paper introduces a concept of a generator coherency-based System Protection Scheme (SPS), addressing interarea oscillation events. The scheme uses wide-area generator speed measurements combined with discrete Fourier transform (DFT) analysis to determine coherency. A test case simulated in the NPCC 68-bus system is used to introduce the scheme's operating principle. The test case is also used to investigate the scheme suitability for different well-established digital signal processing (DSP) methods. Further aspects, such as evolving/sliding window functions, window size, and frequency resolution are analyzed. For the detection of interarea modes, parametric DSP methods turned out to be the most feasible. In general, evolving windows are faster than sliding windows. However, evolving windows require a trigger and were therefore rejected for the design proposed here. A lower frequency resolution may shorten the response time at the expense of the quality of the estimates of the instantaneous speed deviation and the generator coherency. The design proposed here is based on a high-frequency resolution at the cost of a lower response time.

Distribution System Protective Device Coordination in Presence of Distributed Generation

Protection schemes in distribution systems have traditionally been designed assuming the system to be radial, characterized by a single source feeding a network of downstream feeders. After connecting distributed generation (DG), part of the system may no longer be radial, which means the coordination might not hold. This paper explores the effect of DG on protective device coordination, such as fuse-fuse, relay-relay, and fuse-relay. In each case, potential problems in conventional device coordination are identified and a solution is suggested. An actual system is analyzed to illustrate these problems and solutions.

Coordinated system protection scheme against voltage collapse using heuristic search and predictive control

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 also considered as emergency controls, the coordinated scheme reduces the amount of required load shedding by 35% compared to the local scheme.

A flexible approach for overcurrent relay characteristics simulation

Accurate models of overcurrent (OC) with inverse time relay characteristics play an important role for the coordination of power system protection schemes. This paper proposes a new method for modelling OC relays curves. The model is based on fuzzy logic and artificial neural network. The feedforward multilayer perceptron neural network is used to calculate the operating times of OC relays for various time dial settings (TDS) or time multiplier settings (TMS). The new model is more accurate than traditional models. The model has been validated by comparing the results obtained from the new method with linear and nonlinear analytical models.

A new horizon for system protection schemes

Interconnected grid operation, control, and security will be revolutionized by a system protection scheme that safeguards the grid's integrity by adapting its responses to the most severe, unforeseen disturbances. The new approach takes advantage of power system resilience to the initial impact of even the most severe disturbances. The disturbance causes changes of system vulnerability parameters that are used by the protection to direct preselected measures to affected locations. A system protection that sustains system voltage stability and incorporates a simple emergency strategy is outlined. The approach allows practical and reliable, modest cost schemes that can gain considerable financial benefits in the operation and control of the grid.

A New Horizon for System Protection Systems Schemes

Interconnected grid operation, control, and security will be revolutionized by a system protection scheme that safeguards the grid's integrity by adapting its responses to the most severe unforeseen disturbances. The new approach takes advantage of power system resilience to the initial impact of even the most severe disturbances. The disturbance causes changes of system vulnerability parameters that are used by the protection to direct preselected measures to affected locations. A system protection scheme that sustains system voltage stability and incorporates a simple emergency strategy is outlined. The approach allows practical and reliable, modest cost schemes that can gain considerable financial benefits in the operation and control of the grid.

Coordinated System Protection Scheme against Voltage Collapse Using Heuristic Search and Predictive Control

Coordinated System Protection Scheme against Voltage Collapse Using Heuristic Search and Predictive Control

Voltage Sag Mitigation Using Overcurrent Protection Devices

The relationship between distribution system protection schemes and overcurrents, and thus voltage sags, is presented. Sources of interruptions and voltage sags are also reported. The Computer Business Equipment Manufacturing Association (CBEMA) curve is described and adopted as most representative of sensitive equipment capability to withstand voltage sags. A short introduction of the protection parameters, like types of faults, protection device characteristics, and fault prevention, is presented. The six main sag mitigation measures are analyzed, studying their main advantages and drawbacks, with some given examples. The main emphasis is given to the recloser fast tripping elimination, dead time reduction, and the improving of the protection operating speed. Changes in protection criteria and circuit layout can avoid some sensitive equipment dropouts.

Effect of distribution system protection on voltage sags

The general relationship between distribution system protection schemes and voltage sags is presented. The definition, characteristics, and sources of sags are given. The probability of sag occurrence is studied from the three points of view: reliability assessment, historic reliability, and general tendency. General values for the reliability assessment uncertainties and facts related to the historic reliability are proposed. The general tendency is analyzed in normalized form. The reliability index appropriate for the study of the protection scheme interaction with voltage sag are described.

Digital time-domain investigation of transient behaviour of coupling capacitor voltage transformer

This paper reports a set of digital time-domain simulation studies conducted on TEHMP161A Coupling Capacitor Voltage Transformer (CCVT) of Haefely-Trench. The Electro-Magnetic Transients Program (EMTP) is used to develop the CCVT model and conduct the transient studies. The accuracy of the CCVT model is verified through comparison of the EMTP simulation results with those obtained from test results. The investigations demonstrate that the developed model can accurately predict CCVT transient response, e.g. the phenomenon of ferroresonance. The model is developed (1) to determine impact of transients on CCVT response, (2) to design, optimize and compare protective and ferroresonance suppressor devices of CCVT, and (3) to predict CCVT transient response on power system monitoring and protection schemes.