Power system distribution

Time based coordination and protection is the normal basis for coordinating low voltage power distribution systems. Enhancements, such as zone selective interlocking and bus differential protection, may be used to accelerate protective devices. However, these improvements may be costly, difficult to implement, and may not function as expected using commonly available technology. Nevertheless, the potential benefit of fault clearing speed and selectivity are more valued in today's arc-flash and reliability conscious environment than ever before. The writers shall discuss some issues associated with these traditional improvements, pitfalls to avoid and, more effective ways to implement zone-based protection to achieve fast fault protection while maintaining complete selectivity for a broad range of fault magnitudes, system configurations and load types.

A comprehensive study of capacitor placements and real-time control in general unbalanced distribution systems is undertaken. New developments in a loss reduction formula, problem formulations, solution methodology and mathematical justification are presented. The problem is decoupled into two subproblems: the capacitor placement subproblem and the real-time control subproblem. An effective solution algorithm for placing capacitors and determining their real-time control

The reconfiguration of a power distribution system, by exchanging the functional links between its elements, represents one of the most important procedures to improve the performance in the operation of a distribution system. The optimization through reconfiguration (or optimal reconfiguration) of a power distribution system is not a new problem but still represents a difficult one and is specified in some strategies for smart grids. The paper addresses this problem as a single objective one, where, as main criterion, active power losses have been chosen. There is no unique acceptance regarding which approach (based on heuristics, meta-heuristics, genetic algorithms, etc.) is the most proper to use in order to solve this problem. The most important thing is how the specific knowledge of the problem domain is used and modeled in the implementation. Moreover, the indices which can quantify the quality of a reconfiguration method consist in runtime and the obtained solution and these indices can be confirmed only by experimental results. In order to solve the problem (to search and find the optimal solution) an original genetic algorithm based on connected graphs is proposed. Comparative tests performed on some test systems demonstrated the accuracy and the promptness of the proposed algorithm.

At Drexel University, instrumentation and measurement of the Reconfigurable Distribution Automation and Control Laboratory include hardware and software instruments which together form an automated measurement and control system. This system contains special features that were included to enable meter placement and network reconfiguration studies. This paper presents an outline of the measurement and control system for the general laboratory and then focuses on the capabilities purposely added for the meter placement and network reconfiguration studies.

A major goal for managers of electric power networks is maximum asset performance. Minimal life cycle cost and maintenance optimization becomes crucial in reaching this goal, while meeting demands from customers and regulators. This necessitates the determination of the optimal balance between preventive and corrective maintenance in order to obtain the lowest total cost. The approach of this paper is to study the problem of balance between preventive and corrective maintenance as a multiobjective optimization problem, with customer interruptions on one hand and the maintenance budget of the network operator on the other. The problem is solved with meta-heuristics developed for the specific problem, in conjunction with an evolutionary particle swarm optimization algorithm.

This paper presents a model predictive control (MPC) design for the unified power quality conditioner (UPQC), an integration of series and shunt active filters to improve power quality in a power distribution system. The control strategy aims to regulate the load voltage and the source current to the desired references in spite of the existence of harmonic components in the supply voltage and the load current, possible sag or swell in the supply voltage, and non-unity power factor of the supply side. Kalman filters are used to extract the fundamental as well as the harmonic components abovementioned, which will then be used to formulate the desired references and regarded as measurable disturbances, respectively. Based on a state-space model developed for the UPQC, an MPC controller is designed. Simulation studies on a single-phase power distribution system are also presented to verify the performance.

In this paper, an extended impedance-based fault-location formulation for generalized distribution systems is presented. The majority of distribution feeders are characterized by having several laterals, nonsymmetrical lines, highly unbalanced operation, and time-varying loads. These characteristics compromise traditional fault-location methods performance. The proposed method uses only local voltages and currents as input data. The current load profile is obtained through these measurements. The formulation considers load variation effects and different fault types. Results are obtained from numerical simulations by using a

The power quality is a major issue in the distribution system. There will b e problem occurs regarding reactive power transfer in distribution system due to large power angle even with substantial voltage magnitude gradient. Here a DSTATCOM is used as a FACTS device wh ich can compensate reactive power. D-STATCOM is three phase voltage source converter used to compensate voltage and make the system stable by absorbing and generating reactive power. Here simulin k model and control system is designed in MATLA B simu lin k environ ment. Here modeling of the D-STATCOM is also given.

This paper presents special features of shipboard electrical power distribution systems, and explains simulation tools which we can use to model the systems. We also regard the attention on new methods about shipboard power distribution systems. In this study, EMTP-ATP and Matlab-Simulink are considered as simulation tools. The fault simulations are performed on a simple electrical system and the obtained results are given.

This paper presents an overview analysis and a discussion of field experience with different drive configurations used in shovel applications. The analysis includes different drive topologies, shovel duty cycles for a typical truck pass loading, and energy regeneration capabilities. Special attention is given to the interaction between the high power shovel drives and the grid: harmonics injection, reactive power requirements, and voltage regulation. This paper presents operational experiences obtained in copper mine industries. The main characteristics of the newest shovels with active front end (AFE) at the line side are also included. Finally, a critical evaluation of the different topologies is presented, showing that the shovel drive operation strongly affects the behavior of the power distribution system and that the introduction of the AFE technology produces an important performance improvement.

The “smart grid” refers to various efforts to modernize the power grid through the application of alternate sources of energy and intelligent devices. The present national interest in smart grid applications has generated many questions concerning the role of distribution engineering in the future. What features do utility engineers need in distribution system analysis tools to support the future smart grid? This paper will discuss some relevant Electric Power Research Institute research in this area that focuses on selected issues related to smart grid analysis relevant to rural utilities. The essential characteristics of distribution system analysis tools to support analysis of these issues are discussed.

Acea Distribuzione è una delle utility più importanti a livello nazionale nella distribuzione di elettricità (seconda per numero di utenze connesse); gestisce il servizio di distribuzione dell'energia elettrica ad alta, media e bassa tensione nei Comuni di Roma e Formello, servendo 2,7 milioni di abitanti, con un totale di 70 Cabine Primarie e 13.000 cabine MT/BT. L'introduzione del concetto di Smart Grid solleva l'assunzione che la produzione di energia sia una prerogativa esclusiva delle centrali in alta tensione e che i flussi energetici sulle reti di distribuzione possano essere considerati unidirezionali (dal nodo di scambio in alta tensione verso i nodi passivi delle utenze in media e bassa tensione). Ciò impone una nuova forma di gestione del sistema elettrico, in cui "l'intelligenza" (ossia funzioni di controllo e dispacciamento dei flussi energetici) non sia più confinata esclusivamente alla rete di trasmissione, deputata a interconnettere i nodi attivi di produzione ai nodi di scambio con le reti di distribuzione sottese (fino a ieri completamente passivi), ma che coinvolga anche i numerosi ed eterogenei nodi delle reti di distribuzione. ACEA Distribuzione ha implementato la Smart Grid sulla rete di distribuzione della città di Roma seguendo quattro fattori di innovazione:

For smart metering systems (SMSs), this study presents a novel architecture, which allows simple, secure and fast integration of SMSs with other software products. Proposed architecture that combines better features of two models [Common Information Model (CIM) and OPC's Unified Architecture (UA)] has proven in practice as a good basis for a commercial Meter Data Management System. In a case study, created using data from a pilot project, 7 experiments determined memory usage of OPC UA and CIM servers, duration of exporting data out of CIM and importing them to OPC UA, and size of XML export file.

Power lines were originally devised to transmit electric power from a small number of sources (the generators) to a large number of sinks (the consumers) in the frequency range of 50-60 Hz. Initially, the first data transmissions over power lines were primarily done only to protect sections of the power distribution system in case of faults. (In fact, power line protection remains one of the primary functions of power line communications.) In such an event, the fast exchange of information is necessary between power plants, substations 4

This paper presents special features of shipboard electrical power distribution systems, and explains simulation tools which we can use to model the systems. We also regard the attention on new methods about shipboard power distribution systems. In this study, EMTP-ATP and Matlab-Simulink are considered as simulation tools. The fault simulations are performed on a simple electrical system and the obtained

In the field of power electronics converters constitute a major portion of studies and practical applications. Converter can be divided in mainly four types. (I) DC-DC (II) DCAC (III) AC-DC (IV) AC-AC. Amongst them DC-DC converter is the only converter that can be used for both harvesting energy and in consumption as well as storage with minimal losses. A DC converter may have a single or multi input and output. A Multi Input Multi Output (MIMO) converter has many advantages over a Single Input Single Output (SISO), Single Input Multi Output (SIMO) and Multi Input Single Output (MISO) converters. A MIMO converter is allowing for users to have input from various sources and thus utilizing them in different types of loads. Typically such converter helps in integrating many sources which directly generate DC power. This research is the building block to solve the problem of load diversity in the DC system.

This paper presents a novel tool based on Microsoft Excel for analyzing radial distribution systems. New algorithms are developed to draw the network diagrams graphically within the spreadsheet, once the input data is available. A 9-bus radial distribution system is considered for demonstrating the features of the developed tool. Computations and results are verified with an existing benchmarked tool. Network loading analysis is carried out on the sample 9-bus system and results were provided to demonstrate the effectiveness and usefulness of this tool

In a practical power system, automating all the substations is neither affordable nor economically justifiable. On the other hand, the trend for electric power subsidies elimination in some regions, such as Iran, aggravates this situation. To enhance the cost effectiveness of distribution automation system, this paper proposes a novel applicable qualitative-quantitative method using analytical hierarchical process (AHP) to find the optimum placement of remote terminal units (RTU). Entire attempt is to contribute all the crucial technical and practical parameters related to this problem in order to find the most reliable solution. Optimum number of RTUs is determined using the concepts of reliability cost/worth taking into account the total cost of customer interruption and investment cost of RTUs. The effectiveness of the proposed technique is validated on a real distribution feeder of Iran's power grid.

In this paper a short-circuit computation (SCC) procedure for large-scale distribution systems with high penetration of distributed generators based on contemporary technologies is proposed. The procedure is suitable for real-time calculations. Modeling of modern distributed generators differs from the modeling of traditional synchronous and induction generators. Hence, SCC procedures found on the presumption of distribution systems with only traditional generators are not suitable in nowadays systems. In the work presented in this paper, for computation of the state of the system with short-circuit, the improved backward/forward sweep (IBFS) procedure is used. Computation results show that the IBFS procedure is much more robust than previous SCC procedures, as it takes into account all distribution system elements, including modern distributed generators.

This paper summarizes the results from a number of different voltage sag investigations. These investigations involve characterizing the voltage sag performance at a customer facility and evaluating equipment sensitivity to different voltage sag magnitudes and durations. Possible solutions to voltage sag sensitivity problems are also described.

Improved and controlled power quality is one of the essential and fundamental need in any power driven industry for optimum utilization of resources. However critical problems in power quality have been recognized such as sags, swells, harmonic distortions and other interruptions. Out of these sags and swells are predominantly found and have severe impact on the electrical devices or electrical machines and therefore needs to be compensated at an earliest to ensure any mal-operation or failure. To crack these problems custom power devices are used like unified power-quality conditioner (UPQC), distribution-STATCOM (DSTATCOM) and dynamic voltage restorer (DVR). The DVR is a one of the custom power device used for the compensation of voltage sag and swell with an advantage of active/reactive power control. A major volume of literature reported in past several years on different configurations of DVR and different control technique used in it. In context of this a detailed review on DVR has been presented with different possible power circuit topologies and control techniques available to reconcile these power quality issues. This review article will contribute in better selection of control strategy and power circuit for optimum performance of DVR for a particular requirement. Also it presents a very helpful investigation for the researcher in this field.

This article gives the complete information about the Reactive Power compensation given to the distribution system for reducing the Power Losses. In this article, a case study of MPPKVVCL, Jabalpur, India substation of 8MVA at 33/.4 kV data is taken with shunt capacitor bank and without shunt capacitor bank at peak hours is consider. It is seen from load curve that with the switch in of shunt capacitor bank, current of about
10- 12 Ampere is dropped in 11 kV line. This drop of current reduces the burden on the devices of the 11 kV feeder. Also current saved is used for other customers for providing Electrical Power. Further MATLAB simulation is done to show the current drop in 11 kV feeder line with the inclusion of shunt capacitor bank. Also, Annuity is used for Economic analysis for understanding the lifecycle cost saving with the inclusion of shunt capacitor bank is calculated. Nonetheless, this methodology can be used for any configuration knowing the actual saving with the inclusion of shunt capacitor in the distribution system.

The Office of Energy Management of the United States Department of Energy (DOE) has formulated a program for the research and development of technologies and systems for the assessment, operation, and control of electrical power systems when subjected to an electromagnetic pulse (EMP). The DOE EMP program plan is documented in a DOE report entitled Program Plan for Research and Development of Technologies and systems for Electric Power Systems Under the h_uence of Nuclear Electromagnetic Pulses, DOE/NBB-003, May 1983. This report summarizes much of the important results of this research activity for the period 1983 to 1992. The important elements of this work, such as system and component modeling, equipment testing, assessment methodology, etc., are described in the various sections of this report. Each section has its own references pertaining to the particular subject matter being discussed so that it can stand as a self-contained unit. At the end of the report, in Appendix B, a bibliography of ORNL-related publications resulting from this effort are presented.

This work analyzes resistance grounded systems, particularly three standards used in Italian industries: low resistance grounded, medium resistance grounded and high resistance grounded systems are discussed and compared. This comparison is aimed at analyzing the behavior of the three different standards in the presence of the most common fault, that is the line-to-ground fault and the conflicting requirements of service continuity and hardware integrity. The risk-based approach has been used in order to quantify probabilities of the hazardous events identified according to diverse grounding designs whose decision-making factor is assumed to be the distribution network maintenance effectiveness. Protective devices and apparatus availability demonstrate furthermore critical and protection design as well; thus operation in a life cycle approach will turn out to be the validity of the new EN CENELEC 61508 as reference design norm.

Preventive maintenance (PM) for substation with aging equipment was considered in this work. The main objective was to develop PM model to study the impact of PM on cost minimization in a distribution substation. Weibull distribution equation was used to develop the PM cost minimization models which were simulated in MATLAB program to illustrate the impact of PM replacement policy with UST distribution substation as the case study. The total cost minimization was computed with regards to the total failure recorded within the study year. The result shows an inverse relationship i.e. decrease in total cost from 2501.7 to 2500.7and increase in length of the interval from 50000 to 500000. The analysis also revealed that adequate PM replacement policy can minimize the total expected cost which in turn increases the total availability of the electrical infrastructure or equipment. The result suggested that the right scheduling and constant interval replacement policy of PM is important to increase the electrical infrastructure or equipment availability in the substation. It is therefore recommended that regular schedule inspection, testing, and servicing of equipment should be performed in the UST distribution substation.

IEC 61850 was proposed as a standard protocol for communications within the substation. In its current edition, the standard does not cover communications outside the substation, either with the control center or with other substations, for instance for remote protection. However, during the recent years, there has been a general belief that some features of the standard can be efficiently utilized for applications outside the substation as well. With the advent of new monitoring and control technologies the idea of power system automation at the distribution system and feeder level is crossing new boundaries. In such applications, accessing the accurate data is a necessity. With its future-proof object oriented structure, IEC 61850 can provide comprehensive and accurate information models for various components of distribution automation systems. This paper provides some examples on how the standard can be employed for this purpose, and what measures need to be taken to enable it to efficiently respond to some of the emerging technologies in distribution automation systems.

Power electronics based zonal DC power distribution systems are being considered for sea and undersea vehicles. The stability of the DC power electronics based power distribution systems is a significant design consideration because of the potential for negative impedance induced instabilities. In this paper, dynamic properties and control of a buck converter feeding a downstream DC-DC converter are studied. The controller in this system combines an instantaneous current feedback loop using hysteresis with a proportional-integral algorithm to regulate the output voltage of the converter. Based on a large-signal averaged model of the converter, the stability-in-large around the operation point is presented. The complete analysis is carried out considering a buck DC-DC converter operating with a constant power load. Simulations and experimental results are provided to verify the analysis.

Modern power distribution systems often contain multiple power sources integrated within one system. A simple variant may be the common double-ended substation, which can be further complicated by an additional emergency or alternate sources. This presents significant complexity to the designer attempting to design a protection system that will not be fooled by circulating neutral currents. The authors describe how the "single processor concept for circuit breaker protection and control" (M. E. Valdes et al., Proc. PCIC, 2003, pp. 267-275) provides ways to address this sensing problem. One such method is described in further detail. Handling of resistance-grounded systems will be the subject of a related paper.

A challenge to expand biogas production by psychrophilic digestion to colder regions lies in the fact that gas production decreases with temperature and becomes insignificant when temperature drops below 15℃. The thesis assess the feasibility of operating a biogas reactor in colder climates of Bhutan by simulating the thermal loss of modified reactor designs. The digestion temperature is set to 35℃, an optimum temperature using cow manure fed on daily basis. The analysis emphases to the regions where the monthly average temperature drops below 12℃. The designed underground fixed dome digester of 5.5 m3 capacity is analyzed by applying the numerical thermal model. First the digester is insulated with 0.4 m thick rice straw which is cheap and locally available material. From the daily biogas yield of 1.44 m3 comprising 60% of methane, the energy content derived is 6.64 kWh/m3. For the uninsulated digester, external heating elements would have to deliver 181.27 kWh/day to compensate the thermal losses. Increasing the insulation thickness to 1 m is insignificant. Secondly, the reactor is placed inside a greenhouse to increase ambient temperature by 10℃. The average heat loss obtained is 22.50 kWh/day. The calculation shows that even with the proposed improvements in reactor design, it is not energetically feasible to operate in the assessed colder region. The alternative method is to increases the hydraulic retention time but this increases the volume of the digester and cost which limits the affordability of the biogas plant by the rural people. Most reasonable method is to decrease the operating temperature between 18℃ and 28℃. Hence, to expand the dissemination of biogas plants in cold regions in Bhutan further improvements in the design and process efficiency and feasibility study of the heating system are necessary.

The paper discusses the topology and control of a unified power quality conditioner (UPQC) that can be used simultaneously in voltage or current control mode in a power distribution system. In the voltage control mode, the UPQC can force the voltage of a distribution bus to be balanced sinusoids. At the same time it can also perform load compensation resulting in the drawing of balanced sinusoidal currents from the distribution system bus in the current control mode. Both these objectives are achieved irrespective of unbalance and harmonic distortions in load currents or source voltages. We shall discuss a suitable UPQC structure that allows the tracking of reference current and voltage generated to meet the objective stated above. The reference generation scheme along with the switching control scheme is presented in detail. Extensive results of digital computer simulation studies are presented to validate the proposed structure and control.

Electric power distribution systems are expected to function at all times, even under fault conditions. However, When they operate under fault conditions, the system operator receives information which makes it very difficult to make decisions on whether to restore a tripped feeder to normal operation. To cope with this uncertainty in decision making, a fault diagnosis method based on fuzzy logic is proposed. The proposed method aims to ease the burden of decision making on the part of the system operator by presenting a fast and accurate fault diagnosis method to classify and identify the type of fault which occurs on an overhead radial power distribution network.

In this paper, an attempt has been made to develop a new algorithm for distribution system planning. The proposed algorithm does not require prior knowledge of candidate substation location and can automatically select location of a substation, the optimal feeder configuration and the optimal sizes of branch conductors while satisfying constraints such as current capacity, voltage drop and heuristic rules. Several algorithms are proposed for distribution systems planning. A generalized algorithm is developed for obtaining the optimal feeder path and the optimal location of substation on minimum loss criterion. Heuristic rules are incorporated in the above algorithm. Another algorithm is for branch conductor optimizations. Modified load flow method is also presented in the paper, which can handle composite load models. The load flow algorithm is used for solving radial distribution networks (RDN) and branch conductor optimization algorithm. The load flow algorithm and branch conductor optimization techniques are used as subroutine in the generalized distribution systems planning algorithm. Through numerical example the validity of proposed method is verified. #

Bangladesh is an energy hunger country. After the liberation war to meet up power crisis was one of the most important challenges for government. Day by day the challenge becomes really harder to harder to meet up power crisis, especially to meet up power crisis in rural area. So government formed Rural Electrification Board (REB) from Bangladesh Power Development Board (BPDB) to fulfill the power demand for village people. This organization is playing a vital role for the village people. After the establishment of REB now all most 50% of the villages are being electrified. The purpose of this paper is to give an overview of REB and at the same time emphasis is given socio economic impact of REB.

In this paper analysis results of a cooperation of the Unified Power Quality Conditioner (UPQC) with the photovoltaic system are presented. The proposed system consists of a series inverter, a shunt inverter, and some photovoltaic arrays connected in the dc link through the Multi-Input Single-Output (MISO) DC-DC converter. A numerical formulation of the proposed control schemes, which are based on the instantaneous power theory, is presented. The proposed system can improve the power quality at the Point of Common Coupling (PCC) on power distribution systems. The performance of the proposed system was analyzed using simulations with Power System Computer Aided Design/ElectroMagnetic Transients DC (PSCAD/EMTDC) analysis program. Index Terms--Distribution System (DG), Multi-Input Single-Output, photovoltaic array, Power Quality, Unified Power Quality Conditioner (UPQC).

operations that need to be studied to identify mitigation measures and ensure seamless integration. The purpose of this paper is to discuss impacts of PV-DG on power distribution systems planning and operations, including those of steady state and dynamic nature, with emphasis on utility-scale PV-DG. This paper also discusses mitigation measures to address these impacts and presents results of analyses conducted on real distribution feeders and other ramifications of their increased use in distribution networks, especially urban ones.

In this paper, a new active interphase reactor for twelve-pulse diode rectifiers is proposed. The proposed system draws near sinusoidal currents from the utility. In this scheme, a low kVA ( 0.03 per unit ) active current source injects a triangular current into an interphase reactor of a twelve-pulse diode rectifier. The modification results in near sinusoidal input current with less than 1% THD. It is further shown that a low kVA, 12-pulse system with an autotransformer arrangement ( kVA rating of 0.18 per unit ) can be implemented with the proposed modification. The resulting system draws clean power from the utility and is suitable for powering larger kVA ac motor drive systems. Detailed analysis of the proposed scheme along with design equations is illustrated. Simulation results verify the concept.

This paper is intended to present a plan for installing a network of electric vehicle charging stations in the city of Rio de Janeiro. It is important to underline the fact that this text results from a research and development project called Planning and Analysis Methodology for the Implementation of Electric Vehicles in Transport Activities in the realm of the Brazilian electric energy regulatory agency, ANEEL, carried out by the distribution power company Light S.E.S.A. in partnership with the Vehicle Propulsion Systems and Electrochemical Sources Laboratory of the Rio de Janeiro State University – UERJ.

The concept of microgrid was first introduced in 2001 as a solution for reliable integration of distributed generation and for harnessing their multiple advantages. Specific control and energy management systems must be designed for the microgrid operation in order to ensure reliable, secure and economical operation; either in grid-connected or stand-alone operating mode. The problem of energy management in microgrids consists of finding the optimal or near optimal unit commitment and dispatch of the available sources and energy storage systems so that certain selected criteria are achieved. In most cases, energy management problem do not satisfy the Bellman's principle of optimality because of the energy storage systems. Consequently, in this paper, an original fast heuristic algorithm for the energy management on stand-alone microgrids, which avoids wastage of the existing renewable potential at each time interval, is presented. A typical test microgrid has been analysed in order to demonstrate the accuracy and the promptness of the proposed algorithm. The obtained cost of energy is low (the quality of the solution is high), the primary adjustment reserve is correspondingly assured by the energy storage system and the execution runtime is very short (a fast algorithm). Furthermore, the proposed algorithm can be used for real-time energy management systems.