Characteristics Of Distribution System Research Articles

Characteristics of Various Single Wind-Power Distributed Generation Placements for Voltage Drop Improvement in a 22 kV Distribution System

A major challenge in distribution systems is the issue of voltage drop along the distribution line resulting from an increased load capacity connected to the utility. A significant voltage drop can affect the performance of a distribution system and cause quality issues for end users, impacting the system’s long-term sustainability and reliability. Therefore, regulations have been set stating that the voltage level should not be more that 5% higher or lower than the rated voltage. Thus, in this study, we aimed to evaluate the voltage level characteristics of a 22 kV distribution system that replicates the actual distribution system in the Provincial Electricity Authority. A voltage improvement technique based on distributed generation placement was proposed. In addition, the distribution system characteristics with and without distributed generation placement were evaluated under fault conditions. The results indicate that distributed generation placement in the distribution system can improve the voltage level along the distribution line. However, the level of increase in voltage depends on the size of the load, the capacity of the distributed generation, and the location of the distributed generation system on the distribution line. Furthermore, placing a distributed generation system with a minimum capacity at the proposed location can improve the voltage within the utility’s standard level. Thus, the installation of a distributed generation system in the distribution system is beneficial in terms of voltage improvement in the distribution system and provides the power system with a sustainable method to address the issue of voltage drop.

Research on Dynamic and Thermal Effects Based on the Calculation of the Short-Circuit Current in Low-Voltage DC Distribution Systems for Civil Buildings

The verification of short-circuit effects is very important for ensuring the safety of equipment and power systems. Compared with that in alternating current (AC) systems, research on this issue in direct current (DC) systems is scarce, and it is urgently necessary to develop an accurate verification method for applications in DC systems. This research establishes an equivalent model of a pole–pole cable short-circuit according to the characteristics of low-voltage DC distribution systems in civil buildings. Through theoretical analysis and numerical simulation, the development process of a short circuit is summarized, and the methods of verifying dynamic and thermal effects based on the time-domain characteristics of the short-circuit current are specified. By calculating the peak value and Joule integral of the short-circuit current, in comparison with those in the IEC 61660 (1997) standard, this research points out that the method in the IEC 61660 (1997) standard is insufficient. Finally, the short-circuit peak current is greatly affected by the DC-link capacitance, the steady-state current is directly related to the filter inductance of the AC-link; and the verification of the thermal effect requires the calculation of the Joule integral in the transient and steady state.

Identifying key pipe attributes and locations to best determine chlorine decay coefficients within a water distribution system

Abstract Water distribution system (WDS) characteristics can impact drinking water quality. Kinetic reaction coefficients of residual disinfectant associated with bulk water (kb) and pipe wall (kw) during water distribution can lead to water quality degradation. Determining these coefficients can be expensive and time-consuming. The main objective of this study is to determine the most relevant pipe characteristics and locations to best determine chlorine decay coefficients in a WDS. This article aims to evaluate various scenarios of kb and kw values and compare them to measured data in a full-scale WDS. The most accurate scenario is also compared with the lowest-cost scenario to identify the most effective information needed to determine these coefficients, in terms of location within the WDS and pipe characteristics (age, diameter, and material). Results showed that the scenario with the highest kw and kb values corresponds best to the field-measured data. Moreover, determining specific kinetic coefficients was shown to be more accurate for gray cast iron pipes, pipes installed in a period before 1960, and vulnerable zones for residual chlorine decay.

Single-phase grounding line selection method for closed-loop distribution network adapted to medium voltage microgrid access

Aim: The access of the medium-voltage (MV) microgrid changes the radial structure of traditional distribution networks, causing the distribution network to operate in a closed-loop manner. The closed-loop operation complicates the fault characteristics of the distribution network, and the traditional single-phase grounding (SPG) line selection method is no longer applicable. Therefore, it is necessary to propose a new targeted SPG line selection method. Methods: This paper analyzes the network structure of MV microgrids and MV distribution networks and establishes a multi-level closed-loop operation distribution network model with MV microgrid access. Then, the SPG fault characteristics of the closed-loop operation distribution system under the small current grounding mode are analyzed from the perspective of two-level bus nodes. Furthermore, based on the analysis of fault characteristics, a closed-loop operation distribution network line selection method suitable for microgrid access is proposed, and a detailed design is carried out in terms of equipment configuration and communication schemes, forming a relatively complete automatic line selection system. At the same time, the proposed line selection scheme is based on the two-level bus nodes, which can be analogously applied to the multi-level closed-loop operation distribution network. Results: The simulation results show that the proposed line selection scheme can be effectively applied to the closed-loop operation distribution network with MV microgrid access. Conclusion: The traditional SPG line selection method will have misjudgment problems after the MV microgrid is integrated into the distribution network, but the line selection method proposed in this paper has good adaptability.

An approach for voltage drop improvement in 22 kV PEA distribution system based on high voltage capacitor placement

The distribution system has been constantly expanded with rising load demand due to population and economic growth. The result is a distribution line facing a voltage drop issue voltage drop, which results from increasing interconnected load and the distance from the substation. To mitigate this issue, this paper proposed an approach to improve the voltage level on the distribution line using a high-voltage capacitor bank. The system under study is modeled after the Provincial Electricity Authority (PEA) 22-kV distribution line. The placement of the high voltage capacitor bank will be based on the 2/3 rule technique. The PSCAD/EMTDC has been used to simulate the characteristics of the case study distribution system and evaluate the performance of the proposed technique in comparison with the PEA voltage regulation standard. The result has demonstrated the ability to use the proposed high voltage capacitor bank placement technique to improve voltage levels in the distribution system.

Stability and Dynamics of Active Distribution Networks (ADNs) With D-PMU Technology: A Review

Massive integration of converter-interfaced distributed energy resources (CDERs) has resulted in many emerging stability issues and significantly complicated the dynamics of active distribution networks (ADNs). Large quantities of CDER systems with complex structures, time-varying parameters and ‘black-box’ controllers not only make the system modelling nearly an impossible task, but also considerably increase the dimension of dynamic models and thus the computational burden for the model-based stability analysis and control. Distribution-level phasor measurement unit (D-PMU) technology has a superior capability of monitoring, analyzing and controlling the real-time system dynamics. This paper provides a comprehensive overview on the state-of-the-art techniques of dynamics monitoring, analysis and control based on D-PMU technology in ADNs. A special emphasis is placed on the emerging instability incidents induced by CDERs. Although stability monitoring, analysis and control techniques based on PMU technology are well established in the transmission systems, substantial research efforts are required to extend these techniques to deal with the different dynamic characteristics of distribution systems. The application of big-data analytics in analyzing D-PMU data streams becomes prevalent, which can dig more information and thus provide more effective measures for stability analysis and control of ADNs.

Characteristic Evaluation of Wind Power Distributed Generation Sizing in Distribution System

Energy consumption and environmental issues have become major drivers of increasing renewable energy penetration levels. The electricity generated from renewable energy sources is decentralized throughout distributed generation (DG), which is located at the distribution level. However, the presence of DG can change distribution system characteristics and affect protection systems. Thus, this study aims to investigate the impact of DG in term of its sizing and placement on distribution systems under both normal and fault conditions. In addition, the effects on voltage improvement under normal conditions and current under fault conditions are also considered. The case study system in this study was modelled after an actual section of a 22 kV distribution line from the Provincial Electricity Authority of Thailand using PSCAD software. For DG, wind turbine generation was selected as a renewable energy source. The simulation results demonstrated that the presence of DG has a significant impact on both voltage and current characteristics under both normal and fault conditions. These impacts on the distribution system caused by DG can affect the operation of conventional distribution systems, which require further analysis and preventive measures in order to ensure good system reliability.

Data-Enabled Identification of Nonlinear Dynamics of Water Systems using Sparse Regression Technique

The complex, multi-variable, highly nonlinear and strong coupling characteristics of water distribution systems (WDSs) has significantly limited the capability of model-based approaches for control purposes in such systems. With the emerging application of high-resolution metering devices and historical data, model-free identification of WDSs can facilitate the control design without tedious modeling complexities. This paper develops a data-driven framework to facilitate the identification of nonlinear models of WDSs using available data. A quadruple tank system that represents the nonlinear and strong coupling nature of WDSs is considered as the test system and sparse identification of nonlinear dynamics (SINDy) is utilized to identify the nonlinear dynamics from the data. Unlike existing modeling approaches that either heavily rely on knowing the detailed dynamics of the system (model-based) or designs that relay on large historical data and are not interpretable (data-driven approaches), the proposed model-free identification framework is parsimonious, which can accurately capture the dynamics of the quadruple tank process with available measurements suitable for control problems. The effectiveness of the proposed approach is validated using time-domain simulations in MATLAB.

Power Distribution System Characterization With Active Probing: Real-World Testing and Analysis

Power distribution systems are traditionally characterized using passive means such as parameter estimation and topology identification. This work investigates an active way to test and characterize dynamically changing distribution systems. The method actively perturbs local distribution networks with programmable pulses using a Grid Resonance Probe (GRP) and observes the response using a micro-phasor measurement unit ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> PMU). After applying advanced data analytics, the perturbation and response measurements can reveal characteristics of distribution systems, such as feeder parameters and topologies. To validate the proposed approach, three case studies are executed on a real distribution system, including visualization, feeder connection identification, and feeder impedance estimation. Real data processing considerations and sensitivity analysis are also discussed. The proposed testing and analysis approach is expected to provide engineers a new solution to measure, parameterize, and characterize distribution systems.

Overcurrent Relay for Generation Distribution Utilization

Distributed Generation (DG) is the production of electricity from a variety of renewable energy sources that is closer to the customer and load. The addition of distributed generation sources to the distribution networks alters the characteristics of distribution system and has an influence on its protection coordination. Relay protection plays a critical function in protecting a power system from various problems. Relay protection coordination reduces relay operating time and avoids relay failure. As a result, a fault analysis of the distribution network with and without distributed generation installation is required to determine the effects of installing DG at the radial system on overcurrent relay protection. The software programmed ETAP version 19.0 was used to represent an actual distribution system in this research paper. The consequences on the overcurrent protection relay were discovered as a result of the analysis. Simultaneously, the presence of an overcurrent relay following the installation of DG may no longer be dependable. As a result, it is critical to assess the effects of DG installation in order to verify that the protective zone can be properly protected.

Analysis of an unreliable N – policy queue with set-up period under Bernoulli schedule and re-service approach

This research article investigates the stationary N-policy with a set-up time of a single server bulk arrival queueing model rendering two-heterogeneous optional repeated service (THORS) with the factor of unreliability. The server studied here is allowed to take a single vacation after each busy period following Bernoulli Schedule (BS). An extensive analysis of the proposed model is carried out using the Supplementary Variable Technique (SVT) under some suitable transformations. The joint distribution of the server’s state and queue length are obtained under both elapsed and remaining times along with their double transforms. Probability generating function (PGF) of the queue size distribution together with the mean system size of the model are determined for any arbitrary time point and service completion epoch, besides the busy period distribution and various pivotal system characteristics. A suitable linear cost structure of the underlying model is developed, and with the help of a difference operator, a locally optimal N-policy at a lower cost is obtained. Finally, some numerical experiments are carried out in support of the theory.

Optimization of Reclosers Placement in Distribution Networks to Improve Service Quality Indices

The fundamental goal of an electric utility is to provide the power supply in the most reliable and economical way. However, the components of a power distribution system are exposed to faults, or service outages, which in some cases may cause the disconnection of one or more customers of the distribution system. In order to reduce the duration of faults and improve service quality indices in power networks, utilities have installed protection devices, such as reclosers, in appropriate locations in the power distribution networks, due to its ability of coordination with other device and the radial characteristics of distribution system. In addition, the recloser can clear temporary faults and isolate failed feeders without interrupting the service of the whole circuit. This paper presents a methodology for optimization of reclosers placement in distribution networks. A mathematical model of Mixed Integer Nonlinear Programming (MINLP) is used, with the purpose to minimize the SAIDI or SAIFI quality indices. For the model, an objective function is defined, with its respective restrictions to obtain the appropriate locations. This objective function is run in the GAMS software to model and solve optimization problems. The effectiveness of the proposed approach is evaluated on a test system and in a conventional real distribution system.

Examining Impact of Distribution System Characteristics on Transmission Security Assessment of Future Power Systems

The nature and characteristics of distribution systems are changing continuously with the increased penetration of distributed energy resources. With this, the need for examining the transmission and distribution (T&D) interaction while assessing the voltage security has become significant. In much of the analysis and practices reported so far, voltage security assessment studies are performed separately for T&D systems. Thus, a transmission system operator (TSO) is oblivious to the operations and controls taking place at the distribution system (DS) level. Some of the recent studies examine the impact of an active DS on the voltage security assessment of future power systems. However, the effect of various factors like voltage dependency of loads, reactive power capability of renewable energy sources (RES), location of distributed generation units, and network losses on the voltage stability margin (VSM) of transmission system has not been reported comprehensively so far. This paper first theoretically examines the impact of these factors on VSM. Then, to get the more realistic results for VSM, continuation power flow (CPF) is performed in a coordinated fashion including both T&D systems. The simulations show that considering losses, load characteristics dependency on voltage and reactive power limits of RES in a DS for transmission voltage security assessment studies lead to a more rational outcome than when neglected.

A fast-specialized point estimate method for the probabilistic optimal power flow in distribution systems with renewable distributed generation

The increasing presence of renewable distributed generation (DG) units such as photovoltaic and wind power generation is a major challenge for the suitable operation of the electrical distribution systems (EDSs). Uncertainties of renewable DG units and loads, related to the stochastic nature of solar irradiation, wind speed, and consumer behavior, require efficient tools that help the distribution system operator to properly define a control plan of the EDS. Within this framework, the probabilistic optimal power flow (POPF) provides statistical information(e.g. voltage profile, power flows, and power losses) according to the variation of the stochastic variables (e.g. power demand and injection of generation units). Many available POPF methods have been designed for transmission systems and/or are based on Monte Carlo simulation (MCS), which requires a high computational effort. On the other hand, other approaches adopt analytical methods, which are not applied considering the characteristics of distribution systems. This paper proposes a fast-specialized point estimate method for the POPF in EDSs with the presence of renewable DG units, based on a linearization of the Branch Flow equations and Hong’s point estimate method. Due to its convex nature, the advantage of the proposed method is to use well-established linear programming commercial solvers to solve the problem. Numerical results using the IEEE 69-bus and a real EDS demonstrate the efficiency in terms of computational burden and accuracy of the proposed method compared to MCS and Cumulant approaches.

Decentralized Voltage Control in Active Distribution Systems: Features and Open Issues

Voltage control is becoming a key issue in active distribution systems, which are electric distribution networks characterized by a large penetration of DERs. Traditional voltage control devices, as well as the active and reactive powers injected by DERs, can be used as ancillary services to support voltage profiles along the distribution feeders. Due to the peculiar characteristics of active distribution systems, the decentralized control approach presents the most promising technical and economical features. In the paper, the decentralized voltage control structure is hierarchically decomposed into different control levels, characterized by different objectives and time frames. The primary and secondary control levels have been analyzed, always according to a decentralized approach. For each level, the various techniques for solving the voltage control problem that have been proposed in the literature are presented, and their main features compared. The main open issues related to the real time practical implementation of the decentralized architectures at both primary and secondary voltage control levels are investigated, keeping always in mind both technical and economical aspects, which always represent the components of a trade-off solution.

Static Reconfiguration of Unbalanced Distribution Systems with Variable Power using Selective Bat Algorithm

Distribution network reconfiguration (DNR) is one of the most studied and important optimization problems in Electrical Engineering field, being well established throughout the years, as seen in the specialized literature. The majority of studies treats the problem in a conservative way, i.e., considering the systems as balanced with fixed demand. However, the real characteristics of distribution systems may take into consideration the unbalanced nature of loads, as well as the variable demand characteristic according to the type of consumer connected. This comes closer to reflect the real operation of such systems, and thus, studies considering DNR with these aspects are becoming more important in recent years. In this context, the paper here presented proposes modeling unbalanced systems with variable demand using a static reconfiguration (SR). As SR considers the whole studied period to define one single set of switches, it is opposed to a dynamic reconfiguration (DR), which is performed in short periods. Considering the load profiles presented, a comparison is made to discuss the advantages and disadvantages of SR in the expanse of DR in unbalanced systems. To solve the DNR problem, a selective bat algorithm (SBAT) is used, as it presents characteristics from particle swarm optimization (PSO) and harmony search (HS). Tests for SR and DR with variable demand are performed in one balanced system (33 buses) and three unbalanced systems (19, 25 and 123 buses). Results for SR using SBAT are compared with selective PSO and selective HS.

Risk‐averse microgrid cluster switching approach for improving distribution system characteristics considering uncertainties of renewable energy resources

Increasing the world-wide efforts towards low-carbon economy, highlights the role of renewable energy resources (RESs) in power systems. The volatility of RESs, however, is a major challenge for system operators, and there is need to deal with their uncertainty. Regarding this, microgrids (MGs), as the clusters of different RESs and other distributed energy resources, should take the responsibility of dealing with uncertainty. To do so, a risk-averse energy management strategy (RA-EMS) is introduced for distribution systems under the penetration of renewable energy-based MGs. The status of the connecting switches between clusters and their interaction with the distribution system is examined in several cases. In addition to wind turbine and photovoltaic as RESs, the MGs are equipped with electric vehicles, as another environmentally friendly forms of technology, demand response program, and micro turbines. The uncertainty of renewable generation is modelled via information gap decision theory (IGDT) technique. To validate the effectiveness of the proposed model, it is tested on 94 bus actual Portuguese distribution test system. The results show the importance of MG clustering in improving the techno-economic characteristics of the distribution system. Also, it is evident from the results that uncertainty of RESs is a crucial factor in MG clustering.

Mathematical model and topology evaluation of quantum key distribution network.

Due to the intrinsic point-to-point characteristic of quantum key distribution (QKD) systems, it is necessary to study and develop QKD network technology to provide a secure communication service for a large-scale of nodes over a large area. Considering the quality assurance required for such a network and the cost limitations, building an effective mathematical model of a QKD network becomes a critical task. In this paper, a flow-based mathematical model is proposed to describe a QKD network using mathematical concepts and language. In addition, an investigation on QKD network topology evaluation was conducted using a unique and novel QKD network performance indicator, the Information-Theoretic Secure communication bound, and the corresponding linear programming-based calculation algorithm. A large number of simulation results based on the SECOQC network and NSFNET network validate the effectiveness of the proposed model and indicator.

The reliability evaluation research of distribution system considering demand response

In order to evaluate the reliability of distribution system with demand response, this paper established the load peak–valley partition model and demand response model corresponding to every period based on load peak–valley characteristics. Then considering the characteristics of distribution system, the reliability evaluation model considering demand response was established. The example simulation verified that the demand response participated in load reduction strategy could effectively improve the reliability level of the distribution system.

Multi-agent-based Rolling Optimization Method for Restoration Scheduling of Distribution Systems with Distributed Generation

Resilience against major disasters is the most essential characteristic of future electrical distribution systems (EDSs). A multi-agent-based rolling optimization method for EDS restoration scheduling is proposed in this paper. When a blackout occurs, considering the risk of losing the centralized authority due to the failure of the common core communication network, the available agents after disasters or cyber-attacks identify the communication-connected parts (CCPs) in the EDS with distributed communication. A multi-time interval optimization model is formulated and solved by the agents for the restoration scheduling of a CCP. A rolling optimization process for the entire EDS restoration is proposed. During the scheduling/rescheduling in the rolling process, CCPs in EDS are re-identified and the restoration schedules for CCPs are updated. Through decentralized decision-making and rolling optimization, EDS restoration scheduling can automatically start and periodically update itself, providing an effective solution for EDS restoration scheduling in a blackout event. A modified IEEE 123-bus EDS is utilized to demonstrate the effectiveness of the proposed method.