Real-life Distribution Network Research Articles

An all-purpose method for optimal pressure sensor placement in water distribution networks based on graph signal analysis

Many researchers have addressed the challenge of optimal pressure sensor placement for different purposes, such as leakage detection, model calibration, state estimation, etc. However, pressure data often need to serve multiple purposes, and a method to optimize sensor locations with versatility for various objectives is still lacking. In this paper, a graph-based optimal sensor placement (GOSP) framework is proposed, which aims to provide a robust and all-purpose approach to identify critical points for pressure monitoring. By analysing the spatial variation frequencies of WDN pressures, the relationship between measurements and the global variation of original pressures is established. On this basis, the D-optimality criterion is adopted to formulate the objective of GOSP, which aims to maximize the information on the spatial distribution of pressures that can be obtained from measurements. The new-proposed objective ensures that the sensor locations are compatible with various application scenarios. The proposed method was applied to a real-life distribution network, and was compared with other optimal sensor placement methods oriented towards burst detection and pipe roughness calibration. Based on comparative studies in different scenarios including unknown pressure estimation, burst detection, and model calibration, the effectiveness and robustness of the proposed method have been proved.

Reliability Enhancement on Distribution System Using Modified Multi-Objective Particle Swarm Optimization Technique

This research paper introduces an innovative approach for optimizing the placement of fault indicators (FIs) within electric distribution systems. The primary focus is on addressing how the presence of existing protection and control devices affects the time it takes to restore service to customers in the event of a fault. Unlike conventional FI placement methods, this extended approach considers the uncertainties associated with automatic switching and introduces a novel technical objective function known as the Customers' Average Restoration Time Index (CARTI). To tackle the complex task of multi-objective optimization, a solution approach has been devised, with the goal of simultaneously minimizing both economic and technical objectives. This methodology harnesses a Multi-Objective Particle Swarm Optimization (MOPSO) algorithm and incorporates a Modified Particle Swarm Optimization technique to select the most suitable solution from the set of Pareto optimal solutions generated. The proposed method's effectiveness is demonstrated through its application in two scenarios: firstly, in the context of bus number four within the Roy Billinton test system (RBTS4), and secondly, in a practical real-life distribution network. The study assesses technical objectives, specifically the System Average Interruption Duration Index (SAIDI) and CARTI, providing insights into the method's practical utility and its capacity to enhance FI placement for improved distribution system performance.

An analysis of optimal power flow based formulations regarding DSO-TSO flexibility provision

This paper establishes an optimal power flow based framework for quantifying the amount and assessing the ability of DSO to enable the provision of flexibility service to the TSO. Within this framework, a comparison of three different formulations is conducted on several real life distribution networks and IEEE test cases considering computational effort and quality of solution as metrics. By reformulating the branch flow variant of the original problem, a convex approximation approach is established and assessed with regards to exactness and suboptimality of the solution. Based on the results of smaller test cases we develop a method that is able to efficiently solve the problem for large test case instances. The results indicate significant advantages of reformulations over the classical approach on smaller test cases as well as its usefulness when solving more demanding test cases.

Multi-outlet storage tanks to improve water distribution networks in India

ABSTRACT In developing countries, intermittent water supply (IWS) regimes have become a usual mode for operating the water supply systems. The reasons and adverse impacts (inequitable supply, deterioration of pipeline and so on) of the IWS regime are well documented in the literature; however, limited work is available on solutions to improve the IWS regime. Here, we propose the application of multi-outlet storage tanks to overcome the issues in the IWS regime by considering field conditions in India. Two real-life water distribution networks (WDNs) from India were considered as case studies. The distribution networks were optimized followed by hydraulic simulation on various water demand situations to compare the residual pressure in single outlet and multi-outlet storage tank scenarios. The results are encouraging in terms of residual pressures and economy for the multi-outlet storage tank scenario. Additionally, operational benefits of a multi-outlet storage tank make it an ideal low-cost intervention for improving WDNs in India.

A hybrid method for recloser and sectionalizer placement in distribution networks considering protection coordination, fault type and equipment malfunction

An effective way to improve distribution system reliability is to place switches and protective equipment in the optimal location. Commonly, in the placement problem, the use of equipment in the designated location is assumed to be possible. But in practice, to establish protection coordination between the equipment, it is necessary to remove or relocate some of the equipment. This paper aims to increase distribution companies' profits and reduce customer interruption costs through a feasible solution. A new hybrid method for equipment placement has been proposed that simultaneously solves the protection coordination problem. While determining the optimal number and location of reclosers and sectionalizers, the proposed method ensures protection coordination between equipment (new and existing devices). Furthermore, to achieve a more realistic and accurate model, factors such as equipment malfunction, fault types (transient and permanent), and the relationship between these faults have been carefully considered to formulate the proposed method. In this method, to solve the optimization problems related to equipment placement and protection coordination, genetic algorithm, and linear programming in MATLAB software have been used, respectively. A real-life distribution network has been utilized to evaluate the proposed method, and the results show the capability and robustness of this method.

Development of GB distribution networks with low carbon technologies and smart solutions: Methodology

This and the companion paper present key methodological and modelling aspects, as well as key findings and conclusions from the large-scale technical study into long-term development of future electricity distribution networks in Great Britain (GB) undertaken on behalf of all distribution utilities in GB. The objective is to apply traditional and smart solutions for development of diverse distribution networks with increased penetration of low carbon technologies (LCTs) and to assess their impact on the entire GB transmission system. This paper presents the applied methodological framework through system planning methods and principles, key features of the whole suite of undertaken steady-state and dynamic studies, and describes traditional and smart solutions for network development. A brief description of forecast energy scenarios and projections of LCT uptakes are then given in the companion paper. Results of the considered studies are presented for four large-scale real-life distribution networks covering all voltage levels and the integrated GB transmission-distribution system. These results are the basis for generalized conclusions, which give the answers to the key issues raised by the GB industry at the project initiation.

Simultaneous Placement of Fault Indicator and Sectionalizing Switch in Distribution Networks

Automation systems provide substantial improvement in service reliability through speeding up fault management procedure. However, this is at expense of high investments whose justification needs thorough cost/worth analyses. This paper introduces a mathematical model to optimally place automation system devices within distribution networks. The model establishes a trade-off between service reliability improvements and the relevant costs. Among different automation system devices, fault indicators and remote controlled switches are considered here. Also, the impact of manual switches is regarded since their number and location significantly affect the solution of the placement problem. The proposed model is developed in the mixed integer programming format which can be effectively solved via available solvers. The effectiveness of the proposed model is demonstrated through a test system and a real-life distribution network. The obtained results indicate the great performance of the model in enhancing service reliability as well as reducing system costs.

Optimal Placement of Protective and Controlling Devices in Electric Power Distribution Systems: A MIP Model

This paper presents a mathematical model for simultaneous deployment of protective devices (PDs) and controlling devices (CDs) in distribution networks. The PDs include fuses and reclosers and the CDs are remote controlled switches (RCSs) and manual switches (MSs). The model is to minimize equipment costs as well as sustained and momentary interruption costs. It considers the coordination of fuses and reclosers during temporary faults involving fuse saving and fuse blowing schemes. The model is in mixed integer programming (MIP) fashion which can be effectively solved with available solvers. The performance of the proposed model is verified through applying it to Bus 4 of Roy Billinton test system and a real-life distribution network. The results reveal the effectiveness of the model in reducing system costs as well as in improving reliability level.

An Assessment Procedure of Distribution Network Reliability Considering Photovoltaic Power Integration

As photovoltaic (PV) generation has been one of the major renewable energy sources around the world, its PV capacity has also increased. When the large-scale PV systems are integrated into the distribution network, the complexity of the assessment process of the distribution network reliability will increase hazardously. In order to accurately assess this reliability in the distribution network combined with the PV generation, a reliability assessment procedure is proposed. In order to accurately evaluate the impact of the failure of conventional power equipment on reliability, the time-varying failure rate of conventional power equipment is modeled, taking into account the aging period. Then, in order to accurately evaluate the reliability improvement with PV systems integration, the new procedure is proposed highlighting the following contributions: 1) five new indices are added. 2) PV output is modeled so that not only the radiation intensity but also the failure and degradation of PV modules are represented. 3) time-varying islanding operation is considered and integrated. A case study using real-life distribution network topology and data in China is applied to verify that the newly proposed reliability indices display more sensitivity, and the proposed procedure significantly improves the accuracy of the reliability assessment.

Identyfikacja i diagnoza błędów w elektroenergetycznej sieci rozdzielczej z wykorzystaniem rozmytego systemu eksperckiego

In this paper, a fuzzy expert off-line system has been developed for fault diagnosis in the distribution network based on the structural and functional operation of the relay and circuit breakers. Functional operations (correct operation, false operation and failure to operate) of the relays and circuit breakers are described by fuzzy logic. Input data for the proposed fuzzy expert fault diagnosis system (FDS) are status and time stamps of the alarms, associated with relays and circuit breakers. The diagnostic system from a huge number of alarms sets, logically organizes and quantifies the diagnosis. FDS can diagnose correct operation, false operation and failure to operate of the relays and circuit breakers. Also, it can identify and quantify fault location based on the Hamacher’s operator of a fuzzy union. The additional contribution of this paper is in modeling unknown information using linear fuzzy membership function. Statuses of certain components may be unknown due to telemetry failures or are simply unavailable to the operator and proposed FDS can make diagnosis in such a situation. Developed fuzzy expert FDS is tested on the two examples of faults in real life distribution network

Deployment of Fault Indicator in Distribution Networks: A MIP-Based Approach

Fault indicator (FI) plays a crucial rule in enhancing service reliability in distribution systems. This device brings substantial benefits for fault management procedure by speeding up fault location procedure. This paper intends to develop a new optimization model to optimally deploy FI in distribution systems. The proposed model aims to consider a tradeoff between the total customer interruption cost and FI relevant costs, including capital investment, installation, and maintenance costs. As the main contribution of this paper, the problem is formulated in mixed integer programming, which guarantees global optimum solution achieved in an effective runtime. Moreover, the model takes advantages of taking pragmatic fault location procedure into account, which results in more reliable solutions. The effectiveness of the proposed method is scrutinized through various case studies and sensitivity analyses of a test system. In addition, the applicability of the model in practice is appraised by applying it on a real-life distribution network. The resultant outcomes demonstrate the integrity of the proposed model.

Combination of linear power flow tools for voltages and power estimation on MV networks

European grid codes define new network management rules. To answer these decrees, it is important to estimate accurately the voltages and powers inside distribution networks. The intermittent nature of renewable sources leads to consider stochastic variables in power flow algorithms. A review of power flow methods and their ability to comply with these requirements is done, which shows that computationally demanding non-linear methods have to be discarded when dealing with stochastic data and considering limited calculation time. A combination of linear methods is proposed, for which average errors in power and voltage are quite low, when applied to a real-life distribution network. The validity domain of the method is also presented.

Incipient fault location formulation: A time-domain system model and parameter estimation approach

Power systems faults are unavoidable events which affect distribution networks reliability. The fault process in underground cables is gradual and characterized by a series of sub-cycle incipient faults associated with an arc voltage. These events often are unnoticed and eventually result in permanent faults. This paper presents an incipient fault location formulation for distribution networks with underground cables. Presented formulation is composed by a time-domain system model and parameter estimation strategy. System model derivation considers distribution networks inherent features as unbalanced operation and underground distribution cables capacitive effect. Further, incipient fault characteristics as fault arc voltage are considered. The proposed system model is an overdetermined linear system of equations in which the fault location is estimated through a parameter estimation approach. Parameter estimation is made through a Non-Negative Weighted Least Square Estimator (NNWLSE). Smoothing and curve-fitting procedures are applied to input data aiming to decrease the noise effect. A load current compensation strategy is proposed to reduce its effect in the fault current estimation and a back substitution method is proposed for estimation refinement. Validation is performed using real-life distribution network with underground cable data simulated on ATP/EMTP. Test results are encouraging and demonstrate the method’s potential for real life applications. An average error of 1.95% is obtained when compared with 6.48% derived using the state-of-art.

Durability of the non-dezincification resistant CuZn40Pb2 brass in Scandinavian waters

Abstract Typically water quality in Scandinavia has low alkalinity and hardness, and is consequently corrosive to the metallic materials. During the last years brass materials used in drinking water systems have been under discussion because of the amount of the lead content and relevant migration into the drinking water. In Scandinavia the requirement for the use of dezincification resistant brass in drinking water installations is widely utilized and hence, CuZn36Pb2As (CW602N) brass alloy is the type of brass that is mostly installed. In this study, the use of non-dezincification resistant brass alloy CuZn40Pb2 (CW617N) in drinking water systems in Rauma, Finland is examined using real-life distribution network built in the office building Technology Center Sytytin. This brass alloy is accepted to use in fittings or ancillaries in contact with drinking water for example in Germany and in the Netherlands. The acceptance is based on metal leaching data from a long-term rig test (EN 15664-1), showing that the release of lead and other harmful metals is below the parametric values given in the EU's Drinking Water Directive. In this study the brass couplings manufactured from CuZn40Pb2 brass possess dezincification after five years of use in drinking water systems delivering water from Rauma water work. The main reason for the dezincification type of corrosion lies in the high sulfate and chloride concentrations as well as in low alkalinity. In this case the high concentrations of sulfate are mainly responsible of the dezincification of brass couplings. Typically, due to the aggressiveness of the water and consequent general corrosion from all brass materials, the drinking water quality is deteriorated by high dissolved concentrations of lead, copper and zinc. It is evident that CuZn40Pb2 brass cannot be used and demand for the use of dezincification resistant brass in water systems is extremely important in order to avoid expensive failures and problems caused by leakages.

Novel Multi-Stage Stochastic DG Investment Planning with Recourse

This paper presents a novel multi-stage stochastic distributed generation investment planning model for making investment decisions under uncertainty. The problem, formulated from a coordinated system planning viewpoint, simultaneously minimizes the net present value of costs rated to losses, emission, operation, and maintenance, as well as the cost of unserved energy. The formulation is anchored on a two-period planning horizon, each having multiple stages. The first period is a short-term horizon in which robust decisions are pursued in the face of uncertainty; whereas, the second one spans over a medium to long-term horizon involving exploratory and/or flexible investment decisions. The operational variability and uncertainty introduced by intermittent generation sources, electricity demand, emission prices, demand growth, and others are accounted for via probabilistic and stochastic methods, respectively. Metrics such as cost of ignoring uncertainty and value of perfect information are used to clearly demonstrate the benefits of the proposed stochastic model. A real-life distribution network system is used as a case study and the results show the effectiveness of the proposed model.

The optimal number, type and location of devices in automation of electrical distribution networks

This paper presents the mixed integer linear programming based model for determining optimal number, type and location of remotely controlled and supervised devices in distribution networks in the presence of distributed generators. The proposed model takes into consideration a number of different devices simultaneously (remotely controlled circuit breakers/reclosers, sectionalizing switches, remotely supervised and local fault passage indicators) along with the following: expected outage cost to consumers and producers due to momentary and long-term interruptions, automated device expenses (capital investment, installation, and annual operation and maintenance costs), number and expenses of crews involved in the isolation and restoration process. Furthermore, the other possible benefits of each of automated device are also taken into account (e.g., benefits due to decreasing the cost of switching operations in normal conditions). The obtained numerical results emphasize the importance of consideration of different types of automation devices simultaneously. They also show that the proposed approach have a potential to improve the process of determining of the best automation strategy in real life distribution networks.

Fault Indicator Deployment in Distribution Systems Considering Available Control and Protection Devices: A Multi-Objective Formulation Approach

This paper introduces a multi-objective fault indicator (FI) placement method in electric distribution systems. The prevalent FI placement problem formulation is extended by considering effects of existing protection and control devices on customers' restoration time. Moreover, the customers' average restoration time index (CARTI) is proposed, as a new technical objective function with respect to uncertainties of automatic switching. Furthermore, a multi-objective solution approach is developed to simultaneously minimize indispensable economic and technical objectives. The resultant optimization problem is solved through a multi-objective particle swarm optimization (MOPSO) based algorithm, accompanied by a fuzzy decision making method to select the best result among the obtained Pareto optimal set of solutions. Assuming SAIDI and CARTI as technical objectives, the proposed method is applied to bus number four of the Roy Billinton test system (RBTS4), as well as a real-life distribution network with about 5500 customers, followed by a discussion on results.

A Practical Method for Extraction of High-Frequency Parameters of Distribution Cables

Cable parameter extraction is needed for many practical purposes. The main motivation for this research came from a need to extract high-frequency properties of cables used for indoor electricity distribution because they can be utilized for transmission of communication signals, too, by means of the power-line carrier (PLC) technology. These cables have relatively high specific losses, so that indoor broadband PLC applications can use frequencies up to some 30 MHz. In this paper, cable features in the frequency range from 5 to 30 MHz, belonging to the high-frequency band, were studied. The purpose of this paper is to describe a practical method by which the cable parameters in the mentioned indicated frequency range can be extracted rather accurately from measured complex reflection coefficients at a cable end when the other end is terminated by precise open and short terminations, using very simple equipment. The parameters extracted in this way can be used for very precise modeling of real-life multiterminal distribution networks.

Three–Phase Time–Domain Simulation of Very Large Distribution Networks

This paper presents a detailed three-phase analysis of very large real-life distribution networks using the Electromagnetic Transients Program (EMTP). All main network elements, including relay protection devices, are accurately modeled considering their control sequences. Model validation is achieved with steady-state and transient simulations. The time-domain results are compared with field-validated load-flow simulations for several loading conditions including first and second contingencies. Simulations of fault conditions are also matched against known results at different locations around the network. Moreover, time-domain simulations of recorded transient events show very good agreement. Different transient scenarios are investigated. The new program can be used for the assessment of symmetrical as well as unsymmetrical faults, for studies of different switching scenarios, penetration of distributed generation, and smart grid technologies.

Load reallocation based algorithm for state estimation in distribution networks with distributed generators

In this paper is proposed a novel branch flow and weighted least square (WLS) based algorithm for state estimation in three phase distribution networks with distributed generation (DG) units. The basic formulation is simplified by the use of radial property of distribution network and later will be extended to meshed networks. Unmonitored (or partially monitored) loads are initially estimated from normalized daily load profiles (NDLPs) with lower weights (treated as the pseudo measurements). Also, the different types of monitored, partially monitored, or unmonitored DG units are included in state estimation. Their initial power outputs are calculated on the basis of external inputs, such as wind, sun and water inflow forecasts etc. (depending on DG unit type) or by normalized daily generation profiles (NDGPs) obtained from historical generation data. The pseudo measurements obtained by Initial Load/Generation Allocation are re-adjusted additionally by Optimal Load/Generation Reallocation procedure to fit real-time measurements inside WLS-based state estimation. The results and practical aspects of the proposed methodology are demonstrated on two real-life distribution networks.