Sample Distribution System Research Articles

A Method for Fault Section Identification of Distribution Networks Based on Validation of Fault Indicators Using Artificial Neural Network

A fault section in Korean distribution networks is generally determined as a section between a switch with a fault indicator (FI) and a switch without an FI. However, the existing method cannot be applied to distribution networks with distributed generations (DGs) due to false FIs that are generated by fault currents flowing from the load side of a fault location. To identify the false FIs and make the existing method applicable, this paper proposes a method to determine the fault section by utilizing an artificial neural network (ANN) model for validating FIs, which is difficult to determine using mathematical equations. The proposed ANN model is built by training the relationship between the measured A, B, C, and N phase fault currents acquired by numerous simulations on a sample distribution system, and guarantees 100% FI validations for the test data. The proposed method can accurately distinguish genuine and false Fis by utilizing the ability of the ANN model, thereby enabling the conventional FI-based method to be applied to DG-connected distribution networks without any changes to the equipment and communication infrastructure. To verify the performance of the proposed method, various case studies considering real fault conditions are conducted under a Korean distribution network using MATLAB.

Hardware-in-the-Loop Testing for Protective Relays Using Real Time Digital Simulator (RTDS)

With the increasing size and complexity of power systems, it is crucial to have an effective protection system in place to ensure its reliability. One of the important components of the protection system are relays. It is important for a relay to operate dependably and securely so that any fault can be cleared in time to minimize damages to the power network. However, it is important to test a relay in a realistic environment before commissioning it to the network. Testing a relay in the actual network can be expensive with limited fault scenarios. Hence, Hardware-in-the-Loop (HIL) testing is an efficient method to perform closed-loop testing of a relay since numerous fault cases can be simulated to provide a realistic operating environment for the relay under test. This paper sheds light on the HIL testing done for protective relays using a sample distribution system using RTDS. Two SEL-351 relays have been used in this experiment, and proper settings for the relays are calculated for coordination. The paper also describes the procedure of configuring the relay and other RTDS components crucial for interfacing of the relay with RTDS. After test setup, a pre-fault, fault, and post-fault analysis was done for the system. The results obtained from these analyses are cross-checked with the event history of the two SEL-351 relays, obtained with AcSELerator Quickset software. This paper provides thorough information for researchers to replicate the presented study or to develop new HIL experiments. It can also help in developing a fundamental understanding of the HIL testing setup that can be further applied to a more complex power system.

A budget allocation and programming-based RCM approach to improve the reliability of power distribution networks

Reliability-centered maintenance (RCM) has recently emerged as a powerful tool to reasonably cut the operation and maintenance cost of power destruction systems, whilst meeting both power quality and reliability requirements. This study introduces a new RMC approach that allocates maintenance budgets based on component criticality and importance. A new diagnostic importance factor, implemented based on the criticality and importance of each component, is introduced as a new index for prioritizing components for maintenance activities and budget allocation. The process of budget allocation is carried out without using any optimization method and just by multiplying the maintenance budget by this newly designed factor. A multi-attribute decision-making technique (MAXIMAX) is considered to find the appropriate weighting coefficient of failure causes to reduce the effect of human dependency in the modeling failure rate of each component. Based on the priority and amount of budget allocated, a reliability-centered maintenance program for the sample distribution system is designed and implemented. The proposed RMC framework was implemented to a part of a distribution network in Iran to highlight its effectiveness and practicality. The obtained results showed an improvement in reliability indexes, which in turn confirms that prioritizing component criticality in budget allocation and maintenance programming enables reaching the reliability goals. Improvement in reliability indexes leads to maintenance cost reduction in future time intervals and efficient management of limited resources. A further comparison analysis with other approaches have shown that the proposed framework outperforms these methods in terms of speed, accuracy and budget allocation.

The Raman Laser Spectrometer: A performance study using ExoMars representative crushed samples

AbstractThe Raman Laser Spectrometer (RLS) is one of three key analytical instruments incorporated within the body of the ExoMars 2022 rover. The rover will collect samples from different sites on the Oxia Planum plain, using a drill capable of penetrating the near subsurface and rocky outcrops to a depth of 2 m. Samples are passed to the Analytical Laboratory Drawer (ALD) in the heart of the rover vehicle, where the Sample Preparation and Distribution System (SPDS) processes and transports the crushed material into a refillable container (RC), which is then presented to the analytical instruments for exobiology and geological investigation. The final sample grain distribution of the powder sample following the crushing and flattening processes is a critical aspect of the RLS instrument that has a direct impact on its overall performance, related to its mineral identification and operational capabilities. This paper provides a comparative overview of the performance of a set of Raman instruments, the RLS micro‐Raman Laboratory Equipment, the RLS ExoMars Simulator, and the RLS Engineering and Qualification Model (EQM) using Martian representative crushed samples, along with an evaluation of instrument performance as a function of the operational scenario. The results from the work performed by the RLS team confirm the capability of the RLS instrument performances, by acquiring good‐quality spectra from crushed samples provided by the SPDS, whose science return can be further optimized when improving the RLS instrument operation sequence.

Assessment of Voltage Imbalance Improvement and Power Loss Reduction in Residential Distribution Systems in Taiwan

In this study, the non-dominated sorting genetic algorithm II (NSGA-II) is used to optimize the annual phase arrangement of distribution transformers connected to primary feeders to improve three-phase imbalance and reduce power loss. Based on the data of advanced metering infrastructure (AMI), a quasi-real-time ZIP load model and typical sample distribution systems in Taiwan are constructed. The equivalent circuit models and solution algorithms for typical distribution systems in Taiwan are built using the commercial software package MATLAB. A series of simulations, analyses, comparisons, and explorations is executed. Finally, the quantitative evaluation results for improving the voltage imbalance and reducing the power loss are summarized. For the series of studies, the percentage reductions in (1) total power imbalance TSI, (2) total line loss TLL, (3) average voltage drop AVD, (4) total voltage imbalance factors for zero/negative sequences Td0/Td2, and (5) neutral current of the main transformer ILCO are up to 45.48%, 4.06%, 16.61%, 63.99%, 21.33%, and 88.01%, respectively. The results obtained in this study can be applied for energy saving and can aid the authorities to implement sustainable development policies in Taiwan.

A distributed data‐driven modelling framework for power flow estimation in power distribution systems

The power distribution system has increasing importance and complexity as a result of the exponential growth in the adoption of smart grid technologies. The ability to model the power distribution system is critical to ensure a smooth transition to a sustainable power system. This study presents a distributed data-driven framework based on Cellular Computational Networks (CCN) for power distribution system modelling where the CCN framework facilitates for system decomposition. The learning in CCN is distributed and asynchronous, thus adaptive models can be developed. The computational engine of the CCN cells is based on data-driven, physics-driven, or a hybrid approach. The CCN-based distribution system modelling secures the privacy and security of the sensitive utility information, thus allowing third-party application providers access to system models and behaviours. The application of a CCN-based power flow model is illustrated on a modified IEEE 34 test system. Typical results show the suitability of the new approach in modelling the sample distribution system, as well as its enhanced performance when compared with the centralised modelling approach.

Optimal Policy Synthesis from A Sequence of Goal Sets with An Application to Electric Distribution System Restoration

Motivated by the post-disaster distribution system restoration problem, in this paper, we study the problem of synthesizing the optimal policy for a Markov Decision Process (MDP) from a sequence of goal sets. For each goal set, our aim is to both maximize the probability to reach and minimize the expected time to reach the goal set. The order of the goal sets represents their priority. In particular, our aim is to generate a policy that is optimal with respect to the first goal set, and it is optimal with respect to the second goal set among the policies that are optimal with respect to the first goal set and so on. To synthesize such a policy, we iteratively filter the applicable actions according to the goal sets. We illustrate the developed method over a sample distribution system.

Fast heuristic methods for harmonic minimization using distribution system reconfiguration

Power quality problems are one of the main concerns of both consumers and distribution system operators. The request for higher power quality levels by the sensitive devices, while the indices are negatively affected by the modern loads and distributed generation units, has brought the grid operators to a critical challenge. On the other hand, the distribution system reconfiguration which was primarily proposed for loss minimization is newly regarded as an effective solution for many power quality problems in the grids. Accordingly, new reconfiguration solution strategies for harmonic minimization are proposed by researchers in newly-published papers. In this paper, three different heuristic strategies are proposed for reconfiguration problem which can provide Total Harmonic Distortion (THD) minimization with the lowest calculation burden. The high speed and accuracy provided by these strategies make them applicable in real-world online applications. In order to examine the performance of the proposed methods, they are applied to different sample distribution systems and the results are compared to the solutions provided by meta-heuristic methods. According to the results, the effective harmonic reduction using the proposed methods is provided with much lower calculation burden comparing to the meta-heuristic solution strategies.

Market-Based Customer Reliability Provision in Distribution Systems Based on Game Theory: A Bi-Level Optimization Approach

Traditional reliability enhancement programs in power distribution utilities are focused on averaging the reliability improvement for distribution utility customers. The provision of targeted reliability levels at optimized operation costs for individual distribution utility customers is an important feature of smart distribution systems that have been of interest recently. Consequently, a market-based approach is required for identifying the minimum cost of distribution system operation that considers customers’ reliability preferences (outage costs) in a competitive system operation. In this paper, we introduce a proposed market-based approach for setting customer reliability preferences in a smart distribution system. The proposed approach utilizes the game theory as a powerful tool for modeling conflicts among distribution system participants (customers and the utility). In this model, customers will propose their desired reliability level and the distribution system operator makes reliability allocations among customers which minimize the distribution system operation cost. The interactions among participants are modeled and solved using a bi-level optimization approach to determine the optimal customer reliability level. The model can be utilized for operating the existing network or in the case where a utility would invest on the reliability enhancement. The proposed model can suitably encourage the participation of distribution system customers in reliability enhancement by offering several reliability options via two-way communications between customers and the distribution system utility. The simulation tests on a sample distribution system demonstrate the significant features of the proposed distribution reliability model.

Hybrid State Estimation for Distribution Systems With AMI and SCADA Measurements

The number of real-time supervisory control and data acquisition (SCADA) measurements in power distribution systems is scarce. This limits the reliability of state estimation (SE) results for distribution systems. Therefore, some studies seek to enhance the observability and SE accuracy of distribution systems by incorporating advanced metering infrastructure (AMI) data with the SCADA measurements. However, the hourly updated AMI data may be too coarse to capture system changes, especially in the presence of intermittent renewable energy sources. This issue is addressed by proposing a hybrid SE framework integrating a data-driven estimator and a model-based estimator. To be specific, the data-driven estimator combined with a topology identification method is presented to solve the DSSE problem between AMI scans, and the model-based estimator is employed to ensure robust estimation results against gross errors at a lower time scale. The proposed hybrid SE switches from the data-driven estimator to the model-based estimator once the AMI data is updated. Such a solution allows for capturing system changes at different time scales and improving the real-time and reliability of distribution system state estimation. Simulations are conducted on a sample distribution system to illustrate the characteristics of the proposed hybrid SE.

IMARS Phase 2A Draft Mission Architecture and Science Management Plan for the Return of Samples from Mars Phase 2 Report of the International Mars Architecture for the Return of Samples (iMARS) Working Group.

iMARS Phase 2A Draft Mission Architecture and Science Management Plan for the Return of Samples from Mars Phase 2 Report of the International Mars Architecture for the Return of Samples (iMARS) Working Group.

An Adaptive Protection Scheme for Distribution Systems With DGs Based on Optimized Thevenin Equivalent Parameters Estimation

This paper proposes an adaptive protection scheme for distribution systems with distributed generations (DGs). To mitigate the influences on the protection devices by DGs, an online calculation method of fault current under various system operation conditions is presented. By sampling local available measurements in the buses, a proposed optimized estimation method is used to calculate the Thevenin equivalent circuit parameters of the system dynamically. Moreover, the short-circuit current can be calculated accurately to set the overcurrent relay protection value considering the behavior of DGs during the fault. To ensure the accurate operation of the protection devices, a coordinated protection scheme, including primary and backup protection is presented. Performances of the proposed method and scheme have been verified by simulations on a sample distribution system based on PSCAD/EMTDC. The sensitivity and selectivity of the coordination between primary and backup protection are satisfied under different system operation conditions, fault locations, and types.

Decoupled controller for single‐phase grid connected rooftop PV systems to improve voltage profile in residential distribution systems

Unity power factor injection from single-phase photovoltaics (PVs) located towards the end of a residential feeder leads to voltage rise problems. Also, unbalanced current injection due to variable solar insolation results in voltage unbalancing and makes the situation worst. A decoupled controller for a single-phase PV inverter is proposed to improve the voltage profile of the distribution feeders. The proposed controller consists of the following components: voltage regulator (to control the amount of reactive power injection), outer voltage control loop (slow controller to set the reference for the inner current loop), inner current control loop (to control the PV inverters) and modified second-order generalised integrator (to generate fundamental frequency). A sample distribution systems consisting of several PVs located in all three phases and a three-phase induction motor load is considered. The real-time hardware-in-the-loop simulations are performed to test the efficacy of the proposed controller scheme. Results show the improvement in voltage regulation of different buses.

Study of the formation of duricrusts on the martian surface and their effect on sampling equipment

The Powdered Sample Dosing and Distribution System (PSDDS) of the ExoMars rover will be required to handle and contain samples of Mars regolith for long periods of time. Cementation of the regolith, caused by water and salts in the soil, results in clumpy material and a duricrust layer forming on the surface. It is therefore possible that material residing in the sampling system may cement, and could potentially hinder its operation. There has yet to be an investigation into the formation of duricrusts under simulated Martian conditions, or how this may affect the performance of sample handling mechanisms. Therefore experiments have been performed to create a duricrust and to explore the cementation of Mars analogues, before performing a series of tests on a qualification model of the PSDDS under simulated Martian conditions.It was possible to create a consolidated crust of cemented material several millimetres deep, with the material below remaining powder-like. It was seen that due to the very low permeability of the Montmorillonite component material, diffusion of water through the material was quickly blocked, resulting in a sample with an inhomogeneous water content. Additionally, samples with a water mass content of 10% or higher would cement into a single solid piece. Finally, tests with the PSDDS revealed that samples with a water mass content of just 5% created small clumps with significant internal cohesion, blocking the sample funnels and preventing transportation of the material. These experiments have highlighted that the cementation of regolith in Martian conditions must be taken into consideration in the design of sample handling instruments.

Ranking of feeder sections of distribution systems for maintenance prioritization accounting distributed generations and loads using diagnostic importance factor (DIF)

Abstract This paper presents an algorithm for deciding preferences in maintenance activities for feeder sections of distribution systems. A component importance measure, known as diagnostic importance factor (DIF), has been used for this purpose. A methodology has been developed to compute a newly framed weighted cumulative diagnostic importance factor (WCDIF) for each feeder section which represents quantitatively relative significance for prioritization of maintenance activities. The developed methodology includes the effect of distributed generations (DG) and loads. It has been implemented on two sample distribution systems and ranking lists of feeder sections for maintenance activities have been obtained.

Potential for analysis of carbonaceous matter on Mars using Raman spectroscopy

The ESA/Roscosmos ExoMars rover will be launched in 2018. The primary aim of the mission will be to find evidence of extinct or extant life by extracting samples from the subsurface of Mars. The rover will incorporate a drill that is capable of extracting cores from depths of up to 2m, a Sample Preparation and Distribution System (SPDS) that will crush the core into small grains and a suite of analytical instruments. A key component of the analytical suite will be the Raman Laser Spectrometer (RLS) that will be used to probe the molecular and mineralogical composition of the samples. In this work we consider the capability of the proposed Raman spectrometer to detect reduced carbon (possibly associated with evidence for extinct life) and to identify the level of thermal alteration/maturity. The Raman analysis of 21 natural samples of shale (originating from regions exhibiting different levels of thermal maturity) is described and it is shown that reduced carbon levels as low as 0.08% can be readily detected. It is also demonstrated that the Raman spectra obtained with the instrument can be used to distinguish between samples exhibiting high and low levels of thermal maturity and that reduced carbon can be detected in samples exposed to significant levels of oxidation (as expected on the surface of Mars).

Analysis of the scientific capabilities of the ExoMars Raman Laser Spectrometer instrument

The Raman Laser Spectrometer (RLS) is part of the payload of the 2018 ExoMars rover. The Sample Preparation and Distribution System (SPDS) of the rover will crush samples acquired from down to two meters depth under the Martian surface, and provide them to the RLS instrument in the form of flattened powdered samples. The RLS instrument will acquire a minimum of 20 points on the flattened surface of the samples. To be able to obtain the maximum scientific return from the instrument once on Mars, a simulator of the SPDS system has been built to perform a series of experiments in a representative scenario. The crushing process implies the loss of rock structure and texture and, hence, the geological context of the samples. However, qualitative analysis with the RLS simulator on powdered natural samples and rocks showed that the RLS is capable of detecting carbonaceous material occurring in trace amounts in one of the rock samples (a silicified volcanic sand), more easily than with the same analysis on bulk. Furthermore, it is shown that minor phases in carbonate cements that cannot be detected by Raman in the bulk sample can be detected in the powder, thus allowing the identification of all the carbonate phases present in the cement crust. In order to quantify the detection threshold of the instrument, further analysis on controlled samples were performed. The results with the RLS SPDS simulator showed that the instrument can reach detection thresholds down to 1 % on powdered samples. Furthermore, analysis of controlled mixtures showed that performing a very simple intensity-based statistical analysis of the spectra can provide semi-quantification of the abundance of the mineral species with quite linear calibration curves.

Two-Stage Residential Energy Management Considering Network Operational Constraints

This paper suggests a decentralized optimization of residential demand to minimize the cost to the utility company and customers while maintaining customer satisfaction. As an important feature, distribution system constraints such as equipment capacity, line flow limits, and phase balance constraints are taken into account. Due to the large amount of uncertainty in the residential demand, a two-stage pricing is considered. In the first stage, day-ahead prices as well as residential appliance scheduling are determined through interaction of the utility company and residential customers. Uncertainty of the customer demand is also considered in the day-ahead pricing. In the second stage, on the other hand, prices will be updated based on the actual residential loads. Similar to locational marginal price (LMP) in transmission system, customers on different nodes are charged with different prices. Performance of the approach is shown on a sample distribution system.

Fault Location Based on Artificial Bee Colony Algorithm for Distribution Network with Distributed Generators

The access of distributed generators makes distribution network change into a multi-source network with two-way flowing trend and so accurate fault location is becoming more complicated. This paper proposes a new method which applies an artificial bee colony algorithm (ABC) for fault location of distribution network with distributed generators. To reveal the validity of the ABC algorithm, sample distribution systems are examined with different test cases, which includes single fault, multiple fault, information distortion and loss. The outcomes verify that utilizing artificial bee colony algorithm to solving the fault location problem of distribution network including distributed generators has good fault tolerance and stability. Besides, the algorithm possesses a competitive advantage of simple parameters setting.

Simulation of a large electric distribution system having intensive harmonics in the industrial zone of Konya

In this study, measurements were taken at different points of a sample distribution system in order to analyze the levels of harmonics that appear as a day-to-day increasing problem in electrical distribution systems. According to the measurement values, the dominant harmonics have been determined and an electrical model of the system has been prepared using the SimPowerSystems toolbox from MATLAB and Simulink. The accuracy of the electrical model has been verified by the measurement and simulation values. In addition, the transformer connection types' and impedances' simulations have been presented to understand and solve the harmonic problems in electrical distribution systems. With the help of this study, advanced analysis can be performed in the electrical distribution system for power quality analyses and this study can be a background for similar kinds of simulation studies.