An improved algorithm for reliability evaluation of flow networks

Network reliability evaluation for a stochastic flow network (SFN) can be computed in terms of all lower boundary points (LBPs). Although several algorithms have been presented in the literature as solutions for the LBP problem, the efficiency is always occurring at the present for the large SFN. In this paper, a binding technique generating binding-flow vectors is therefore developed to narrow down the searching range of flows for demand. This technique is able to reduce the loading of the candidate comparison procedure greatly. An algorithm based on this binding technique is proposed to solve the LBP problem. We compare the performance of the proposed algorithm to well-known algorithms in terms of CPU time, through three benchmark networks and a practical case. The experimental results show the functional efficiency of our proposed binding LBP algorithm.

The efficiency of power systems is based mainly on the continuity of the service, avoiding faults that suppose economic losses for utilities and users. It is very important to detect, locate and eliminate the faults of power systems, especially on power transmission lines. This paper presents a new method based on non–linear frequency analysis for online detection and location of the high impedance faults on power transmission lines, which has been one of the most difficult problems in power transmission and distribution systems. The proposed technique is based on the non–linear characteristics of the high impedance faults and severely contaminated insulators on power lines. The non–linear frequency responses related to the signal of power line carrier were used to detect the occurrence of the high impedance fault. The location of the fault and the degraded insulator on the power lines could be determined by detecting the position of the non–linear component in the power transmission system. The effectiveness of the method has been verified through simulation studies. The results demonstrated that the proposed method has the potential to be applied in practice to resolve high impedance fault real time monitoring problem.

In the process of power supply to final consumers, an important amount of energy is lost in the transmission and distribution systems due to technological and non-technological losses. Technical losses represent an economic loss with environmental effects at national level, and its optimization should be performed from an overall national's perspective, regardless of the institutional organization of the sector and ownership of operating electricity utilities. The volume of energy losses in the power transmission and distribution systems is important, as it is generally up to 3 - 13%. The volume of power losses in Romanian power transmission and distribution systems is important, the level being of about double to the average in Europe. The current paper presents the research results of the authors regarding the real time monitoring and analysis systems for power losses, in electrical transmission and distribution systems.Within the research project, it was developed a dedicated system, successfully tested within a 5 years partnership with CNTEE “Transelectrica” - SA, on a transformer of 250/250/80MVA 400/121/20 kV from 400/110 kV Pelicanu Substation and respectively on the 400 kV overhead power line (118 km) Bucuresti Sud - Pelicanu.The tests results showed the importance of evaluation by real-time measurements, compared to the results of evaluations by calculations, of active power losses at power transformers and overhead power lines, respectively. Values several times higher were found for the values of active power losses measured online, in real time, than those determined by calculations.Online measurements have shown that there may be cases when large industrial consumers produce current and voltage harmonics well above the maximum allowable limits specified in the standards. The harmonics are transmitted practically undamped by the windings of the power transformers and on the transmission power lines (in the case of tests, even more than 100 km away from the place of their production).The online measurement of active power losses on the 400 kV overhead power line, 119 km, showed that corona losses are insignificant especially during periods of atmospheric humidity below 85%, and that active losses on power lines are practically resistive losses. The resistive losses on the measured high voltage overhead power lines are much higher than the calculated ones. The difference is determined by the fact that the calculation of active power losses on power lines includes the value of ohmic resistances of conductors evaluated based on line conductor resistivity or possibly based on ohmic resistance measured at a certain moment, and not the real value of the ohmic resistance of the line in real time (which changes over time due to the change in the state of the multitude of joints of the OHL conductor sections).

This paper presents a supervisory control and data acquisition (SCADA) testbed recently built at the University of New Orleans. The testbed consists of models of three industrial physical processes: a gas pipeline, a power transmission and distribution system, and a wastewater treatment plant--these systems are fully-functional and implemented at small-scale. It utilizes real-world industrial equipment such as transformers, programmable logic controllers (PLC), aerators, etc., bringing it closer to modeling real-world SCADA systems. Sensors, actuators, and PLCs are deployed at each physical process system for local control and monitoring, and the PLCs are also connected to a computer running human-machine interface (HMI) software for monitoring the status of the physical processes. The testbed is a useful resource for cybersecurity research, forensic research, and education on different aspects of SCADA systems such as PLC programming, protocol analysis, and demonstration of cyber attacks.

A simple algorithm for reliability evaluation of a stochastic-flow network with node failure

DOE's mission under the Distributed Energy and Electricity Reliability (DEER) Program is to strengthen America's electric energy infrastructure and provide utilities and consumers with a greater array of energy-efficient technology choices for generating, transmitting, distributing, storing, and managing demand for electric power and thermal energy. DOE recognizes that distributed energy technologies can help accomplish this mission. Distributed energy (DE) technologies have received much attention for the potential energy savings and electric power reliability assurances that may be achieved by their widespread adoption. Fueling the attention has been the desire to reduce greenhouse gas emissions and concern about easing power transmission and distribution system capacity limitations and congestion. However, these benefits may come at a cost to the electric utility companies in terms of lost revenue and other potential impacts on the distribution system. It is important to assess the costs and benefits of DE to consumers and distribution system companies. DOE commissioned this study to assess the costs and benefits of DE technologies to consumers and to better understand the effect of DE on the grid. Current central power generation units vent more waste heat (energy) than the entire transportation sector consumes and this wasted thermal energy is projected to grow by 45% within the next 20 years. Consumer investment in technologies that increase power generation efficiency is a key element of the DOE Energy Efficiency program. The program aims to increase overall cycle efficiency from 30% to 70% within 20 years as well. DOE wants to determine the impact of DE in several small areas within cities across the U.S. Ann Arbor, Michigan, was chosen as the city for this case study. Ann Arbor has electric and gas rates that can substantially affect the market penetration of DE. This case study analysis was intended to: (1) Determine what DE market penetration can realistically be expected, based on consumer investment in combined heat and power systems (CHP) and the effect of utility applied demand response (DR). (2) Evaluate and quantify the impact on the distribution utility feeder from the perspective of customer ownership of the DE equipment. (3) Determine the distribution feeder limits and the impact DE may have on future growth. For the case study, the Gas Technology Institute analyzed a single 16-megawatt grid feeder circuit in Ann Arbor, Michigan to determine whether there are economic incentives to use small distributed power generation systems that would offset the need to increase grid circuit capacity. Increasing circuit capacity would enable the circuit to meet consumer's energy demands at all times, but it would not improve the circuit's utilization factor. The analysis spans 12 years, to a planning horizon of 2015. By 2015, the demand for power is expected to exceed the grid circuit capacity for a significant portion of the year. The analysis was to determine whether economically acceptable implementation of customer-owned DE systems would reduce the peak power demands enough to forestall the need to upgrade the capacity of the grid circuit. The analysis was based on economics and gave no financial credit for improved power reliability or mitigation of environmental impacts. Before this study was completed, the utility expanded the capacity of the circuit to 22 MW. Although this expansion will enable the circuit to meet foreseeable increases in peak demand, it also will significantly decrease the circuit's overall utilization factor. The study revealed that DE penetration on the selected feeder is not expected to forestall the need to upgrade the grid circuit capacity unless interconnection barriers are removed. Currently, a variety of technical, business practice, and regulatory barriers discourage DE interconnection in the US market.

Traditional marketing models are swiftly being upended by the advent of online social networks. Yet, practicing firms that are engaging with online social networks neither have a reliable theory nor sufficient practical experience to make sense of the phenomenon. Extant theory in particular is based on observations of the real world, and may thus not apply to online social networks. Practicing firms may consequently be misallocating a large amount of resources, simply because they do not know how the online social networks with which they interact are organized. The purpose of this dissertation is to investigate how online social networks that are in stark contrast to real-world social networks behave and how they get organized. In particular, I explore how network structure and information flow within the network impact each other, and how they affect the phenomenon of influence in online social networks. I have collected retrospective data from Twitter conversations about six YouTube product categories (Music, Entertainment, Comedy, Science, Howto and Sports) in continuous time for a period of three months. Measures of network structure (Scale Free Metric, Assortativity and Small World Metric), network flows (Total Paths, Total Shortest Paths, Graph Diameter, Average Path Length, and Average Geodesic Length) and influence (Eigenvector Centrality/Centralization) were computed from the data. Experimental measures such as power law distributions of paths, shortest paths and nodal eigenvector centrality were introduced to account for node-level structure. Factor analysis and regression analysis were used to analyze the data and generate results. The research conducted in this dissertation has yielded three significant findings. 1. Network structure impacts network information flow, and conversely; network flow and network structure impact the network phenomenon of influence. However, the impact of network structure and network flow on influence could not be identified in all instances, suggesting that it cannot be taken for granted. 2. The nature of influence within a social network cannot be understood just by analyzing undirected or directed networks. The behavioral traits of individuals within the network can be deduced by analyzing how information is propagated throughout the network and how it is consumed. 3. An increase or decrease in the scale of a network leads to the observation of different organizational processes, which are most likely driven by very different social phenomena. Social theories that were developed from observing real-world networks of a relatively small scale (hundreds or thousands of people) consequently do not necessarily apply to

This report discusses the effects of the late-time high-altitude electromagnetic pulse (HEMP) on electrical transmission and distribution (T D) systems. This environment, known as the magnetohydrodynamic electromagnetic pulse (MHD-EMP), is a very slowly varying electric field induced in the earth's surface, similar to the field induced by a geomagnetic storm. It can result in the flow of a quasi-dc current in grounded power lines and in the subsequent magnetic saturation of transformers. This saturation, in turn, causes 6-Hz harmonic distortion and an increase in the reactive power required by generation facilities. This report analyzes and discusses these phenomena. The MHD-EMP environment is briefly discussed, and a simplified form of the earth-induced electric field is developed for use in a parametric study of transmission line responses. Various field coupling models are described, and calculated results for the responses of both transmission- and distribution-class power lines are presented. These calculated responses are compared with measurements of transformer operation under dc excitation to infer the MHD-EMP response of these power system components. It is found that the MHD-EMP environment would have a marked effect on a power system by inducing up to several hundreds of amperes of quasi-dc current on power lines. These currents will cause transformers to saturate which could result in excessive harmonic generation, voltage swings, and voltage suppression. The design of critical facilities which are required to operate during and after MHD-EMP events will have to be modified in order to mitigate the effects of these abnormal power system conditions.

The offshore oil and gas industry is developing subsea processing systems far away from the shore and in ultra-deepwater. These subsea systems are usually power intensive, and thus a reliable electrical transmission and distribution (T&D) system is desired. In this paper, the modular stacked direct current (MSDC) architecture is presented to meet the technical challenges of the ultra-deepwater subsea systems. Instead of using a bulky centralized high voltage direct current (HVDC) converter station, the high dc voltage is achieved by stacking a number of power converter building blocks in series on both the on-shore station and the seabed stations. The dc-link current is controlled to be constant, and the dc-link voltage will vary according to the loading condition. This architecture renders fault-tolerant capability and feasibility for field extension. The details for the system architecture, the control algorithm, the simulation and experimental results will be described. The test results and the studies show that the MSDC system is a very attractive solution for subsea applications. Introduction The diminishing conventional oil and gas reservoirs and the always growing energy consumption have been driving the efforts to explore the deep-sea water petroleum resources, as shown in the diagram in Fig. 1. These resources are usually in ultra-deepwater and far away from the shore, where subsea process is usually preferred for technical and/or economic reasons. Subsea processing is especially attractive for the locations with tough topside environment since the manned topside platform can be removed. However, in order to achieve subsea process, turbo machines, e.g., pumps and compressors, and other processing equipment need to be deployed on the seabed. Accordingly various electrical equipment, including variable speed drives, power supplies, motors, connectors, switch gears, etc., are required to drive the machinery loads subsea. The overall power requirement ranges from tens of kW to tens of MW. As the scale and power consumption of the subsea process continue to grow, there is a clear need for a reliable power transmission and distribution system to power the subsea equipment over long step-out. Long step out distances and the ultra-deepwater environments have brought significant technical challenges to the electrical system. In ultra-deepwater and long step-out situation, accessibility of any equipment deployed in the subsea field is extremely limited. Subsea operation and maintenance is dependent on availability of vessels with remotely operated vehicles (ROV) and sufficient lifting/installation capacity, hence unplanned stops due to failures will cause large losses in production due to lost time. The cost of the vessel and offshore operation is also significant. Therefore, other than being designed for installation in ultra-deepwater, the electrical system must be very reliable and require minimum regular maintenance in its lifetime. The electrical system should also be as compact as possible and modularized, so that they can be installed and retrieved without heavy vessels and lifts which have very limited availability. In addition, the electrical system should be flexible and easy to be reconfigured since the power requirement, the tie-back length, and the number of loads will vary from site to site. And it should also have the flexibility for future expansion since additional field might be found in the adjacent area. In order to meet the above mentioned challenges and requirements, the MSDC architecture has been developed for the subsea power transmission and distribution with long step-out. This paper compares different technology options for subsea transmission and distribution (T&D), presents the MSDC architecture, describes the details of the system operation, and discusses the results of the field case simulation and the lab demo.

The study was aimed at analyzing the rate of diffusion of agricultural technology (direct seeded rice) in India through social network analysis technique. The present study is based on 240 purposely selected farmers’ responses gathered using different data collection methods such as snowball method, focus group discussion etc. during the year 2021-2022. Using SPSS and UNI-NET 6 software, the collected data were analysed using the sociometric matrix, percentage and frequency, mean, and standard deviation. The study's findings demonstrated that government institutions had a major role in the network's diffusion process.. All the stockholders of governments hold central position in the network flow. The network's information flow was unidirectional. The qualities of various networks differ from one another. It is concluded that governments agencies plays an important role in diffusion of innovation in India hence the government agencies should be strengthens for the diffusion of innovation.

This study proposes a distributed load restoration method to effectively model and solve the load restoration problem of integrated power distribution and natural gas systems (IDGSs) after faults for resilient operation. The IDGS load restoration problem is devised as a mixed-integer second-order cone programming (MISOCP) model to minimize the total load loss cost of IDGS. This model considers distribution network reconfiguration and the coupling effect between the power distribution system (PDS) and natural gas system (NGS). Moreover, a bidirectional gas flow model is used to offer more flexibility for load restoration when the NGS is faulty. By considering the independent management and information privacy of each energy subsystem, the proposed model is solved using an alternating direction method of multipliers (ADMM) algorithm in a distributed manner. Furthermore, an adaptive-ADMM algorithm is used for convergence acceleration. Finally, numerical studies are conducted to validate the proposed methods effectiveness.

BackgroundUnderstanding health information flow in social networks is important for designing effective health communications strategies and to achieve health literacy. Limited information is known about variation in social networks and health information sharing in the COVID-19 pandemic by demographic factors. Young people are of particular interest given their heavy exposure to digital media sources, which include considerable health misinformation.MethodsHawai'i (n = 324) residents between 18-35 completed a Spring 2021 online survey including questions on health information flow in social networks: (1) how many they talked to and (2) listened to about health. Two Poisson regression models were fit with gender, education, and race/ethnicity predicting social network size.ResultsRespondents were 67.6% female. Respondents discussed their own health with 2-3 people (M = 2.18, SD = 2.95) and listened to roughly the same number. Respondents who talked with a greater number of individuals about their own health were significantly more likely to have larger networks for listening to others (r (317) = .614; p< .001). In the model for discussing their own health, as education increased so did social network size. For the model predicting discussing others’ health, gender was significant (p = 0.003); women listened to 30.6% more individuals than men. Most (73%) respondents had conducted a recent digital health search for either themselves or someone else, including for parents, grandparents, and children. Facebook (63%) and Instagram (58%) were the most popular online sources for COVID-19 health information.ConclusionsUnderstanding social networks and digital health sources in young people are important for designing effective health communications to reach all communities, especially those experiencing health inequities, given the amount of health misinformation circulating and the need to build trust in public health communication.Key messages• Social networks provide access to critical health information including information obtained from digital sources.• Gender and education were important predictors of social network size in COVID-19 health communications.

The nonaffine transient network theory is used to study the time development of the shear and normal stresses under start-up shear flows in networks formed by self-assembled telechelic, hydrophobically modified water-soluble polymers. The initial slope, strain hardening, and overshoot of the shear stress are studied in detail in relation to the nonlinear tension-elongation curve of the elastically active chains in the network. The condition for the occurrence of strain hardening (upward deviation of the stress from the reference curve defined by the linear moduli) is found to be gamma > gammac(A), where gamma is the shear rate, gamma(c) is its critical value for strain hardening, and A is the amplitude of the nonlinear term in the tension of a chain. The critical shear rate gamma(c) is calculated as a function of A. It is approximately 6.3 (in the time unit of the reciprocal thermal dissociation rate) for a nonlinear chain with A = 10. The overshoot time t(max) when the stress reaches a maximum and the total deformation gamma(max) = gamma(t max) accumulated before the peak time are obtained in terms of the molecular parameters of the polymer chain. The maximum deformation gamma(max) turns out to depend weakly upon the shear rate gamma. The first and second normal stress differences are also studied on the basis of the exact numerical integration of the theoretical model by paying special attention to their overshoot, undershoot, and sign change as a function of the shear rate. These theoretical results are compared with recent rheological experiments of the solutions of telechelic hydrophobically modified poly(ethylene oxide)s carrying short branched alkyl chains (2-decyl-tetradecyl) at both ends.

The urban rail transit traction power supply cable bears the important tasks such as power connection and power transmission among the main substation, the traction and buck stations. Due to the greater length of the power supply cable, the series parallel resonance problem caused by the charging capacitor is a serious threat to the safe and stable operation of the rail transit system. In order to ensure the safe and stable operation of power supply and distribution system of urban rail transit system, this paper studies the design and selection of traction power supply cable for urban rail transit under the harmonic constraint. The method can effectively avoid the safety problem of the harmonic series-parallel resonance due to cable charging capacitance in the traction power supply system for urban rail transit users. At the same time, it also has guiding significance for the design of cable length and charging capacity of other power supply and distribution system.

Several Ideas on Fire Detecting Alarm for Power Supply and Distribution System