Relay Model Research Articles

Transition Rates Assessment of Protective Relay Reliability Models With Incomplete Data

Usually the residence intervals in various states of power equipment are known, yet information about the number of transitions from one state to another is either missing or incomplete. This is mainly caused by a difficulty in recording of the state changes in the protection equipment or poor data acquisition and recording by power utilities. The transition rates are key parameters in all power system reliability models. Partial information on protection systems poses a challenge to construct or complete a transition rate matrix for reliability assessment. This paper addresses an issue of reliability evaluation of protective relays, operating in harmonic polluted environment. It presents a solution to the problem of finding transition rate matrix for a Markov chain of a simplified digital distance relay model. In this approach, the power system network and its associated protection is designed in a graphical preprocessor to Alternative Transients Program (ATPDraw). Parametric simulations of different circuit topologies during nominal and fault conditions are executed, processed, and analyzed automatically through batch and MATLAB scripts. Statistical calculations are implemented to obtain reliability parameters. An example is used to demonstrate the interactive protection system simulation, developed using the new approach.

Buffer-Aided Relay Systems under Delay Constraints: Potentials and Challenges

Relay transmissions can help improve system coverage and throughput, and hence information- theoretic analysis of relay channels has been at the forefront of research for decades. While providing powerful results, information-theoretic studies generally assume no buffer at the relay, and the performance is limited by the worst conditions of the transmitting and receiving channels of the relay. Recently, it has been shown that the achievable throughput can be significantly improved with the introduction of a buffer-aided relay model. Specifically, buffer-aided relaying can provide significant gains in terms of throughput, diversity, and signal-to-noise ratio without delay constraints. This article considers buffer-aided relay systems under delay constraints specified by limitations on delay violation probability. The necessary research tools and several results on different relay networks including two-hop and three-node relay channels are discussed. Certain challenges associated with buffer-aided relaying under delay constraints and topics for future research are outlined.

An Intelligent Hybrid Approach Using KNN-GA to Enhance the Performance of Digital Protection Transformer Scheme

This paper presents a novel hybrid K nearest neighbor-genetic algorithm (KNN-GA)-based digital protection transformer scheme, which effectively discriminates its internal faults with noninternal faults. The internal faults include the faults within the current transformer (CT) locations on two sides of the transformer. The noninternal fault includes magnetizing inrush current, sympathetic inrush current, recovery inrush current, external faults (faults outside the CT locations), and overfluxing. In conventional differential protection of a transformer, many maloperations of differential relay have been reported under certain working conditions. A new hybrid KNN-GA algorithm is put forward to improve the performance of the differential relay of a transformer. In this paper, real-time experimental results are presented for laboratory custom built differential relay model of a transformer. The generated experimental data for one power frequency cycle for various operating conditions is used by MATLAB to test the performance of a proposed algorithm. The proposed scheme has also been implemented on a digital signal processor TMS 320C6416T for a real-world application. The performance evaluation shows that compared with conventional methods, the proposed algorithm has a good reliability in terms of discrimination between internal and noninternal faults.

Beyond the Synapse and Hebb';s Rule: Is the Rest of the Neuron More Important for Psychiatric Disorders?

The neuronal synaptic action potential is still considered the basic unit of signaling in the brain underlying mental states, behavior and psychiatric disorders. However, exponentially deepening and mind boggling progress has been made during the last 30 years in the molecular and cellular understanding of what drives action potentials. The classical “synaptic relay model” of the action potential is now considered to be a special, minor case, most relevant to “machine-like” mentation and behavior. Volume transmission, not involving synapses, but certainly driving neuronal action potentials, is now understood to be far more prevalent, complex, and more relevant to “soul-like” mentation and behavior. Only a few very brief or highly technical accounts of this scientific revolution have been published specifically for psychiatrists despite the fact that psychiatry is the discipline most likely to gain in the short term, with neurology following more in the long term. We review here what we think are the most relevant aspects of extrasynaptic signaling for psychiatry in a manner we hope is most useful and enlightening for practicing psychiatrists. Keywords: Synaptic signaling, extrasynaptic signaling, wiring transmission, volume transmission, psychiatric disorders, neurological disorders.

A commercial relay model for the RTDS validated against the actual relay

This paper presents a relay model based on a manufactured differential transformer relay, SEL-787, developed in a real-time digital simulator. The objective of this study was to develop the model and to compare its performance to the actual relay and to a generic built-in model. With the proposed model, it is possible to implement studies in real-time simulators not only with the physical relay under analysis, but also with the surrounding protection system. The use of many relays for a real-time simulation test can be very expensive and complex. This paper presents the possibility of using models, based on actual relays, in the surrounding areas to cover all possible protection problems. The proposed model presents a new modeling technique and the comparisons to the relay itself and to the built-in generic model were made not only in terms of algorithms but also in terms of response time. The model’s performance was studied for different situations that interfere with the relay daily operation and it presented good adherence to the actual relay. This could not be observed in the built-in real-time simulator model.

Prony method implementation in distance relays to mitigate the effect of series-compensated transmission lines

This paper characterizes the error in distance relay operation due to the existence of asynchronous frequency components when a fault in a line with series compensation occurs. The distance relay model and the impact of non-filtered frequency components using the conventional digital filters is presented, an error will appear in voltage and current fundamental frequency phasors estimation and, by consequence an error, in apparent impedance estimation. Then, the proposed distance relay algorithm using the Prony method as a filter and its application considerations are described. Next, the line series compensation effects in distance relay estimation are presented, showing the importance of the estimation of the fundamental frequency phasor. Afterward, the effect of series compensation in distance relay performance is characterized by evaluating a simulated fault event. Finally, the proposed algorithm is evaluated in reach and operation time of the simulated and real fault events using a 3D operation characteristic of the relay.

Electric grid hardening and resiliency: part II, real-time modelling and simulation

This paper addresses and provides methodologies for use of real-time simulators in hardening existing or designing new robust transmission systems. Authors' methodology focuses on modelling and simulation of a system in two time domains to include “steady state” of the system when the transients from the system equipment have settled and to include “electromagnetic transients” that are present in relays, transformers, transmission lines, and generators when the transmission system is exposed to fault energy. Planning for robust electric grids using dynamic models and real-time response of equipment to system disturbances are addressed. Modelling and simulation of electromagnetic dynamics of static VAR compensator (SVC) and protective relays under independent pole operation (IPO) are described as examples of hardware-in-the-loop (HIL) simulation performed at University of New Orleans Power and Energy Research Laboratory. They present modelling of transmission lines, transformers, generators, and relays for HIL simulation of existing or new electric grids for improving robustness – hardening – and resiliency of the grid. While the methodology and removal of technical barriers in modelling for real-time simulation are tested on small-scale test systems and on part of the real-size electric grid in the Gulf Coast region, it may be implemented for studying other power systems.

국내 교류 전기철도 급전계통 보호용 과전류 계전기 모델링 및 과부하 보호 협조에 관한 연구

국내 교류 전기철도 급전계통 보호용 과전류 계전기 모델링 및 과부하 보호 협조에 관한 연구

A Novel Protection Method for Single Line-to-Ground Faults in Ungrounded Low-Inertia Microgrids

This paper proposes a novel protection method for single line-to-ground (SLG) faults in ungrounded low-inertia microgrids. The proposed method includes microgrid interface protection and unit protection. The microgrid interface protection is based on the difference between the zero-sequence voltage angle and the zero-sequence current angle at the microgrid interconnection transformer for fast selection of the faulty feeder. The microgrid unit protection is based on a comparison of the three zero-sequence current phase directions at each junction point of load or distributed energy resources. Methods are also included to locate the minimum fault section. The fault section location technology operates according to the coordination of microgrid unit protection. The proposed method responds to SLG faults that may occur in both the grid and the microgrid. Simulations of an ungrounded low-inertia microgrid with a relay model were carried out using Power System Computer Aided Design (PSCAD)/Electromagnetic Transients including DC (EMTDC).

Relay model for recruiting alcohol dependent patients in general hospitals--a single-blind pragmatic randomized trial.

BackgroundA large proportion of the Danish population consumes more than the officially recommended weekly amount of alcohol. Untreated alcohol use disorders lead to frequent contacts with the health care system and can be associated with considerable human and societal costs. However, only a small share of those with alcohol use disorders receives treatment. A referral model to ensure treatment for alcohol dependent patients after discharge is needed. This study evaluates the i) cost-effectiveness ii) efficacy and iii) overall impact on societal costs of the proposed referral model - The Relay Model.Method/DesignThe study is a single-blind pragmatic randomized controlled trial including patients admitted to the hospital. The study group (n = 500) will receive an intervention, and the control group (n = 500) will be referred to treatment by usual procedures. All patients complete a lifestyle questionnaire with the Alcohol Use Disorders Identification Test embedded as a case identification strategy. The primary outcome of the study will be health care expenditures 12 months after discharge. The secondary outcome will be the percentage of the target group, who 30 days after discharge, reports at the alcohol treatment clinics. In order to analyse both outcomes, difference-in-difference models will be used.DiscussionWe expect to establish evidence as to whether The Relay Model is either cost-neutral or cost-effective, compared to referral by usual procedures.Trial registrationhttps://register.clinicaltrials.gov/by identifier:RESCueH_Relay NCT02188043 Project Relay Model for Recruiting Alcohol Dependent Patients in General Hospitals (TRN Registration: 07/09/2014)

On the Performance of Relay Aided Millimeter Wave Networks

In this paper, we investigate the potential benefits of deploying relays in outdoor millimeter-wave (mmWave) networks. We study the coverage probability from sources to a destination for such systems aided by relays. The sources and the relays are modeled as independent homogeneous Poisson point processes (PPPs). We present a relay modeling technique for mmWave networks considering blockages and compute the density of active relays that aid the transmission. Two relay selection techniques are discussed, namely best path selection and best relay selection. For the first technique, we provide a closed form expression for end-to-end signal-to-noise ratio (SNR) and compute the best random relay path in a mmWave network using order statistics. Moreover, the maximum end-to-end SNR of random relay paths is investigated asymptotically by using extreme value theory. For the second technique, we provide a closed form expression for the best relay node having the maximum path gain. Finally, we analyze the coverage probability and transmission capacity of the network and validate them with simulation results. Our results show that deploying relays in mmWave networks can increase the coverage probability and transmission capacity of such systems.

Hedgehog Signaling Strength Is Orchestrated by the mir-310 Cluster of MicroRNAs in Response to Diet.

Since the discovery of microRNAs (miRNAs) only two decades ago, they have emerged as an essential component of the gene regulatory machinery. miRNAs have seemingly paradoxical features: a single miRNA is able to simultaneously target hundreds of genes, while its presence is mostly dispensable for animal viability under normal conditions. It is known that miRNAs act as stress response factors; however, it remains challenging to determine their relevant targets and the conditions under which they function. To address this challenge, we propose a new workflow for miRNA function analysis, by which we found that the evolutionarily young miRNA family, the mir-310s (mir-310/mir-311/mir-312/mir-313), are important regulators of Drosophila metabolic status. mir-310s-deficient animals have an abnormal diet-dependent expression profile for numerous diet-sensitive components, accumulate fats, and show various physiological defects. We found that the mir-310s simultaneously repress the production of several regulatory factors (Rab23, DHR96, and Ttk) of the evolutionarily conserved Hedgehog (Hh) pathway to sharpen dietary response. As the mir-310s expression is highly dynamic and nutrition sensitive, this signal relay model helps to explain the molecular mechanism governing quick and robust Hh signaling responses to nutritional changes. Additionally, we discovered a new component of the Hh signaling pathway in Drosophila, Rab23, which cell autonomously regulates Hh ligand trafficking in the germline stem cell niche. How organisms adjust to dietary fluctuations to sustain healthy homeostasis is an intriguing research topic. These data are the first to report that miRNAs can act as executives that transduce nutritional signals to an essential signaling pathway. This suggests miRNAs as plausible therapeutic agents that can be used in combination with low calorie and cholesterol diets to manage quick and precise tissue-specific responses to nutritional changes.

Effective Capacity of Buffer-Aided Full-Duplex Relay Systems With Selection Relaying

In this work, the achievable rate of three-node relay systems with selection relaying under statistical delay constraints, imposed on the limitations of the maximum end-to-end delay violation probabilities, is investigated. It is assumed that there are queues of infinite size at both the source and relay node, and the source can select the relay or destination for data reception. Given selection relaying policy, the effective bandwidth of the arrival processes of the queue at the relay is derived. Then, the maximum constant arrival rate can be identified as the maximum effective capacity as a function of the statistical end-to-end queueing delay constraints, signal-to-noise ratios (SNR) at the source and relay, the fading distributions of the links, and the relay policy. Subsequently, a relay policy that incorporates the statistical delay constraints is proposed. It is shown that the proposed relay policy can achieve better performance than existing protocols. Moreover, it is demonstrated that buffering relay model can still help improve the throughput of relay systems in the presence of statistical delay constraints and source-destination link.

Simulation of Low-Nickel-Content Alloys for Industrial Ground Fault Circuit-Breaker Relays

The aim of this paper is to simulate the performances of a ground fault circuit-breaker (GFCB) relay with new low-nickel-content alloys. Indeed, in the construction industry, the materials become more expensive as their nickel content increases. Moreover, the demand for nickel is particularly sensitive to the economic conjuncture. Therefore, an original electromagnetic relay model has been developed and validated in different working conditions (current amplitude, frequency, and temperature). A dedicated magnetic characterization of materials is needed, using basically a usual and industrial GFCB relay for reference and design data in modeling. First, the magnetic model of the relay is built and checked against experimental data. The simulation may predict the tripping current threshold of the relay. On the other hand, new low-nickel-content alloys for relay parts are studied in this framework, thanks to the developed model. The effects of temperature on the magnetic properties of the candidate materials and the electrical performances of the virtual relays are presented. The results, analysis, and conclusions are given. Finally, a first attempt to predict the economic gain obtained with a change of material is made.

Development of frequency‐based anti‐islanding protection models for synchronous distributed generators suitable for real‐time simulations

This study proposes simulation and analytical models of frequency-based protection functions (under and over frequency, rate of change of frequency and vector surge) used to detect islanding of synchronous distributed generators. All relay models are validated by using the concept of performance curves and two commercial relays. By using the performance curves, it is possible to make a comparison between the models and the commercial relays for a large number of islanding situations. In addition, the simulation models are suitable for real-time analysis. A real time digital simulator operating in a closed-loop mode is used to run the simulations and data acquisition. The results indicate that the models and commercial relays present a similar behaviour, showing that the models are able to properly simulate the commercial relays for islanding detection analyses of distributed generators, being acceptably accurate.

Energy cooperation for throughput optimization based on save-then-transmit protocol in wireless communication system

Green communication and energy saving have been a critical issue in modern wireless communication systems. The concepts of energy harvesting and energy transfer are recently receiving much attention in academic research field. In this paper, we study energy cooperation problems based on save-then-transmit protocol and propose two energy cooperation schemes for different system models: two-node communication model and three-node relay communication model. In both models, all of the nodes transmitting information have no fixed energy supplies and gain energy only via wireless energy harvesting from nature. Besides, these nodes also follow a save-then-transmit protocol. Namely, for each timeslot, a fraction (referred to as save-ratio) of time is devoted exclusively to energy harvesting while the remaining fraction is used for data transmission. In order to maximize the system throughput, energy transfer mechanism is introduced in our schemes, i.e., some nodes are permitted to share their harvested energy with other nodes by means of wireless energy transfer. Simulation results demonstrate that our proposed schemes can outperform both the schemes with half-allocate save-ratio and the schemes without energy transfer in terms of throughput performance, and also characterize the dependencies of system throughput, transferred energy, and save-ratio on energy harvesting rate.

A joint subcarrier selection and power allocation scheme using variational inequality in OFDM‐based cognitive relay networks

AbstractIntroducing orthogonal frequency division multiplexing (OFDM) into cognitive radio (CR) can potentially increase the spectrum efficiency, but it also leads to further challenges for the resource allocation of CR networks. In OFDM‐based cognitive relay networks, two of the most significant research issues are subcarrier selection and power allocation. In this paper, a non‐cooperative game model is proposed to maximize the system throughput by jointly optimizing subcarrier selection and power allocation. First, taking the direct and relay links into consideration, an equivalent channel gain is presented to simplify the cooperative relay model into a non‐relay model. Then, a variational inequality method is utilized to prove the existence and uniqueness of the Nash equilibrium solution of the proposed non‐cooperative game. Moreover, to compute the solution of the game, a suboptimal algorithm based on the Lagrange function and distributed iterative water‐filling algorithm is proposed. The proposed algorithm can jointly optimize the process of subcarrier selection and power allocation. Finally, simulation results are shown to demonstrate the effectiveness of the proposed joint subcarrier selection and power allocation scheme. Copyright © 2015 John Wiley & Sons, Ltd.

Optimization of Relay Graph Splicing Based on Repulsion-Tension Algorithm

At present, distributed integration setting calculation mode is widely used in power system. However, there are cross and overlap issues in protection relay model splicing process. Deeply researched in the characteristic of integrated relay splicing, according to power system network topology, an intelligent substation locating method based on the repulsion tension algorithm is applied in this paper. Finally, an example is used to verify the feasibility of the method.

Generalized Interrelay Interference Cancelation for Two-Path Successive Relaying Systems

This paper proposes a generalized interrelay interference cancelation (gIRIC) scheme for a two-path relay model in multisource systems. Both the sources and the relay adopt complex field network coding (CFNC) to remove the interrelay interference (IRI) caused by the two-path relay. Furthermore, we introduce two detecting modes (gIRIC-noSD and gIRIC-SD) for destination in our scheme. Two switching rules are given to select a suitable detecting mode between treating the signal of a direct link as noise (gIRIC-noSD) and utilizing the direct link to assist signal detection (gIRIC-SD). The bounds of average symbol error probability (SEP) and throughput of our scheme are derived.

Substation Locating Method in Integrated Relay Graph Splicing Based on Improved Genetic Algorithm

Distributed protection relay value setting is widely applied in china. There is a graph chaos problem in protection relay model splicing process. Deeply study the characteristic of integrated relay splicing, combined with the substation voltage level, a substation locating method based on improved genetic algorithm is proposed. To enhance the graph splicing, a voltage level based method is applied. At last, a practical example is used to validate the effectiveness of the method.