Transmission Reliability Evaluation Research Articles

Reliability Evaluation and Improvement of Power Transmission Systems Using Series Compensation

Reliability Evaluation and Improvement of Power Transmission Systems Using Series Compensation

Transmission reliability evaluation of wireless sensor networks considering channel capacity randomness and energy consumption failure

The reliable transmission of data packets is the basis of ensuring the Internet of Things applications. Therefore, how to ensure the transmission reliability of wireless sensor networks has already become a hotspot. However, the existing researches ignore the effects of multiple fault modes and random factors on transmission reliability. Firstly, in the node reliability modeling, few studies have considered the effects of random failure and energy consumption failure comprehensively. Secondly, in the link reliability modeling, existing studies ignore the effect of the channel capacity randomness, which can lead to the erroneous estimation of transmission reliability. To overcome the above shortcomings, we propose a more realistic transmission reliability model. Firstly, considering the comprehensive effects of two failure modes, we establish a new node reliability model to better characterize the node performance. Secondly, considering the channel capacity randomness, we propose an improved SNR-Capacity connection model by deriving the one-hop connectivity probability, which can better characterize the link reliability. Then, we propose a transmission reliability evaluation model, and give the corresponding exact and approximate algorithms for its solution. Finally, taking the military Internet as an example, the effectiveness of the proposed method is verified.

Transmission reliability evaluation of the wireless mobile ad hoc network considering the routing protocol and randomness of channel capacity

AbstractDue to the characteristics of self‐organization, flexibility, and low cost, Mobile ad hoc networks (MANETs) have been applied in many fields, such as disaster rescues and military actions. However, in reality, the successful route establishment based on routing protocols is the prerequisite of data transmission. Besides, the transmission reliability of MANETs is affected by resource constraints, such as channel capacity and energy, and environmental factors. Hence, how accurately modeling and evaluating the transmission reliability of MANETs is very important to ensure their application. Whereas, existing studies ignore the impact of routing protocols and do not fully consider the influence of some factors on transmission reliability, such as environmental randomness, channel capacity, and energy consumption. To solve the above problems, we first propose a signal‐to‐noise‐ratio‐Capacity connection model to better describe the characteristics of wireless links, and the probability of one hop connection is deduced considering the capacity demand randomness. Then, considering the influence of routing protocol on the MANET link establishment, we take the ad hoc on‐demand distance vector routing protocol as an example, and propose an evaluation algorithm of the MANET transmission reliability based on algebraic graph theory and Monte Carlo simulation. Finally, the effectiveness of the proposed method is demonstrated by a numerical example of an unmanned aerial vehicle search and rescue scene.

Dynamic Reliability Evaluation and Life Prediction of Transmission System of Multi-Performance Degraded Wind Turbine

Wind power is a kind of important green energy. Thus, wind turbines have been widely utilized around the world. Wind turbines are composed of many important components. Among these components, the failure rate of the transmission system is relatively high in wind turbines. It is because the components are subjected to aerodynamic loads for a long time. In addition, its inertial load will result in fatigue fracture, wear and other problems. In this situation, wind turbines have to be repaired at a higher cost. Moreover, the traditional reliability methods are difficult to deal with the above challenges when performing the reliability analysis of the transmission system of wind turbines. To solve this problem, a stress-strength interference model based on performance degradation is introduced. Based on considering the strength degradation of each component, the improved Monte Carlo method simulation based on the Back Propagation neural network is used to obtain the curve of system reliability over time. Finally, the Miner linear cumulative damage theory and the Carten-Dolan cumulative damage theory method are used to calculate the cumulative damage and fatigue life of the gear transmission system.

Reliability evaluation of composite generation and transmission systems via binary logistic regression and parallel processing

In power system planning studies that involve the search for optimal investments with low risks for the power grid, probabilistic reliability assessments provide very useful tools and indices. A challenge faced in the application of these tools is related to the computational effort demanded by the evaluation process, especially when the combined effects of failure of generation and transmission equipment are considered. In this context, the present work proposes a new method for efficient estimation of the main composite reliability indices by combining Binary Logistic Regression (BLR) technique, a machine learning tool used for binary data classification, with the non-Sequential Monte Carlo simulation (NS-MCS) method. In addition, a computational parallelization strategy is incorporated to the proposed method to improve even more the efficiency of the composite reliability assessment. The performance of the proposed approach is analyzed by evaluating composite reliability indices for the IEEE-RTS considering two different generation and load scenarios, in addition to a real large-scale power system. The results obtained are compared with those using the NS-MCS method in its conventional version.

RELIABILITY EVALUATION OF COMPOSITE SYSTEM WITH AGING FAILURE

Reliability is concerned with the system capability of survival. In the past forty years, customer expectations have been increasing in response to evolving new technologies. As part of these evolutions, they are demanding from their suppliers: products with higher quality, low initial cost, improved customer support and products that are easy and inexpensive to maintain. For a supplier to survive, succeed and be profitable in todays market, It must do the following: a) Constant improvement in the quality of the products. b) Minimization of the cost. c) Be flexible and responsive to the customers requirement. This deals with reliability evaluation of combined generation and transmission system known as composite system. It describes a technique calculate composite system reliability with aging failure. The reliability evaluation deals with the a) Calculation of aging failure rate & aging repair rate of all Components of the system. b) Calculation of EENS value of all Components of the system by performing Reliability Analysis using SKMS PTW 6.5.

Early prediction method for assembly precision of mechanical system and assessment of precision reliability

Assembly precision is an important index, because it can ensure the quality of mechanical products and the final basis, and determine the overall performance of the products. In the early design stage, the prediction of assembly precision of schemes is significant. Therefore, considering part processing error, we proposed a prediction method for assembly precision of mechanical transmission system. Based on meta-action theory and small displacement torsor (SDT) model, common geometric elements were analyzed under multi-tolerance coupling and the error transfer of joint-surface for meta-action unit. Thus, we established the error model of joint-surface and qualitatively determined the potential error’s accumulative transmission paths of transmission system. We also quantitatively built the assembly precision prediction model of transmission system combining with the Jacobian-Torsor method, and calculated the precision reliability value. Finally, the effectiveness was verified by an example of NC machine tool’s transmission system. The method provides a way of thinking about solving the precision prediction and reliability evaluation of mechanical transmission systems in the early design stage and a basis for the final assembly precision prediction, simulation and testing of mechanical products.

Analytical model for fast reliability evaluation of composite generation and transmission system based on sequential Monte Carlo simulation

This paper proposes an analytical reliability evaluation (RE) model for composite generation and transmission system (CGTS) based on the sequential Monte Carlo simulation (MCS) method. The main idea is to partition the chronological system state sequence produced by sequential MCS into a set of mutually exclusive events based on the law of total probability. An analytical model is developed by extracting the component reliability parameters (CRPs) from system reliability index calculation formula of each mutually exclusive event. Once the proposed model is established, system reliability indices with variable CRPs can be obtained directly, rather than repeatedly performing the time-consuming sequential MCS process. In addition, sensitivity coefficients of system reliability indices with respect to CRPs can be obtained using the developed analytical model. A 4-unit generation system, the CGTS of IEEE-RTS system and a 91-bus power system are used for case study to validate the correctness and effectiveness of the proposed analytical RE model.

Impact‐increment based decoupled reliability assessment approach for composite generation and transmission systems

Improving the computational efficiency of reliability assessment is a long-term goal for researchers. Regarding this issue, an impact-increment-based decoupled reliability assessment approach (IID) is proposed in this study. First, a new formulation of reliability indices is derived by decoupling the reliability index of composite systems into two parts: generation adequacy and transmission reliability. Then, an impact-increment-based state enumeration reliability assessment method is implemented to both the parts, which are more efficient than tradition methods. Thereafter, a reduction technique for the higher-order contingency states is developed for the transmission reliability evaluation. With this technique, the number of analysed contingencies can be significantly reduced, which improves the computational speed significantly. Finally, the overall framework of the proposed IID approach is demonstrated. Case studies are performed on the RTS-79, RTS-96 and a provincial system of China. Results indicate that the proposed method has superior performance to the traditional reliability assessment methods in terms of accuracy and computational speed, particularly on large-scale composite systems.

A Bilevel Optimization Model for Risk Assessment and Contingency Ranking in Transmission System Reliability Evaluation

This paper presents a bilevel optimization model for the risk assessment of transmission systems. Specifically, the lower level model is expected to provide a generation redispatch by minimizing the total load shedding, and the upper-level model is to maximize the severity risk by constructing a binary optimization model to identify the worst N - k contingency. To further reduce the complexity of the proposed model, the logarithmic transformation and linearization techniques are utilized, leading to a general mixed integer linear programming. In addition, a recursive method is proposed for contingency ranking based on the bilevel optimization model. Compared with the benchmark analytic method, the proposed method does not need to enumerate every contingency, reducing the computational burden. In contrast to the traditional Monte Carlo Simulation method, the proposed method can give as precise a risk assessment result as the analytic method and has higher evaluation efficiency. Numerical results on three test systems verify the effectiveness of the proposed method.

Probabilistic evaluation and planning of power transmission system reliability

Modern power systems are designed prudently and then operated according to the permitted equipment limits set out in standards, policies, and procedures. To meet the growing demand, utilities apply transmission expansion tools for planning and updating their transmission assets. However, due to their unpredictable nature, transmission contingencies cannot be easily integrated during the planning stage. Although computationally cumbersome, probabilistic planning is an approach that could enable an objective comparison of the economic risk associated with a contingency event versus the cost of upgrades. In the context of the development of a generic assessment tool for such a process that could be employed by utilities, this study presents a systematic approach for transmission system expansion planning that includes consideration of an N − 1 contingency. The proposed method provides an estimate of the potential economic losses that could occur due to contingencies related to transmission, which are quantified as the cost of expected energy not supplied. The study then introduces a proposed formulation that computes an optimal plan for transmission system reinforcement that will eliminate the economic losses associated with N − 1 contingencies. The results reveal that in specific cases, upgrading the system has economic merit as well as offering the benefits to be derived from a robust transmission system.

Data transmission reliability evaluation of a stochastic computer network through minimal paths with a retransmission mechanism

Multipath Transmission Control Protocol is a new networking protocol which can allow data transmission and retransmission across multiple minimal paths. It can reduce data transmission time and ensure data integrity. In computer networks, the capacity of each arc should be considered as stochastic because there are different situations such as failures, partial failures, and maintenance. This article focuses on a stochastic retransmission flow network to evaluate data transmission reliability that the data can be transmitted successfully through multiple minimal paths within transmission time threshold. We first propose an algorithm to generate all minimal capacity vectors satisfying both constraints and requirements and to obtain data transmission reliability. A numerical example and a large-scale case study of the Pan-European Research and Education Network are presented to illustrate the algorithm.

Reliability Evaluation of Double 12-Pulse Ultra HVDC Transmission Systems

Double 12-pulse ultra HVDC transmission systems of $\pm $ 800 kV and $\pm $ 660 kV have larger transmission capacities, more complicated configurations, more complex operation modes, and more components, in comparison to $\pm $ 500 kV or less HVDC transmission systems. Hence, the reliability evaluation of the ultra HVDC transmission system is more complicated than that of the HVDC system. To thoroughly describe different operating modes, this paper presents two new reliability measures for ultra HVDC transmission systems, that is, partial monopole forced outage times and partial bipole-forced outage times. Reliability evaluation models for individual subsystems, including converter transformers (CT), ac filters, converter valve groups, and smoothing reactors have been built considering operation modes and configuration characteristics. In particular, the reliability model of the CT subsystem was built by considering the type and the number of standby CTs, and that of the ac filter subsystem was built by considering the capacity state table of filters. A reliability evaluation model for ultra HVDC transmission systems was proposed by combining reliability logic relationships among subsystems and using the state enumeration method. Case studies of practical ultra HVDC transmission systems illustrate the correctness of indices and the proposed models. In addition, sensitivity analysis and standby analysis of major components were also conducted.

Transmission Reliability Evaluation for Wireless Sensor Networks

Network reliability of Wireless Sensor Networks (WSNs) is difficult to be evaluated because of its complexity, multistates, and dynamic characteristics. To satisfy the user's need of reliability evaluation for network transmission we propose some evaluation models and a dynamical evaluation framework. The evaluation models are mission-oriented and based on transmission paths (uplink and downlink). The dynamic evaluation framework can be on-demand customized and it will be autoupdated once the communication environment changes or the nodes fail. Finally, we simulated clustered and mesh WSNs with NS-2. Simulation result shows that the proposed evaluation framework was effective and accurate.

Research on Reliability Evaluation Methods of Composite Generation and Transmission System

The basic mathematical method for power system reliability evaluation was indicated, the simple and complex system was respectively introduced, several methods of reliability analysis of simple was given in this paper, and the reliability evaluation indexes system and methods of composite generation and transmission system was analyzed, then focused on state enumeration method applied in the reliability assessment of system, the detailed example analysis was given and the adequacy reliability indexes were computed in detail. Finally, the current reliability evaluation and status of composite generation and transmission system was summarized simply and its reliability evaluation algorithm steps applied in current actual engineering projects was given.

Accelerated State Evaluation and Latin Hypercube Sequential Sampling for Composite System Reliability Assessment

This paper proposes improvements in the sequential Monte Carlo (MC) simulation based approaches for reliability evaluation of composite generation and transmission systems. The main idea is to compute a threshold load level to facilitate the process of state evaluation, which is very time-consuming mainly due to optimal power flow computations. Two main sampling techniques namely random sampling (RS) and Latin Hypercube sampling (LHS) are applied to the proposed sequential MC simulation technique. Their performances in terms of simulation time as well as solution accuracy are compared. Case studies using the IEEE Reliability Test System (IEEE RTS) are utilized to demonstrate the performance of the proposed approach. Reliability indices including loss of load probability, expected unserved energy, loss of load frequency and duration are estimated. It is shown that the proposed approach considerably reduces the computational requirements during state evaluation, and that the application of LHS can further decrease the simulation time and required sample size to reach convergence.

Reliability Evaluation of Generation and Transmission Systems Considering the Effects of Wind Farm

Because wind energy fluctuates randomly, the output power of wind turbine generators is uncertain. The reliability of power systems including wind generation is analyzed in this paper. In this paper, the reliability model of wind generators and the model of transmission network are combined by considering the sequential and autocorrelation of wind speed, the output power function and the forced outage of wind units. Then a reliability evaluation model of generation and transmission system, in which the system security constraints are satisfied, is built and the objective function is LSC. Taking IEEE-RTS96 system as an example, the reliability index which can reflect the effects of wind farms is calculated. The result provides the scientific reference for connecting wind farms to power systems.

Short-Term Reliability Evaluation of Transmission System under Strong Wind and Rain

The impact of strong wind and rain loads will adversely affect the reliability of the overhead lines, it’s necessary to study changes in risk of transmission system and establish the reliability model of overhead lines through the strong wind and rain loads. In this article, the stochastic properties of overhead lines’ strength and loads were used, according to principles of structural reliability, time-dependent failure probability model of overhead lines was established under the impact of strong wind and rain loads. Simulation of the IEEE-79 system demonstrates that failure probability model is effective. This simulation result also shows that the impact of strong wind and rain loads will seriously affect reliability indices of system loads, rain loads cannot be ignored under strong wind and rain loads.

Short-Term Reliability Evaluation of Transmission System Using Lightning Strike Probability Prediction

The transmission lines are exposed to the atmosphere nature and will be affected by adverse weather such as lightning storm, so that it will affect the reliability of transmission system. This paper studies the fault probability model of transmission line during the lightning storm, and evaluates the short-term reliability of transmission system in the forecasting weather condition. Firstly, build the lightning strike fault probability model of the transmission line based on historical lightning record information, then calculate the lightning strike probability under the forecasting weather conditions, furthermore evaluate the reliability index of transmission system. Utilizing IEEE RTS-79 system to verify the validity of the proposed model and the results show that lightning has great negative influence on the transmission lines and the reliability of transmission system. The reliability evaluation model proposed in this paper can guide the short-term operation and online scheduling for transmission system operators.

Incorporating multiple correlations among wind speeds, photovoltaic powers and bus loads in composite system reliability evaluation

This paper presents a composite generation and transmission system reliability evaluation method incorporating multiple correlations among wind speeds, insolations and bus/regional load curves. The proposed method can accurately model any probability distribution and all the correlations between wind speeds, between solar insolations, between load curves, between wind speeds and solar insolations, between wind speeds and load curves, and between solar insolations and load curves. The IEEE-Reliability Test System (RTS) with additional two wind farms and two PV power stations is used to demonstrate the application of the presented method in composite system reliability evaluation.