正确选择非专利数据库在电性能、电故障测量领域中的重要性

由于非专利数据库种类繁多,并且电性能、电故障测量领域中,涉及检测对象以及检测方法纷乱无章,因此,在电性能、电故障领域的非专利的检索中如何选择非专利数据库对检索效率有着很大的影响。本文结合电性能、电故障领域案例介绍了在非专利的检索中针对不同类型案件,选择不同非专利数据库的检索策略。

用油中特征气体数据分析及判断变压器故障

对变压器油中乙炔、一氧化碳两种特征气体含量与电性、热性故障的关系进行了讨论,并通过诊断实例提出了诊断方法。

变压器内部常见故障分析

对变压器内部常见故障如热性故障、电性故障及受潮产生的原因和特征气体进行了分析,并以包头供电局桥西2号变过热故障、福永4号主变放电故障及忽鸡沟2号变进水受潮故障为例,从色谱监测数据及故障发展过程及采取的技术措施等入手,对变压器内部常见故障进行了探讨。

关于气相色谱法对变压器故障类型的判断

自气相色谱法问世以来，这种新型的物化分离分析法就成为我们检测变压器内部故障的有效手段。此种方法的最大优点是检测故障、预告故障均不要求运行设备停电。气相色谱法用气体作载气，把被分析的、具有不同特性的混合气体分离开，并逐一定性和定量，分析绝缘油中溶解的气体，从而对变压器故障类型进行准确的分析判断。

Research on large-scale cascading failure of power systems using synergistic effect

This paper discusses the primary causes from the point of synergistic effects to improve power system vulnerability in the power system planning and safety operation. Based on the vulnerability conception in the complex network theory the vulnerability of the power system can be evaluated by the minimum load loss rate when considering power supply ability.Consequently according to the synergistic effect theory the critical line of the power system is defined by its influence on failure set vulnerability in N-k contingencies.The cascading failure modes are proposed based on the criterion whether the acceptable load curtailment level is below a preset value.Significant conclusions are revealed by results of IEEE 39 case analysis weak points of power networks and heavy load condition are the main causes of large-scale cascading failures damaging synergistic effects can result in partial failure developed into large-scale cascading failures vulnerable lines of power systems can directly lead the partial failure to deteriorate into a large blackout while less vulnerable lines can cause a large-scale cascading failure.

变压器气体试验项目的评估及其相关问题探析

早期预测变压器设备内部故障,对于安全发供电,防止事故于未然,是极为重要的。作为绝缘监督的手段,过去国内外广泛采用直流泄漏、绝缘电阻、介损测量、交流耐压和局部放电测量等电气绝缘特性试验。但是,这些试验的共同特点是要求被试验设备停运,很难测出事故发生前的极小的内部故障。虽然局部放电试验是检出绝缘局部缺损的较好的方法,但往往受外部干扰,影响检测的准确性。

APPLICATION OF ASSOCIATIVE MEMORY NEURAL NETWORK IN HIGH VOLTAGE TRANSMISSIONLINE FAULT DIAGNOSIS

Effective methods of enhancing the fault-tolerance property are proposed for two kinds of associative memory (AM) neural network (NN) used in high voltage transmission line fault diagnosis. For feedforward NN (FNN),the conception of 'fake attaction region' is presented to expand the attraction region artificially,and for the feedback Hopfield bidirectional AM NN (BAM-NN),the measure to add redundant neurons is taken to enhance NN's memory capacity and fault-tolerance property. Study results show that the NNs built not only can complete fault diagnosis correctly but also have fairly high fault-tolerance ability for disturbed input information sequence. Moreover FNN is a more convenient and effective method of solving the problem of power system fault diagnosis.

Application of extension method to fault diagnosis of transformer

A novel extension diagnosis method was proposed for enhancing the diagnosis ability of the conventional dissolved gas analysis. Based on the extension theory a matter-element model was established for qualitatively and quantitatively describing the fault diagnosis problem of power transformers. The degree of relation based on the dependent functions was employed to determine the nature and the grade of the faults in a transformer system. And the proposed method was verified with the experimental data. The results show that accuracy rate of the diagnosis method exceeds 90% and two kinds of faults can be detected at the same time.

Particle swarm optimization based RVM classifier for non-linear circuit fault diagnosis

A relevance vector machine (RVM) based fault diagnosis method was presented for non-linear circuits. In order to simplify RVM classifier, parameters selection based on particle swarm optimization (PSO) and preprocessing technique based on the kurtosis and entropy of signals were used. Firstly, sinusoidal inputs with different frequencies were applied to the circuit under test (CUT). Then, the resulting frequency responses were sampled to generate features. The frequency response was sampled to compute its kurtosis and entropy, which can show the information capacity of signal. By analyzing the output signals, the proposed method can detect and identify faulty components in circuits. The results indicate that the fault classes can be classified correctly for at least 99% of the test data in example circuit. And the proposed method can diagnose hard and soft faults.

Hybrid Operation of Fault Current Limiter and Thyristor Controlled Braking Resistor

The effectiveness of a combination of fault current limiter and thyristor controlled braking resistor on power system stability enhancement and damping turbine shaft torsional oscillations has been studied. If both devices operate at the same bus, the stabilization control scheme can be carried out continuously and with flexibility. As a result, the fault currents are limited, and the generator disturbances and the turbine shaft torsional oscillations are converged quickly. In this paper, the effectiveness of the combination of both devices has been demonstrated by considering 3LG （three-lines-to-ground） fault in a two-machine infinite bus system. Also, temperature rise effect of both devices with various resistance values and weights has been demonstrated. Simulation results indicate a significant power system stability enhancement and damping turbine shaft torsional oscillations as well as with allowable temperature rise.

Dynamic Response during the Online Compensation of Misalignment Based on Auxiliary Electromagnetic Support

A new support structure,named auxiliary electromagnetic support,is introduced to adjust the position of rotor shaft online.The auxiliary electromagnetic support consists of sliding bearing,iron core,radial spring,pedestal and electromagnet that could adjust the rotor position.In a rotor system adopting two auxiliary electromagnetic supports,the online compensation of misalignment was achieved without stopping work.Using the proposed auxiliary electromagnetic support,the analytical solution of dynamic response was obtained by analyzing a simulated single-degree-of-freedom(SDOF)system.And the dynamic response of the multi-degrees-of-freedom(MDOF)system in the experiment is acquired using Newmark variable step-size integration method.Further the new design is tested in a symmetrical single-disk rotor-bearing system.With both the theory analysis and the experimental results,some conclusions are obtained about the relationship between the vibration and the system damping which are related to system stability.

IEC 62059 Standards' Application in Reliability Prediction and Verification of Smart Meters

This article introduces the current situation of the smart then describes the relationship of meter reliability characteristics meter＇s reliability and the failure mechanisms at first, and combined with its Bathtub Curve. It also introduces both the feasible failure tree model for meter lifecycle prediction based on actual experiences and meter reliability prediction methodology by SN 29500 norms based on this model. This article also brings forward that it is necessary that the ＂Learning Factor＂ shall be adopted in meter reliability prediction for new materials, new process, and customized parts by referring to GJB/Z299C. Thereafter, this article also tries to apply IEC 62059 and JB/T 50070 to introduce the feasible method for the lifecycle prediction result verification by accelerated lifecycle test. Furthermore, the article also explores ways to increase the firmware reliability in smart meter.

Study on lifetime and reliability for power battery pack based on single battery failure

Single battery failure will change other batteries＇ load in a power battery pack. Based on the cumulative failure probability equality principle, this paper considers the relationship between the load and the battery life distribution, and constructs a reliability model for the parallel subsystem of the battery pack when a single battery fails, and then compares the lifetime and reliability as a function of load and cell design. The result proves that the k-out-of-n system approaches closed to the parallel subsystem of the power battery pack.

Reliability Investigation of PCs＇ SMPSs

Today reliability is one of the serious requirements of electronic systems. The numbers of system failures, repair cost, guarantee, etc. are estimated by reliability estimation. In this paper reliability of a switching power supply, which is used for personal computers, is evaluated. It will show that the most of failure rates depends on power circuit because of more stresses and dissipations. Derating effect of devices on the failure rate is discussed. A prototype power supply＇s waveforms are used for stress detection and calculation of dissipations.

Reliability Optimization in the Islanded Mode of Microgrid

A microgrid is a combination of distributed energy resources and controllable loads. The main objective of this research is to optimize energy flow within a microgrid with regards to reliability in grid connected mode. A microgrid with combined heat and power, natural gas generator, diesel generator, solar energy, wind energy, and battery energy storage along with a critical load is considered in this research. An event oriented analytical method called FTA （fault trees analysis） is implemented for reliability optimization using PTC Windchill Solutions software in a microgrid. The reliability of each component in each energy source of the microgrid is calculated using FTA. The reliability of the critical load is evaluated. The quantitative and qualitative results of FTA are evaluated in order to interpret the results of fault tree. The sensitivity and uncertainty of the fault tree results for critical load is deduced by calculating the importance measures such as risk achievement worth, risk reduction worth, criticality importance and Fussel-Vesely importance. Finally from the results the components that are sensitive and at high risk are deduced.

Enhancement of Real Power Transfer Capability of Transmission Lines

As power system interconnections become more prevalent, there has been an increase in use of thyristor controlled shunt connected compensation devices for dynamic power compensation and enhancement of real power transmission capacity. In this paper, an enhancement technique of real power transfer capacity of transmission lines is presented. A SVC （static var compensator） is designed and applied to a simple power system for this purpose. Increase in power flow and improvement in bus voltage profile are observed after using the SVC. Stability analysis of the system after experiencing fault as well as consequent fault clearance by time domain analysis has also beeu performed and satisfactory results are obtained.

浅谈溶解气体分析法诊断变压器故障中的有关问题

1.概述溶解气体分析法简称DGA,是诊断变压器内部故障的技术手段。这一方法在《电力设备预防性试验规程》中排在首位,其重要性毋庸置疑。本文仅对诊断中的几个问题提出以下看法。 2.变压器故障诊断的步骤变压器油中溶解气体经脱气、检测、得到一组数据,然后按照以下步骤进行工作(见图1)。 3.问题及讨论 DGA方法在我国已有30多年的应用历史,笔者根据实践经验,并参考有关文献,认为DGA方法需要解决以下问题: (1)变压器油中特征气体的注意值不是判断变压器内部故障的标准。

Failure modeling of folded dielectric elastomer actuator

When subjected to voltage,the dielectric elastomer membrane reduces its thickness and expands its area under the resulting compressive force.This characteristic enables the dielectric elastomer actuators of different structures to be designed and fabricated.By employing the thermodynamic theory and research method proposed by Suo et al.,an equilibrium equation of folded dielectric elastomer actuator with two generalized coordinates is established.The governing equations of failure models involving electromechanical instability,zero electric field,electrical breakdown,loss of tension,and rupture by stretch are also derived.The allowable areas of folded dielectric elastomer actuators are described.These results could provide a powerful guidance to the design and performance evaluation of the dielectric elastomer actuators.

Transient stability probability of a power system incorporating a wind farm

An analytical approach for probabilistic evaluation of transient stability of a power system incorporating a wind farm is presented in this study. Based on the fact that the boundary of practical dynamic security region(PDSR) of a power system with double fed induction generators(DFIG) can be approximated by one or few hyper-planes in nodal power injection space, transient stability criterion for given configurations of pre-fault, fault-on and post-fault of a power system is to be expressed by certain expressions of linear combination of nodal injection vector and the transient stability probability(TSP) is further obtained with a much more simplified expression than the complex integral. Furthermore, considering uncertainties of nodal injection power including wind power and load, TSP is calculated analytically by Cornish-Fisher expansion, which can provide reliable evaluation results with high accuracy and much less computing time compared with Monte Carlo simulation. TSP and its visualization can further help operators and planners be aware of the degree of stability or instability and find critical components to monitor and reinforce. Test results on the New England 10-generators and 39-buses power system show the method's effectiveness and significance for probabilistic security assessment.