Evaluation of Power Quality Based on the Method of Matter-element

The synthetic quantified evaluation for power quality is one of the gist to weigh excellent or inferior of the power quality, and this is propitious to realize the electricity-purchase principle of discussing the price according to quality and high quality high price, thereby serve as to build the equitable electric power market. This paper proposes to use the method of matter-element for power quality evaluation, and then build the model based on the method of matter-element. Considering the non-compatible feature between the single recognition and evaluation results as well as the complexity of the evaluation for power quality, a model is approached for the evaluation of the power quality by using the matter-element and extension set. Case results show that use the proposed model is objective and reasonable, with a special advantage when used in power quality evaluation.     

Method of Grey Clustering Decision-making to State Assessment of Power Transformer

The assessment of health state of power transformer is a key step to realize Condition-based Maintenance of transformer. Research on health state assessment of transformer has very important actual significance. Transformer can be recognized as a typical grey system. The assessment of its healthy state using grey clustering decision-making method is put forward. The grey classes of transformer are given, the whitenization weight function of grey classes is established, the information involved in assessing the state of transformer is analyzed, and finally steps of state assessment of transformer using grey clustering decision-making are presented. The analysis of actual example demonstrates that the method has provided a new method to assess the health state of transformer.     

An assessment method for the reliability of on-load tap-changer of power transformer

Based on the thorough analysis of typical failure modes and influences of on-load tap-changers in power transformer, the fault-tree of tap-changers is set up using fault-tree analysis techniques and the assessment method for the reliability of tap-changers, combined with the index of the importance and the weight integration method based on the multi-objective decision-making theory and subjective and objective integrated weights, is put forward. The assessment examples show that the method can deduct and ratiocinate the failure modes of tap-changers clearly, find out the weaknesses in time during the operation, reflect the influence degree of each fault modes, obtain the reliability level of tap-changers in the operation and get better assessment results.     

Matter-element Evaluation Model on the Personal Credit of University Students Loan and It''s Application

This paper analyzes the current situation of university students' credit evaluation and set up an evaluation index system of university students' credit to compensate a loan.Based on this index system,this paper sets up a matter-element evaluation model on the individual credit of university students loan by means of extensible engineering method.The grade of individual credit and the index for evaluating the level of individual credit are made as matter-element,meanwhile,the classical field,the segment field,the weight coefficient are obtained.Dependence function is established based on the grade of individual credit and then the grade is judged by calculating the synthetic dependence degree.Finally,this paper presents the evaluation method by giving an example.This method is simple in calculation,reasonable in evaluation with high applicability.     

Three Phase Harmonic Power Flow Using PhaseComponent for Asymmetric Network

With the increasement of the harmonic quantity in power system ,single phase harmonic power flow calculation can't meet the needs. This paper discusses the components model in detail under harmonic condition in three phase distribution power system, include generator,transformer,line and load. Particularly, the transformer model considers the winding connection, the phase shifting among primary and secondary windings, and the off-normal tapping.The three-phase model of transformer, used in traditional harmonic power flow, may the preuent the model from converging, so the paper proposes a three phase back forward sweep harmonic load flow algorithm based on phase-components. At last, a test example was used to prove the algorithm. The results indicate that the proposed method is efficient.     

Parameter uncertainty analysis for probability distribution of bulk power systerm reliability

Component reliability parameters are of uncertainty and are affected by the component type, operation time, and weather conditions. So do the reliability indices of bulk power systems. The calculation of its probability distributions and its alteration law affected by parameters uncertainty are researched to provide practical engineering reference with exploring the impact of the parameter uncertainty on reliability assessment. The point estimate method is firstly proposed based on the two-loop Monte-Carlo simulation, and then the improved Monte-Carlo simulation is presented to enhance the calculation efficiency further. Moreover, their theories, merits and faults are explained in detail. It can be seen from the evaluation results for the RBTS power systems that the accuracy of the three methods are similar but the improved Monte-Carlo simulation has the highest efficiency, followed by the point estimate method. The IEEE-RTS 79 power system is evaluated by using the improved Monte-Carlo simulation, and the results verify its validity.     

Control Method of Voltage-reactive Power of Substation Based on the Real Time Adjusting Voltage Calculation

The main means of the voltage-reactive power control of substation are adjusting the taps of load-tap-changing transformer or the reasonable capacity of parallel compensating capacitors according to the operation condition of substation.The "nine-area control strategy" is widely used to adjust voltage in the stated range and reduce the transmission capability of reactive power for power system at present.By analyzing the existent shortages of nine-area control mode for voltage-reactive power,an adjusting voltage calculation method is put forward,input data of which are the real time data of current,voltage and power of the substation.Then operation decision of voltage-reactive power control method of substation is made.By the simulating analysis,predigesting method of upper system is built,based on which an applied real time calculating model and calculating steps is given.     

The Influence of Air Inlet on Ventilation Effect in Indoor SubstationTransformer Rooms

Ventilation design is the difficulty of transformer room design. Temperature field and velocity field in a transformer room was simulated by CFD method . By comparing simulation value with the experimental value in related document , the effectiveness of the mathematical model was verified. Based on it, an indoor substation transformer built was taken as the simulation object, then designed and simulated six kinds of ventilation condition by changing the location and area of air inlet, focused on the influence of air inlet on the ventilation effect by comparing the temperature field ,velocity field and temperature characteristic value in different condition. The simulation results show that when air inlet area is fixed, the air inlet should be arranged in the radiator side and its center height should be controlled in the radiator center height or slightly offset position, it should not be higher than the radiator. When the air inlet location is fixed, air inlet area should be increased along the high direction to improve ventilation effect. The conclusions can provide technical support for the ventilation design of transformer room.     

A novel control method for controllable reactor of transformer type

Conventional control methods for controllable reactor of transformer type generally depend on the parameters of transformer and cannot control capacitor voltage effectively. A novel control method for controllable reactor of transformer type is proposed. Based on a novel algorithm for fundamental extraction, the proposed approach can control the reactance accurately in real time mode by monitoring the condition of primary voltage and current. It also can control the capacitor voltage effectively and keep the capacitor voltage stable by introducing the feedback of capacitor voltage to control the phase of secondary current. Simulation has been carried out to proof the effectiveness of the method.     

An improved dynamic model of transformer hotspot temperature based on top oil temperature

The winding hot spot temperature of the oil immersed power transformer is an important parameter. It has a great influence on the transformer insulation aging and a close relationship with the transformer top oil temperature. The changes of non linear thermal resistance, open circuit impedance, and oil viscosity and winding losses with temperature are also taken into account. An improved model added on the transformer top oil temperature to calculate transformer winding hot spot temperature by using the viscosity and loss correction factors is proposed. Model parameters are estimated by Levenberg Marquardt method. In the end, by comparing with the measured data tested under different conditions, the model shows good consistency under underload (90%), rated load (100%) and overload (110%) conditions respectively, and describes the temperature variation more accurately in the dynamic loading profiles.     

An Improved Genetic Algorithm for Optimum Design of Power Transformers

In order to enhance the ability of global searching for genetic algorithm in power transformers optimization design, some interrelated key technique problems such as encoding method, genetic operators, restrict condition, fitness function for the traditional genetic algorithm are further reformed. An Improved Genetic Algorithm (IGA) is developed. The optimal results of a representative mathematical example show that IGA has high efficiency of global searching. At the same time, a multi-objective algorithm based on IGA is studied in this paper. IGA is applied to the single and multi-objective optimum design of S9 power transformers for the first time. All the achievements in the paper are verified a practical S9-1000/10 kV power transformer. All the optimization results are satisfactory and show that IGA has powerful ability of global searching, excellent solution precision and has a bright application prospect in the fields of power transformers design.     

区域土壤环境质量的可拓物元评价

为了更加客观评价区域土壤环境质量,使土地资源得到合理规划和利用,将物元法引入土壤环境质量评价体系中,构建土壤环境质量评价的物元模型。通过实地土壤取样、测量,用物元分析法得出土壤中各种影响因子对一定区域内土壤环境质量的影响程度。实验结果表明：评价区内土壤中Cu含量为II级,其他重金属含量均符合I级标准,综合土壤环境质量评级结果为I级,具体等级值为1.342,即精确的等级是介于I级和II级之间,更偏重于I级。该评价方法可以科学、有效地应用监测数据,评价结果较为可信,能较科学地判定土壤环境质量级别,同时也可反映各污染因子对土壤环境质量的影响程度,并对污染程度加以区分和量化。     

Influential factors analysis on photoacoustic signal of photoacoustic spectroscopy monitoring trace gases

Photoacoustic spectroscopy (PAS) is a highly sensitive gas analyzing method without the shortcoming of gas consumption, which can be used in transformer oil trace gases dissolved in on line monitoring. The photoacoustic signal is detected with a microphone, which is the only feature in gas concentration analysis. A portable and tunable experimental setup has been developed based on the photoacoustic spectroscopy fundamental. Through the photoacoustic signal stimulate mechanism analysis, this paper thoroughly discusses the influences of gas pressure, temperature, laser power, gas concentration, background gas, chopped frequency and the resonant frequency drift on the gas photoacoustic signal. The theoretical and experimental results supply reference and technical support for further improvements in oil gas photoacoustic spectroscopy of on-line monitoring system.     

AN ON-LINE ALGORITHM FOR PREDICTING THE TEMPERATURE OF POWER TRANSFORMER WINDINGS

The paper presents an on-line algorithm for predicting the average temperature of power transformer winding according to its load current. The algorithm has accounted for the whole history of load current and variations of ambient temperature. The overload capabilities of transformer can be increased by monitoring and controlling the winding temperature and the necessary durability of the transformer can be ensured. The algorithm can also forecast the future winding temperature and the time of reaching the max, permitted the assumed future load current and oil temperature.     

Hybrid Power Supply Based on One Cycle Control

A hybrid power supply is composed by both a linear and a switching source connected in parallel and it can improve the dynamic response. But the hybrid power supply cant not effectively reject the perturbations in the power supply. A hybrid power supply based on one cycle control theory is proposed in order to improve the capability and the control precision. A switching source based on one cycle control is adopted in the hybrid power supply. The analysis results indicate that the hybrid power supply can effectively reject the perturbations in the power supply. And the analysis results also show that not only the control precision is improved, but also the control circuit is simple. The simulation resuits given verify the correctness and effectiveness of the proposed method.     

On line tool breakage monitoring method based on power information and cross-correlation algorithm

In order to reliably monitor unexpected tool failure and prevent workpiece or machine tool from possible damages in batch machining, a tool breakage on-line monitoring method based on power information and cross-correlation algorithm is proposed. In this method, wavelet coefficients of spindle-power signal are used as the characteristic vector of machining information, and then the vector sequence extracted from a normal machining process via Mallat wavelet is defined as the reference template for monitoring cutting tool condition. In batch machining, real-time characteristic vector of the workpiece in machining process is extracted via an improved real-time wavelet algorithm. The correlation of two vector sub-sequences within a sampling time window, which is described by generalized cross-correlation coefficient, decreases apparently when the tool is broken. The generalized cross-correlation coefficient is defined as tool condition index (TCI), and tool breakage can be detected by monitoring the TCI with a threshold value. Experiments show that the method can accurately identify tool breakage failures in normal machining condition, and thus it is practical.     

Application of Improved Matter-element Extension Method in Comprehensive Assessment of Shallow Groundwater

Taking shallow groundwater in Jinjiang City,Fujian Province for example,it was found that the classical element-matter analysis shows deficiency in calculation of correlation function,so the improved matter-element method was applied for the comprehensive assessment of shallow groundwater in Jinjiang City,and the spatial distribution was shown in maps.The assessment results demonstrated that ground water quality of most regions in the study area belonged to Grade I and II,thus the overall quality of shallow groundwater was good.The groundwater of Grade IV and V(relatively poor and extremely poor) was mainly distributed in Dongshi Town,Chendi Town,Zimao Town,and Shenhu Town,major exceeding-standard factors that influence shallow groundwater quality in the local area included TDS,Mn~(2+),NO_3,NO_2,NH_4~+ and Cl~-,which mainly owed to invasion of seawater,original geological conditions,industrial and agricultural discharge,and human life.     

Simulation analysis of the thermal-electric analogy calculation model of transformer winding hot-spot temperature

The winding hot-spot temperature is one of the most critical parameters that determines the power transformer overloading capability and the aging rate of the oil-paper insulation. Based on the traditional thermal theory, the paper proposes a simulation model to predict transformer winding hot spot temperature taking into account oil viscosity changes with temperature, and combined with the thermal-electric analogy method and hot spot temperature rise model recommended by IEEE. The Runge-Kutta method is used to calculate top-oil temperature and winding hot-spot temperature of the transformer, and then compare them with the measured data obtained from the 100 kVA/5 kV (ONAN) experimental transformer. The simulation results are in good agreement with experimental data.     

The Optimal Method of Calculation of Earthwork Volume of Transformer Substation

With the development of electric power industry, more and more projects of building transformer substation need a great deal of fund. More exact evalution of projects becomes more important.In evalution of projects, calculation of earthwork volume may be a very important part.According to the requirement of most projects and on the basis of traditional method , we have created a new method of optimal calculating earthwork and auto-balance. Minute-dividing technology and interpolating way are used to enhance the simulation of Grids.The new method can better simulate the landform and more effectively promote the precision and speed of calculation of earthwork .Auto-Balance can do what can't be reached by manual work.