超临界条件下甲基萘与甲醇烷基化反应

Alkylation of methylnaphthalene with methanol is one promising technology for producing 2,6-dimethylnaphthalene. When the alkylation is carried out under ambient pressure by using HZMS-5 catalysis, the reaction activity is very low and obvious deactivation of catalyst is observed in a short run.This paper aims at slowing down catalyst deactivation and improving reaction activity of alkylation of methylnaphthalene with methanol by taking advantage of some special properue: of supercritical fluids,such as higher solubility than gases and higher diffusivity than liquids. The results indicate that the reaction under supercritical condition will achieve high reaction activity and long catalyst life. When the reaction was carried out at 460℃ and 7.0MPa which is above the critical temperature and pressure of the inert reaction solvent, 1,3,5-trimethylbenzene, the reaction activity increased by 3 times and catalyst life was extended by 25 to 30 times than those under ambient pressure and at the same temperature.     

Calculating Methods of Inertia Moment of TurboGenerator Rotor Using Load Rejection Test

Calculated results of inertia moment of turbo-generator rotor can be quite different by methods used in load rejection tests. In view of fluctuation features of rotor speed rise curve during load rejection tests, the measurement principle of rotor inertia moment was expounded. Based on the measured data in load rejection tests for an imported type of domestic 300-MW generating unit, the rotor speed rise curve was fitted with three kinds of functions to get initial runup rate, but the obtained results differed a lot from each other. According to analysis on the mechanism of rotor speed rise, m=2 consecutive points averaging or FFT (Fast Fourier Transform) smoothing technology was introduced to process test data, and then the initial runup rate was determined by the method of linear fitting of rotor speed in the range of governing valve closing time. Although the obtained curves had a fluctuating shape, the results of rotor inertia moment for 50% and 100% load rejection tests were of good consistency.     

Calculating Methods of lnertia Moment of Turbo- Generator Rotor Using Load Rejection Test

Calculated results of inertia moment of turbo-generator rotor can be quite different by methods used in load rejection tests. In view of fluctuation features of rotor speed rise curve during load rejection tests, the measurement principle of rotor inertia moment was expounded. Based on the measured data in load rejection tests for an imported type of domestic 300-MW generating unit, the rotor speed rise curve was fitted with three kinds of functions to get initial runup rate, but the obtained results differed a lot from each other. According to analysis on the mechanism of rotor speed rise, m=2 consecutive points averaging or FFT （Fast Fourier Transform） smoothing technology was introduced to process test data, and then the initial runup rate was determined by the method of linear fitting of rotor speed in the range of governing valve closing time. Although the obtained curves had a fluctuating shape, the results of rotor inertia moment for 50% and 100% load rejection tests were of good consistency.     

Off-Line Identification of Induction Motor Parameters

This study presented an off-line identification method of induction motor (IM) paranmters. Before startup,the inverter drive performed automatically a modified DC test, a locked-rotor test, a no-load test and a step-voltage test to identify all the parameters of an induction motor. No manual operation and speed signals were required in the process. In order to obtain effective messages and improve the accuracy of identification, the discrete fast Fourier transform (DFFT) and the least-squares were used to process the signals of currents and voltages. A phase-voltage measuring method for motors was also proposed, which measured directly the actual eooducting time of three upper switches in the inverter without need for a dead-time compensator. The validity, reliability and accuracy of the preseutod methods have been verified by the experiments on a VSI-fed IM drive system.     

Polarization modulation with optical lock-in detection reveals universal fluorescence anisotropy of subcellular structures in live cells

The orientation of fluorophores can reveal crucial information about the structure and dynamics of their associated subcellular organelles.Despite significant progress in super-resolution,fluorescence polarization microscopy remains limited to unique samples with relatively strong polarization modulation and not applicable to the weak polarization signals in samples due to the excessive background noise.Here we apply optical lock-in detection to amplify the weak polarization modulation with super-resolution.This novel technique,termed optical lock-in detection super-resolution dipole orientation mapping(OLID-SDOM),could achieve a maximum of 100 frames per second and rapid extraction of 2D orientation,and distinguish distance up to 50 nm,making it suitable for monitoring structural dynamics concerning orientation changes in vivo.OLID-SDOM was employed to explore the universal anisotropy of a large variety of GFP-tagged subcellular organelles,including mitochondria,lysosome,Golgi,endosome,etc.We found that OUF(Orientation Uniformity Factor)of OLID-SDOM can be specific for different subcellular organelles,indicating that the anisotropy was related to the function of the organelles,and OUF can potentially be an indicator to distinguish normal and abnormal cells(even cancer cells).Furthermore,dual-color super-resolution OLID-SDOM imaging of lysosomes and actins demonstrates its potential in studying dynamic molecular interactions.The subtle anisotropy changes of expanding and shrinking dendritic spines in live neurons were observed with real-time OLID-SDOM.Revealing previously unobservable fluorescence anisotropy in various samples and indicating their underlying dynamic molecular structural changes,OLID-SDOM expands the toolkit for live cell research.     

锦屏—苏南±800kV特高压直流输电工程换流站过电压及绝缘配合(英文)

Regarding to the problems of equipments manufacturing and layout in Jinping-Sunan ±800 kV UHVDC transmission system,overvoltage protection and insulation coordination in converter stations were studied.Configuration of arresters was studied at first,and scheme of MH arresters and V arresters connected in series was used to protect the high voltage Yy transformer’s valve side of dual 12-pulse converters.Overvoltage caused by DC faults and the withstand level of equipment in converter stations were studied using electromagnetic transient simulation.Based on operation parameters and characteristics of AC and DC system,equivalent models of both systems were set,together with most of the equipment in converter stations which would influence simulation results.The AC arresters’ transient response to AC faults was also simulated.For the most severe case,the peak voltage on AC bus arresters is up to 752 kV,along with stresses about 12.0 MJ in energy and 12.4 kA in current.Simulation results of transient overvoltage in converter stations were used to verify insulation coordination by comparing with the design value.The maximum insulation level would be less than 1 600 kV,which is no more than that in former UHVDC projects.     

On-Line Life Monitoring Technique for Tube Bundles of Boiler High-Temperature Heating Surface

High-temperature heating surface such as superheater and reheater of large-sized utility boiler all experiences a relatively severe working conditions. The failure of boiler tubes will directly impact the safe and economic operation of boiler. An on-line life monitoring model of high-temperature heating surface was set up according to the well-known L-M formula of the creep damages. The tube wal] metal temperature and working stress was measured by on-line monitoring, and with this model, the real-time calculation of the life expenditure of the heating surface tube bundles were realized. Based on the technique the on-line life monitoring and management system of high-temperature heating surface was developed for a 300 MW utility boiler, An effective device was thus suggested for the implementation of the safe operation and the conditinn-based maintenance of utility boilers.     

变压器直流偏磁及其与接地电阻关系的研究

Recently years,UHVDC transmission system is paid more attention to in the field of China’s power system.It takes key part in the China electrical power development stratagem.But,many problems are caused by UHVDC system,such as DC bias,corrosion of metal underground and so on.DC bias is harm to the transformers nearby UHVDC grounding polar.In this paper,the influences of DC grounding current on transformer are introduced and some suggestions of DC bias solution were provided.And,the relationship between UHVDC Grounding Current and grounding Resistance of Substation was analyzed.Firstly,two-part network circuit was used to equivalent the grounding circuit.Then,an analysis of rules was done between DC bias current and grounding resistance.Finally,the conclusion is given that DC bias current rises fast as DC grounding resistance or AC grounding resistance rises.It drops when resistance of AC transmission line or interaction resistance between DC grounding system and AC grounding system rises.Decreasing AC grounding resistance and DC grounding resistance is important to restrain DC bias current.Increasing resistance of AC transmission line such as adding resistance into transformer neutral-point grounding is a useful way to limit DC bias current.     

直接涂膜技术用于质子交换膜燃料电池膜电极制备

A new membrane electrolyte assembly (MEA) preparation method for polymer electrolyte membrane fuel cell (PEMFC) was developed by applying the directly printing catalyst on membrane technique. This method was simple and easy to be controlled as verified by repetition experiment. When the membrane with catalyst prepared by the new technique and the electrode with diffusion layer was only sandwiched but not hot pressed, this kind of MEA was called not-hot-press MEA (NPMEA) and its fuel cell performance was better than that of MEA which was hot pressed (HPMEA). The effects of 6 different kinds of solvents in catalyst mixture ink on the performance of fuel cell were assessed. It was discovered that iso-propanol was the best solvent in catalyst mixture ink and showed the best performance of fuel cell. Finally several MEAs prepared by different ways were tested on fuel cell station and it was reported that the performance of MEA prepared by the directly printing catalyst on membrane technique was the best in the whole voltage region.     

Effects of Crosswind on an Automobile Under Dynamic Conditions

This paper presents results of a series of experiments carried out on models of a car and a truck in a wind tunnel to observe the pressure coefficient variation when the truck was overtaken by the car. However, conventional wind tunnels are not equipped to measure the yaw moment and side force created due to pressure difference created as a result of the interaction of two vehicles and the cross wind. An additional attachment for the wind tunnel was de-signed and built to measure the yawing moment and the side force experienced by the car when the cross wind is ap-plied. The attachment consists of a “top plate” which is independent from the wind tunnel frame and free to rotate. The car model is fixed to the “top plate” the top plate is connected to the base plate via a load measuring shaft which is connected to load cells that enable to measure the yaw moment. The pressure coefficient variation was measured by a series of pressure tapings provided by the circumference of the car. The two models were tested independently in the wind tunnel for their pressure coefficient variation. It was found that the pressure coefficient around the car varies substantially when it is overtaking the truck. It was also observed that when the cross wind is applied the yawing moment and the side force on the car increases with the air speed. The attachment was calibrated prior to the investigation and have been able to obtain consistent results. To relate the observations to real world conditions, fur-ther investigations are necessary.     

植物绝缘油对绝缘纸热老化速率的影响及其机理(英文)

With the development of new insulation materials,vegetable oil-the best substitute for mineral oil-has gradually been widely used in the liquid insulation of transformers.To investigate the influence of vegetable oil on the thermal aging rate of oil paper,Kraft paper impregnated with mineral oil and vegetable oil have been underwent thermally accelerated aging at three different temperatures.The degree of polymerization(DP) of Kraft paper was measured to indicate the aging degree of insulation paper.The aging rate of Kraft paper in mineral oil and vegetable oil was compared quantitatively,and results showed that vegetable oil retarded paper’s degradation rate and extended its useful lifetime.The reasons contributing to such phenomena were analyzed using X-ray Photoelectron Spectroscopy(XPS) and molecular simulation software.Kraft paper in vegetable oil had larger activation energy.Due to the larger interaction force between water and natural ester molecules,water molecules were easily bonded with natural ester,weakening the hydrolysis process of cellulose.Cellulose was chemically modified by natural ester during the thermal aging process,and the reactive-OH(hydroxyl) groups on the cellulose became esterified with fatty acid esters.Water molecules were firmly bounded to the ester groups on glucose produced by esterification.The long-chain fatty acid esterified to cellulose was parallel with cellulose chains and acted as a "water barrier" to further weaken the hydrolysis process.     

油纸绝缘电介质响应低频弥散的极化机理(英文)

Both the real part and imaginary part of complex permittivity approximately have a log-linear frequency dependency at low fre- quencies, especially at ultra-low frequencies under conditions of different moisture concentrations and temperatures, which is recognized as the low frequency dispersion (LFD). In order to explain this dispersion, a new mechanism of dielectric response of LFD of oil-paper insula- tion is proposed. A simplified one-dimensional mathematical model of concentration polarization carrier caused by slow migration is developed and solved, which indicates that ion mobility is closely related to the size of gap and the adsorption capacity of cellulose molecu- lar chains to ions. A stochastic statistical model of the carrier mobility induced LFD is also developed. Moreover, actual tests under 50 °C and 2% moisture content were put forward, as well as simulations with according current waveforms. The simulation results agreed well with the experimental data in that concentration polarization of carriers caused by slow migration is the probable cause of low frequency dispersion of dielectric response for oil-paper insulation diagnosis.     

Analysis on Frequent Flameout of HG- 1025/18.2- YM6 Boiler

Based on reason analyses for frequent flameout of HG- 1025/18.2-YM6 boiler in a given power plant after coal quality variation, major factors such as unreasonable burner structure and inappropriate secondary air distribution were discussed in detail. A new mode of secondary air distribution was introduced to optimize the combustion performance, and a lower burner was retrofitted by increasing the relative distance between the primary air fuel rich-lean nozzles and reducing the size of waist air nozzles as well. As a result, the recirculating zone became more stable and the burner＇s combustion stability was improved. Practical operation shows that the modifications are so effective that the flameout problems caused by instable combustion never occur in operation.     

第二次全国电力系统计算机在线应用学术会议九月五日至九日在大连举行

The second Conference on Computer On-Line Application to Power Systems organized by the Chinese Institute of Electrical Engineers Automation and Computer Application Society was held on September 5-9,1981 at Dalian: Liaoning Province. 100 papers were advanced and 159 persons were present at the meeting.Following the first conference in 1979,this conference reflected the achievements in the on-line application of computers in China.The participaters were divided into three panel sessions to read the papers and discuss the problems dealing with the security control of power nettvorks by computers, the calculating methods used in on-line application of computers, and the design and debug of application software or system software separately.     

Corrosion control experience and water chemistry studies on fossil-fired plants

BackgroundThe power industry has long been plagued with complicationsand outages related to corrosion of plant components.Prior to the mid-sixties,corrosion of boiler water-wall tubeswas one of the prominent problems in power plants.Water-walltubes corrosion proceeding under iron oxide deposit caused causticgouging or acidic embrittlement of tube metal.Many boiler tubesfailed by sudden rupture.Field and laboratory studies showed that,carbonate alkalinity and neutral salt in boiler make up water treated     

基于脉冲电压法的10kVXLPE电缆绝缘诊断非线性分析(英文)

The diagnosis of water trees of cable insulation is of great importance as the water-treeing is a primary cause of aging breakdown for the middle voltage cables. In this paper, it is described how the water-tree-aged 10 kV XLPE cables were diagnosed. The cables were subjected to electrical stress of 5.9 kV/mm and a thermal load cycle in a curved water-filled tube for 3, 6 and 12 months of aging in accor- dance with the accelerated water-tree test method. The aged cables were used as the samples for water-tree diagnosis. First, the water-tree degraded cable, was charged by a DC voltage, and then the cable was grounded while a pulse voltage was applied to it for releasing the space charge trapped in the water trees. The amount of the space charge, which corresponds to the deterioration degree of the water trees, was calculated. The effects of DC voltage amplitude, pulse voltage repetition rate and aging conditions on the amount of the space charge were studied. Obtained results show that the amount of the space charge has a positive correlation with the applied DC voltage and the ag- ing time of the cables, and that a peak value of space charge appears with the increase of the pulse voltage repetition rate. An optimum pulse voltage repetition rate under which the space charge can be released rapidly is obtained. Furthermore, the releasing mechanism of space charge by the pulse voltage is discussed. Accumulated results show that the presented method has a high resolution for the diagnosis of water tree degradation degree and is expected to be applied in practice in future.     

Process Analysis of Double Circuit Transmission Line Trip-out on the Same Tower Due to Lightning

In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave threat to the power grid security.The cause of the accident and the accident process were studied for the sake of further understanding of the impact of lightning on power grid.As an example,110 kV double circuit transmission line(Xilong-line) was analyzed.At first,the system topology was given.Through the analysis on relay protection actions and the fault recorder data,over voltage on the insulator strings was calculated.Based on the analysis and the calculation,accident cause and the process were presented respectively.Secondly,it comes to the conclusion that the lightning failure was caused by counterattack.The wave of the lightning over voltage would spread to the not grounded neutral point of the transformers,and make the neutral protective gap breakdown,then cause freewheeling with the frequency of 50 Hz.As results of the relay protection,the double circuit transmission line all tripped out.Finally,the causes of the accident were proposed that included terrain features,large corner towers,strong thunderstorm weather and poor grounded contact of the tower.     

电晕放电脉冲电流波形和相位分布的测量、分析与仿真(英文)

Partial discharge(PD) is one of the most important phenomenon in high voltage insulations.In most cases, the appearance of partial discharges is related to insulation defects.Understanding partial discharges is important for diagnosis on insulation condition.Corona discharges appear when extremely high electric field appears on the conductor surface exceeding the electric field strength of the gas.The high electric field may occur at around protrusion with very sharp tip.This paper reported a holistic approach of corona discharge investigation.The needle-plane electrode system was used.The medium between the electrodes was air.The needle was made from steel with radius of curvature of 3μm(Ogura needle).Sinusoidal as well as triangular applied voltages were used.The waveform of the corona discharges was measured using a digital oscilloscope.The corona discharge pulses were measured using a phase-resolved PD measurement system.The system was able to measure the magnitude(q) and phase angle position(φ) of each PD pulses,as well as the number of discharge pulses(n).The role of applied voltage was investigated using phase-resolved analysis of corona discharge pulses through pulse sequence,pulse magnitude and pulse number analysis. Experimental results indicated that corona discharge current waveform was an impulse with rise time of about several ns and the impulse width of about 100 ns.The Fast Fourier Transform analysis indicated that the corona discharge current waveform had several spectrum peaks at frequency of 7.8 MHz,85.9 MHz,109.4 MHz and 195.3 MHz.The experimental results also showed that discharge pulses were concentrated around the peak of applied voltage for both sinusoidal and triangular voltages.The discharge magnitude,as well as its probability of occurrence,was strongly dependent on the instantaneous applied voltage.The shape ofφ-n,as well asφ-q-n PD patterns,were strongly reflected by the shape of applied voltage.In order to get deep understanding of the corona discharge,by utilizing results of the phase-resolved analysis,electrical equivalent circuits of corona discharges were proposed.The electrical equivalent circuit contained capacitances and a spark gap.For deeply understanding of PD phenomenon,computer simulation was done by using the proposed electrical equivalent circuits.The similarity of the measured and simulated PD patterns was assessed by comparing measured and simulated theφ-q-n andφ-n PD patterns.The results indicated that simulated PD patterns similar to those obtained from experiment.     

采用Fisher判别法对GIS中局部放电类型的识别(英文)

To monitor the condition of online power apparatus accurately and provide appropriate guidance on their maintenance,a fundamental ultra-high frequency(UHF) database of partial discharges corresponding to different types of defects is presented for the observation of insulation state of gas insulated switchgear(GIS).In order to imitate the defects in a GIS online,five types of typical partial discharge(PD) sources(i.e.floating metal,protrusion,bouncing particles,void in spacer,and particle on the surface of solid insulation) were designed and fabricated.A wideband UHF sensor and an amplifier were applied to obtain UHF signals.Based on the characteristics of the five different defects,nine meaningful parameters which were independent of the phase of the applied voltage were extracted from the PD samples and then discussed.In this paper,Fisher discriminant analysis(FDA),a pattern recognition algorithm,was applied for the purpose of classifying the defects.In this way,there was no need to set complicated parameters and kernel function,and the total discrimination accuracy of test samples was 97.6%.It indicates that based on the nine especial parameters,the typical defects in GIS can be identified exactly by means of FDA.Hence the analysis method could be possibly regarded as a universal classification method.