Calculation of distribution system voltage and power flow state using measured values

This paper describes a techique of calculating voltage and power flow state of a distribution system using the information measured with two or more switches with sensors installed in a distribution system. In the proposed technique, a set of the power distribution section where two or more switches with a sensor are connected is defined as the large section, and the active power and reactive power consumption in the large section are calculated based on measurement information, voltage (RMS), current (RMS), and power factor. Using the simple distribution system model consisting of the large sections, the power consumption of the large section is calculated by the power flow calculation to separate power consumption and power distribution loss. It is distributed to the small sections that constitute the large section, and detailed power flow calculation is performed. Verification of the proposed technique and basic estimation of the calculation error were performed using the simple power distribution system model. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(4): 33–42, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20416     

EFFECTS OF UNDERSCOUR DEPTH AND HORIZONTAL SPACING BETWEEN TWO BED PROTECTION BLOCKS ON STABILITY OF FRONTAL BLOCK

The stability of a river-bed protection block in a flood event is affected by underscouring of the block. The effects of block spacing on block stability were investigated in different underscour conditions. Three blocks were placed at the bottom in a flume, and the underscour depth of the frontal block and distance between the first and second blocks were changed. Drag and lift forces were measured directly in each experimental condition. Particle Image Velocimetry (PIV) was used to visualize the flow and eva- luate the streamline pattern. Pressure measurements around the block to understand the pressure distribution show that the pressure distribution on the rear and bottom surfaces of the block is significantly affected by changes in block spacing and underscour depth. The experimental results show that for the same underscour gap, lift, and drag coefficients decreased with increasing space between the two blocks. In addition, if the underscour gap is increased with the same horizontal spacing, the lift coefficient increases and drag coefficient decreases. These results demonstrate that wider spacing enhance stability of the frontal block in the underscour condition. Moreover, analysis of block stability with changing underscouring and horizontal spacing shows that bed protection blocks seem to have more stability when the gap between two bed protection blocks was equal to height of the blocks.     

后过渡金属镍络合物及其催化烯烃聚合的研究进展

对后过渡金属镍络合物及其催化烯烃聚合的研究进展进行综述。按配体的不同,将镍络合物分为4类:P-O配体型、N-O配体型、N-N配体型及P-N配体型。对各类镍络合物的烯烃聚合特点进行了介绍,并给出了部分聚合机理。     

考虑暂态稳定约束的可用传输能力计算

提出了一种考虑暂态稳定约束的可用输电能力(ATC)的计算方法。建立了在传统的静态ATC模型中加入暂态稳定约束的有效方法,并在此基础上给出了动态ATC问题的优化计算模型。同时提出了求解动态ATC问题的内点非线性规划算法。该算法不仅具有强大的处理等式约束和不等式约束的能力,而且具有良好的收敛性,能够有效求解动态ATC问题。所提出的模型与算法已在若干系统得到了验证,文中以IEEJ-WESTlO和IEEJ-WEST30系统的计算结果为例说明了该方法的有效性。     

利用最大泡压法研究扩散控制的溶液表面吸附动力学

In studying the diffusion-controlled adsorption kinetics of aqueous surfactant solutions at the air/solution surface by means of the maximal bubble pressure method, Fick's diffusion equation for a sphere should be used. In this paper the equation was solved by means of Laplace transformation under different initial and boundary conditions. The dynamic surface adsorption (t) for a surfactant solution, which was used to describe the diffusion-controlled adsorption kinetics at the solution surface, was derived. Different from the planar surface adsorption, the dynamic surface adsorption (t) for the short time consists of two terms: one is the same as WardTordai equation and the other reflects the geometric effect caused by the spherical bubble surface. This effect should not be neglected for the very small radius of the capillary. The equilibrium surface tension γeq and the dynamic surface tension γ(t) of aqueous C10E6 [CH3(CH2)9(OCH2CH2)6OH] solution at temperature 25°C were measured by means of Wilhelmy plate method and maximal bubble pressure method respectively. As t → 0, the theoretical analysis is in good agreement with experimental results and the dependence ofγ(t)on(√t r0/√πD)2 is linear.     

Evaluating uncertainty in accident rate estimation at hydrogen refueling station using time correlation model

Hydrogen, as a future energy carrier, is receiving a significant amount of attention in Japan. From the viewpoint of safety, risk evaluation is required in order to increase the number of hydrogen refueling stations (HRSs) implemented in Japan. Collecting data about accidents in the past will provide a hint to understand the trend in the possibility of accidents occurrence by identifying its operation time However, in new technology; accident rate estimation can have a high degree of uncertainty due to absence of major accident direct data in the late operational period. The uncertainty in the estimation is proportional to the data unavailability, which increases over long operation period due to decrease in number of stations. In this paper, a suitable time correlation model is adopted in the estimation to reflect lack (due to the limited operation period of HRS) or abundance of accident data, which is not well supported by conventional approaches. The model adopted in this paper shows that the uncertainty in the estimation increases when the operation time is long owing to the decreasing data.     

Feedback control of the position of the levitated superconducting magnet in the RT-1 device

The Ring Trap-1 (RT-1) device confines a high- plasma in a magnetospheric configuration which is generated by a high-temperature-superconducting coil levitated in a vacuum chamber. The levitated coil is unstable with respect to the vertical motion when it is attracted from above. The vertical motion has been analyzed from the equation of motion and the flux conservation law and the response of the PD (proportional-derivative) feedback system of RT-1 has been formulated by using a transfer function. The result of the model analysis has shown sufficient agreement with experiments. To meet the various requirements in order to conduct the plasma experiments and measurement, the feedback gains are optimized to suppress a feedback noise in parallel with ensuring the stability of the system.     

Disconnection detection using earth capacitance measurement in photovoltaic module string

A disconnection detection method using an earth capacitance measurement in photovoltaic (PV) module string was experimentally studied. In the experiments with disconnections between PV modules in the string, the earth capacitance of the string was increased in proportion to the module number, and this feature resulted in that the disconnection position between the modules could be estimated by comparing the earth capacitance value of the failed string with that of the good string. Since the earth capacitance was not affected by the irradiance change, the detection method could be applied anytime to locate the disconnection position in the string without the effect of the irradiance change. Moreover, this method could be applied not only to the string consisting of the crystalline Si modules but also to the string consisting of the amorphous Si modules. Copyright © 2008 John Wiley & Sons, Ltd.     

Hysteretic Phenomenon of Shock Wave in a Supersonic Nozzle

In recent years, hysteretic phenomena in fluid flow systems drew attention for their great variety of industrial and engineering applications. When the high-pressure gas is exhausted to atmosphere from the nozzle exit, the expanded supersonic jet with the Mach disk is formed at a specific condition. In two-dimensional expanded supersonic jet, the hysteresis phenomenon for the reflection type of shock wave is occurred under the quasi-steady flow and the transitional pressure ratio between the regular reflection and Mach reflection is affected by this phe- nomenon. However, so far, there are very few researches for the hysteretic phenomenon of shock wave in a supersonic internal flow and the phenomenon has not been investigated satisfactorily. The present study was concemed with the experimental and numerical investigations of hysteretic phenomena of shock wave in a supersonic nozzle, and discussed the relationship between hysteresis phenomenon and rate of the change of pressure ratio with time.