Acoustic partial discharge localization methodology in power transformers employing the quantum genetic algorithm

Partial discharge (PD) is one of staple reasons resulting in the deterioration of insulation system in power transformers and power faults. If the PD activity can be located at an early stage, preventive maintenance measures can be taken effectively. Therefore, the localization techniques of the PD do play an extraordinarily momentous role to enhance the operating reliability and stability of the system. It is proposed that a methodology based on the quantum genetic algorithm (QGA) adopting acoustic emission (AE) techniques for locating PD in power transformers. Results of the calculating example confirm the localization effectiveness and accurateness of the proposed method are ideal and satisfactory, and that precision of localization is enhanced compared to some other localization algorithms. The acoustic localization methodology based on the QGA is feasible and of suitability for the field applications.     

Vibration transmission from internal structures to the tank of an oil-filled power transformer

The vibration of a transformer tank is related to the transformer’s noise radiation and health condition. Therefore, it is important to understand the transmission of vibration from internal vibration sources in the windings and core to the transformer tank. The characteristics of this transmission are determined by direct mechanical coupling between the internal structures and the tank, and by indirect coupling through fluid–structure interaction induced by the transformer’s cooling oil. In this paper, the transmission of vibration is examined experimentally in a 110-kV power transformer with and without cooling oil. Under respective mechanical and electrical excitations, vibrations of the internal structures and transformer tank are measured simultaneously. The results allow an evaluation of the transmission efficiency of vibration from the internal structures to the tank, and the effects of fluid–structure coupling on the transmission. This experimental work improves understanding of vibration transmission in oil-filled power transformers, and explains the characteristics of a transformer’s on-line vibration.     

LTD模块气体开关电极材料烧蚀性能实验

针对直线变压器驱动源(LTD)对开关的长寿命需求,基于前期研制的200kV低抖动多间隙气体开关电极几何参数以及开关通流水平,详细开展了不同电极材料(钼、黄铜、铜钨合金、高密度石墨、304和321不锈钢)的烧蚀性能实验。实验结果表明,在单次电荷转移量15.4mC,脉冲电流20kA条件下,体积烧蚀速率从大到小依次为:石墨、黄铜、铜钨合金、钼、不锈钢。电极烧蚀微观形貌分析表明,不锈钢是用于LTD开关相对较好的电极材料。根据不锈钢电极的体积烧蚀速率,可知理论上LTD开关的运行寿命可以超过1×106次,但前提是开关外壳需保持足够的绝缘强度。     

基于编码器的复摆设计与实验研究

针对复摆实验,设计了一种基于编码器的复摆实验装置。该装置将摆锤和多孔摆结合起来,可以采用多种方式对重力加速度、转动惯量进行求解,并验证了刚体的平行轴定理。在实验过程中,采用Matlab进行最小二乘法线性拟合,创新性地完成了对重力加速度的求解和平行轴定理的验证。实验结果表明,相比于传统的复摆,该装置更为简便,精度更高。     

Electrical–thermal aging characteristic research of polymer materials by infrared spectroscopy,

Traditional insulation paper (pressboard) used in power transformers has weaknesses such as poor thermostability, low breakdown voltage, and high permittivity, which leads to its degradation or even breakdown over time. For this paper, in order to judge if they could be used as new insulation materials for transformers, polycarbonate and polyester films were selected for electrical–thermal aging tests in temperatures of 110°C and 130°C in comparison with the insulation paper. Several infrared spectral tests were carried out on the three materials under a scanning electron microscope to analyze their electrical–thermal aging characteristics, mechanical behaviors, and degrees of polymerization. The functional group whose absorption peak intensity decreased drastically with aging was referred to as the characteristic functional group, and its peak absorption intensity was used to reflect its aging level. This paper found that the polycarbonate had a better aging resistance than both the insulation paper and PET. Copyright © 2014 John Wiley & Sons, Ltd.     

8-3线优先编码器74LS148的级联分析及研究

74LS148是一种带扩展功能的8-3线优先编码器,将多片74LS148集成8-3线优先编码器级联构成不同的编码器,能够灵活、有效地扩大编码器的使用范围。不同的74LS148进行级联时,任何时候只对其中优先级别最高的输入信号进行编码,编码器的工作状态由使能输入端决定。     

NIRS feature extraction based on deep auto-encoder neural network

As a secondary analysis method, Near Infrared Spectroscopy (NIRS) needs an effective feature extraction method to improve the model performance. Deep auto-encoder (DAE) can build up an adaptive multilayer encoder network to transform the high-dimensional data into a low-dimensional code with both linear and nonlinear feature combinations. To evaluate its capability, we experimented on the spectra data obtained from different categories of cigarette with the method of DAE, and compared with the principal component analysis (PCA). The results showed that the DAE can extract more nonlinear features to characterize cigarette quality. In addition, the DAE also got the linear distribution of cigarette quality by its nonlinear transformation of features. Finally, we employed k-Nearest Neighbor (kNN) to classify different categories of cigarette with the features extracted by the linear transformation methods as PCA and wavelet transform-principal component analysis (WT-PCA), and the nonlinear transformation methods as DAE and isometric mapping (ISOMAP). The results showed that the pattern recognition mode built on features extracted by DAE was provided with more validity.     

三导体螺旋脉冲形成线的输出特性

 采用横电磁波传输理论,分析了三导体螺旋脉冲形成线（PFL）（包含内筒、螺旋中筒和外筒）的脉冲形成过程,给出了螺旋PFL的波阻抗、慢波系数、输出脉冲的平顶波动幅度等特征参数的计算公式。研究表明:三导体螺旋PFL具有与螺旋传输线同样的波阻抗和慢波系数;螺旋PFL的输出脉冲平顶波动,随着慢波系数或负载阻抗的增大而减小。     

延时效应对直线变压器电子束源的影响

 从长脉冲直线变压装置故障试验出发,对其波形顶部展宽、前沿变短现象进行了分析。利用电流传导理论,探讨了波叠加延迟效应。通过3维仿真分析,得到了不同时序激励的输出波形。结果表明：靠近二极管端单元为首模块时,开关触发延时与波叠加传输延迟可相互抵消,实现波形优化目标。     

应用超声光栅测量变压器油中超声波速度

近几十年来,由于压电换能原件效率的提高和低噪声的集成元件放大器的应用,超声波传感器在变压器的在线监测及局部放电检测中得到广泛的应用．准确测量变压器油中超声波的传播速度,对变压器局部放电检测研究具有非常重要的意义．根据超声波在液体中传播时能够形成超声光栅的特点,介绍了一种应用分光计精确测量变压器油中超声波速度的方法．实验测得29．3℃时变压器油中超声波速度为1432m／s,与超声手册中标准值符合得很好,相对误差仅为0．5％．该方法有助于提高变压器在线监测及局部放电检测的精确度．