Modeling and Analysis for Practical CT Based on Transient Test and Parameter Identification

In the transient process of power grid faults,the transferring distortion of current transformer(CT)can seriously affect relay protection performance.Under these conditions,it is difficult to analyze the ferromagnetic characteristic of the magnetizing branch in the transient equivalent circuit of CT.The Jiles-Atherton hysteresis model(J-A model),which is widely used in digital simulations,can accurately describe the hysteresis and saturation process of the core characteristics;however,to acquire the parameters of the J-A model of current transformers in practical use is still a challenging problem.In this paper,physical tests based on a practical CT and parameter identification are presented to solve the problem.The basic hysteresis loops of P,PR,and TPY class of practical current transformers are obtained through physical tests.Thus,the J-A model parameters are identified using a hybrid genetic/simulated annealing algorithm,based on which transient simulation models of different class CTs are constructed.The effectiveness of the proposed method is verified via dynamic physical simulation tests.A typical accident is analyzed based on these models.

Impact of Typical Steady-state Conditions and Transient Conditions on Flow Ripple and Its Test Accuracy for Axial Piston Pump

The current research about the flow ripple of axial piston pump mainly focuses on the effect of the structure of parts on the flow ripple. Therein, the structure of parts are usually designed and optimized at rated working conditions. However, the pump usually has to work in large-scale and time-variant working conditions. Therefore, the flow ripple characteristics of pump and analysis for its test accuracy with respect to variant steady-state conditions and transient conditions in a wide range of operating parameters are focused in this paper. First, a simulation model has been constructed, which takes the kinematics of oil film within friction pairs into account for higher accuracy. Afterwards, a test bed which adopts Secondary Source Method is built to verify the model. The simulation and tests results show that the angular position of the piston, corresponding to the position where the peak flow ripple is produced, varies with the different pressure. The pulsating amplitude and pulsation rate of flow ripple increase with the rise of pressure and the variation rate of pressure. For the pump working at a constant speed, the flow pulsation rate decreases dramatically with the increasing speed when the speed is less than 27.78% of the maximum speed, subsequently presents a small decrease tendency with the speed further increasing. With the rise of the variation rate of speed, the pulsating amplitude and pulsation rate of flow ripple increase. As the swash plate angle augments, the pulsating amplitude of flow ripple increases, nevertheless the flow pulsation rate decreases. In contrast with the effect of the variation of pressure, the test accuracy of flow ripple is more sensitive to the variation of speed. It makes the test accuracy above 96.20% available for the pulsating amplitude of pressure deviating within a range of ~6% from the mean pressure. However, with a variation of speed deviating within a range of ±2% from the mean speed, the attainable test accuracy of flow ripple is above 93.07%. The model constructed in this research proposes a method to determine the flow ripple characteristics of pump and its attainable test accuracy under the large-scale and time-variant working conditions. Meanwhile, a discussion about the variation of flow ripple and its obtainable test accuracy with the conditions of the pump working in wide operating ranges is given as well.

正弦扫描振动模拟瞬态振动环境等效性研究

使用正弦扫描振动模拟低频瞬态振动环境是航天工业的一种传统试验方法,其对产品的环境考核可能同时存在欠试验和过试验。首先对两者等效性进行分析,进而采用冲击响应谱、最大响应谱等相关理论,对等效正弦扫描振动试验条件制定中的扫描速率、阻尼系数进行了研究,并给出参数选择建议。最终提出了制定正弦扫描振动环境试验条件的步骤,为采用正弦扫描试验进行低频瞬态环境适应性考核提供借鉴。

导叶叶片数对喷水推进泵瞬态特性的影响

为揭示喷水推进泵不同导叶叶片数时的瞬态特性规律,基于DES混合模拟和FEM声学有限元方法,对喷水推进泵流场和声场进行数值模拟,并进行试验,验证了瞬态特性数值计算方法的准确性,研究了不同导叶叶片数(Z=5,6,7)对喷水推进泵推力、压力脉动、内流诱导噪声等性能的影响规律.结果表明:随着导叶叶片数增大,喷水推进泵推力先减小后增大,流量逐渐减小,转矩逐渐增大;导叶叶片数对叶轮出口压力脉动分布规律影响较小,对压力脉动主频处幅值有较大影响,轮毂处压力脉动幅值受导叶叶片数增大先减小后增大,轮缘和流道中心处幅值随着导叶叶片数增大逐渐减小;导叶叶片数变化会改变内流诱导噪声主频,增大导叶叶片数有利于降低喷水推进泵内流诱导噪声主频处幅值和总声压级.

短路电流对二次设备电磁干扰分析及抗干扰措施

目前智能配电网的建设不断推进,加快了配电开关一二次设备相关技术的发展,也对长期处于复杂电磁环境下的二次设备提出了更高的要求。文中基于合成试验回路搭建了短路电流对配电开关二次设备电磁干扰试验平台,开展开断故障电流对相关干扰对成套设备的影响研究,分析干扰信号产生原因、频谱特性。针对干扰的特性设计一套抗干扰测量系统,利用ATP-EMTP模拟合成回路进行仿真分析并进行实际测试验证。结果表明:成套设备进行开断试验时,二次设备端口会受到较大的干扰。电流波形也会发生畸变,干扰电流的最高可到26 A,且干扰电流受电流互感器磁饱和和退饱和的影响,通过增加抗干扰措施,二次设备输出准确度与之相比提升约40%。本次的试验结果可为一二次融合成套设备中二次设备电磁兼容研究提供相关依据。

古兜山隧道富水段探测与处置技术研究

为探明古兜山隧道富水情况,通过超前钻孔、瞬变电磁法探测隧道富水段情况;针对古兜山隧道的富水情况,开展现场注浆止水加固试验研究,提出富水区注浆止水关键技术;综合考虑隧道地下水排放量与植被生态的平衡,给出隧址区的地下水允许排放量。研究结果表明:选择普通水泥-水玻璃双液浆用于钻孔揭露隧道涌水量较大的区域,确保注浆效果;综合考虑地下水压力、地层岩性、浆液的性质和浓度及注浆扩散半径等因素,确定注浆终压取值为5~6 MPa;针对植被、生态环保要求,按2年内恢复原始地下水位,确定泄洪口区、水库连接区及隧道近出口区的地下水允许排放量。

基于LSTM的半航空瞬变电磁资料去噪方法研究

随着干扰电磁环境的因素越来越多,半航空瞬变电磁数据所含噪声的特性难以正确地处理和分析,而去噪是提高瞬变电磁场信号处理和分析精度的重要手段之一。相较于传统的去噪方法大都依赖频率特征、耗时较长以及计算参数难以确定,LSTM(Long Short-Term Memory)神经网络不依赖频率特征的同时能够很好地处理非线性时间序列。因此笔者将LSTM应用于半航空瞬变电磁数据处理,在一维正演数据添加各类噪声的基础上,分为训练和测试,训练采用监督学习方式进行,从而捕获信号的特征和结构信息,测试阶段也采用监督学习方式进行,利用有标签训练数据对网络进行优化进一步提高去噪效果。最后将测试效果良好的模型应用于实际资料中,结果表明此方法能够有效地去除晚期道中的噪声,是一种能够用于半航空瞬变电磁数据去噪的可行手段。

一种无回跳特性TVS的快速建模方法及验证

瞬态抑制二极管是一种常见的电磁防护器件,在静电防护、浪涌防护、强电磁脉冲防护中有着广泛应用,其瞬态行为对于指导电磁防护设计具有重要意义,但市面上一般没有现成可用的模型。文中基于ADS软件建立一种无回跳特性TVS的仿真模型,使用复杂度较低的TVS模型框架。在建模过程中,分析了模型参数对于精度的影响,并利用S参数测试方法和TLP测试方法获取实测数据,最终构建了两款TVS的完整仿真模型。模型验证结果表明,该模型仿真与实测数据在TVS未工作、即将工作和进入工作状态时都较为一致,仿真与实测误差最大不超过10%,说明其精度足够支撑TVS瞬态仿真。所建立的模型可直接用于TVS的瞬态仿真,该方法也可用于其他无回跳特性TVS的模型构建,为电磁防护设计提供支持。

基于温度计算的肘型电缆接头压接状态评估方法

附件是电缆线路的薄弱环节,温度是反映电缆运行状态的重要参数,研究环网柜中肘型电缆接头运行温度具有重要意义。建立柜内肘型接头三维暂态磁热流耦合场数学模型,基于阶跃电流温升试验验证了模型的正确性;仿真研究了夏季严酷场景肘型接头多物理场及其温度时空分布,研究了肘型接头外皮温度和温差的影响因素。结果表明,肘型接头外皮温差受环境温度和负荷曲线形状的影响较小,与负荷电流峰值近似呈二次关系,与压接电阻比率基本呈线性单增关系,因而可以作为识别肘型接头压接状况的参数。最后提出基于接头外皮温差的肘型接头压接状态评估方法,对接头温度监测和故障预警有重要的参考价值。

基于法拉第效应的宽频光学电流传感器研制及其性能研究

当前智能电网和新型电力系统中存在大量高频暂态电流分量。高频暂态电流是反映电力系统扰动及故障过程的重要信息,对其波形、频率、幅值等信息参数进行实时观测是预防和确保电网安全稳定运行的前提。而传统电流测量方式存在频带窄、易受电磁干扰、绝缘配合难度大等问题,难以对暂态电流进行有效检测。故提出并设计了一种具有抗干扰能力的螺线管式宽频光学电流传感器,基于传感器性能测试平台,研究了传感器的灵敏度、线性度以及频率特性,结果表明目前传感器的灵敏度为62.57 mV/A且带宽可以达到1 MHz以上;此外搭建了直流电弧实验平台对直流电弧进行了测量。试验结果表明,该传感器可实现对直流至高频电弧分量的有效测量,其测量结果与标准电流探头的线性相关度可达0.9971,多次实验结果表明相关系数的相对变化率小于2%,具有一定工程使用价值。

某车型涡轮增压执行器及接插件热害问题研究

基于CFD流固耦合瞬态分析对某反置式发动机车辆的涡轮增压电子执行器及接插件热害问题进行整车及机舱热管理,通过优化发动机装饰罩的引流结构、优化涡轮增压器隔热罩的形状、改变风扇停机延时策略三种优化方案来降低涡轮增压电子执行器及接插件的温度,并在实车上进行试验验证。仿真和试验结果表明,仿真结果与试验结果吻合较好,综合三种优化方案可满足设计需求,最终解决了执行器和接插件超温问题。

二自由度超声波电机瞬态特性测试研究

多自由度超声波电机具有集成度高、动态响应快等特点,是实现复杂巧妙动作的理想驱动源。为发展其动态控制技术,提出一种新型的基于测速模块的二自由度电机瞬态特性测试系统。首先,介绍瞬态特性测试机构的结构形式和工作原理;其次,阐明瞬态特性的速度测试方法;最后,在两组驱动输入参数下,完成瞬态特性的比对测试。实验证明,设计的系统满足二自由度电机瞬态特性的测试要求,电机的启动与关断响应时间均很短,电机的动态性能较好。

特高压GIS用磁环型阻尼母线VFTO抑制性能试验研究

GIS中的隔离开关在操作过程中由于断口重复击穿会产生特快速瞬态过电压(very fast transient overvoltage,VFTO)。VFTO幅值高、波前陡,严重威胁电气一次绝缘,并会产生电磁干扰问题。目前,实际工程中除采用带投切电阻的隔离开关抑制VFTO外,还可以采用磁环型阻尼母线对VFTO进行抑制。为了保证GIS的可靠性,磁环型阻尼母线抑制性能的优劣至关重要。为此,亟需研究提出一种在试验室进行磁环抑制效果的评定方法。文中针对磁环型阻尼母线的抑制性能,设计了专门的抑制性能试验回路,该试验回路中主要包含套管、阻尼电阻、放电间隙、磁环型阻尼母线、GIS短母线、VFTO传感器以及VFTO测量系统。该试验回路的额定电压为1100 kV,回路中的套管和母线可承受的额定工频电压为1100 kV,阻尼电阻的阻值为560Ω或1500Ω,放电间隙可以通过电极间距的调整产生不同等级的放电电压值和放电陡波,陡波上升时间可以达到30 ns。应用该试验回路在试验室进行模拟试验的方法检验磁环型阻尼母线的抑制效果,试验结果表明,该试验回路可以完成磁环型阻尼母线抑制效果的检验,可以定量地给出抑制效果的优劣。该方法可以推广到其他电压等级的GIS产品中,有助于推动实现磁环型阻尼母线的工业化设计、制造及检验。

某工业设备钢结构平台振动问题的动力测试与分析

以某工业设备钢结构平台外激励下的振动问题为背景,对该平台振动设备开启状态与自然扰动状态下典型位置加速度、速度响应进行了动力测试,采用3D3S(V14.10)软件建立了整体与局部模型并进行了模态分析;然后,采用ABAQUS软件对考虑简化振动条件下的结构进行了谐响应分析,分析结果表明,激励频率并非共振显著频率;最后,进行了简化振动条件下的瞬态动力学分析,并对增加板厚与加大梁柱截面2种加固方式进行了减振效果对比分析,分析结果表明,对该类型钢结构平台,增加楼板刚度及结构刚度不能够显著降低振动水平,针对类似结构,应采取隔振措施来解决设备激励导致的结构振动问题。

基于瞬态动力学的汽车轮毂落锤试验分析

汽车轮毂是汽车运行的主要部位之一,瞬态动力学是一种动态特性分析方法,可用于评估轮毂的结构和性能。针对汽车轮毂落锤试验模型,利用三维制图软件和ANSYS,通过测算与仿真,得到汽车轮毂落锤试验的应力应变变化规律。结果显示,落锤试验中汽车轮毂的最大等效应力位于轮毂气孔附近,最大形变和最大切应力位于轮毂气孔下端面处。轮毂气孔附近是危险点,与实际落锤试验结果相符。该结果对轮毂结构的设计与优化具有一定意义。

航空发动机燃油阶跃试验供油规律

为了分析燃油阶跃逼喘试验中供油规律对发动机的影响,以小涵道比混合排气涡扇发动机为研究对象,将发动机模化为典型的基本部件组成的系统,构建考虑转子动力学方程及容积效应的平衡方程。对发动机燃油阶跃逼喘过程进行仿真,理论计算结果与试验数据误差在4%以内,验证了计算方法的准确性。通过仿真获取了阶跃供油规律的关键影响因素,仿真结果能够为发动机燃油阶跃试验的试验提供理论基础,降低发动机在燃油阶跃逼喘过程中的超温、超转风险,具有一定的工程意义。

地下水示踪试验中穿透曲线的解析——以平果县平南赤泥堆场地下岩溶系统为例

地下水示踪试验中的穿透曲线解译是一项重要的技术,通过这一技术,可以获得关于地下岩溶管道的信息,如管道的尺寸、连通性、分布和方向等。然而,在实际应用中,仍存在许多问题需要解决,以提高对穿透曲线的解释准确性和可靠性。以平果县平南赤泥堆场地下岩溶系统为例,利用荧光计获取示踪数据结合Qtracer2软件对示踪剂回收率、平均滞留时间、弥散系数、地下水平均流速等参数进行计算,并结合当前被广泛认同的结论对穿透曲线中的多峰、异常波动等现象进行解释。由于本次研究区的岩溶管道规模小,将岩溶管道的复杂性降低到了可计算程度,对并联岩溶管道长度近似值进行计算,最后排除曲线尾部的峰值为溶质暂态存储现象,分析表明研究区属于多管道岩溶系统,地下水主要表现为“岩溶水扩散流”特征。本研究为地下水数值模型提供了依据,为研究如何分析岩溶复杂介质运移特征提供参考。

A well test model for stress-sensitive and heterogeneous reservoirs with non-uniform thicknesses

In view of the anisotropy,heterogeneity and stress-sensitive permeability in low permeability reservoirs,an analytical well test model was established by introducing the concept of permeability modulus.This model considered the permeability stress-sensitivity,wellbore storage effect,and the skin effect.The perturbation technique and Laplace transformation were used to solve the mathematical model analytically in Laplace space,and the bottom-hole pressure type curves were plotted and analyzed in real space by using the Stehfest numerical inversion.

Executive function during transient ischemic attacks

BACKGROUND： Recent researches demonstrate that damage of executive function is an early manifestation of vascular cognitive disorder. OBJECTIVE： To investigate the executive functions of patients with transient ischemic attack （TIA）. DESIGN： Case control. SETTING： Department of Neurology, the First Affiliated Hospital of Xinxiang Medical College. PARTICIPANTS： A total of 83 TIA patients （46 males and 37 females, aged 32 - 74 years） were selected from Department of Neurology, the First Affiliated Hospital of Xinxiang Medical College from July 2005 to December 2006. The diagnosis of TIA was established by the criteria of cerebrovascular diseases made by the Fourth National Cerebrovascular Disease Meeting. In these cases, forty-five patients （54%） were involved in internal carotid artery, and thirty-eight patients （46%） were involved in vertebral basilar system. Fifty healthy adults （Control group： 28 males and 22 females, aged 32 - 74 years） were chosen from retiree in community and family of patients. All of them were right-handedness, without cerebrovascular disease, cerebral trauma, inborn oligophrenia, and heating and visual disorders; also they had no anxiety and depression nearly one week. In addition, all the subjects cooperated with examination. METHODS： After TIA diagnosis, all patients received neuropsychological examination, including attention and inhibition, working memory, flexibility, planning and diversion, based on Stroop tests （C and CW） and the Wisconsin card sorting tests （WCST）. ① WCST test： The edition revised by Nelson was used. We would take the times of sorting, incorrect response, persistent incorrect response, and randomly incorrect response as the index of evaluation.② Stroop tests： The edition revised by Trenarry was used and this test had two types： form color and form color-word. Their incorrect response and response time were recorded for data analysis in the end. MAIN OUTCOME MEASURES： Results of WCST test and Stroop tests. RESULTS： A total of 83 TIA patients and 50 healthy subjects were involved in the final analysis. Items of Stroop tests, including response time of Stroop-C test, incorrect response of Stroop-C test, response time of Stroop-CW test and incorrect response of Stroop-CW test, and items of WCST, including incorrect response, persistent incorrect response and random incorrect response, between internal carotid artery system and vertebral basilar artery system were （93.87±24.39） s, 3.16±3.97, （228.46±68.13） s, 12.91 ± 10.56, 55.42± 20.38, 26.58± 10.41, 28.62±11.22; （96.76±24.75） s, 3.89±4.77, （223.46±72.54） s, 18.71 ± 13.80, 52.47 ±22.25, 28.82± 16.20, 23.39±9.72, respectively; this was higher than those in the control group [（52.10± 12.18） s, 1.68± 1.97, （134.86±34.15） s, 4.22±4.21, 32.46± 17.97, 14.42±8.47, 18.24± 10.24, P 〈 0.05 - 0.01]. Times of sorting of WCST between internal carotid artery system and vertebral basilar artery system were obviously lower than those in the control group （8.27±2.73, 8.66±2.77, 11.22±2.41, P 〈 0.01）. However, there were no significant differences between internal carotid artery system and vertebral basilar artery system （P 〉 0.05）. CONCLUSION： Patients with TIA have executive dysfunctions, and the dysfunctions have no difference between internal carotid artery system and vertebral basilar artery system.

变电站开关柜“在线监测+带电检测”双模式研究与应用

高压开关柜是电力设备的重要组成部分,由于高压开关柜在长期运行过程中受到环境的温度、湿度以及电力设备的材质性质、电动力产生的震动等因素的影响。为保障高压开关柜安全稳定运行,采用“在线监测+带电检测”双模式监测,将在线状态监测与局部放电检测有效结合,通过温度、湿度、风机在线监测实现对高压开关柜运行状态实时监测,采用暂态地电压检测与超声波检测实现高压开关柜局部放电检测,有效预防开关柜过热或凝露情况,及时发现电气设备潜在隐患及变化趋势,有效降低开关柜故障率。