基于有限元法的单芯电缆接头线芯温度计算

对电缆接头线芯温度进行监测可以有效评估电缆接头的状态,但直接测量线芯温度较为困难且容易破坏电缆接头结构,因此常通过表皮温度估算线芯温度。为提高电缆接头线芯温度计算精度,本文在有限元软件COMSOL中建立电缆中间接头的仿真模型,并进行电磁-热耦合计算。研究环境温度和负荷电流对电缆接头线芯和表皮温度的影响,并对各种工况下的仿真数据拟合分析得出由电缆接头表皮温度和环境温度对线芯温度的表达式,最终验证其有效性。该计算方法可以快速、准确地进行电缆接头线芯温度计算,为电缆中间接头温度的监测和状态评估提供依据。     

基于Dolph-Chebyshev窗的电力电缆中间接头定位诊断

提出一种基于Dolph-Chebyshev窗的配电电缆中间接头定位改进方法。根据电缆传输线模型说明频域反射法（frequency domain reflectometry,FDR）的定位原理,建立定位仿真模型进行验证,通过仿真对比分析选择基于Dolph-Chebyshev窗的FDR改进方法;同时搭建电缆总长为20 m、接头位置为10 m的中间接头冷热循环受潮平台,探究其受潮发展规律;建立多接头仿真模型,探究接头在不同缺陷程度时的定位幅值关系。结合诊断模型,在2 800 m多接头10 kV XLPE电缆上进行验证。仿真及实验结果表明：所提方法能够准确定位各接头并有效识别出缺陷接头;验证了所提方法对电缆异常接头定位及诊断具有可行性。     

XLPE表面缺陷对电场及击穿电压的影响

电缆中间接头施工过程中易造成XLPE表面划伤、附着污染颗粒和表面受潮三种缺陷,为评估缺陷对接头运行性能的影响,建立了电缆中间接头XLPE绝缘片状模型,分析了不同缺陷下电场的变化,探究了不同缺陷对电场及击穿电压的影响程度。结果表明,XLPE在划伤时划痕处的电场产生严重畸变,为非划痕处的1.6倍;受潮时XLPE表面附着污染水中导电杂质越多,污染水的电导率越高,从而使其导电性能增强,电场强度变大,是同界面处非受潮部分的1.22~1.40倍;XLPE表面附着污染颗粒时,颗粒与其交界面处电场发生较严重畸变,是同界面无缺陷时的1.50倍左右,划痕对XLPE绝缘的电场影响最严重。通过试验结果显示正常无缺陷时的击穿电压为129.6kV,划伤缺陷的击穿电压为59.1kV,受潮缺陷的击穿电压为69.7kV,杂质缺陷的击穿电压为59.2kV,划痕对XLPE绝缘的击穿电压影响最严重。研究成果为探究不同缺陷对电缆中间接头XLPE绝缘性能的影响提供了重要依据。     

一起XPLE电缆中间接头故障解体分析实例

电缆中间接头因其复杂的绝缘结构,现场制作安装受工艺水平、环境条件、运行环境影响等已成为电缆运行的薄弱环节,特别是沿海地区高水位的运行环境,成为电缆中间接头故障的一个诱因。针对天津地区一起电缆中间接头事故,首先给出了电缆、电缆中间接头及保护动作情况,然后对电缆中间接头进行了解体分析,并分析了故障原因,最后给出了避免此类故障发生的具体措施。     

一起35 kV电缆中间接头故障分析及对策研究

针对一起近期发生的35 kV电缆中间接头击穿故障,进行了故障接头解体检查和故障原因分析,指出了电缆中间接头压接管施工工艺存在严重缺陷,导致了压接管、电缆主绝缘及预制式接头之间存在台阶气隙,以及局部场强高度集中引起局部放电,最终导致中间接头绝缘击穿,提出了因施工工艺不当导致电缆接头故障的防范措施。     

消息报道

西安电炉研究所与无锡钢铁厂协作试制的电弧炉用大截面水冷电缆,已于八六年十二月底制出样品(见图)。其中截面4000mm~2的水冷电缆将用在无锡钢铁厂新建的30t电弧炉上。这种多股导线与接头一次冷压连接的大截面水冷电缆,以前都是从国外引进。据悉在87年下半年我国自行设计制造的大截面水冷电缆将接受用户订货。     

基于递推回归法的电缆热路模型特征参数实验分析方法

为了精确地估计电缆温度,基于递推回归原理研究电缆热路模型特征参数的一种精确、快速的获取方法,并提出一种相应的算法。设计实验平台,在Matlab集成开发环境中分别基于该递推回归法、传统的IEC法分析实验用电缆的特征参数。分别利用基于这些特征参数的电缆热路模型估计电缆内的各层温度。实验结果表明,基于递推回归法分析出的特征参数的电缆热模型得到的电缆温度误差小于基于IEC法的,从而验证该递推回归法分析电缆热路模型特征参数的有效性与精确性。     

新型35kV及以下预制绕包式电缆中间接头关键技术研究与产品研发

针对国内35 kV及以下配电线路中绕包式电缆中间接头的故障,通过分析电缆中间接头的材料、整体结构设计及安装工艺,总结现有绕包式电缆中间接头的不足之处,分别从电缆中间接头结构优化、绝缘材料以及带材等方面进行研究,设计新型预制绕包式电缆中间接头,大幅提升了35 kV及以下电缆中间接头的电气性能及安全裕度,简化安装工艺,从而更好地确保35 kV及以下配电线路的安全可靠运行。     

翅片管风冷法在电缆接头冷却中的应用

为解决电缆熔融接头的快速冷却问题,分别采用自然冷却法、光管风冷法和翅片管风冷法对包裹电缆熔融接头的交联聚乙烯绝缘材料层进行冷却,并采用数值模拟的方法对其冷却效果及交联聚乙烯的材料性能进行验证和分析。模拟结果表明,翅片管风冷法的效果远优于其他两种冷却方式,证实了翅片管风冷法的有效性,对于解决普遍存在的电缆熔融接头的交联聚乙烯绝缘材料层的快速冷却问题具有一定的参考价值。     

110 kV电缆护层中操作过电压的暂态特性分析

teristic 摘要： 近年来在110 kV电缆线路中, 发生多起断路器合闸时电缆接头爆炸的事故。文中选取一发生典型接头击穿故障的电缆线路, 使用PSCAD建立了该电缆线路的电磁暂态仿真模型。由于该线路中间接头击穿故障发生在电缆充电后。因此文中仿真了空载合闸时的电磁暂态过程。首先计算了电缆线路各个接头处的线芯过电压, 由于空载线路电容效应, 各个接头处线芯过电压逐渐升高。应用傅里叶变换对过电压进行频率分析, 线芯过电压中包含较多的1~2 kHz的高频成分。其次对线路不同接头处的护层电压进行计算, 可得电压最大值出现在靠近线路首端的接头护层处。与线芯过电压相比, 空载合闸时的护层感应电压中含有大量的1~3 kHz、超过10 kHz的高频分量。最后改变护层交叉互联与单端接地的联结方式, 计算可得各处护层电压出现较大变化, 最大护层电压有所上升。改变2种护层联结方式的顺序后, 其对应的接头护层处电压的高频成分含量也出现变化。由于大量的高压单芯电缆护层采用混合联结方式, 因此文中的研究结果对优化电缆护层的配置方式具有指导意义。     

电缆渗水缺陷模型及识别波形特征研究

电缆长期处于潮湿地下环境中,外部水分会渗入电缆内部引发绝缘故障,因而电缆渗水缺陷的研究至关重要。为实现电缆渗水缺陷精准定位,构建电缆中间接头及渗水缺陷模型,通过PSCAD搭建电缆传输线路计算模型,根据不同阻抗点特征波形分辨渗水缺陷;对含渗水缺陷电缆进行仿真,根据时域反射(TDR)定位原理确定渗水缺陷位置,并通过渗水缺陷定位试验进行验证。结果表明,TDR检测电缆渗水缺陷时会产生独特的反射波形,该波形与渗水缺陷在电缆中位置无关,但会因渗水量的不同改变其幅值与振荡频率,从而分辨出缺陷,达到精确定位的目的。     

Experimental study of thermal field deriving from an underground electrical power cable buried in non-homogeneous soils

The electrical cables ampacity mainly depends on the cable system operation temperature. To achieve a better cable utilization and reduce the conservativeness typically employed in buried cable design, an accurate evaluation of the heat dissipation through the cables and the surrounding soil is important. In the traditional method adopted by the International Electrotechnical Commission (IEC) and the Institute of Electrical and Electronics Engineers (IEEE) for the computation of the thermal resistance between an existing underground cable system and the external environment, it is still assumed that the soil is homogeneous and has uniform thermal conductivity. Numerical studies have been conducted to predict the temperature distribution around the cable for various configurations and thermal properties of the soil. The paper presents an experimental study conducted on a scale model to investigate the heat transfer of a buried cable, with different geometrical configurations and thermal properties of the soil, and to validate a simplified model proposed by the authors in 2012 for the calculation of the thermal resistance between the underground pipe or electrical cable and the ground surface, in cases where the filling of the trench is filled with layers of materials with different thermal properties. Results show that experimental data are in good agreement with the numerical ones.     

高拱坝蓄水水位对横缝开度的影响研究

研究了蓄水水位对横缝开度的影响．确定坝前允许最高水位以满足灌浆需要是工程上亟待解决的问题。推导了上游水压作用下横缝宽度变化量的计算公式．并采用模拟拱坝浇筑、灌浆和蓄水过程的有限元仿真方法.研究不同蓄水水位对横缝开度的影响。结果表明．当水位达到距灌浆区底部高程以下30～40m时．水压对缝宽的压紧闭合效果开始变得显著。     

紫坪铺水利枢纽垫层管取代伸缩节的地震响应分析

结合紫坪铺水利枢纽工程的实际，采用三维有限元方法对该工程发电引水系统取消伸缩节后的抗震性能进行了研究。计算结果表明，主厂房上游永久分缝处以一段垫层管代替常规伸缩节以后，压力管道在地震荷载和内水压力等荷载组合作用下，结构的动力响应可以满足使用要求。从而达到取消伸缩节、节省工程投资的目的。     

交联聚乙烯电缆中水树枝诊断的研究现状

交联聚乙烯(XLPE)电缆因其具有优良的导电性、较好的耐热性和机械强度,自问世以来已广泛应用于输电线路和配电网中。然而,当电缆绝缘处于潮湿的环境中时,在电场的作用下会产生水树枝老化。随着水树枝的生长,电缆的绝缘性能下降并可能导致绝缘击穿,从而影响电网的安全运行。总结了交联聚乙烯电缆中水树枝老化的研究现状,概述了水树枝的产生机理及近年来水树枝老化的诊断方法,最后对各种诊断方法进行了简单比较。     

Comparative study of the behaviour of conventional gasketed and compact non-gasketed flanged pipe joints under bolt up and operating conditions

Bolted flanged joints comprise an assembly of a number of important individual components, which are required to perform well together in service. The ideal requirement for a bolted flange joint is a ‘zero-leak’ condition. However, whilst recommended design procedures for bolted flange joints are available in international codes and standards, leakage problems are still faced by industry. These are common in both normal operating (internal pressure loading) and critical event conditions. The drive is, therefore, to find a flange joint assembly, which provides ‘zero-leak condition’ and requires little or no maintenance and handling. Considerable investigation in the area of optimised bolted joints has been in progress for the past 10 years comparing traditional gasketed joints and ‘compact non-gasketed’ joints, using both analytical and experimental approaches. In this present study, two-dimensional non-linear finite element studies have been performed for both gasketed and non-gasketed bolted flange pipe joints. Based on the stress results for the flange and the bolt and the flange rotation/displacement, compact non-gasketed flange joints are shown to be a viable and preferable alternative to the conventional gasketed flange joints. Recommendations are made for a best-fit flange model for static load conditions with ‘zero-leak’ sealing in a flange joint.     

Analysis of Fin-Tube Joints in a Compact Heat Exchanger

This article deals with an analysis of fin-tube joints as functions of topological alterations of the joint fillet size. Based on numerical predictions of a joint topology formed by the surface tension driven reactive flow of molten metal, and subsequently verified by empirical evidence gathered through both laboratory and industrial testing, the topology alterations were identified for thermal integrity studies. Subsequently, thermal characteristics of corresponding fin-tube joints were determined in terms of two models of the thermal contact resistance. Model predictions of the fin efficiency with an altered topology of the joint zone were compared with the simulation results from a computational fluid dynamics study, and the results fit well. Numerical predictions of joint topology were devised using an in-house-developed finite-element code, and verified by the Surface Evolver code. Such prediction provided quantitative joint topology information that was needed in assessments of the joint thermal performance. Experimental data were obtained using a computer-controlled transparent hot zone with an ultra-high-purity nitrogen background atmosphere under tightly controlled conditions, and also by an analysis of the state-of-the-art manufacturing process data obtained from an industrial setting. It is demonstrated that a value of fin efficiency, assumed as recommended by traditional sizing design procedures, may drastically differ from actual values.     

节理参数对水电站地下洞室围岩地震反应的影响研究

以节理受力特性为出发点,基于FLAC3D软件平台,改进了Interface单元的法向刚度及切向刚度的输入取 值方法,定义了节理参数的敏感度,并以含有一给定方向节理的某实际水电站地下洞室为背景建立了数值试验模 型,根据场地条件输入人工地震波进行地震反应分析,探讨了对洞室围岩地震反应影响较大的节理参数,以期为 含节理的地下岩石洞室动力稳定性分析提供参考。     

节理裂隙滑移对某抽水蓄能电站地下洞室喷砼支护破坏的影响规律

地下岩石工程中的裂隙等岩体结构对喷砼等支护结构的受力、变形及破坏具有重要影响。以某抽水蓄能电站为依托,针对开挖过程中揭露的节理裂隙及其分布特征,采用节理单元和Timoshenko梁单元对大型地下洞室群开挖过程节理的滑移和喷砼的破坏开展了施工全过程分析,研究了开挖过程中顺、反倾向节理裂隙的滑移变形发展规律和喷砼的轴力、剪力和弯矩的演化及其与节理位置的关系,并采用强度包络线方法判别了不同区域围岩喷砼支护的破坏类型,揭示了裂隙滑移对喷砼破坏的影响规律。研究结果表明,顺倾裂隙在地下洞室群开挖过程中的滑移变形较反倾裂隙明显,特别是在高边墙区域,顺倾裂隙滑移变形对围岩变形和喷砼影响显著;顶拱处喷砼内力受节理裂隙的影响明显高于高边墙处,喷砼开裂破坏易出现在与顺倾节理相交的顶拱和高边墙处,破坏类型为压剪和压弯破坏;洞室开挖过程中裂隙滑移对喷砼破坏的危害程度影响规律为高边墙顺倾节理裂隙>顶拱节理裂隙>高边墙反倾裂隙。