全膜电容器热稳定试验研究

全膜电容器由于绝缘性能优良，比特性远优于其它介质电容器。但正因为如此，其散热面积也远小于其它介质电容器。因此，其热的稳定特性并不一定就优于其它电容器。本文通过对电容器比例单元热稳定性能的试验研究，确定了内部最热点与外壳最热点的关系，为更好地做好电容器热稳定性能试验提供了参考依据。     

特高压工程用并联电容器单元热稳定性

温度对电容器单元的运行可靠性有重要影响。电容器单元需要通过热稳定性试验来检验其在最严酷运行条件下的最热点温度是否超过允许值。由于最热点温度测量方法缺少研究基础,目前电容器单元热稳定性试验结果的准确度较低。为此以特高压工程用BAM6.56–556–1W型电容器单元为研究对象,利用有限元分析软件,进行了热稳定性计算;同时在电容器单元内部埋设多个光纤光栅温度传感器,测量电容器单元热平衡时的温度分布。研究得到了电容器单元内部最热点的温度和位置,并分析得出内部最热点温度与外壳温度的关系。最后仿真分析了放置方式、结构参数及环境温度对电容器内部温度分布的影响。研究成果可为特高压工程用并联电容器单元提供一种热稳定性最热点温度相对精确而简便的测量方法,同时为电容器的散热设计提供参考。     

高压全膜电容器热稳定性能试验条件下的温度场特性

为了获得高压全膜电容器在热稳定性能试验条件下外壳与内部的温度分布,在Fluent 15.0中建立了电容器温度场仿真模型,并利用有限体积法进行了求解。仿真结果表明:对于电容器外壳,其小侧面温度较高,外壳最热点在小侧面,而电容器最热点则位于靠近尾部的中轴线上。由于电容器内部结构复杂,导致电容器外壳表面温度分布不均匀,并非规则的温度升高或降低的趋势,而是存在局部较热的区域。为了验证仿真模型的正确性,利用光纤光栅温度传感器及红外成像仪分别对热稳定性能试验条件下的电容器内部及外壳温度进行了实际测量,实测与仿真结果基本吻合从而验证了仿真模型的正确性。     

大容量电热电容器热稳定试验研究

1.概述电热电容器热稳定试验是为了测得产品最热点温度,考核其在允许最高环境温度和最高工作电压下长期运行的热稳定性,并鉴别所用介质的性能和工艺的好坏。由此可见,热稳定试验在型式试验里处在重要的地位。     

并联电力电容器热稳定性试验条件的分析

本文就电力电容器的热稳定性试验条件进行了分析探讨,指出:热稳定性试验应与电容器的最大平均发热功率相联系,即与电容器的允许最大介损tgδnax相联系;并导出了热稳定性试验的试验电压Us的公式;tgδnax值应以行业实际平均水平tgδpj为基础来确定,宜采用tgδa(?)/tgδp=1.2,并据以提出了tgδnax的建议值;指出热稳定试验时芯子热点温升应与电容器的热老化寿命相联系.本文拟对并联电力电容器热稳定性试验的电气条件进行分析讨论.     

并联电容器可靠性的试验研究(下)

七、试验研究本文上篇已经对目前国外可靠性试验作了比较详细的综述,这里介绍我们的一些探讨性的试验,以便寻求可靠性试验的方法,选取合理的试验参数。甲、试验内容和参数 1.θ、tgδ和热稳定试验温升θ和介质损耗tgδ值是并联电容器的重要特性参数,热稳定试验则是考核产品热稳定性能的手段。从过去的试验结果来看,对于油纸高压并联电容器,温升θ约为(15～25)℃,介质损耗tgδ值略低于0.3％,θ和tgδ是影响并联电容器寿命的二个重要因,近年来,由于矿物油浸渍电容器纸的并联电容器     

直流滤波电容器剩余预期寿命的试验研究

针对已运行多年的直流输电用直流滤波电容器进行试验研究,探索其剩余的预期寿命。试验研究设计了检测电容器及其介质老化性状、元件组加速寿命试验和元件耐电强度试验3个流程。试验发现电容器性能已严重减退,绝缘介质已处于老化状态;通过加速寿命试验结果,估算了电容器剩余寿命,推测此类电容器已临近其寿命末期。由于该批电容器已运行了10余年,且运行中有多台发生故障,试样品质和运行经历也有差异,因此其介质性能的离散性较大,较难发现温度对寿命影响的规律,研究方法也有待进一步改进。本试验研究的结果能供直流滤波电容器使用方和制造方借鉴。     

金属化膜电容器在模块化多电平换流器工况下温升特性分析

自愈式金属化薄膜电容器由于储能密度高、寿命长、可靠性高而被广泛应用于模块化多电平换流器(MMC)中,温度作为电力电容器寿命与稳定性的主要影响因素成为研究热点。本文基于实际柔性直流输电工程,分析电容器在其运行工况下的热应力。在COMSOL有限元仿真软件中建立金属化薄膜电容器三维温度场仿真模型,对其运行时的温升特性进行研究分析,并进行了试验验证。根据研究结果,金属化膜电容器在MMC换流器子模块中所承受的电流应力和电压应力是相对复杂的交、直流相互叠加的复合变量；电容器最热点位于元件内部,最高温升为11.1℃,外壳温度最热点在侧面,最高温升为7.75℃。为金属化薄膜电容器在MMC换流器中的运行维护提供了参考。     

500kV断路器均压电容器介质损耗超标分析

针对目前变电站中500 kV高压断路器均压电容器在10 kV试验电压下介损试验值超标的现象,对均压电容器的特性进行分析,并在实验室进行了升高试验电压下介质损耗试验。试验数据分析表明:在均压电容器中存在Garton效应,加上现场的高电压及强磁场的干扰,常规10 kV介质损耗试验电压远低于额定电压,很难真实反映均压电容器的绝缘缺陷。而升高试验电压或额定电压下的介损试验可以反映绝缘内部潜在缺陷的类型和发展情况,可以消除Garton效应的影响,更真实地反映均压电容器在运行状况下的介质损耗情况,该方法对于500 kV高压断路器均压电容器的现场试验和绝缘分析有较大的参考价值。     

防火电容器热稳定性研究

防火电容器作为一种新型电力电容器,非常有必要研究其热平衡问题。本文建立了防火电容器的热平衡数学模型,并分析了其热传导过程与现有并联电容器的差别。然后,通过热稳定试验研究了外壳散热面积和防火介质对防火电容器温升的影响。研究成果能为防火电容器的散热设计提供参考。     

高压并联电容器箱壳爆裂及其对策

分析了高压并联电容器在运行中发生箱壳爆裂的起因和必要条件,认为只有当具备电容器的内部发生贯穿性击穿、电容器接入处系统有足够大的短路容量或并联电容器容量足够大及故障电容器的端子与系统或与并联的完好电容器间具有1条低阻抗放电通道这3个条件时才会发生箱壳爆裂,提出了为防止高压并联电容器在运行中发生箱壳爆裂事故所应采取的对策和...     

On‐off discrete control of series capacitors for power system stability with torsional oscillation countermeasure

Application of controlled series capacitors with antiparallel thyristor combination across the capacitor segment is a new and promising countermeasure for enhancement of power system stability. The line reactance can be directly controlled by the controlled series capacitors; hence, it is very effective to apply the capacitors for damping power system disturbances. However, the segmented series capacitors may cause subsynchronous resonance (SSR) that can lead to turbine‐generator shaft failure and electrical instability at oscillation frequencies lower than normal system frequency as well as the conventional capacitor may cause. In this paper, we describe the following. (1) The response of turbine‐generator shaft torque is analytically discussed when the number of inserted series capacitors in the power system is changed. (2) It is proposed for SSR countermeasure that the control system will be designed to avoid the number of series capacitor segments which may cause SSR in addition to selecting better on‐off timing of series capacitors. (3) The effects of the proposed countermeasures are confirmed by the results of EMTP simulations using both simplified two‐mass shaft model and detailed five‐mass shaft model of turbine‐generator. © 1999 Scripta Technica, Electr Eng Jpn, 128(3): 31–42, 1999     

Real-time VAr control by SCADA

The operation and advantages of the SCADA (supervisory control and data acquisition) capacitor control called CAPCON (capacitor control) are presented. CAPCON is used to control VArs systemwide by switching substation capacitor banks based on real-time VAr and voltage data instead of the traditional time clock method. CAPCON has many benefits, which should increase as it is expanded to more capacitor banks on the system. There are cost savings in line losses, generator fuel, and better planning and utilization of substation equipment. Control is based upon real-time conditions, providing much more efficient and precise operation of capacitors and a resulting improvement in reactive power flow. By improving the control of capacitors, CAPCON has given the company the ability to serve its customers better     

Thermal simulation for geometric optimization of metallizedpolypropylene film capacitors

In this paper, the authors use an analytical model to calculate the losses in the metallized polypropylene film capacitors. The model is validated experimentally for capacitors having the same capacitance but different geometry. For each group of capacitors, a temperature distribution in the roll is assumed with the aim of optimizing its thermal performance. It appears that the heating of a long capacitor is higher than that of an equivalent flat capacitor subjected to the same electric stresses     

直流滤波电容器试验问题研究

本文分析了高压直流输电用直流滤波电容器试验中的几个关键试验,通过对局部放电试验的分析,认为直流滤波电容器的局部放电性能应该以放电脉冲数来衡量,这与试验研究的结果是一致的;本文还提出了直流滤波电容器的热稳定性试验应该考虑的问题和交流热稳定性试验的试验电压确定方法;通过对极性反转试验和直流滤波电容器的耐久性试验进行分析,对极性反转试验方法提出了建设性的意见,建议对全膜电容器在直流电压下的老化问题进行深入研究.     

高压直流滤波电容器直流局部放电的试验研究

高压直流滤波电容器在高压系统中应用广泛,是高压设备中的关键元件,同时作为直流输电工程中的重要设备,其绝缘性能直接关系到整个直流输电系统的可靠性。由于其本身的绝缘性能可能存在先天缺陷和运行过程中受到腐蚀、振动或受潮等原因而受到损坏,导致局部放电,而局部放电信号包含了很多绝缘性能的变化信息,所以通过局部放电测试对高压电容器的绝缘性能的优劣进行评估是很有效的手段。笔者主要针对大电容试品的直流局部放电测试系统而展开工作,从局部放电的原理出发,针对不同缺陷类型的模拟电容器进行直流局部放电试验,通过测量系统的数据采集和对数据的后续处理,作出不同模拟试品在直流电压下的局部放电的特征参量图谱,通过对图谱来分析对比不同缺陷的放电特点。     

高压并联电容器箱壳爆裂及其对策

分析了高压并联电容器在运行中发生箱壳爆裂的起因和必要条件,认为只有当具备电容器的内部发生贯穿性击穿、电容器接入处系统有足够大的短路容量或并联电容器容量足够大及故障电容器的端子与系统或与并联的完好电容器间具有1条低阻抗放电通道这3个条件时才会发生箱壳爆裂,提出了为防止高压并联电容器在运行中发生箱壳爆裂事故所应采取的对策和措施。     

Artificial neural network-based optimal capacitor switching in a distribution system

One of the most important control decision functions in a modern distribution automation system is volt–var control. The objective of volt–var control is to supply controlled reactive power by switching optimally the switchable capacitors installed in the distribution system such that the voltage drop and real power loss is minimum. Traditionally, this problem of optimal capacitor switching has been solved through various optimization techniques. However, as the time taken by these traditional optimization methods are quite significant, these methods may not be much suitable for online application. To reduce the time required to solve the optimal capacitor switching problem, an artificial neural network (ANN)-based approach has been developed in this paper. It has been found that the ANN-based technique is at least a 100 times faster than the traditional optimization methods for a practical number of capacitors in the system. Moreover, as the number of capacitors in the system increases, the effectiveness of the ANN over the traditional approach (in terms of the solution time) increases.     

The fundamentals of aging in HV polymer-film capacitors

This paper covers the basic phenomena involved in the aging of capacitors constructed using polymer films as the major dielectric material. A wide variety of aging phenomena can be identified, ranging from simple electrical, dielectric, thermal, radiation, chemical and physical aging, to aging originating from the specific construction of the capacitor. Some phenomena occur quickly, such as some morphological changes in the polymer, others occur progressively, and others occur later in the life of the capacitor. The polymers covered range from biaxially-oriented polypropylene, which is widely used in commercial utility and industrial capacitors, to polymers like polycarbonate, polysulfone, polyimide, and polyvinylidene fluoride, which are used in high-energy density, outer-space, high-temperature, or other special applications. The paper addresses two constructions of polymer film capacitor where the aging phenomena are significantly different due to the differences in construction: polymer/foil capacitors and metalized film capacitors. Metalized polymer film capacitors have the quality of clearing or self healing that is not present in film/foil capacitors. The discussion of aging in this paper is given from the perspective of these two designs