Progress in Japan in electrical insulation at high temperatures

It is expected that the use of electrical equipment at high temperatures will increase in the future, and the demand for heat-resistant insulation that can be used at temperatures above 300°C will increase. In addition, this high temperature electrical equipment will need to be higher in voltage and have a larger capacity. Accordingly, research and development will be needed to study the high temperature behavior of insulating materials, the insulation manufacturing process, and functional evaluation methods of insulation systems. Progress in Japan in R&D of insulation systems at higher temperatures is discussed     

乐都变电站110kV母线谐振现象分析和防范措施

运行中的电气设备,当系统运行方式发生变化,或者系统出现接地故障时,由于设备自身的工作特点,就会发生铁磁谐振,影响到设备的绝缘寿命,并危及到电网的安全运行。针对乐都变电站110 kV母线在倒闸操作过程中发生的铁磁谐振现象,从理论上进行分析该现象发生的原因,提出防范措施,以保证电气设备正常运行,提高系统供电可靠性,降低设备事故率。并本着安全、经济、可行的原则,理论结合现场实际,提出了在以后操作中避免谐振发生的措施。     

几组电气设备绝缘在线监测数据的分析

简要阐述了变电站电气设备在线监测的一些基本问题,指出在线监测是实现高压设备状态检修的必要手段。介绍了泉州电业局已经装设的变电站电气设备在线监测的基本情况,并在大量在线监测数据积累的基础上,分析了几组异常的电气设备绝缘在线监测数据,分析了一些影响在线监测结果的可能因素:介损测量结果稳定性和重复性较差,受PT角差影响较大;通讯信号采集部分的故障率较高;数据分析不能根据现场的运行方式自动改变;监测系统缺少必要的分析判断功能。     

Electrical insulation technology for superconducting magnets inJapan

Electrical insulation of superconducting magnets needs to endure a variety of voltages with a large range of shapes, magnitudes and duration under normal operation, during coil quenching, and at withstand voltage tests. The author reviews the current state of electrical insulation technology for superconducting magnets in Japan. He maintains that Japan will continue to aggressively pursue the research, development and application of superconducting magnets. In accordance with this, the main technical subjects to be solved in the insulation of the superconducting magnets in the near future will be: (1) the development of insulation that has high electrical, mechanical and radiation-resistant properties at the cryogenic condition; and (2) investigation into the long-range effects of insulation on the stability of superconducting magnets     

用最大放电量增加率评定定子绝缘老化状态

进行了大电机定子线棒多因子老化实验 ,实验表明在电机定子线棒多因子老化过程中其最大放电量没有明显的变化规律 ,仅用最大放电量评定定子绝缘的老化状态有一定的局限性。提出了用最大放电量增加率来评定电机绝缘老化状态的新方法并验证了该方法的有效性     

电容式电压互感器故障实例及分析

通过对电气设备绝缘进行介质损耗与电容量测量,可以发现设备绝缘缺陷。但对于电容式电压互感器与耦合电容器等绝缘结构的设备,在进行绝缘诊断时,应更重视电容量的变化。结合电容式电压互感器的故障实例．理论分析了试验结果出现介质损耗变化不大而电容量变化明显的原因,并提出应加强在线电容量测试,实时监测绝缘运行状态。     

Research and development of electrical insulation ofsuperconducting cables by extruded polymers

This is a review to show the importance of electrical insulation in ac superconducting cables. An attractive superconducting cable has to be designed for the voltage range of 60-270 kV. Therefore, a reliable insulation design is imperative. Two types of insulation have been compared. One is composite insulation, namely laminar paper or plastic tape, impregnated with coolant. The other is solid insulation of extruded polymer on the conductor. The composite insulation has a lengthy history and, in the constructions to date, has been the insulation design used for superconducting cables. Some prototype superconducting cables with this type of insulation have been developed and successfully tested. However, the partial discharge in butt gaps may affect their long-term reliability. The solid insulation, on the other hand, can separate the coolant from the electrical insulation and can exploit the benefit of the super electrical insulation characteristics of polymers in the cryogenic region. Some attempts have been made to use this design with liquid nitrogen and liquid helium. One example incorporating extruded ethylenepropylene rubber (EPR) for insulation was found to satisfactorily go through the cool-down to a liquid helium temperature and to endure the simultaneous voltage and current tests. EPR, and possibly some other polymers, seem to be promising materials for solid insulation in the cryogenic region     

Electrical breakdown in high-voltage winding insulations of different manufacturing qualities

Due to an increasing demand for new, or the refurbishment of power stations, high-voltage rotating machines continue to play a significant role in generating electrical energy. An important component of these machines is their electrical insulation. Although much research has been done to improve the material, about a quarter of all failures still are related to insulation problems. Research to improve winding insulation is very complex because a large number of factors influence insulation life, among them the raw materials, size of the mica tapes, geometrical characteristics of the bar and taping- or manufacturing techniques. The results show that electrical tree propagation is the main electrical degradation mechanism that leads to breakdown of the main wall insulation and that poor impregnation of the insulation and type of taping can reduce time to breakdown significantly.     

非线性有限元法在出线装置复合绝缘结构电场计算中的应用

极性反转是换流变压器出线结构复合绝缘的一种特殊工作状态,极性反转时由于空间电荷作用可导致绝缘介质内部及界面处电场畸变。另一方面,绝缘介质电性能参数是温度的函数,因此温度梯度导致的电性能参数改变同样会影响绝缘结构在极性反转过程中的瞬态电场分布。基于此,为了较准确地模拟复合绝缘结构在考虑温度分布条件下的极性反转瞬态电场,提出应用非线性有限元法对以上2种瞬态电场影响因素进行耦合分析。首先研究了油浸纸复合绝缘体系电性能参数与温度的关系;然后详细介绍了基于非线性有限元法的瞬态电场计算流程,并通过双层同轴复合绝缘结构模型验证了其有效性;最后对实际换流变压器出线装置的油纸-环氧浸渍典型复合绝缘结构建立了二维轴对称仿真计算模型,在考虑材料非线性的条件下对其极性反转瞬态电场变化过程进行了仿真分析。计算结果表明传统模拟方法与考虑材料非线性时的结果存在较大差异,且极性反转过程中复合绝缘结构易出现畸变严重的局部高场强区。     

发电机定子线圈绝缘诊断与寿命预测

发电机定子线圈绝缘在运行过程中要遭受电、热、机械等应力的联合作用而老化,随着中国高龄发电机组日益增多,及时掌握定子线圈绝缘的运行状态显得尤为重要。笔者总结了当今国内外发电机定子线圈绝缘诊断与剩余寿命预测的方法,并以一台18.5 MW/10.5 kV水轮发电机为例,介绍了一种实用的根据电气参量对定子线圈进行绝缘诊断与剩余寿命预测的方法。     

不同含水量对油纸绝缘老化速率的影响

电气绝缘是电气设备的重要组成部分,是电气设备安全运行的关健因素之一。油纸绝缘系统受潮会使绝缘材料降解老化、介质损耗增加及绝缘电阻降低,最终导致设备的运行寿命受到严重影响。分析了绝缘受潮后对油纸绝缘系统的影响,并通过对不同受潮程度的油纸绝缘试样的老化试验,研究了不同含水量对油纸绝缘系统老化速率的影响。研究表明,受潮会加速绝缘老化,缩短电气设备的绝缘寿命。     

交联聚乙烯电缆中电树枝的研究现状

总结了电树枝研究的最新进展,特别是交联聚乙烯电缆绝缘中电树枝的研究现状。对电树枝的分类以及在电树枝引发和生长过程中的一些影响因素进行了讨论。最后从实际应用出发,简要介绍了交联聚乙烯电缆中电树枝的诊断方法。     

Space charge in XLPE power cable under dc electrical stress andheat treatment

It is well known that the existence and accumulation of space charge in insulation can be harmful to polymer power cable. Although there is much research done on space charge distribution in various samples, there are still some important problems left unsolved, such as the mechanism of formation and elimination of space charge in dielectrics. Because of its superiority, the pulsed electro-acoustic (PEA) measurement method is used widely in the measurement of space charge in various geometries of samples such as the multiple layer plate and cylindrical cables. The space charge in crosslinked polyethylene (XLPE) power cable under dc voltage and heat treatment is investigated by the PEA method in this paper. After heat treatment, the space charge, which previously formed in cable insulation under the applied voltage, disappears. If electrical stress is applied to the insulation again, space charge will appear once more. However, after the cable is heated and degassed in vacuum for a long time, no matter how long the dc voltage is applied to the cable, no more space charge will be formed in the cable. The mechanism of formation and elimination of space charge under the effect of electrical and thermal stress is discussed     

单回路直流系统绝缘电阻检测装置技术研究

现代生活日新月异,人们一刻也离不开电,必然会有用电安全问题。在电器设备中,存在着许多单回路电器系统,包括了配电设备、电动汽车系统、直流电机等,这些设备的绝缘电阻达到了兆欧级别。一般的检测方法包括了兆欧表测量,无源接地方法,辅助电源法,低频信号注入法以及电压注入法等,在电压注入法的基础上,提出一种变换分压电阻的方法,能够扩大绝缘电阻测量范围,并能较准确的测出绝缘电阻值。     

导电杂质影响下35kV电缆终端绝缘特性研究

35 kV电缆终端在现场安装过程中,易混入导电颗粒、压铅微粒等导电杂质,严重影响其运行可靠性。为研究导电杂质影响下电缆终端绝缘性能的特征状况,首先利用有限元分析软件,通过在电缆终端绝缘与应控管交界处设置导电杂质,文中建立终端缺陷模型,模拟导电杂质影响,探究了电缆终端在运行电压下,其内部电场分布的情况。然后,根据仿真结果与实际情况,文中制作了含导电杂质的电缆终端样品,利用局部放电测试平台测试电缆终端样品的局部放电信息。研究结果表明,导电杂质的引入将增大电缆终端内部的电场畸变,严重影响终端的绝缘性能;同时也加强了电缆终端的放电活动,使得放电量明显加大,严重降低了35 kV电缆终端的电气绝缘性能。     

基于ANSYS的GIS隔离开关短路事故分析

笔者基于一起真实的GIS短路事故,对隔离开关动静触头不对中造成的屏蔽罩变形和弹簧断裂作了认真分析,并采用ANSYS软件对屏蔽罩变形情况进行了电场仿真计算。分析发现GIS内部绝缘强度对电场畸变非常敏感,任何外界因素改变GIS内部的电场均匀性,都会造成电场强度超过允许值,造成内部绝缘击穿。     

Estimation of state of paper electric insulation based on results of measuring recovered voltage

Based on the multicomponent analysis of the recovery voltage curve, a new approach to assessing the condition of electrical insulation has been justified that allows one to monitor changes in the volume charge state and electric conductivity of insulation using the results of one measurement. For cables with impregnated paper insulation, this approach enables one to monitor typical defects in operation, such as drying out the impregnation compound and humidifying the insulation along the entire trajectory of its aging from unfailing up to marginal state.     

Measures and technologies to enhance the insulation condition monitoring of large electrical machines

The utility of condition monitoring of the stator insulation structure of large machines has been enhanced substantially by the use of computer-based analysis of partial discharge signatures. A number of indices are examined through tests in a multistress aging facility to assess their promise in describing insulation degradation in machine insulation. In transitioning such tests to the field environment, an operational test is also described which offers some promise in identifying degradation without prior baseline data for a machine. On the basis that most electrical failures have mechanical precursors, acoustic methods are described for assessing stator bar mechanical integrity. This includes both using the conductors as waveguides and also employing acoustic emission for the location of large discharges.     

挤包绝缘高压直流电缆制造与应用中的径向梯度效应

挤包绝缘高压直流电缆在直流输电工程中应用广泛,但制造与应用中的梯度效应显著影响其直流电气性能.以500 kV交联聚乙烯直流电缆为研究对象,首先,通过仿真计算理想均匀绝缘电缆中的场强分布;然后,计算交联和脱气过程中绝缘层的温度分布,并对电缆绝缘切片取样,测量不同径向位置绝缘的相态结构和直流电气性能;最后,根据实测电导率对...     

电缆终端绝缘击穿原因分析及对策探讨

介绍了35 k V单芯交联聚乙烯电缆在四川江口水力发电(集团)厂的运用情况。从电和热两方面对电缆终端头屏蔽层断口处绝缘频遭破坏的原因进行了分析,探讨了克服绝缘快速老化击穿的方法。