共查询到18条相似文献,搜索用时 234 毫秒
1.
2.
本文对"第二电流急增点"试验方法进行了探讨,别特是对环氧粉云母绝缘的单根线棒进行了试验研究工作,提出了采用直流毫安表测取电流的合理性及其相应的试验线路,以及试验时电源加装滤波器,试验线棒加屏蔽的必要性等,最后提出了试验程序. 相似文献
3.
4.
电机在长期运行中,绝缘不断的老化。如何判断评定电机绝缘的状况、老化程度以及使用寿命,对电网的安全经济运行有着十分重要的意义。近年来的实践证明,利用第二电流急增点来予测发电机定子绕组绝缘的交流击穿电压范围,以及根据电流—电压特性曲线等因素来综合判定绝缘的老化程度,是一项行之有效的方 相似文献
5.
6.
《吉林电力》1975,(4)
在发电机定子线圈或线棒的交流耐压试验中,为了掌握其绝缘的电气性能,予测交流击穿电压的数值,目前应用比较广泛的是测量出现电流第二急增点的电压数值(Pi_2),在具体应用中必须做出电压——电流特性曲线,才能得出Pi_2的数值,使用一般电流表,由于型式、量程和误差的影响,使得在绘制曲线后确定Pi_2时不够明确,因而这一方法在现场使用中带来一定的困难,为此,我们试制了一台平衡电位差计,利用它可以在试验中直接得出Pi_2的数值,并可以根据其平均电流表绘制电压——电流特性曲线,对测得的Pi_2数值进行校正。这对于我们掌握发电机线圈或线棒绝缘性能,以及进一步积累应用Pi_2予测交流击穿电压的数值会较为方便。 相似文献
7.
一、概述运行中的电机,在电气、温度、机械和化学的作用下,其绝缘性能和机械强度在逐渐降低。为此,如能掌握绝缘老化的速度和变化规律,将对电机的安全运行及开展绝缘监督工作起到较好的作用。电机绝缘试验中交流击穿电压值是评价绝缘性能的重要依据之一,也是判断发电机线圈绝缘老化程度的重要尺度。所以,利用第二电流急增点法,在电机绝缘未被击穿的情况下预测出击穿电压值,来判断和监视绝缘变化,是目前电力系统中普遍采用的方法。我厂发电机已运行十八、九年,绝缘寿命已接近晚期。从1977年开始利用发电机大 相似文献
8.
9.
10.
11.
12.
硫化工艺对抗水树交联聚乙烯绝缘电力电缆工频击穿性能的影响 总被引:1,自引:0,他引:1
为了研究不同硫化工艺对抗水树枝交联聚乙烯绝缘电缆击穿性能的影响,建立了相应的试验手段和评价程序。将使用相同导体屏蔽料、抗水树绝缘料、绝缘屏蔽料,并采用5种不同硫化工艺(A、B、C、D、E)生产的电压等级、型号规格相同且结构相似的电缆作为研究对象,每种电缆取6段作样品,共30段。分别对老化前和老化180d后的5种样品进行工频击穿试验,并观察击穿后样品切片的水树枝、界面微孔、突起和绝缘中的微孔、杂质。试验结果表明:经过180d的加速老化后,5种样品中均无微孔、界面光滑、有少量尺寸较小的杂质,不会导致击穿性能下降;不同硫化工艺生产的电缆工频击穿性能表现出明显差异,其中,A硫化工艺生产的电缆工频击穿强度下降了53.53%,击穿后的样品中观察到了水树枝,B、C硫化工艺生产的电缆工频击穿强度也有不同程度的下降,而D、E硫化工艺生产的电缆的工频击穿强度没有降低,说明硫化工艺对工频击穿强度有直接的影响,并建议实际生产中确定硫化工艺时,各区温度设定应逐渐降低,且初始硫化温度不应过低,生产线速度应适当。 相似文献
13.
Hisayasu Mitsui Ryoji Kumazawa Rie Aizawa Tatsuki Okamoto Tetsuo Ito Masaki Kanegami 《Electrical Engineering in Japan》1999,129(4):24-31
Experiments and investigations were carried out on the voltage life of a bar-coil model with a nickel-plated copper conductor covered with mica-alumina composite insulation at a temperature range of 550–850 °C. Diffusion of copper into the insulation layer was observed on the specimens aged for a long period. Insulation with mica paper gave faster diffusion speed and shorter voltage life than insulation with mica flake. The diffusion speed became higher with an increase in temperature. The ac current gradually increased with aging time and increased rapidly just before breakdown. There was the relationship I = aEn (a, n: constants) between ac current I and applied stress E, and n was approximately equal to 1 in the region where thermal unbalance did not occur. Arrhenius's law held in the relationship between ac current and aging time. Therefore, the breakdown mechanism might be that the effective insulation thickness decreased due to copper diffusion into the insulation layer and the ac current increased gradually until thermal breakdown in the last stage. If copper diffuses into the insulation layer, even with no voltage application, the aging time required to decrease the breakdown voltage to a certain level (the voltage life) obeys Arrhenius's law. If the voltage life is dominated by diffusion into the insulation layer, the activation energy for voltage life in the aging test becomes twice that for diffusion, both with and without voltage application. © 1999 Scripta Technica, Electr Eng Jpn, 129(4): 24–31, 1999 相似文献
14.
为查找35 kV户外真空断路器绝缘击穿故障原因,对ZW7-40.5型真空断路器进行了交流耐压、瓷套绝缘电阻试验。分析了该型号的断路器外绝缘采用真空绝缘脂,此绝缘脂属于液体绝缘介质,设备在运行及安装过程中,会增加液体介质水分含量,易导致绝缘击穿引起设备故障。通过分析交流耐压试验数据,找到了绝缘击穿故障部位。介绍了绝缘击穿事故处理的查找方法,提出了避免断路器击穿的防范措施。 相似文献
15.
Walton M.D. Bernstein B.S. Thue W.A. Smith J.T. III 《Power Delivery, IEEE Transactions on》1999,14(3):750-755
This paper reviews two sets of failure information, the GMTF (a parameter obtained from time-to-failure results) and GMBD stress (a parameter that is calculated from AC breakdown test results), and suggests a correlation. The test results were obtained from accelerated aging experiments on full-sized medium voltage cables in carefully controlled and monitored water-filled tanks. Results show that the ambient temperature AC breakdown strength for equivalently aged cables is influenced primarily by voltage stress during aging-not by the aging temperature. The AC breakdown strength on equivalently aged cables was also shown to decrease with reductions in the aging voltage at all aging temperatures 相似文献
16.
《Power Delivery, IEEE Transactions on》2004,19(4):1532-1537
This paper provides data on four commercial tree retardant crosslinked polyethylene (TR-XLPE) and one cross-linked polyethylene (XLPE) insulated 15 kV cables supplied by three manufacturers. The cables have "super-smooth" conductor shields and "extra-clean" insulation and insulation shields. AC and impulse voltage breakdown and selected other characterization data are presented for cables that were aged immersed in room temperature water (15-30/spl deg/C) up to 24 months of a planned 48 months aging program. The five cables have high ac voltage breakdown strength, three of the TR-XLPE cables, actually increased in breakdown strength during aging. The one TR-XLPE cable that had the lowest ac voltage breakdown had vented trees at the insulation shield and high dissipation factor, which the other cables did not have. The impulse voltage breakdown strength of all cables decreased during aging; the cable with the lowest ac voltage breakdown also has the lowest impulse voltage breakdown. The dissimilar performance of the TR-XLPE cables and the excellent performance of the XLPE cable indicates evaluations at longer times are required to differentiate between modern TR-XLPE and XLPE insulated cables. 相似文献
17.
Hasegawa T. Hatano M. Yamaji K. Kouan T. Hosokawa N. 《Power Delivery, IEEE Transactions on》1997,12(4):1526-1531
Among special insulation tests for DC power converter transformers, polarity reversal tests can be substituted by applied AC voltage tests from a stress similarity in oil ducts. In order to investigate equivalent levels of other insulation tests to polarity reversal tests, the dielectric strength of a transformer at polarity reversals was examined by use of a model of typical oil/paper composite insulation. From the comparison of polarity reversal and other insulation tests, it was found that dielectric strength of transformer insulation at polarity reversals is phenomenally similar to that under switching impulse stresses. Equivalent AC test voltage to polarity reversal test was also estimated from the experimental results. The breakdown characteristics of polarity reversal tests showed that partial discharges at polarity reversals impose less harmful stress on insulation barriers than those at usual AC or impulse tests 相似文献
18.
高压XLPE电缆绝缘V t特性研究综述 总被引:2,自引:0,他引:2
交联聚乙烯(cross linked polyethylene,XLPE)绝缘电力电缆是输电线路的重要电
力设备。针对高压交流和直流电缆系统的运行现状,介绍了运用V t特性(击穿电压与击穿时间的关系)曲线描述XLPE电缆绝缘的电老化寿命模型,分析了国内外高压交、直流XLPE电缆绝缘V t特性的研究方法及相关结果。已有的研究结果表明,交流XLPE电缆绝缘的电老化寿命指数n值在9~25之间,直流XLPE电缆绝缘的电老化寿命指数n值在13~20之间。国内目前尚未见有关直流电缆绝缘V t特性研究的文献报道。 相似文献