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1、 50MW发电机缺陷线棒的查找程振伟，陈列，袁章福（浙江华电乌溪江水电厂，浙江 衢州 324000）摘要本文介绍了大型水轮发电机在大修前的交流耐压试验中发现定子线棒击穿的经过，并详细阐述了降低故障点的对地阻抗和发现缺陷线棒的过程及机理，开创了用红外成像仪查找定子缺陷线棒的先河。 关键词定子线棒； 缺陷； 红外； 查找一、 事情经过2005年2月18日，在湖南镇电站四号机大修前定子B相的交流耐压试验中，当电压升至15.3kV时，听到发电机内部发出“啪”的一声，随即试验设备开关跳开。试验人员马上用2500V摇表测量，发现B相对地绝缘电阻为零，后用数字万用表测量只有2.1k，其它两相的绝缘电阻均为2
2、500M。以上情况表明，湖南镇电站四号机定子B相对地发生击穿。在排除外界的因素后，确定是定子B相的线棒有缺陷。二、 湖南镇电站四号机的定子情况湖南镇电站四号机系天津发电设备厂制造，容量为42.5MW，功率因素为0.85,投产年月为1979年1月，2004年经浙江电力试验研究院温升试验后确认可增容至50MW, 功率因素为0.9。该发电机定子共有270槽，并联支路数a=2，为分数槽结构，线棒的绝缘等级为B级，每相占有90槽，共有180根线棒。在此之前的大小修中，均没发现定子绝缘问题，四号机一直安全运行。在180根线棒中究竟是哪根（或者是几根）线棒有缺陷，成了试验人员的难题。三、 缺陷线棒的查找为查
3、找缺陷线棒，试验人员用直流烧穿法、大电容放电法，试图用肉眼发现缺陷线棒的具体位置，但均告失败。后来用红外成像法成功发现了缺陷线棒，其过程如下：先在定子B相和地之间通一定的交流电流（不超过4A，否则会破坏定子铁芯的绝缘）等其稳定30分钟以后，用红外成像仪进行扫描，发现有弧型的亮点，经分析是19槽的下层线棒为缺陷线棒。其机理如下：缺陷线棒的等效图如下所示： 线棒Rx CX Rg 定子铁芯其中：Rx-线棒对地绝缘电阻CX-线棒对地电容Rg-故障点的接地电阻(2.1 k)很明显，线棒对地击穿后，其对地的电阻为RgRxRg，所以故障点的等效阻抗Z1= Rg/( Rg wCX+1)由于CX0.410-6(
4、F)，所以Rg wCX2.1 k XL-线棒本身的电感由于回路的总阻抗较大,只有用高电压、大电流的试验变压器才能使故障点的电流增大，从而有利于故障点的烧穿。但由于Rg是可变的阻抗,当有一定的电流时，故障点就要发热，从而扩大其碳化通道，使故障点的阻抗下降，进一步又可使故障点的电流增大。继而故障点的阻抗又进一步下降。这是一个正反馈的过程。其过程如下图所示：发现缺陷线棒 局部过热红外成像设备扫描定子线圈B相和地之间通一定的交流电流。（不超过4A）电流逐渐增大降低B相故障点的对地阻抗故障点的对地阻抗逐渐降低现场应用：用5kV、5A的试验变压器升压，其试验接线图如下： 当试验变压器高压侧的电流I=3.5
5、A时, 试验变压器高压侧的电压U=36V,其对地阻抗Z3=U/I=36/3.5=10.3()，由此可见，经交流烧穿后，故障点的对地阻抗已大大下降，这经现场试验得到了证实。这样一来,故障点的发热功率大约为P=I2R=3.5210.3126(W)我们知道红外成像仪是探测物体表面辐射的不为人眼所见的红外线的设备,它反映物体表面的温度场.物体的温度愈高,它辐射的红外线的能量愈多,因此它对过热点是最敏感的.当故障点有3.5A电流通过时,一定时间后势必在此形成局部过热，从而用红外成像仪就很容易发现过热的故障部位,即缺陷线棒的准确位置，相当方便!四、 注意事项1、 用红外成像仪查找缺陷线棒，应用交流烧穿法降
6、低故障点的对地阻抗，但不能太低，否则不会形成过热点。金属性接地（直接接地）不能用此方法。2、 故障点的电流必须控制在4A以下，以防止定子铁芯的绝缘遭到破坏。同时同电流的时间也不能太长，一般宜在30分钟左右。3、 红外成像仪扫描时，应先以人体当参照物，调整好焦距和光圈，再开始不间断扫描，发现有亮点后，再精确定位。参考文献：1、电力设备故障红外诊断陈衡 侯善敬著，中国电力出版社，1999 2、高压电气设备试验方法，水利电力出版社，1984作者简介：1、程振伟，男，1968年生，电气设备试验工程师2、陈列，男，1970年生，电气设备技术主管3、袁章福，男，1969生，电气设备点检工程师程振伟联系电话
7、：13957025960Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and
8、 through the crackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in
9、the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear m
10、y foot tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.待添加的隐藏文字内容2Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall
11、 from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in
12、 a vertical straight line we would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgart
13、ner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thic
14、ker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head lo
15、w in mission control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or hu
16、midity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitud
17、e of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unc
18、lip. He will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it wi
19、ll not be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as h
20、e approaches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-
21、square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned
22、, it wont. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
