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1、大型单元式机组装设发电机出口断路器（GCB）优劣性之比较阮伟 （广东惠州天然气发电有限公司，广东 惠州 516082）摘要 本文针对大型单元式发电机组在设计时是否装设发电机出口断路器（GCB）的问题，结合广东惠州LNG电厂的实际，从机组的运行和投资两方面进行了比较和分析。指出发电机装设GCB，在提高厂用电的可靠性，简化继电保护接线，缩短故障恢复时间，提高机组可用率方面效果是显著的，而在建设的一次性投资上，其经济性需要考量。关键词 发电机 出口断路器（GCB） 接线设计 Compared the advantage and inferiority of installed GCB on a un
2、it generator Ruanwei （Guang-dong Hui-zhou LNG Power Plant，Guang-dong Hui-zhou 516082）Abstract Aimed at whether installing GCB on a unit generator at the period of design. On the base of the connection design of Guang-dong Hui-zhou LNG Power Plant, the article compared the advantage and inferiority o
3、f GCB form the generator operating and investment. Installed GCB, a unit generator can be improved the operating reliability and availability , simplified protection system design and shorted the time of fault recovery. But its efficiency of investment should be considered. Keywords generator genera
4、tor-circuit breaker(GCB) connection design0 引言惠州LNG电厂一期工程为3390MW燃气蒸汽联合循环机组，母线为双母线接线方式。发电机引出线到主变低压侧、厂高变高压侧均采用全链式离相封闭母线。发电机与主变压器之间装设断路器和隔离开关，厂用分支装设断路器，在主封母上T接励磁分支封母至励磁变压器和发电机出口电压互感器及避雷器柜。在一期工程的设计投标阶段，就发电机与主变压器之间是否装设断路器和隔离开关各厂家有过不同的考虑。GE、Siemens电力公司提供的大型燃机主接线图纸中，发电机出口没有装设GCB，其原因一方面是因为GCB价格昂贵，在技术经济比较中往往
5、处于不利地位，另一方面原因是国外燃机电厂的作用多数是带基本负荷，机组启停次数较少，使用GCB优势不明显。而ABB、Alstom电力公司提供的主接线图纸上都有装设GCB，主要原因与其具有GCB制造方面的优势有关。而惠州LNG电厂建成投产后，主要的作用是系统调峰，综合机组运行方式和技术经济等各方面因素考虑，确定发电机与主变压器之间装设GCB。具体的分析如下：1 基于电厂运行方式的比较电厂的运行主要分三个阶段：1) 调试和维护；2) 同期和正常运行；3) 非正常运行。下表就GCB在电厂的运行、维护的作用以表的形式所做分析：比较项目装GCB不装GCB调试和维护调试时，可通过GCB将发电机一变压器组分成
6、发电机部分和变压器部分，从而将发变组保护分为若干部分逐级测试。此外，厂用电由主变供电时，发电机可在欠励磁条件下进行测试。继电保护的通流试验要求进行多次厂用电源切换和主回路短路连接的装卸。不仅工作量大，而且加大了二次调试人员出错的机率。机组同期同期点由中压系统的GCB来实现，由于GCB装在屏蔽的全属壳内操作的环境条件好，其充分的绝缘强度保证同期操作更加灵活、可靠。GCB是三相机械联动，无三相不一致问题。 GCB机械寿命达10000次。用220KV断路器进行同期并网，断路器不是机械联动，有可能发生单相或两相拒动的情况。220KV高压断路器可接受的机械寿命3000次。机组正常起停发电机组正常起动电源
7、通过主变倒送电方式从6KV厂用母线获得，从机组起动到并网发电不需要进行厂用电源切换。发电机组首先通过起动/备用电源获得起动电源，直到发电机建立正常电压带一定的负荷后，再通过厂用电切换装置切换到正常工作厂用变压器供电。停机过程与之相反。每次切换操作对厂用电机，特别是大容量厂用电机造成冲击。事故切换只有在主变、厂用变压器故障时，才需要厂用电切换。主变故障、发电机故障、厂变故障、燃机故障、汽机故障、重要辅助故障都需要进行厂用电切换。通过以上的分析表明：装设了GCB，在机组正常起停时，以及在发电机、汽机、燃机发生故障引起跳机时，不需要进行厂用电源的切换操作，提高了厂用电的可靠性。 以往厂用电切换一般采
8、用工作开关辅助接点直接（或经低压继电器、延时继电器）起动备用电源投入。这种方式，若合闸瞬间厂用母线反馈电压与备用电源电压间相角差较大，或可能接近180，将对电动机造成很大的合闸冲击。对加固定延时的切换方式，也因切换时系统运行方式、厂用负荷、故障类型等因素，不能可靠保证躲过反相点合闸。如待残压衰减到一定幅值后投入备用电源，则由于断电时间过长，母线电压和电动机的转速都下降很大，将严重影响厂用电运行工况，在这种情况下，一方面有些辅机势必退出运行，另一方面，备用电源合上后，由于电动机成组自起动电流很大，母线电压将可能难以恢复，从而导致自起动困难，甚至被迫停机停炉。虽然惠州LNG电厂设计时引入了国内最新
9、的厂用电快速切换装置，在很大程度上保证了厂用电切换的可靠性，但快切能否实现，不仅取决于开关条件，还取决于系统接线、运行方式和故障类型。无论是正常切换还是事故切换，均有相当的风险，成功与否直接威胁着机组的安全。装设GCB可有效减少厂用电切换操作，减轻电厂运行人员工作强度，尤其是在机组故障时，减少操作人员的工作量和紧张性。装设GCB除了减少厂用电切换操作外，还有以下优越性：1) 主变或高厂变内部故障时，迅速跳开发电机侧断路器和高压侧断路器，切断供电电源，对保护主变和高压厂变有利。如果不装设GCB，由于发电机励磁电流的衰减要经过一定的时间，只切开高压系统供电电源，发电机仍继续向故障点供电，从而扩大了
10、主变或厂高变的损坏程度，国内外已有报道该种故障引致严重损坏主变压器的事例；2) 采用了GCB，不仅实现了发电机，变压器有选择的保护跳闸，简化了保护接线，而且多数保护无需动作高压断路器，从而避免了厂用电源的失去，这对于一些瞬时性故障特别是来自于锅炉、汽机的热工误发信号的排除，尽快恢复机组的运行和避免因误操作而导致损失非常有益。根据广东沙角C电厂的经验，三台机组（3680MW）装设的GCB在机组调试期间共计动作800余次，多数情况下可在数十分钟内恢复机组的运行；3) 发电机系统各种故障发生时，不解列厂用电而断开GCB，当故障消失时，允许发电机快速的再次接入。GCB可以避免由不平衡负荷运行引起的过大
11、的负序电流对发电机转子表面的损害，若使用GCB，会在5080ms以内把机组与故障分隔开，从而有效地保护机组；4) 减少厂用备变的台数和容量，只作机组安全停机用。综上所述，大型发电机组采用GCB有明显的技术优势。GCB具有使机组调试和维护阶段更加方便；大大改善同期条件；避免或减少厂用电切换带来的风险，提高厂用电可靠性；简化继电保护接线，缩短故障恢复时间，提高机组可用率等技术优点。GCB不仅能在事故发生时避免或减少对设备的损害程度，而且还能有效地防止或减少事故的发生。2 基于技术经济的比较发电机装设GCB，从经济性上来看也存在一些不足，主要表现为以下几点:1) 投资较大幅度提高。建设一台单元式发电
12、机组在GCB上的投资约为620万元。2) GCB故障或检修时将影响整个机组的运行，而这种故障是可能的。3) 主变既要满足倒送厂用起动、停机电源的要求，又需有升压变压器的功能，两种不同情况时主变压器高压侧母线的电压波动较大，为了保证厂用电动机起动时高压厂用母线的电压水平，主变压器或厂用变压器一般需采用有载调压型，这进一步增加了投资，也降低了发电厂运行的可靠性。4) 对于在惠州LNG这样的燃机电厂中安装使用GCB，在机组停机过程（约12小时/日），每台主变空载损耗将增加了运行费用约40万/年.台。待添加的隐藏文字内容3根据DL5000-2000第13.3.13条的规定：“容量为200MW-300M
13、W的机组，每两台机组可设一台高压厂用起动/备用变压器”；“容量为600MW的机组，当发电机出口不装设断路器或负荷开关时，每两台机组可设一台或两台高压厂用起动/备用变压器,当配置两台时，应考虑一台高压厂用起动/备用变压器检修时，不影响任一台机组的起停；当发电机出口装有断路器或负荷开关时,四台及以下机组可设一台高压厂用备用变压器，五台及以上同容量机组可设置一台不接线的高压厂用工作变压器”。 装设GCB后，机组正常启动或停机的高压厂用电源可以通过主变从系统倒送，不需启动/备用变压器来提供厂用电源（该变压器应称为高压备用变压器），仅在高压厂用变压器故障或检修时，才由它替代工作，或者当主变或高变故障时提
14、供紧急停机厂用电源。装设GCB后，惠州LNG电厂全厂6台机组可以共用一台高压备用变压器，比不装设GCB时节省了两台高压启动/备用变压器和2个220kV GIS间隔。从经济上比较，对于惠州LNG电厂一期3台机组，装设GCB约3450=1350万元，不装设GCB，需增加一台高压起动/备用变的费用约240万元，启备变与升压站之间的电缆连接的费用约240万元，升压站进线间隔的费用约250万元，共计730万元，装设GCB比不装GCB的方案增加设备费约620万元。3 结论惠州LNG电厂工程，每台机组年运行小时数根据设计约为3900h，主要作为调峰机组，起停频繁，发电机出口装设断路器主要好处是避免起动电源与
15、工作电源间较频繁的切换操作，提高厂用电的可靠性，简化继电保护接线，缩短故障恢复时间，提高机组可用率，相对于为此增加的投资而言，利大于弊，因此最后决定采用装设发电机出口断路器（GCB）的接线方式。【作者简介】 阮伟 （1971） 男，工程师，从事发电厂电气运行及检修技术管理工作Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to t
16、yphoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and 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 fir
17、st 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 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 met
18、eorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie flo
19、ating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall 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
20、balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in 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 f
21、aith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, 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 fille
22、d balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker 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
23、 the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low 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 mi
24、ssion. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity 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 cli
25、mb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude 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
26、will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. 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 swim
27、ming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will 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 s
28、ound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he 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 ca
29、n be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-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
30、 parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, 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 no
31、t 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.
