【正文】 s Liaoning province, decades ago. The solider gave the old man a handmade saddle when they bid farewell. The story inspired Nasun to write Carved Saddle, a song that later became one of his most popular numbers. Now, every year, Nasun recruits young singers and dancers for the troupe. The troupe has also designed a new repertoire, which is mostly based on the daily lives of Mongolian people, especially the lives of nomadic families, and has bined contemporary musical elements with folk songs of the region. Haimu, a 25yearold khoomei (a local variant of overtone singing) singer, joined the troupe three years ago. Along with a sixmember band, he performs fast songs and soft ones that he writes－ all while playing the horsehead fiddle.Although I learned the piano since childhood and grew up listening to various kinds of music, to me, the folk music of Inner Mongolia is the root, he says. Performing in remote villages is pleasant. I feel at home on the boundless grasslands, and the warm people there make me feel fulfilled. The first round of spring auction season in Beijing ended last week, but it failed to create much spring in the art market. Although two pieces of Chinese painting fetched more than 100 million yuan, the decline in trading volume and sa le rate showed a downturn this year. In the ―Grand View: Chinese Painting Highlight‖ session at China Guardian 2021 spring auctions, Pan Tianshou’s representative work Eagle, Rock and Flora hit a record auction price of 279 million yuan, while Li Keran’s masterwork Jinggang Mountain fetched million yuan, an unexpected high in recent years. However, the trading volume fells to billion yuan from billion yuan in the same period the year before. The Huangchen 2021 Spring Auctions, which recorded million yuan in total sales, experienced the same. The section number went down to 5 from 12 pared to last year. According to expert Shao Jianwu, the art market did not attract much excitement this year due to the booming stock market and the persistent problems of fery and fake deals. The two pieces of Chinese painting notched up high price this spring due to their own value not due to a revival in the market. The successful transaction of two works with a hammer price of more than 100 million yuan once again confirms that valuable and rare works of high quality always earn the longlasting high price. Chinese painting and calligraphy is still the pillar of the market. However, the overall sales rate has dropped slightly, which reflects the demand for the ordinary auction goods has weakened,‖ said the president of China Guardian’s Hu Yanyan. Besides, the entry of new buyers also makes certain changes to the direction of purchasing. In a word, the overall market trend is very unpredictable. Although China Guardian 2021 Spring Auctions has achieved remarkable results, it does not mean that the market has walked out of the predicament. We still have to wait for the big economic boom to invigorate the art market.‖ Even so, the hot pursuit of some special items appeared this spring. A special session of China Guardian Spring Auctions titled ―Fine Gi。s Poly Theater. Their show, titled Ulan Muqir on the Grassland, depicted the history and development of the art troupe. Being from the region allowed me to embrace the culture of Inner Mongolia and being a member of the troupe showed me where I belonged, Nasun, the art troupe39。s performers of the troupe still tour the region39。t have a formal stage. The audience just sat on the grass. Usually, the performances became a big party with local people joining in. For him, the rewarding part about touring isn39。80s. We sat on the back of pickup trucks for hours. The sky was blue, and we couldn39。s Shaanxi province pass through a stop on the ancient Silk Road, Gansu39。 定子不對(duì)稱過(guò)負(fù)荷保護(hù) 勵(lì)磁回路接地保護(hù)同步發(fā)電機(jī)失磁保護(hù) 。此電流在發(fā)電機(jī)空氣隙中建立的負(fù)序旋轉(zhuǎn)磁場(chǎng)相對(duì)于轉(zhuǎn)子為兩倍的同步轉(zhuǎn)速，因此將在轉(zhuǎn)子繞組、阻尼繞組以及轉(zhuǎn)子鐵心等部件上感應(yīng)出 100Hz 的倍頻電流，該電流使得轉(zhuǎn)子上電流密度很大的某些部位（如轉(zhuǎn)子端部、護(hù)環(huán)內(nèi)表面等），可能出現(xiàn)局部的灼傷，甚至可能使護(hù)環(huán)受熱松脫，從而導(dǎo)致發(fā)電機(jī)的重大事故。為提高可靠性，兩部 分的保護(hù)區(qū)應(yīng)相互重疊。但隨著單機(jī)容量的增大，特別是大型水內(nèi)冷機(jī)組，要求在保護(hù)區(qū)內(nèi)任何一點(diǎn)發(fā)生故障時(shí)均能反應(yīng)。 過(guò)去認(rèn)為發(fā)電機(jī)為全絕緣的設(shè)備，在正常運(yùn)行中中性點(diǎn)電壓低，不容易發(fā)生接地故障，即使發(fā)生，由于接地電流較小，不會(huì)對(duì)鐵心造成故障。當(dāng)接地電流比較大，能在故障點(diǎn)引起電弧時(shí)，將使繞組的絕緣和定子鐵心燒壞，并且也容易發(fā)展成相間短路，造成更大的危害。 反映轉(zhuǎn)子回路 2 次諧波電流的匝間短路保護(hù) 縱向零序電壓式匝間保護(hù) 發(fā)電機(jī)縱向零序電壓式匝間保護(hù)，是發(fā)電機(jī)同相分支匝間短路及同相不同分支之間匝間短路的主保護(hù)。 同步發(fā)電機(jī)定子繞組匝間短路保護(hù) 發(fā)電機(jī)定子匝間短路保護(hù)可以有多種方案，應(yīng)根據(jù)發(fā)電廠一次設(shè)備接線情況進(jìn)行選擇。 為了快速消除發(fā)電機(jī)內(nèi)部的故障，在保護(hù)動(dòng)作于發(fā)電機(jī)斷路器跳閘的同時(shí)，還必須動(dòng)作于自動(dòng)滅磁開(kāi)關(guān)，斷開(kāi)發(fā)電機(jī)勵(lì)磁回路，以使轉(zhuǎn)子回路電流不會(huì)在定子繞組中再感應(yīng)電動(dòng)勢(shì)，繼續(xù)供給短路 電流。 1其他的異常工況保護(hù)。 對(duì)于轉(zhuǎn)子回路的過(guò)負(fù)荷，在 100MW及以上并采用半導(dǎo)體勵(lì)磁系統(tǒng)的發(fā)電機(jī)上應(yīng)裝設(shè)轉(zhuǎn)子過(guò)負(fù)荷保護(hù)。 b、 對(duì) 汽輪發(fā)電機(jī)勵(lì)磁回路的一點(diǎn)接地，一般采用定期檢測(cè)裝置；對(duì)大容量機(jī)組則可以裝設(shè)一點(diǎn)接地保護(hù)；對(duì)兩點(diǎn)接地故障，應(yīng)裝設(shè)兩點(diǎn)接地保護(hù)，在勵(lì)磁回路發(fā)生一點(diǎn)接地后投入。 對(duì)于水輪發(fā)電機(jī)定子繞組過(guò)電壓，應(yīng)裝設(shè)帶延時(shí)的過(guò)電壓保護(hù)。 對(duì)于由不對(duì)稱負(fù)荷或外部不對(duì)稱短路而引起的負(fù)序過(guò)電流，一般在 50MW 及以上的發(fā)電機(jī)上裝設(shè)負(fù)序電流保護(hù)。 b、 負(fù)荷電壓（負(fù)序電壓及線電壓）啟動(dòng)的過(guò)電流保護(hù)。 對(duì)于發(fā)電機(jī)定子繞組的匝間短路，當(dāng)繞組接成星形且沒(méi)相中有引出的并聯(lián)支路時(shí)，應(yīng)裝設(shè)單繼電器式的橫聯(lián)差動(dòng)保護(hù)簡(jiǎn)稱橫差保護(hù)。 對(duì)于發(fā)電機(jī) — 變壓器組，一般在發(fā)電機(jī)電壓側(cè)裝設(shè)作用于信號(hào)的接地保護(hù)；當(dāng)發(fā)電機(jī)電壓側(cè)接地電容電流大于 5A時(shí)，應(yīng)該裝設(shè)消弧線圈。 5． 2 發(fā)電機(jī)保護(hù)類型 針對(duì)上述故障類型及不正常運(yùn)行狀態(tài)，發(fā)電機(jī)應(yīng)裝設(shè)以下繼電保護(hù)裝置： 對(duì)于 1MW以上發(fā)電機(jī)的定子繞組及其引出線的相間短路，應(yīng)裝設(shè)縱聯(lián)差動(dòng)保護(hù)簡(jiǎn)稱電力工程系畢業(yè)設(shè)計(jì)（論文） 28 縱差保護(hù)。 d) 由于突然甩負(fù)荷引起的定子繞組過(guò)電壓；調(diào)速系統(tǒng)慣性較大的發(fā)電機(jī)，在突然甩負(fù)荷 時(shí)，可能出現(xiàn)過(guò)電壓，造成發(fā)電機(jī)繞組絕緣擊穿。 c) 由于外部不對(duì)稱短路或不對(duì)稱負(fù)荷而引起的發(fā)電機(jī)負(fù)序過(guò)電流和過(guò)負(fù)荷；在轉(zhuǎn)子中感應(yīng)出 100Hz 的倍頻電流，可使轉(zhuǎn)子局部灼傷或使護(hù)環(huán)受熱松脫，而導(dǎo)致發(fā)電機(jī)重大事故。 2） 異常工況狀態(tài) 異常工況狀態(tài)主要分為以下幾種： a) 由于外部短路引起的定子繞組過(guò)電流。 1） 故障類型及危害 發(fā)電機(jī)結(jié)構(gòu)主要由轉(zhuǎn)子與定子兩大部分組成，因而發(fā)電機(jī)故障包括定子與轉(zhuǎn)子故障。當(dāng)同步發(fā)電機(jī)處于異常工況狀態(tài)時(shí)，保護(hù)裝置應(yīng)及時(shí)發(fā)出信號(hào)，以便運(yùn)行人員快速處理。 第 5 章繼電保護(hù)的配置和考慮 5． 1 概述 發(fā)電機(jī)的安全運(yùn)行對(duì)保證電力系統(tǒng)的正常工作和電能質(zhì)量起著決定性的作用，同時(shí)發(fā)電機(jī)本身也是一個(gè)貴重的電器元件，因此，應(yīng)該針對(duì)各種不同的故障和不正常運(yùn)行狀態(tài)，裝設(shè)性能完善的繼電保護(hù)裝置。 電力工程系畢業(yè)設(shè)計(jì)（論文） 26 母線的最小截面積： 2236 3 mmmKtCIS jdz ?????? ??? ?? 因此， 22 2051491 mmSmmS zx ??? ，滿足熱穩(wěn)定性。 校驗(yàn)動(dòng)穩(wěn)定 電流互感器的內(nèi)部動(dòng)穩(wěn)定能力用動(dòng)穩(wěn)定倍數(shù) mK 表示，動(dòng)穩(wěn)定倍數(shù) mK 等于互感器內(nèi)部允許通過(guò)的極限電流（峰值）與 2 倍一次額定電流（ 1NI ）之比。 動(dòng)穩(wěn)定校驗(yàn)： kAikAi imp