功率變壓器老化和延壽中英對(duì)照

1、功率變壓器老化和延壽便攜式-電力變壓器是一個(gè)關(guān)鍵的和任何電力公共事業(yè)昂貴的資產(chǎn),世界各地許多變壓器的電弧服務(wù)接近或超出其設(shè)計(jì)的范圍。有一種日益注重?cái)U(kuò)展現(xiàn)有變壓器維護(hù)范圍，以最大限度的增大投資回報(bào)率。變壓器故障的統(tǒng)計(jì)資料展明大部分的故障發(fā)生前均達(dá)到其額定壽命。由于介質(zhì)的問題而引起的變壓器故障據(jù)報(bào)道高達(dá)75，在石油中出現(xiàn)的呋喃化合物提供了一個(gè)固體電介體惡化的指標(biāo)，它很重要的對(duì)監(jiān)定電介體的惡化階段及其敏感程度的老化。老齡問題是還強(qiáng)烈依賴于溫度，氧氣和水的水平，通過控制這些變數(shù)變壓器壽命能被最大化。本論文介紹了一種模糊邏輯基礎(chǔ)的方法既使用主要指示器用于估計(jì)電力變壓器的壽命，例如濕氣和呋喃化合物。索引期

2、限-變壓器年齡評(píng)估、壽命延長(zhǎng)、可靠性.導(dǎo)言電力變壓器的功率老化有到達(dá)一緊要關(guān)頭的水平。接近預(yù)期壽命的現(xiàn)有設(shè)備是在考慮減少重要的開支當(dāng)替換這些變壓器費(fèi)用太高時(shí)而進(jìn)行的。因?yàn)榇蟛糠葸@些變壓器正在操作超過他們的額定壽命，設(shè)備在最高負(fù)荷下面的可信度不能是確定。變壓器失靈正在數(shù)字上增加而且有嚴(yán)重的沖擊在電壓、燈火管制、收入和環(huán)境中。變壓器絕緣退化、加速的老化和災(zāi)難性故障發(fā)生由許多原因引起，例如極端操作的情況、不利的周圍情況(高溫度和濕度指數(shù)),完全故障、巨涌(轉(zhuǎn)變/閃電)和地磁氣的暴風(fēng)雨。變壓器老化總是被加速.由于缺乏維護(hù)和適當(dāng)?shù)倪^失診斷。絕緣系統(tǒng)的退化伴隨著自身參數(shù)的變更或其它的行為現(xiàn)象。絕緣紙和油降

3、格生產(chǎn)的濕氣和爐氣為火爐常態(tài)和加速老化負(fù)責(zé)。由于過熱，瓦斯在絕緣系統(tǒng)被釋放,部分的解除(pd)和劇烈進(jìn)行.同樣,水分含量在降低和絕緣的失敗鏈中擔(dān)當(dāng)了一個(gè)重要的角色。纖維素和油之間的含水量和它的運(yùn)動(dòng)是溫度受扶養(yǎng)者。過失瓦斯的常數(shù)監(jiān)聽,熱點(diǎn)溫度和含水量(wc)在發(fā)現(xiàn)過失類型方面幫助,強(qiáng)烈和,直到善行范圍,它的位置為止。熱的情況監(jiān)聽變壓器(包括負(fù)荷輕打變更者)臺(tái)子重要的為變壓器操作的計(jì)劃在個(gè)別項(xiàng)目在最高負(fù)荷和在緊急載入。加速的老化發(fā)生由于濕氣和氧水平的增加在那油。濕氣和氧水平是溫度受扶養(yǎng)者和增加與溫度濕氣索引(thi)的增加 .比較高度濕氣和氧能領(lǐng)引到一泡沫能引起悲慘的失敗的形成。增加的可信度變壓器

4、需要對(duì)負(fù)荷和溫度根據(jù)以可接受的濕氣極限為基礎(chǔ)的一個(gè)操作的標(biāo)準(zhǔn)。在有效的延壽方面分別采用嚴(yán)格和有效的沖擊對(duì)氣體處理的來源監(jiān)定非常重要。對(duì)于確定類型和嚴(yán)重過失，用正確的解釋溶解瓦斯分解(dga)是識(shí)別的方法之一。在線 dga 、pd和診斷對(duì)于建立資產(chǎn)正直非常的重要，例如在繞組運(yùn)動(dòng)中的頻率回應(yīng)分析 (fra)、恢復(fù)電壓測(cè)量(rvm)。變壓器診斷和監(jiān)聽數(shù)據(jù)重要選定操作的標(biāo)準(zhǔn),資產(chǎn)管理和可信度為壽命延長(zhǎng)集中了維護(hù)(rcm)策略。比較好的資產(chǎn)管理能達(dá)到與在線監(jiān)聽和有效的診斷。準(zhǔn)確性壽命評(píng)估結(jié)果對(duì)壽命延長(zhǎng)的服務(wù)資產(chǎn)是必要。.變壓器老化決定設(shè)備的情況和老化過程是很困難的當(dāng)它包括多數(shù)變數(shù)演變同時(shí)又是一種合成物。

5、在油/纖維素絕緣系統(tǒng)中的老化過程是一種在熱應(yīng)力壓迫和可測(cè)量作用力之下不能分的電介體系統(tǒng)的化學(xué)反應(yīng)。電介體溫度是引起老化的關(guān)鍵參數(shù)，這就是機(jī)械和電材料變化的原因。紙絕緣中包含有約40%纖維素。聚合的程度(dp)是測(cè)量每一分子鏈中的葡萄糖單元的平均數(shù)值。dp超過1000時(shí)，紙絕緣出現(xiàn)高度電介體和可拉長(zhǎng)單元,當(dāng)dp值較少的超過300時(shí)，紙絕緣出現(xiàn)很少的電介體和很差的機(jī)械性能。在絕緣系統(tǒng)中，水和氧的出現(xiàn)加速了老化現(xiàn)象。對(duì)于判斷變壓器的老化、可靠性和安全性濕氣是一個(gè)很好的指示器。水解、熱分解和氧化是三個(gè)同時(shí)進(jìn)行的機(jī)理。老化機(jī)理影響著電介體和電介質(zhì)的機(jī)械性能。111. 壽命評(píng)估的目標(biāo)在相同的服務(wù)期內(nèi)，同一

6、變壓器的剩余壽命因?yàn)樗慕^緣性能可能改變。絕緣性能依賴于溫度、濕度和含氧量。操作環(huán)境(高度,周圍情況，光照和氣流),電動(dòng)裝置,系統(tǒng)阻抗,配電系統(tǒng)和照明巨涌(在電壓之上),完全故障和污染是加速資產(chǎn)老化的主要因素。經(jīng)濟(jì)的和壽命評(píng)估的目標(biāo)是必要的，為現(xiàn)有的老化設(shè)備計(jì)劃維護(hù)、再布置或退役。呋喃化合物和水分含量是壽命評(píng)估的主要指標(biāo)?；馉t化合物是由起初的過失引起常態(tài)老化絕緣紙(纖維素)降格產(chǎn)生的。由于降格過程,紙的張力和電介體減少。由于故障電流，電磁力有嚴(yán)重的沖擊在絕緣紙上從而降低它的可張力。好的相互關(guān)系能在呋喃化合物和化合物和聚合 的程度(dp)之間獲得 .因此,出現(xiàn)在油中的火爐化合物的量是壽命評(píng)估的一

7、個(gè)很好的指標(biāo)。變壓器使用年限特征是基于呋喃化合物在不同的年限中的出現(xiàn),如圖 1 所示.剩余壽命 (年限)圖1：有關(guān)于呋喃系的變壓器老化特性(c4h4o).因年限出現(xiàn)的絕緣降格增強(qiáng)了呋喃系呋喃系產(chǎn)生是由于遍及所有溫度的上升就像在局部的熱生產(chǎn)過程被活性中斷.基于分析，設(shè)備可能被識(shí)別由于呋喃系產(chǎn)生的常態(tài)老化或局部故障。用質(zhì)量較差的包裝紙操作設(shè)備可能造成災(zāi)難性故障連帶威脅著環(huán)境和附帶損害。對(duì)監(jiān)視器的包裝紙退化趨勢(shì),夫喃系分析在所有的評(píng)估中扮演著關(guān)鍵的角色。它是非常有用的診斷,決定著故障變壓器是否應(yīng)該修復(fù),還是出現(xiàn)了再創(chuàng)傷或扔棄。溫度、氧和濕氣在加速老化的過程中是主要因素。操作溫度和周圍溫度在變壓器的使

8、用周期內(nèi)始終存在,影響絕緣壽命。研究和經(jīng)驗(yàn)領(lǐng)域表明逐漸增加溫度將減少設(shè)備最大負(fù)荷絕緣的壽命。在常態(tài)操作溫度下,每上升7設(shè)備將減少50%的壽命.由于包裝紙熱電運(yùn)動(dòng)的降格,在絕緣鏈中生成了濕氣(含水量)倒不如老化油。在大氣出現(xiàn)的潮氣穿透過弱的密封劑改變氣壓梯度。在變壓器中的水可溶性礦物油增加伴隨著溫度的增加。濕氣影響分子鏈分解,加速纖維素老化過程,非同一般的張力和電介體設(shè)備的絕緣系統(tǒng)。介質(zhì)擊穿濃度伴隨著濕氣增加?；谠诮^緣鏈中出現(xiàn)濕氣，變壓器風(fēng)險(xiǎn)評(píng)估對(duì)它的有效壽命延長(zhǎng)和比較好的設(shè)備管理是必要的,如表1所示.表 1 濕氣消除及變壓器失靈危險(xiǎn)區(qū)域絕緣平均濕度評(píng)估4%進(jìn)入危險(xiǎn)地域5%6%相當(dāng)多的失靈風(fēng)險(xiǎn)

9、7%即將出現(xiàn)的失靈濕氣在包裝紙和油之間交換和它的動(dòng)力學(xué)是高度地依靠溫度。從包裝紙到油的濕氣動(dòng)力學(xué)增加伴隨著溫度的增加,但是濕氣返回到包裝紙時(shí)卻伴隨著溫度的緩慢的減少。為測(cè)量在油中的濕氣,標(biāo)準(zhǔn)方法是 karal fischer 反應(yīng)測(cè)試(美國(guó)材料試驗(yàn)學(xué)會(huì) d 1533).這個(gè)測(cè)試由于它的高選擇性和敏感被高度地推薦而且廣泛地使用。絕緣系統(tǒng)的含水量應(yīng)該保持最小量到維持必需的電介性能。變壓器老化特性基于不同的壽命周期內(nèi)出現(xiàn)的含水量,如圖 2 所示.剩余壽命 (年限)圖 2:由于老化和熱電磁-動(dòng)力的降格出現(xiàn)的變壓器老化特性用濕氣的增加量表示iv.基于模糊邏輯的壽命判斷模型通常夫喃系和濕氣同時(shí)地以最復(fù)雜的

10、模式被產(chǎn)生而且是在識(shí)別設(shè)備的剩余壽命方面是主要因素。兩者的出現(xiàn)在設(shè)備性能和壽命方面有嚴(yán)重的沖擊,不理睬一可以誤導(dǎo)判斷。模糊邏輯模型和分析被逐漸實(shí)行獲得比較好設(shè)備剩余壽命判斷。圖 3&4表示的是濕氣和夫喃系為輸入變量時(shí)的壽命評(píng)估模糊邏輯模型。圖 5表示的是設(shè)備的使用周期當(dāng)做輸出變量時(shí)的模型。輸入變量 濕氣 圖 3: 輸入變量“濕氣”(成員函數(shù))為變壓器年限模型輸入變量 夫喃 圖 4: 輸入變量“夫喃”(成員函數(shù))為變壓器年限模型mamdani的模糊推論方法是用來對(duì)設(shè)備的壽命估計(jì)。 (1)x 是和 y是,或x是和y是,在此是關(guān)聯(lián)的含義.如果x是及y是，然后z是 (2)x表示濕氣,y表示夫喃系作為輸

11、入(變量)和z為變壓器的老化程度而且是輸出變數(shù)。, , 表現(xiàn)他們各自的功能。規(guī)則范圍限定在: and (3)在模糊設(shè)置中，是x在的全體值集合而是y在的全體值集合。輸出變數(shù) 年限 圖 5: 輸出變量年限(成員函數(shù))綜上所述由于易受影響的輸出量(設(shè)備壽命)，地心引力運(yùn)算法則集中用來計(jì)算區(qū)域ai和中心區(qū)域每元函數(shù)(mf)的mi. (4)在此： (5) (6)使用上面的模型,易受影響的輸出量既變壓器壽命是關(guān)于濕氣和夫喃系的已被確定和描述在了圖6中.圖 6:變壓器年限模型, 以濕氣和夫喃系當(dāng)做輸入變量為基礎(chǔ)v.壽命延長(zhǎng)現(xiàn)有變壓器數(shù)量的壽命延長(zhǎng)是一個(gè)重要實(shí)效的議題。有足夠的安全性和涉及操作老化單位方面的環(huán)

12、境風(fēng)險(xiǎn)接近外面的監(jiān)視和評(píng)估的載入極限。利用正確及時(shí)的評(píng)估可以控制老化過程, rcm申請(qǐng)和適當(dāng)?shù)牟僮鳂?biāo)準(zhǔn)落實(shí)了廣大的剩余壽命與可接受的安全性和可改良的可靠性能達(dá)到比較好的有成本效益的利用。經(jīng)典的診斷用現(xiàn)實(shí)做解釋，因此rcm對(duì)設(shè)備延長(zhǎng)壽命是至關(guān)重要的。通過貫徹適當(dāng)?shù)牟僮鳂?biāo)準(zhǔn)(動(dòng)力載荷)可以改良現(xiàn)有老化設(shè)備的利用和有效率的/有效的維護(hù)對(duì)維持/升級(jí)絕緣系統(tǒng)。由于它在強(qiáng)調(diào)失敗結(jié)果方面定義了失敗的問題根源，利用rcm能完成比較好的結(jié)果。如圖7流程圖中所表示，利用rcm可以有效地實(shí)現(xiàn)設(shè)備延長(zhǎng)壽命.rcm有助于經(jīng)濟(jì)有效的維護(hù)，方便操作,增強(qiáng)安全性而且減少環(huán)境的風(fēng)險(xiǎn)?；谠诰€監(jiān)聽和診斷,倘若可能壽命延長(zhǎng)的rcm

13、策略能被比較好實(shí)現(xiàn)。-設(shè)備的關(guān)鍵部件和他們各自的功能已經(jīng)完全已知。-設(shè)備的可能故障和他們的結(jié)果包括所有的系統(tǒng)已知已知，如輸出變量,被迫的儲(chǔ)運(yùn)損耗(中斷),收入,修理,再磨光,替換費(fèi)用、安全和環(huán)境的連帶損害。 圖 7: 變壓器壽命延長(zhǎng)和管理流程圖vi.總結(jié)利用輸入變量的濕氣和呋喃化合物模糊模型可以預(yù)測(cè)紙包裝變壓器使用年限 。壽命判斷將有助于最大化實(shí)現(xiàn)可實(shí)行的操作效率。系統(tǒng)可靠性和設(shè)備實(shí)用性能被確保，通過改良系統(tǒng)性能。過早的故障風(fēng)險(xiǎn)能被最小化。設(shè)備及時(shí)的翻新、替換或再布置能被規(guī)劃。正確的操作和維護(hù)策略能被改進(jìn)和貫徹以得到最大的回報(bào)。間接的和環(huán)境的損害能被有效地最小化。 power transfor

14、mer aging and life extensionabstract-power transformer is a critical and expensive asset for any power utility.many transformers around the world are serving close to or beyond their designed lie.there is an increasing focus on maintenance and lie extension of existing transformers to maximize the r

15、eturn on investment.transformer failure statistics exhibit that most of the failures have occurred before reaching their rated life.transformer failures due to dielectric problems are reported as high as 75%.furnace compounds presence in oil provide an indication of solid dielectric deterioration.it

16、 is important to identify the deterioration stages of dielectrics and its degree of sensitivity towards aging.ageing is also strongly dependent on temperature,oxygen and water levels in the transformer.the transformer life can be maximized by controlling these variables.this paper presents a fuzzy l

17、ogic based approach to estimate the age of a power transformer using key indicators such as moisture and furnace compounds.index terms-transformer age assessment,life extension, reliability .introductionpower transformers aging population has reached a critical level.existing assets that are close t

18、o their expected life are being considered for further utilization in order to reduce capital expenditure as the replacement cost of these transformers is too high.since many of these transformers are operating beyond their rated life,asset reliability under peak load cant be ensured.transformer fai

19、lures are increasing in number and having serious impact on forced outages,blackouts,revenue and environment. transformer insulation degradation,accelerated aging and catastrophic failures occur due to many reasons such as extreme operational conditions,adverse ambient conditions (high temperature a

20、nd humidity index),through faults,surges (switching/lightning) and geomagnetic storms.transformer aging is also accelerated.due to lack of maintenance and proper fault diagnosis.the degradation of insulation system is accompanied with the phenomenon of changing physical parameters or its behavior.in

21、sulation paper and oil degradation produce moisture and fiurnace which are responsible for normal and accelerated aging.gases are released in the insulation system due to overheating,partial discharge (pd) and arcing.also,the presence of moisture plays an important role in the degradation and failur

22、e of insulation chain.water content and its movement between cellulose and oil is temperature dependent.constant monitoring of fault gases,hotspot temperature and water content (wc) helps in detecting faults types,intensity and,up to a good extent,its location.thermal condition monitoring of transfo

23、rmer (including load tap changer) stands vital for transformer operational planning in particular at peak load and at emergency loading.accelerated aging occurs due to increase in moisture and oxygen level in the oil.moisture and oxygen levels are temperature dependent and increase with the increase

24、 in temperature humidity index (thi) .higher level of moisture and oxygen can lead to a bubble formation that can cause catastrophic failure.increased reliability of a transformer requires an operational criterion that is based on acceptable moisture limits according to load and temperature.it is vi

25、tal to identify the sources of gassing with their respective severity and impact on the asset remnant life.dissolved gas analysis (dga) with accurate interpretation isone of the methods for identifying the type and severity of the fault.online dga,pd and diagnostics such as frequency response analys

26、is (fra) for winding movement, recovery voltage measurement (rvm) are important to establish assets overall integrity.transformer diagnostics and monitoring data are important to decide on the operational criteria,asset management and reliability centered maintenance (rcm) strategies for life extens

27、ion.better asset management can be achieved with on-line condition monitoring and effective diagnostics.end of life assessment with accuracy is essential for an asset to serve for its extended life.transformer agingit is difficult to determine the assets condition and aging process as it involves ma

28、ny variables acting at the same time in a complex manner.the aging process in the oil/cellulose insulation system under thermal stress and their measurable effects are due to chemical reactions in the inseparable dielectric system.the dielectric temperature is a critical aging parameter that causes

29、a change in the mechanical andelectrical properties of the material.paper insulation is composed of approximately 40% cellulose.degree of polymerization (dp) is a measurement of average number ofglucose units per molecular chain.paper insulation,with dp greater than 1000,exhibits high dielectric and

30、 tensile properties,where as dp value less than 300 shows a paper with poor dielectric and mechanical properties.presence of water and oxygen in the insulation system accelerates the aging phenomenon.moisture is a good indicator to determine the aging,reliability and safety of the transformer.hydrol

31、ysis, pyrolysis and oxidation are the three mechanisms,acting simultaneously.the aging mechanism affects the electrical and mechanical properties of the dielectrics.111.end of life assessmentresidual life of identical transformers,with same period of service,may vary because of its insulation behavi

32、or.insulation behavior depends on temperature,moisture content and oxygen ingress.operating environment (altitude,ambient conditions,sunshine and airflow),dynamic loading,system impedance,switching and lighting surges(over voltages),through faults and contaminations are the major factors towards ass

33、ets accelerated aging.economic and end of life assessment are essential for the existing aged assets to plan for the maintenance,relocation or retirement.furnace compound and moisture contents are the key indicators for life assessment.furnace compounds are generated due to insulating paper (cellulo

34、se) degradation with normal aging as well as due to incipient faults.due to degradation process,paper tensile and dielectric strength decreases.electromagnetic forces due to through fault current have serious impact on the paper life by lowering its tensile strength .good correlation can be obtained

35、 between furnace compound and degree of polymerization (dp).therefore the furnace compound quantity present in the oil is a good indicator for life assessment.the transformer age characteristics based on furnace compound present in different age groups is shown in figure 1. remnant life ( years)figu

36、re 1 transformer aging characteristic with respect to furan (c4h4o).furan increases due to insulation degradation with age.furans are generated due to over all rise in temperature as well as due to the heat produced by active fault in any localized area.based on the analysis,asset could be identifie

37、d for furans produced due to normal aging or localized fault.asset operating with poor paper strength may result in catastrophic failure with serious threat to environment and collateral damages.to monitor the paper degradation trend,furan analysis can play key role in the over all assessment.it is

38、a very useful diagnostic for assessing whether a failed transformer should be repaired,rewound or scrapped.temperature,oxygen and moisture are the key factors in accelerating the aging process.operating temperature and ambient temperature exists throughout the life of the transformer,affecting the i

39、nsulation life.studies and field experience show that gradual increase in temperature reduces the peak load insulation life of the asset.a rise of 7celsius above normal operating temperature decreases assets life by 50%.moisture (water content) in insulation chain is produced due to thermo-kinetic d

40、egradation of the paper as well aging of the oil.moister present in the atmosphere penetrates through weak sealant with the change in the pressure gradient.the water solubility in the transformer mineral oil increases with the increase in temperature.the moisture influences the decomposition of the

41、molecular chain,accelerates the cellulose aging process,affecting the tensile and dielectric properties of the insulation system.dielectric breakdown strength decreases with increase in moisture.based on the moisture presence in the insulation chain,transformer risk assessment is essential for its e

42、ffective life extension and better asset management,table 1.table imoisture levels and transformer failure risk zonesinsulation average moisture contentassessment4%entering fisk zone5%6%considerable failure risk7%failure imminentmoisture is exchanged between paper and oil and its dynamics are highly

43、 temperature dependent.moisture dynamics from paper to oil increases with increase in the temperature,but with the decrease in temperature the moisture moves back to the paper slowly.the standard method for measuring the moisture in oil is karal fischer reaction test (astm d 1533).this test is highl

44、y recommended and is widely used due to its high selectivity and sensitivity.water content in the insulation system should be kept to a minimum to maintain the required dielectric properties.the transformer age characteristics based on moisture contents,present in different age groups is shown in fi

45、gure 2.remnant life ( years) figure 2:transformer aging characteristics with increase in moisture content due to aging and thermo-kinetic degradation.iv.life estimation model using fuzzy logicusually furan and moisture are generated simultaneously in a very complex manner and are key factors in iden

46、tifying assets remnant life.presence of both has serious impact on the asset performance and life,ignoring one could mislead the estimation.the fuzzy logic modeling and analysis has been carried out to get better assets remnant life estimation.figure 3&4 represents the moisture and furans as input v

47、ariables for the life estimation fuzzy logic model.figure 5 represents the assets age as an out put variable of the model.input variable “moisture” figure 3: input variable “moisture” (membership functions)for transformer age model input variable “furan” figure 4: input variable “furan” (membership

48、functions)for transformer age model mamdanis fuzzy inference method is applied to estimate the assets life. (1)where x is and y is ,or x is and y is and so on as a conjunction of implications.if x is and y is， then z is (2)where x represents the moisture,y represents furan as inputs (variables) and

49、z the age of the transformer and is the output variable. ,then represent their respective membership functions.the extent to which a rule is activated: and (3)where is the membership value of x in the fuzzy set and is the membership value of y in the fuzzy set.output variable “age” figure 5: output

50、variable age (membership functions)defuzzificarion:for crisp output (asset life),center of gravity algorithm is used to calculate the area ai and center of area mi for each member function (mf). (4)where: (5) (6)using the above model,the crisp output transformer age with respect to moisture and fura

51、n is determined and is represented in figure 6.figure 6:transformer age model,based on moisture and furan as input variablesv.life extensionlife extension of existing transformer population is an important issue for the utilities.there is an ample safety and environmental risk involved in operating aged units close to loading limits with out surveillance and assessment. aging process can be controlled with accurate in time assessment,rcm application and proper operational criteria implementation extended residual life with acceptable safely and imp