力特 有效保护变压器和控制变压器的重要性(英文).pdf

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力特 有效保护变压器和控制变压器的重要性(英文)pdf,力特 有效保护变压器和控制变压器的重要性(英文)
Transformer Protection Basics A Littelfuse Ihle 1: Fuses ot transformers over lloret For more specific sizing recommendations, refer to Tables Maximum国a国Pt 4 and 5 for Class J fuse protecton and Tables 6 and 7 for af Transormer Rated Curent Class CC fuse protection Transormer Prim Secasdarr hise Raling Rated 6Dwt60vo舞a Table 4 shows recommended Class J fuse ratings for standard transformers below doo volts without Toois in or less in orless in secondary protection, while Table 5 shows the similar CE Ige recommendations in applications wrth secondary protection Not oie then 200m 125 Clss J Fuse Protection ofstandard Transformers Wanmowf Secondary indent mr enma 2 12E F0—55vl别兽-P tan 10R IEC and LL Mxr四ab匹m叫WDyp pCpch . Littelfuse SR LINRKlSBr骤R貌几时_照 tine-delay fa s8a may be rated at t25% cf tawiormer seoondary curent SEsgle-PhaseSingle-PhaseSingle-Paase mh:时[n感pm“ted Transterm暗r Primary JTD ar Primary JTD or Pimary JTD or k冒真 Currenl D Crrent TD D JTo D 3.如hi引算 iiseis not required i the primary cicuit目 grester then 300% of transformer primary curent (A) Series (A) Serles\ CAI 015 aBS 192 3 012 Transformers Rated 600 Volts and Less 0213四的08212 UL Industrial Control Standards (No. 508l and Motor 一4133 Control Center Standards (No, B45l speedy contro power 31745 5 3 transformer protection coresponding to NEC Article 2 4 430.72iCh. In addition, UL requires the primary of control 0Amt45一3船5 power transformers usEd in controlers having short-circuit. 1新t5543 04日 ratings in excess of 10 000 amperes to be protected b 13112652期5 1522 71 10 uL Class CCiJ,R, or T iuses. For maximum fuse rating permitted by the NEC, refer to Table 2 for sizing af primary 5214318715871 800347845V32589112 fusing and Table 3 for sizing of secondary fue ne 5358745T25143520 214 3 25 Table 2: Mazimum Acceptable Rating of Primary 0w打磨 限配mn丽b雷mm列hrbh时fary Rated Primary Maxinum Ratingaf nercarmeat Pmlcctive Demic rd帮Tah4he %oI THnsianet Priiniaty Current Rating MO secondary Sondar fusing prided n Table 4n hsm ported atewrdanse with Tite 7 20 Ra瞬Pnr Manuum Rating ot Fe dd Iarstommar bRaless thang 1 CuITHaI Antes Prinary Curent Hating INio Secondany Fusing Rideal 自m旧 1售2 Thle 3 2如上出ng Maximum McGepiable Rating ol Secondary Overcurrent Device Hu ni Rated seenadiary Maximum Rating of Onereanmeat Proactive Deuice GN粪 mineRS Saof Transformer Secondary Current Rating lalmTuybe a Lass tan 9 HL=LidL这C如 HO mle t, 50is far alet dircuit camiolpwut trans omit 2‖125%dmct8ndd向 seating the rient hgher sten时 「myue RdM472E观解险2最1a2uL的金71 andIr 单10L出 .s PUTR-GAAD Prodcis wwY IrtbsHtuse com Transformer Protection Basics Littelfuse EGsp时DEC吧 Thle 5 Claasd Fin Piotrchoa Of Standard Transfomer WM Secendary Table 6 shows recommended Class CC fuse ra tings for Prolection觊4躬W器 transformers with sing a-winding 240 Volt primaries while EU国目A国下明国的 Table 7 shows similar recommendations for tansforrrefs V5P瞬kPh5 s Yalis shgliFh with single-winding 480 volt pr maries STOEr Pri=aN JTD JD Cumant/A)JTD O TOUr Transtormer PrInay,TD_D Table 6 Errant A UraNtiA ere围 Class CC Fn P吨i0mss皆 nding Primal 00110BK3 2帽 WorPrinury ellie Par imim Alcwable Fising Camps Hacumnendatt 21 LIE 3 B 1 wth Inly Primary Prchrtizn 0 3百 13 L 21 174 Transor-er Primary Cortrd Pomer e uentIAl Transome transtar KL DR SEriE 2hL m 200 8而 01 250 10B 五E 12 4 Bln 13315512 31 -12 B/TO 2 152 12 15 5201妇2B20 212 DBa5 G4 0 13 8 as 2 1-1 3 2 31 212 F用mm图四以国npMC 1应 ETT 31 57,B5111am111额司 n chaib 520 Table 5H IIT 5 Shigatse ra es pwrissha my wten entry palatin is prmi in sonora with Errant山rpre (5esonedr FuNn Ffe dei Its#A ISae ImwE sdH asMc】LL less ran 2 TableT cscF瞬Pc叶 Transtar E With sigla-indin primar 4 Molf Primary 9Ml明积 HEra l mai TEhle 5C Jwa写apo 1最量 t严raas Hated Secondary Maui-um Fating d F-seM d Trarsisrmar CuTErEAPses SsEanEary C rant Hatrg HatEr H Hi-er I Da nI Es 矿m if 1a 52 uxs not uspo o astrand ss Hting, ie nent wie ssas ntinu Li H 4 2 HAI For Maximum Acceptable hating Primary decurrent DevicE roberto Taha? For Maximun具ccp阻 Seconda Ower理te refer to Table ic 单团1市 PCMR-EAAD Prodc www.Irth=hfusecom Transformer Protection Basics Littelfuse Erase Applied Arses DelNeed Transformer Protection for Medium Voltage pad-mounted transformers, and at other similar locations Applications (above 600 Volts) When properly appled, E-Rated tuses can protect against high and low va ue fault currents, A supplemental device is Introduction needed ir sares to remove currents below the r nigrum Medium voltage fuses are applied quite ditferenuy than meltng current rating of the fuse fuses rated 60t volts and less, The biggest difference is that mediurm voltage fuses are not intended to proide overload Gurdefiries for E-Rated Fuses protecton. They shoud only be apped in situations where Fuses with a rating of 100E or less wrill open iblowvt it w not be required to opan small overcurrents Medium within 300 seconds 5 minutes at a current between vo tage fuses offer a much wider range of system voltages, 2009 and 240% of the"E rating thereby resulting in a correspond ngly large number af fuse Fuses with a rating above tODE will open [? within voitage ratings 600 seconds (10 minutes] at a current between 220% Descriptions and ratings of Litteluse and 264 of the Ratna medium voltage fuses, along with Fuse Sring some application data, are located in the Medium voltage Fuse section of Fuses are sized at a percentage of the talNoad current the Littelfuse POWR-GARD Catalog Generally, fuse size is based op 33%0150%al To download a copy visit full load current. www国tu客ecom/ catalogs Always round up to the neet stanDard fuse rating As an example with afull kad cogent of 104 amperes For questions, contact our Techrical Support and the fuse size bead oh i33% of fu load current would be a Engineering services Group at B0O-TEC-FUSE 13B amare& Sucha fuse rating size does not exist, so [800-832 3873). Definitions of terms used in this while t is pe hissiblbara recdmmended to round up to the next paper can be found in the Technical App caton Guide secton ol the POWR-GAAD Catalog standar! sze werich in this instance is 150 amperes (150E) The fo lowing is a mare deta led discussion of facters which Be sure to note that nuisance fuse openings can occur if must be considered when property selecting ahd appling the fuse is sized too closely. medium voltage fuses in electrical systems. table H Suggested Minimum current l imifing medium voltage fuse current ratings for What are Medium VoltagerEusesa ce24155Wprs呵单plc Littelfuse medium voltege fuses are'siNer sand non-expu'tsion design, curieint-limiting type devices F Whan properly app fed, then are designed to carry their nominal current rating corfondously wthout "fatigue failure. fawletwrlw This means that the fuse wn not age, become brittle, or SelCal 品品总 deteriorate under the most severe duty cycling 3内[ Whan talking current-limiting medium voltage fuses, there are two basic types general purpose and back-up. Gene 35 15E2 purpose fuses have the ability to interrupt both large and I sma short-circu ts down to currents that would cause the fuse to open within one hour. They are used to provide 16 short grcuit protecton for transtormers, switchgear, and 11 们 5敏 5 similar equipment Back up fuses are designed to protect only against high 1的8 fault currents, and must be used in series with equipment sT缸 that provides the circut's requred overload and low value 22 15 short-c cuit protecton 24 4508 45 154 Whla"R-Rated"medium voltage (Mv) fuses are specifically 20 designed to prowide short-circuit prote ction for medium voltage motor controllers and associated equpment, 4 E-Rated"Mw fuses ara considered to be general purpose 3BH 12 fuses. Their mounting dimensions permit them to be 4 installed in a wide variety of medium voitage switchEs, in 单 Lits L- PTTIR-EAADP Prodcis www.Irtt=hfusecom Transformer Protection Basics Littelfuse E匙即sD Continu ng with sing of E-Rated fuses, the transformer , And where and whenever possible, fuses should siz ng gude in Table 8 shows the suggested mimimum protect the transformer against higher impedance current limiting medum voltage fuse current ratings fol secondary fau ts, seif-codled 2.4-15.5 ky power transtormer applications Transformer magnetizing or inrush current depends on several factors including the transtormers design. the amount of residual fiu in the transformer core et the Transformer Protection instant the transformer is energized, the point an the A princip|use吖 i mediu w睡ga和 uses is to prodi voltage wave at which tha switch is cosed and the primary short circut protecton for transformers characteristics of the electrical system powering the When salecting Mv fuses to protect transformers, transformer, A power transtormers in-rush current the follow ing factors must be considered in descending pproximates 12 times the transformer full load current, order of importanc while a distribution transformers in-rush current can 自eed25te4 a tim es0 f the tu山‖ load current. The 1. The fuse, s voltage and interrupt ng ratings must equal current genera ly lasts less than one-tanth of a second or exceed system requ rements at tha point where the fuses w be applied Figure 2 Typical Example of Double ended Loadcenter Operated with 2, The fuses continuous current rating must be large enough to withstand transformer mag netiz ng Iin nshi current MInimum Fuse Hatngl 3. The fuses continuous current rating must be able to withstand transformer overload ng and emergency operation, while masting all NEC requrements. MAximum Fuse Hat ng 4. Fuses must protect the system on the line side of the fuse from the effects of short circuits on the load sided of the fuses ITil ty System Coordination 5. Fuses must coordinate with the transformer seconday protection where and wheRowor pos ole. Faclt Systerm Coordination 6. Fuses must protectin trans mer against secondary bolted faults FLue 1 rimes curent Curves ior TransiormarFrotech四pp Tt derermine the min mum eize use thet will withstand the in-rush current, it is recommended that the in-rush current be obtained from the transformer manufacturer 4 Then, note the current on the fuse s minimum maltin< time-current cuves Et o 10 second. this is lustrated in 验备敌到 d凸」 more detail in Figure 1. The fuse whose minimum meiting n|围 curve is just to the right and above the transtormer inrush point becomes the minimum fuse rating to use for properly 直Pa protecting tha sYstem 萄验 Med um voltage fuses with Gurrent ratings that equal or exceed a transformers self-cooled, fu load current will usually meet such a requ remant when the in-rush gurrent doas not exceed 12 times transformer fu load current InOut theroad However, transformers are generally operated at close to full L【at load current on a continuous basis and are of ten overloaded under emergency conditons. A typical example is a double- ended loadcenter operated with a normally open bus tie See Figure 2 n“=岛帛器器离量 GLRHENT IN AMPERES 单 Lit L- PTTR-EAAD Prodcts www.Irttclfusscom Transformer Protection Basics Each transformer is rated to carry 150% of the load on its half of the adcenter with loss of service to one transformer, the ma n switch for that ine is opened and the bus the switch is closed. This shifts all load to the remaining transformer. The system is operated in an overloaded state until the other line is back in service. If the outage continuas for a long period of 1me, manual load shedding can be used to control transformer overloading Other similar operating schemes also result in transformer overloading. As a result, medium voltage fuses usually have continuous current ratings larger than required to withstand transformer in-rush current NEC Arucle 450 cowers transformer installations and establishes the max mum ratings of transformer overcurrent protective devices. Regarding med um voltage fuSES, NEC Article 450.3 states, in part Overcurrent Protection al transformers shall comply with NEC Arbcle 450,3(A-Trangformers Over 600 volts Nominal, and sha l be prowided in accordance with Table 9 NOTE In this section, he word" fransformer shelp mean a transformer or polyphase bank of twvo or mone sMgle-phase transformers operating as a single unt. ThE ble s Based on NEC Table 450.Ai Maximum Rating ot setting or overcurrent Protection for Transformers over 600 volts das a Percentage of Trantsfotmer-Rated CurrentI Pinti Flection ler Secandary prutetlioa ISet Note2l Ower ho lotts Transormer累aed Circuli breaker Location Limitations 酯an4 saN口4 Fisi Rating Cireuliereaker or Fuse Rating 间 miy than h f lsea Note ll U 25 1% 点 y locatin aB%bmm的 10%M=1 401 5 1 Anr IHe Ne 1 3125 25 Not Required Hot hauled wer Reig supervised Not mmid than Bison Rotn i lo Scondary Frcloct on 可U 25 2 Note 3h ean6bmm的的 10aIsee\ ute 5 for Secondary 4 T 5 Hieetomk -Mmwd阳同四g邮M时m阻财贴e3 g ngy he 1ser M2-Msm面ya数这 mon chan sa brers or suLs af fuses my be waupun Ln a ant foration器 1 Immie dRumm Mns im 3-Ah和w四whmm容的c铜州hmp血ane 四mdm 4-品aaca出励糖a活出m前部w黏 cimtirinidng ai fion d mhe dirui anthor mohd 5-刚四时B风m加和mg砂hm物 mal oneed purest pmdb Additional techmical in formation and applicate data for Littel tuae POWR-CAHDprotectiee relays, tuses and ather cireuit protectmn and safety produts cailbetounanwww.lttellttecdi.fOrquestionseammactoutTachnicalSupportGroupIn-832-3873).dEfinitionsottersuaedinthhawhitepapercail he found in the Technical Aoplicsiiae Guide section of the POWR-GARD Catal1 onload e copy visit wwI后世国e,Em/ Glial目 Feam lie PFr53 单1LuP[ TR-GAADPP四c5 www IrtteHtuse com

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