INSTRUCTION, OPERATION AND MAINTENANCE MANUAL

Transcription

1 INSTRUCTION, OPERATION AND MAINTENANCE MANUAL DISTRIBUTION TRANSFORMER

2 Cntents Table f Cntents GENERAL Page N Preface....1 Intrductin 2 General 3 Safety Instructins..3 Cnstructin 4 Tap changer.4 Transprtatin and Lifting 5 Check and acceptance at purchaser s premises...5 Guarantee/Warrantee.6 INSTALLATION Installatin & Cmmissining 6 Lcatin 6 Spark gap f Arching Hrns...8 Energizatin.8 OPERATION Operatin..9 Ambient Cnditin and Temperature Rise...9 Operatin abve the Rated Vltage...9 Operatin abve the Rated Current..9 Vltage Regulatin.10 Parallel Operatin..10 i

3 Cntents Page N Circuits f Auxiliaries (Cling Prtectin & CT s)...10 Signals..10 Strage..11 Strage with Oil...11 Strage withut Oil..11 ACCESSORIES Accessries (Purpse and Functinality)...12 Buchlz Relay...12 Oil Temperature Indicatr.14 Oil level Indicatr 16 Pressure Relief Device (PRD).18 Tap Changer 20 Current Transfrmer & Bushing...23 Silicagel Breather.25 Thermmeter...26 Bushing Terminatin, Earthing and Ventilatin..27 TRANSFORMER MAINTANENCE Transfrmer Maintenance..27 Rutine Inspectin and Maintenance 28 Preventive Inspectin and Maintenance 29 Preventive Maintenance Chart..30 Truble Shting 31 ii

4 Cntents Page N ANNEXURE Annexure A...34 Transfrmer Failure Reprt Frm Annexure B...37 Test Reprts Annexure C..38 Safety Checklist befre Cmmissining Annexure D...42 Recmmended Trque Chart Annexure E...43 Standards Annexure F 44 Recmmended trque values in Nm fr varius cnnectins iii

5 PREFACE PEL Transfrmers are designed, manufactured and tested with care. With prper attentin during installatin and use, the user shuld receive frm it the maximum expected service. Befre installing the transfrmer, read this manual carefully. This manual has been prepared t prvide infrmatin n assembly, installatin, cmmissining and regular maintenance f the transfrmers and shall frm part f Instructin Manual. This manual des nt intend t cver peratin and maintenance f the transfrmer under abnrmal cnditins. Shuld further infrmatin be needed r any prblem arises which is nt cvered by these instructins, please refer t the HV Transfrmer Divisin f Pak Elektrn Limited (PEL) fr further infrmatin. During perating f the transfrmer, care shuld be taken that lading limits, as specified by the nameplate data, are strictly fllwed. 1

6 INTRODUCTION Thank yu fr purchasing ur transfrmer. This unit was manufactured using the mst mdern techniques available and has been fully tested in ur Quality Cntrl Divisin befre it left the factry. It is pssible, hwever, that during shipping, installatin r peratin the transfrmer culd be damaged thrugh imprper handling r ther unimpeded events. Thus, it is crucial that yu read this manual carefully. This instructin manual cvers a brief descriptin abut the installatin, energizatin, cmmissining, peratin, rutine/preventive maintenance and precautinary activities fr the il immersed distributin transfrmer. In additin t that fllwing useful data is als included t help the custmer t perate the transfrmer truble free. Purpse and functinality f the accessries explained with the help f pictures. Failure reprt frm is included t help the custmer t explain its prblem t the manufacturer in detail, in case f a fault arises in the transfrmer. Rutine and Preventive maintenance chart is available in the manual fr perfrming the maintenance activities at the custmer end. Fr n site truble shting a truble-shting chart is als included t help the custmer t rectify the prblems, which can easily be handled at the site. In additin t this guide, the manufacturer shuld be cnsulted fr specific recmmendatins n special cnditins. 2

7 General This manual describes general peratin / maintenance f 3-phase tw winding il immersed distributin transfrmers manufactured accrding t IEC / BS standards. Technical parameters f transfrmers are stated n the rating plate and in the factry rutine test reprt. Safety Instructins All persnnel invlved in installatin, cmmissining, peratin, maintenance r repair f the equipment must be suitably qualified and strictly bserve these perating instructins. Imprper peratin r misuse can lead t reductin in the efficiency f the equipment, damage t equipment and prperty f the user, serius r fatal injury. Safety instructins in this manual are presented in three different frms t emphasize imprtant infrmatin. This infrmatin indicates particular danger t life and health. Disregarding such a warning can lead t serius r fatal injury. This infrmatin indicates particular danger t the equipment r ther prperty f the user. Serius r fatal injury cannt be excluded. These ntes give imprtant infrmatin n a certain tpic. 3

8 INSTALLATION, OPERATION AND MAINTENANCE MANUAL A safety checklist is incrprated in Annexure C, fr the ready reference, and t be thrughly implemented during installatin and cmmissining and befre first energizatin. The lcal management shall infrm the labr, respnsible fr the peratin f the transfrmer, abut any hazards, which culd affect the health and safety requirements. Cnstructin The transfrmer is cmpsed f cre, cils, il, tank, bushings, nameplate, tap changer & ther accessries as required by the custmer. Details are mentined in the dimensin drawings, prvided with the transfrmer. Tap Changer Tapping switch munted n tank cver r sidewall is used t adjust the vltages. Befre changing the tapping switch (tap changer) ensure that transfrmer is cmpletely islated (denergized) frm high & lw vltage sides in case f ff-lad tap changer. In case f On-Lad, tap changer (OLTC) the tapping can be adjusted with the transfrmers energized. Fr details, please refer t OLTC peratin manual. Fr tap changer adjustment accrding t desired vltage, please refer nameplate f the transfrmer. The transfrmer is fitted with ff-lad tap-changer. Be very sure t de-energize the transfrmer befre step changing. The tap changer must be perated t all its tappings nce a year t ensure prper peratin and safety. 4

9 Transprtatin & Lifting Take special care in transprtatin, tie the transfrmer with prper rpe in a place specified by the manufacturer, and maintain clearance between tw transfrmers transprted n ne vehicle. During transprtatin, the rad cnditin must als be taken int cnsideratin & during transprtatin slpe f the transfrmers shuld nt be ver 15. Never try t lift the transfrmer ther than the crrect fittings (lifting lugs) prvided fr this purpse. The transfrmer is designed fr rad as well as railway transprtatin. It can be transprted by means f trailer f adequate lad carrying capacity. Main cmpnents have t be dismunted in rder t decrease the size and weight f the transfrmer bdy. Never stay under the lifted transfrmer r any f its parts. All infrmatin can be fund n the Outline drawing fr transprtatin. Check & Acceptance at purchasers premises After receiving the transfrmer verify immediately that the transfrmers is in cnfrmity with the rder cntract & accrding t delivery dcuments. Als, check any external damages & psitin f the accessries. Any abnrmality must be reprted immediately t PEL r its authrized representative. Upn arrival f the transfrmer at the purchasers premises, please make sure all the sealing pints are intact and the prduct is free frm any damage 5

10 Guarantee/Warranty If any f the sealing, pints f the transfrmer are fund damaged / tempered, that might vid the warranty f the transfrmer. Please d cnsult the manufacturer befre undertaking such activity. During the guarantee perid, draying, treatment f il and all peratins that invlve transfrmer pening, must be carried ut by skilled persnnel f Pak Elektrn Limited, therwise the guarantee may vid. Installatin and Cmmissining Lcatin Transfrmers, as is the case with mst electrical equipment, generate a substantial amunt f heat during peratin. This heat must be remved in rder t allw the transfrmer t maintain its designed maximum temperature limits, if a transfrmer is lcated utdrs the heat will be remved by natural cnvectin cling unless the radiatr airflw is restricted by surrunding bjects. Indr installatins require adequate ventilatin t remve the heat f transfrmer peratin. Inlet ventilatin penings shuld be as lw as pssible, and utlet ventilatin penings as high as pssible. Average temperature ver 24 hurs must nt exceed 30 C and the temperature f the rm shuld nt exceed 40 C. Care shuld als be taken t prevent restrictin f air circulatin. Adequate space must be maintained between transfrmers, r between transfrmers and nearby equipment r walls. Separatin is especially imprtant near the transfrmer radiatrs, with spacing equal t the radiatr panel depth being recmmended. During installatin, the fllwing rules must be fllwed in rder t ensure that the transfrmer perates crrectly 6

11 a. The lcal regulatins fr installing liquid-filled transfrmer is buildings n a ple, in a cabinet r in the pen air must be fllwed t the letter in relatin t, amng thers, fire safety, prtectin against leaking (sump r il-catchments tank), accessibility, electrical regulatins. b. The place where the transfrmer is set up must be adequately ventilated in rder t enable dissipatin f the heat given ff by the transfrmer. We are at the dispsal t d relevant calculatins and t explain the precautins t be taken. Fr distributin transfrmer set up in buildings r steel sheet substatins this means that there must be a regular supply f fresh air frm utside, that there is adequate ventilatin and enugh free space abve the transfrmer. c. Oil sample plug, tap changer and any ther perating and prtectin equipment must be easily accessible. Mnitring apparatus such as thermmeters must be clearly visible and/r readable. d. Setting up the transfrmer parallel with a wall is nt advisable as this can increase the nise. Antivibratin pads under the wheels can reduce the transfer f the nise vibratins t the grund. e. The area in which the transfrmer is placed must be inaccessible t pets, birds, rdents We nce again remind yu that lifting the transfrmer by taking it under the cling fins is abslutely frbidden. This will create leaks After installatin & befre putting int peratin it is recmmended t perfrm the fllwing checks / tests n transfrmers. Visual Inspectin Oil level checks Cnnectins f Cables, Bus Bars r Overhead Cnductrs t Bushings Earthings Measurement f Insulatin Resistance f the Windings (Megger Test) Measurement f Vltage (Turns) rati Measurement f Winding Resistance Measurement f dielectric strength f il Open Circuit Test & Shrt Circuit Test (If pssible, t be perfrmed) Functinality test and Physical check f all accessries, parts and cmpnents. 7

12 Spark Gaps f Arcing Hrns Adjust the spark gaps f the arcing hrns (if available) t cmply with the dimensin drawing, the lcally applicable regulatins r the instructins f the custmer. Please find belw the maximum gap width. Rated Vltage (kv) Gap width (mm) Energizatin When a transfrmer is energized fr the first time the tap changer psitin shuld be set at nminal vltage & transfrmer t be run at n-lad cnditin fr few hurs, check fr abnrmal sund (nise) if any, if n abnrmality is bserved then gradually increase the lad. We cannt accept any liability and cannt include any guarantees fr damage t equipment, which is due t the imprper peratin f the transfrmer! Fr any abnrmality, please cntact qualified service persnal. Repair & service f transfrmer is a highly skilled jb and might cause damage / injury t man and equipment if nt carried ut by prfessinally skilled persns 8

13 Operatin The transfrmer is designed fr the cntinuus peratin at rated vltage and current assigned t each tapping psitin as specified in the data sheets in nrmal service cnditins. Wave shape f the supply vltage has t be practically sinusid, its frequency 50 Hz. The three phases has t be practically symmetrical. Ambient cnditins and temperature rise Transfrmers are designed fr nrmal peratin in the fllwing ambient cnditins: The highest altitude fr installatin and peratin f transfrmer is 1000m abve sea level Air ambient temperature may nt exceed value given in technical characteristics f transfrmer. Under these cnditins, guaranteed temperature rise (maximal temperature rise f il and average temperature rise f windings) abve the ambient temperature will nt exceed values given in technical characteristics f transfrmer. If the ambient temperature exceeds value given in technical characteristics f the transfrmer it will endanger the life time f the transfrmer even if the transfrmer perate with rated lad (IEC 354). In that case allwable temperature, rises need t be reduced t the sme degree by means f reducing the transfrmer pwer. Operatin abve the rated vltage The permitted maximum cntinuus peratin vltage is 105% f the rated vltage referring t the actual tap-psitin. Operatin abve the rated current The general limitatins and effects f lading beynd the nameplate rating shall be cnsidered as specified in the Lading Guide fr Oil-immersed Transfrmers issued by IEC

14 Vltage Regulatin The vltage regulatin f the transfrmer is realized by means f a hand-driven ff-lad tap changer installed in the tank. The ff-lad tap changer has the functin t change the transfrmatin rati by adding the turns f the regulatin winding t the turns f the high vltage winding while maintaining the lad cnditins f the transfrmer unchanged. The hand wheel cntrl cmplies with the step-by-step switching. After de-energizing the transfrmer, rtate the hand-wheel f the ff-lad tap-changer t the desired psitin. Then reenergize the transfrmer again. Parallel Operatin Tw r mre transfrmer in case f parallel peratin, each transfrmer has t be in equal vltage value and vectr grup. The circuits f the auxiliaries (cling, prtectins & CTs) The circuits f auxiliaries and the terminal strips are shwn in the Dcumentatin. Descriptin abut the devices can be fund in the cming chapters, the adjusting values are t described in detail. Signals Alarm and trip signals are given accrding t the cntrl drawing. Cnnect the trip signal f the devices t the transfrmer main circuit breaker r t the prtectin system! 10

15 Strage If the intentin is t keep the transfrmer in strage fr sme time, prir t its energizatin, then make sure strage is dne prperly. Fr this purpse, the main bdy f the transfrmer must be cvered, t prtect it frm dust. When a transfrmer is received frm the manufacturer, it shuld be preferably placed (stred) at its final installatin place in rder t minimize handling. All the parts that are nt fitted shuld be unharmed, t. These are t be stred n wden pillws in cvered stre prtected against humidity. The cmpnents can be stred in transprt packing prvided it is cnsidered in gd cnditin. Check all parts f the transfrmer als fr mechanical damages. If the transfrmer is ut f peratin fr mre than a mnth, the heater f the marshalling kisk / terminal bx must be cnnected and put in service in rder t prevent cndensed misture inside the cabinet. If this is nt pssible, bags with at least 0.6 kg silicagel must be put int the cabinet. Strage with il Fr lnger strage perid, it is highly recmmended t fill the transfrmer with il and the cnservatr is fitted. In the curse f lnger strage, check the transfrmer n mnthly basis, whether the il level is crrespnding t the level relating t the ambient temperature. Make sure breathing mechanism (where applicable) is intact with the transfrmer with the help f temprary r permanent breather prvided with the transfrmer. Strage withut il Fr shrter strage perid, the transfrmer can be stred withut il but filled with nitrgen. Nt mre than fur weeks, it can be stred withut any special actin. Only the pressure f the nitrgen must be will be checked and maintained effectively. 11

16 Accessries (purpse and functinality) Buchhlz Relay Purpse: Functinal Check: Buchhlz Relay is the main prtectin device f the transfrmer. It is used t detect, Gas frmatin in the transfrmer tank up t the level 200cm 3, (First Alarm and then tripping (if the gas frmatin is cntinued)), sudden flw f 1 m/s frm tank bdy twards the cnservatr (nrmally internal flashvers are the causes f il flw) causing direct tripping. Mstly all f the Buchhlz relays are equipped with tw Nrmally Open (NO) Cntacts (see Figure 1). The functinal test (cntinuity) f these cntacts can be perfrmed via a push buttn available n the relay (see figure 3). Half press f this buttn will change the state f Alarm cntact frm Nrmally pen (NO) t Nrmally Clse (NC) Full press f this buttn will change the state f Trip cntact frm Nrmally pen (NO) t Nrmally Clse (NC) t Tw Nrmally Open (NO Cntacts) Earthing pint f Buchhlz relay Figure 1 : Buchhlz relays are equipped with tw Nrmally Open (NO) Cntacts 12

17 Befre the energizatin f the transfrmer buchhlz relay must be subjected t bleeding (remval f trapped air), pssible via a bleeding pint (see Figure 2) Bleeding Pint Cntacts Prtectin Cap Cntacts functinal check knb Figure 2 : Bleeding Pint, Cntacts Prtectin Cap & Cntacts functinal check pint Transprtatin and Prtectin f Cntacts: Fr the prtectin f cntacts during transprtatin f the transfrmer, a red (r black) clred small rubber piece is prvided in the cap ver the functinal test push buttn (see Figure 3). This rubber piece must be remved befre energizatin f the transfrmer. Red Clred Rubber Piece Figure 3 : Red clred rubber piece installed fr the prtectin f cntacts 13

18 Oil Temperature Indicatr Purpse: Oil Temperature Indicatr is used t mnitr the tp il temperature f the transfrmer. Mstly all f the temperature indictrs are lcated n the tp plate. Usually three types f temperature indicatrs are used. Withut cntacts With 2 cntacts (First Alarm and then tripping) (See Figure 5) With 4 cntacts (First Fan OFF, Secnd Fan ON, Third Alarm & Furth Trip) Alarm Setting Tab Trip Setting Tab Fans ON Setting Tab Fans OFF Setting Tab Resetting knb Indicatr shwing Temperature f the il Indicatr shwing Maximum Temperature reached at any instant f time Figure 4 : Different types f Oil Temperature Indicatrs 14

19 Functinal Check: Temperature indicatrs can be checked fr the prper functinality f their cntacts (see Figure 4). Mstly all f the cntacts are Nrmally Open (NO) cntacts. Sliding the alarm tab belw the il temperature indicatr will change the state f Alarm cntact frm Nrmally pen (NO) t Nrmally Clse (NC) Sliding the trip tab belw the il temperature indicatr will change the state f Trip cntact frm Nrmally pen (NO) t Nrmally Clse (NC) Fr the settings f Alarm and Trip cntacts please refer nameplate data. Settings f Fan OFF and Fan ON cntacts are n custmer s wn will. Hwever typical settings are: i. Fr Fans OFF 60 C fr ht areas and 70 C fr cld areas ii. Fr Fans ON 70 C fr ht areas and 80 C fr cld areas The maximum temperature knb can be rest at any time via a knb available n the indicatr (see Figure 4) Example: Ambient Temperature : 50 C (Frm Name Plate) Oil Temperature : 40 C (Frm Name Plate) i. Alarm Setting: = Ambient Temperature (C) + Oil Temperature (C) - 10(C) = = 80 (C) ii. Trip Setting: = Ambient Temperature (C) + Oil Temperature (C) = = 90 (C) 15

20 Figure 5 : Oil Temperature indicatr widely used Oil Level Indicatr Purpse: Oil level indicatr is used t mnitr the il level in the cnservatr. Mstly all f the il level indicatrs are lcated n the sidewalls f the cnservatr. Usually tw types f il level indicatrs are used. Withut cntacts, (see figure 6) 16

21 With cntacts (see Figure 7) Figure 6 : Oil level indicatrs (withut cntacts) i. Maximum level (MAX) having tw cntacts (1 NO and 1 NC) ii. Minimum level (MIN) having tw cntacts (1 NO and 1 NC) Maximum level display Oil level indicatr pinter Minimum level display Chamber cntaining cntacts f the indicatr Figure 7 : Different parts f Oil Level Indicatr Functinal Check: The display is typically labeled with MAX, +20 C & MIN values. If the il level reaches t the maximum level the tw cntacts (1 NO and 1 NC) change their state. The same prcedure repeats when the il is lwered until minimum level. The functinality f the cntacts can be electrically checked by checking the cntinuity and discntinuity f the cntacts when their state changes. 17

22 The level indicatr pinter culd be mved manually t make/break these cntacts. The display is graded in terms f temperature, because the il expansin and cntractin is the temperature dependent phenmena, since during the peratin f transfrmer, il quantity desn't changes nly the temperature variatins changes its vlume (level) Pressure Relief Device (PRD) Purpse: Pressure relief device is used t give a relief t the il pressure built up in case f a shrt circuit is develped inside the transfrmer. In the absence f this device the dangers f explsin r tank defrmatin exists. Mstly the pressure relief device is used n tp plate. The spring type cnstructin enables the PRD t autmatically reset itself as sn as the il pressure is released. Usually tw types f PRD are used. Withut cntacts, (see Figure 8). With cntacts (1 NO cntact and 1 NC cntact) (see figure9). Figure 8 : Pressure Relief Device (PRD) withut cntacts 18

23 Pinter is ejected ut in case PRD perates Chamber cntaining cntacts f PRD Figure 9 : Different parts f PRD The yellw pinter as shwn in the picture needs t be reset manually. Functinal Check: The functinality f the cntacts can be electrically checked by checking the cntinuity and discntinuity f the cntacts when their state changes. A lever as shwn in the picture sets the PRD and anther lever resets its cntacts t their initial state (see Figure 10). Lever t set the PRD Lever t reset the PRD Figure 10 : Set and Reset levers f PRD 19

24 Tap Changer Purpse: Vltage variatins ccurred at high vltage side is regulated by the tap changer and a cnstant utput vltage is available at the utput f the transfrmer. There are mainly tw types f tap changers. OFF Lad tap changers ON Lad tap changers OPERATION OF TAPCHANGER: Fr OFF-Lad tap changers, prper placement and tap selectin is very imprtant fr truble free peratin f the transfrmer. Fr the tap selectin, first check the incming vltage t the transfrmer and then fr exact matching with transfrmer tapping refer nameplate f the transfrmer. Befre tap changing activity, it must be insured that the transfrmer is islated (denergized) frm bth incming and utging sides. Almst all f the tap changers are perated in the same manner (see Figure 11) Revlving handle Tap psitin indicatr Interlcking Pin Figure 11 : Different parts f tap changer 20

25 See Figure 12 & Figure fr pictrial demnstratin f different types f tap changers First rtate the lever clckwise / anticlckwise, Secnd rtate it t the desired tap psitin, Third place (push) the lever dwnwards t its final resting psitin Initial resting psitin f tap changer First, pull the lever upwards Secnd, rtate it t the desired tap psitin Third place (push) the lever dwnwards t its final resting psitin Figure 12 : Prper peratin f Tap Changer (large transfrmers) 21

26 INSTALLATION, OPERATION AND MAINTENANCE MANUAL First rtate the lever clckwise / anticlckwise, Secnd rtate it t the desired tap psitin, Third place (push) the lever dwnwards t its final resting psitin Initial resting psitin f tap changer First, pull the lever upwards Secnd, rtate it t the desired tap psitin Third place (push) the lever dwnwards t its final resting psitin Figure 12: Prper peratin f Tap Changer (small transfrmers) Fr prper peratin f ON-lad Tap changer, please refer perating manual f the tap changer 22

27 SAFETY OF TAP CHANGER: T keep the cntacts f the tap changer in healthy cnditin it is recmmended t perate the tap changer n all f its tap psitins at least nce a year. Any prlnged peratin n a particular tap may cause carbnizatin r ht spt frmatin at the cntact. Fr ON lad tap changers befre energizatin, bleeding f tap changer is must (see Figure 13). Secndly On lad tap changers need preventive maintenance after a certain number f peratins r after a certain length f time depending upn the manufacturer and type f the tap changer (please refer ON lad tap changer manual fr the details f preventive maintenance f the tap changer) Bleeding pint f the ON lad tap changer Figure 13 : Bleeding Pint f ON lad Tap changer Current Transfrmer (CT) and Bushings Purpse: Fr sme particular applicatin, fr example transfrmers with Autmatic Vltage Regulatrs (AVR) r Winding Temperature Indicatr (WTI), current transfrmers are installed in distributin transfrmers. Cnnectin and Safety f CT: Either the secndary circuit f CT, in every case, in use r when nt in use, must be cmplete. Opening the CT secndary circuit, during peratin f the transfrmer, is hazardus t the persn perating the device and might damage the CT as well. 23

28 When intended t use, the CT secndary circuit must be thrughly checked and verified by electrical testing, recmmended is t check the CT circuit by secndary current injectin sets. Fr the secndary circuit ne terminal f the CT must be earthed fr the safety f the CT. In case when the CT is nt used, all the terminals f the CT must be shrted tgether and earthed. The same practice shuld be adpted fr the CT in case f transprtatin f the transfrmer (see Figure 14). There are few types f Bushings, which are prvided with the bleeding pint. Such bushings must be subject t bleeding prir t the energizatin f the transfrmer (see Figure 14). Make sure that the bushings are nt in tensin due t its terminatin When nt in use the CT secndary terminals must be prperly shrted and earthed Bushings with prvisin f bleeding, must be subject t bleeding befre energizatin f the transfrmer Figure 14 : CT terminatin and bleeding pint f Bushing 24

29 Silicagel Breather Purpse: The purpse f silicagel is t absrb the misture during the cntractin f the il in the transfrmer. During this prcess, transfrmers inhales air frm the atmsphere. The air intake must be misture free. Absrptin f misture by the il will affect (decrease) the dielectric strength, will increase the misture cntent in il and will ultimately cause flashver in the transfrmer. Majrity f the breathers are withut any cntact. See Figure 15 fr example. Windw t view the clr f the silicagel Figure 15 : Silicagel breather Cnditin f Silicagel: Usually blue clr shws the healthiness f the silicagel (see Figure 15Figure 15 : Silicagel breather). With the passage f time, after misture absrptin, the clr f the silicagel will turn t pink. This shws that the silicagel is exhausted, either it has t be regenerated r shuld be replaced. 25

30 Thermmeters Purpse: The purpse f this instrument is t measure the temperature in il filled transfrmers and is suitable fr indr installatins. Temperature sensing system is f expansin type. See Figure 16 f typical thermmeters used in transfrmers. Figure 16 : Thermmeters Bushing Terminatin, Earthing and Ventilatin Bushing Terminatin: Terminatin f HV terminals (bushings) is very imprtant and if prper and suitable prcedures are nt adpted then it causes il leakages frm bushings gasket / sealing. Nrmally either cable terminatins are used r fr heavy currents bus bar arrangements are implied. Fr bth arrangements, n tensin whatsever (axial r radial) shuld affect the bushings. The bushings must be abslutely tensin free. Fr bus bars arrangements ne additinal care must be taken regarding thermal expansin f the bus bars. AT the time f energizatin, the temperature f the bus bars cincides with the ambient temperature. Hwever, when the transfrmer is laded and temperature f its il increases s the bus bar temperature nrmally rises t. This causes thermal expansin f the bus bars and ultimately exerts tensin n the bushings gasket. 26

31 Suitable measures shuld be taken t avid the effects f thermal expansin. Fr that reasn, usually bus bar is cut int tw halves and in-between flexible cnducting jints are prvided. Smetimes depending n the weight, length and size (area) f the bus bar additinal insulatrs are als prvided alng the length t supprt the bus bars s that weight and thermal expansin effects d nt travel t wards the bushings. Earthing: Fr the safety f equipment itself, the lad cnnected t the transfrmer and the persnnel, earthing is very imprtant. The transfrmer must be earthed at the pint where the manufacturer has prvided the earthing terminatin. Earth resistance must be checked peridically fr the healthiness f the earthing. Except live parts, n ther part f the transfrmer shuld be at any flating ptential. Ventilatin: Prvide suitable ventilatin system fr the heat exhaust f the transfrmers, installed indr. Transfrmer Maintenance The scpe f rutine and preventive maintenance cvers fllwing activities, Rutine Inspectin and Maintenance Preventive Maintenance & Chart Truble Shting During peratin, transfrmer is expsed t atmspheric cnditins and electrical and mechanical stresses. In rder t ensure uninterrupted peratin, it is necessary t inspect and maintain the transfrmer carefully. Inspectin and maintenance can be categrized int rutine and peridic inspectin and maintenance. 27

32 Rutine Inspectin and Maintenance Rutine inspectin and maintenance can be carried ut while the transfrmer is On-line. Pay attentin t the fllwing parameters: Abnrmal nises, irregular vibratins, external damages, silicagel cnditin and deteriratin f paint A recrd f the readings/recrdings, frm the meters/gauges prvided n the transfrmer, shuld be maintained and cmpared with the past values. In case f abnrmalities suitable measures shuld be taken Rutine inspectin and maintenance shuld include, but nt limited t the fllwings: Transfrmer Temperature : Take and recrd the reading f il/winding temperature indicatr Oil Level : Take and recrd the reading f il level indicatr Nise : Check fr abnrmal sund/nise Oil Leakages : Check il leaks especially n lcatin f valves, Indicatrs, packing and welded parts Breather : Pay attentin t the clr f silicagel. Regenerate r replace if clr has changed, (frm healthy cnditin t the exhausted cnditin, the clr change depends n the type f the silicagel being used ) Bushings : Check fr excessive bushing cntaminatin 28

33 Preventive Inspectin and Maintenance The perid fr the inspectin is nt abslute and is dependent n atmspheric and perating cnditins f each transfrmer. The recmmended perid under nrmal cnditins is ne year. Preventive maintenance and inspectin shuld include but nt limited t the fllwing (Many f these require the transfrmer t be shut dwn). Tank : Check fr il leaks and paint finish Radiatrs : Check fr il leaks, paint finish and cntaminatins Bushing : Check fr lcal heating, damages, cntaminatin and il leaks Insulating il : Check fr dielectric strength, carbn sludge, ffensive dr and disclratin Dehydrating breather : Check fr disclratin f silicagel breather Indicatrs 1 : Check fr prper functining Physical Checks : Visual Inspectin f cmplete transfrmer, Oil level checks, Cnnectins f Cables, Bus Bars r Overhead Cnductrs t Bushings & Earthings Recmmended Electrical Tests : Measurement f Insulatin Resistance f the Windings (Megger Test) Measurement f Vltage (Turns) rati (TTR) Measurement f Winding Resistance Measurement f dielectric strength f il Open Circuit Test & Shrt Circuit Test (If pssible, t be perfrmed) Functinality test and physical check f all accessries, parts and cmpnents Cmplete Chemical Analysis f Transfrmer Oil (nce after every five years, please cnsult PEL fr the details regarding the chemical analysis f the il) Measurement f capacitance and dissipatin factr f insulatin system f bushings (if applicable) and transfrmer. Any Abnrmality / Malfunctining / Deteriratin, if nticed shuld be rectified immediately. D nt delay in any crrective actin 1 meters, gauges, relays and ther devices 29

34 Preventive Maintenance Chart S. N. Wrk t be carried ut Duratin f Time Interval wrk hur w 2 m 3 y 4 v 5 1- Tank and cnservatr 1.1 Checking the il temperature < Checking the dehydrating breather < Checking the il levels < Checking the flanged jints and welds fr il leakage < Checking the paint finish and declining the surface Checking the earthing systems (prtective earthing) Oil sampling (fr il analysis) < Cling system 3.1 Checking the il temperature < Checking the butterfly valves < Checking the il sight pt < Checking the fans Checking the clers (radiatrs) Cntrl cubicle and terminal bx 4.1 Checking the heating f the cntrl cubicle. < Checking the enclsure fr water tightness < Bushing 5.1 Checking fr il leaks < Checking the prcelain Cleaning the prtective spark gaps. < Current Transfrmers 6.1 Checking the terminal cnnectins < Cleaning the terminal earthing < Mnitring devices 7.1 Checking the Buchhlz Relay < Checking the diverter switch relay and Pressure relief diaphragm/device < Checking the thermmeters < Checking the temperature mnitrs < Checking the il level indicatrs < Checking the pressure relief device n the transfrmer tank < Checking fr gas in the Buchhlz relay ~1 6 2 w= week 3 m= mnth 4 y= year 5 v= variable 6 Maximum 2 hurs, if the desiccant is t be replaced 30

35 Truble Shting Prtective, mnitring devices and varius cmpnents Fault Pssible Cause Remedial Measures Operatin can be cntinued. Hwever, fllwing tests and examinatin fr fault analysis shuld be made as sn as pssible. Buchhlz relay Buchhlz relay Thermal Replica Buchhlz relay-alarm Buchhlz relaytripping Winding r il temperature t high. Oil lss. Accumulatin f air. Gas generatin due t inside failure. Vilent vibratin False tripping. Oil lss. Vilent il surge due t inside flasher. Vilent gas generatin due t inside failure. Vilent vibratin. False tripping. Transfrmer verlad r inadequate cling. Incrrect temperature adjustment. Faulty temperature gauge 1- Check il level, pipes, psitin f valves 2- Check the electrical cnnectins 3- Check the tripping mechanism f the Buchhlz relay 4- Pass part f the gas thrugh the gas analyzer 5- Take il sample (1liter) frm tank bttm and check fr dielectric strength 6- Und all bushing cnnectins and make the fllwing measurements 6.1.Measure the insulatin resistance between the winding and tank wall and between the winding themselves. (Rugh guide value: 1 M hm per kv rated vltage) 6.2.Rati measurement either by Rati meter r by applying lw vltage t the HV side 6.3.Measure the DC winding resistance DC 6.4.Measure the n-lad current by applying lw vltage 6.5.Cmpare the result with the factry test results f transfrmer 7- Vent the transfrmer and put it back int peratin when it is a false tripping (cnfirmed) r faults have been eliminated Maintain shutdwn status. Carry ut tests and measurements described under pint (1-) t (7-) Vent the transfrmer and put it back int peratin when it is a false tripping (cnfirmed) r faults have been eliminated Reduce lad f the transfrmer. Put fans r cling equipment in service. Clean the cling equipment. Check psitin f butterfly valves. Adjust incrrect temperature setting Check the prper functining f thermmeter, d cmparative measurement. Check the electrical cnnectin and the tripping mechanism. Check cntrl device fr cling equipment. Check the current transfrmer and thermal replica calibratin 31

36 Thermal Replica Winding r il temperature t high. Transfrmer verlad r inadequate cling. Incrrect temperature adjustment. Faulty temperature gauge Reduce lad f the transfrmer. Put fans r cling equipment in service. Clean the cling equipment. Check psitin f butterfly valves. Adjust incrrect temperature setting Check the prper functining f thermmeter, d cmparative measurement. Check the electrical cnnectin and the tripping mechanism. Check cntrl device fr cling equipment. Check the current transfrmer and thermal replica calibratin Magnetic il level Indicatr Oil level t lw. Nt enugh il. (lw temperature r il lss) Check fr tightness, leaks and il level Tp up il. Dehydrating breather The drying crystals turn frm blue t pink (depending n the type f the silicagel being used. Frm belw twards the tp High atmspheric humidity Misture penetrating in transfrmer thrugh ther parts (usually leaks r gasket failures) rather thrugh breather Damaged breather (usually glass f the breather Replacement f dehydrating agent (silicagel) Seal leaks and gasket failures; check the il fr misture cntent Flush the cnservatr with dry air r nitrgen. Electrical break-dwn f vltage in il Usually in the frm f earth fault r shrt circuit Breather inperable r transfrmer in service since very lng and silicagel exhausted Misture cntents in il t high and weak dielectric strength f il Put breather int peratin Seal r repair leaks and gaskets Centrifuging/dehydratin f il t be perfrmed till the required dielectric strength f il is reached and misture cntents are reduced t the required levels (refer IEC fr details) Prtective spark gap n bushing Frequent peratin Electric arcing distance n lnger crrect Incming vltage at the terminals f the transfrmer is far greater than the rated terminal vltage Adjust the clearance between the arcing hrns and screw them tight Check the incming vltage and cmpare with the rated terminal vltage, try t adjust with the help f tap changer (if pssible), if nt then get the adjustment at the incming frm the surce (usually grid statin) 32

37 Terminal/cable lugs n bushings Disclratin f cnnecting parts Pr cntact making causing ht spt frmatin Clear and clean, the cntact faces. Tighten the screws. Cntrl cabinet Electrical Apparatus des nt perate prperly. Cntacts crrded r cntaminated Apparatus husing bent. Excessive humidity in cntrl cabinet Water r dust inside the cabinet Excessive high temperature in the cabinet. Set the cabinet heater t a higher temperature t eliminated the misture Seal the cabinet dr; fit a dust filter if necessary Prtect the cabinet against slar irradiatin, prvide fr better ventilatin and check whether the thermstat settings are t high Excessive Clean the cntacts tighten the screws and check the currents due t electrical distances Earthing cnnectin Earthing line interrupted external flashvers Impermissible Open up clse current lps. Prvide adequate earthings at specified paths with a sufficient crss sectin. current lps Check earth resistance with the help f earth tester, thrugh multiple earth resistance shuld be within the specified earthing. limits Dial Type thermmeter Oil temperature t high Transfrmer verlad r inadequate cling. Incrrect temperature adjustment. Faulty temperature gauge Reduce lad f the transfrmer. Put fans r cling equipment in service. Clean the cling equipment. Check psitin f butterfly valves. Adjust incrrect temperature setting Check the prper functining f thermmeter, d cmparative measurement. Check the electrical cnnectin and the tripping mechanism. Check cntrl device fr cling equipment. Check the current transfrmer and thermal replica calibratin 33

38 Annexure A Transfrmer Failure Reprt Frm 34

39 35

40 36

41 Annexure B Test Reprts Enclsed please find test reprt f the transfrmer 37

42 Annexure C Safety Checklist befre Cmmissining 38

43 39

44 40

45 41

46 Annexure D Recmmended Trque Chart 42

47 Annexure E Standards Fr mre infrmatin n transfrmers, in general yu can have a lk at the fllwing IEC and CENELEC standards: IEC : Pwer Transfrmers IEC : General IEC : Temperature rise IEC : Insulatin levels, dielectric tests and external clearances in air IEC : Ability t withstand shrt-circuit IEC : Applicatin guide (used t be IEC 606) IEC : Determinatin f sund levels (used t be IEC 551) IEC : Lading guide fr il-immersed pwer transfrmers IEC : Terminal & tapping markings fr pwer transfrmers IEC : Specificatin fr unused mineral insulating ils fr transfrmers and switchgear IEC : Supervisin and maintenance guide fr mineral insulating ils in electrical equipment IEC : Methd f sampling liquid dielectrics IEC : Guide fr the sampling f gases and f il frm il-filled electrical equipment and fr the analysis f free and disslved gases IEC : Mineral il-impregnated electrical equipment in service Guide t the interpretatin f disslved and free gases analysis EN : Bushings abve 1kV up t 36kV and frm 250A t 3150A fr liquid-filled transfrmers HD 428 : Three-phase il-immersed distributin transfrmers 50Hz, frm 50 t 2500kVA with highest vltage fr equipment nt exceeding 36kV HD 596 : Bushings up t 1kV and frm 250A t 5kA fr liquid-filled transfrmers 43

48 Annexure F Recmmended trque values in Nm fr varius cnnectins Threadsize M6 M8 M10 M12 M16 M20 M30 M42 M48 Spannersize A)BushingInsulatrs Lwvltage(LV)DIN A 630A 1000A 2000A 3150A 1.Fixingfbushingterminalstud: Crkgasket(Nm) Bunagasket(Nm) 2.CnnectinbetweenNuts(Nm) 3.Fixingfflagcnnectrt terminalstud (bltinstainlesssteel)(nm) 4.Bltstflagcnnectrsurface (Nm) 5.Fixingmnblcnflange:crk andbunagasket(nm) HighVltage(HV)DIN Fixingftpfterminalstud (terminalstudandnutsinbrass) (Nm) 2.Cnnectintterminalstud (terminalstudandnutsinbrass) (Nm) 3.Fixingfbase (studandnutinstainlesssteel)crk andbunagasket(nm) Pluginbushing CrkandBunagasket(Nm) 1020 B)LVcnnectingbusbar Intercnnectin (pinandnutin8.8steel) (Nm) C)Cver/frame Bltandnutinstainlesssteel(pitch =60mm)=crkgasket(pitch= mm)=Bunagasket (Nm) D)Busbarbushings Fixingncver(Nm) 815 Tppiecentbttmpiece(Nm) 5.46 Max. Value: applied trque, Min. Value: checking trque. (If the trque, that yu measure, is lwer than Min. Value --> re-apply Max. trque Value). Checking recmmended trque values is required: When setting up/installing the transfrmer. When cnnecting the transfrmer t the HV / LV cnnectrs, and When carrying ut maintenance wrk. We recmmend re-applying Max. Trque Value 4 weeks after replacement f the seals. 44

49 Factry and Main Office 14-km Ferzepur Rad Lahre, Pakistan Tel: Fax: , Branch Office- Karachi Khinr Building, 25 west wharf Rad, karachi-74000, Pakistan Tel: , , Fax: Branch Office- Islamabad 1404, 14 th flr Green Trust Twer, Blue Area, Islamabad, Pakistan Tel: , Fax: