On-Load Tap Changer Type T Inspection Instructions PDF

ON-LO AD TAP CHAN GER TYPET I n s p e c t i o n Instructions  MASCHINENFABRIK...

ON-LO AD TAP CHAN GER TYPET I n s p e c t i o n Instructions  MASCHINENFABRIK REINHAUSEN IA 96/83 en — 0784/500 Maschinenfabrik Reinhausen Printed i n Germany Gebriider Scheubeck GmbH & Co KG Postfach 120360 D-8400 Regensburg Telefon (0941) 440-1 Telex 6 5 8 8 1 ON-LOAD TAP CHANGER TYPE T Inspection instructions no. 96/83 Contents Page 1. G e n e r a l.......... o o i i i i i i i n n. Creare J | 1.1 Operational principle of the on-load tap changer 1.2 Designation of the on-load tap changer models 1.3 Principal parts of the on-load tap changer 1.4 Inspection intervals 1.5 Summary of inspection works Preparations.............. Chena OP 2.1. Tools and spare parts 2.2 Grounding 2.3 Operating position at removal of the diverter switch unit Removal of the diverter switch unit.......................... 8 Cleaning the oil compartment and diverter switch unit......... 9 > Inspection of the diverter switch unit...... Cerin PR 5.1 Removal position 5.2 Measuring the transition resistors 5.3 Contact wear of main switching contacts and transition contacts 54 Measuring the contact wear 5.5 Removing the sectorial contact shells 58 Cleaning the diverter switch 5.7 Cleaning the diverter switch insulating shaft 5.8 Reinstalling the sectorial contact shells 5.9 Checking the protective circuitry Reinstalling the diverter switch unit......................... 18 Filling i n t h e o i l.............. ~ OP Cea |+ Final checks...... Creer, Citra 19 8.1. Drive shafts 8.2 Functional test of tap changer and motor drive 8.3 Protective relay RS 2001 ’ 84 Voltage regulator Contents 9. Appendix.............. Creare aera 9.1 Evaluation of the contact wear 9.2 Replacement of the diverter switch contacts 9.3 Checking the protective circuitry 9.4 Coupling of tap changer and motor drive 9.5 Inspection tools 9.6 Lifting device 9.7 Parts of the diverter switch 9.8 Spare parts list 9.9 Adjustment plans  T h e diverter s w i t c h e f f e c t s t h e transfer of the current from the tap 1.1 Operational principle of the in service t o the preselected tap. on-load tap changer (fig-1) During this quick change-over, oh- mic resistors are cut in on the cir- A tap change operation is initiated cuit t o ensure no-break transfer of by the tap selector preselecting the the current. desired tap on the regulating win- ding of the transformer. Motor drive unit Tap selector Diverter switch I l Time i n seconds 13 10 08 53 [ | | CS EL PN RIR2 R2R1 RIR2 R2 Ri Circuit diagram 9 H E I J[NI J | 1117 ELC | EL 117 1111 A aala2lb2blb B A aalazf{b2bl b B A aala2{b2bl b B Contact movement Fig. 1 Tap-change operational sequence 1.2 Designation of the on-load tap changer models ( f i g.2) ON-LOAD TAP CHANGER Every tap changer type i s available in many different models varying T I 601 —10/ B — 1019 1W according t o : number of poles, max. rated through-current, insula- tion level, tap selector size, and TYPE | BASIC CONNECTION basic circuit diagram. The model DIAGRAM designation takes account of these characteristics and enables t o NUMBER OF TAP SELECTOR SIZE POLES unambigously indentify the tap MAX.RATED THROUGH - changer. CURRENT I N AMPERES AND ADDITIONAL INDICATION The basic circuit diagram code con- O F MODEL tained in the model designation i s determined by: contact circle pitch SERIES VOLTAGE of the tap selector, number of INSULATION TO GROUND1 operating positions, number of mid- positions, and type of change-over selector. Example i n fig. 2; On-load tap changer type T, BASIC CONNECTION DIAGRAM single-pole, max. rated through- current 600A, i n s u l a t i o n level t o ground 110KkV, tap selector size B, 10 1 wx! basic circuit diagram code 10 19 1W meaning: contact circle pitch 10, 19 operating positions, one of them a mid-position, reversing PITCHOF ~~ MAX.NUMBEROF MID.POSITIONIS) CHANGE -OVER switch used as change-over TAP SELECTOR SERVICE POSITIONS | SELECTOR selector. CONTACT CIRCLE 0 / : COARSE REVERSING ‘TAP SELECTOR SWITCH IANCESOYER SELECTOR G Ww me P yf y x) 10 10 09 19 NO DESIGNATION WITHOUT 12 12 11 23 CHANGE- OVER SELECTOR 1% 1% B27 16 16 1% AN 18 18 17 35 Fig. 2 Designation of tap changer model and basic circuit diagram 1.3 Principal parts o f the on-load Inspection of the tap changer i s tap changer (fig. 3a, b) limited t o the diverter switch unit and the inside of the tap changer The principal parts of the on-load head and of the diverter switch oil tap changer are: compartment. — the tap changer head, The other parts of the tap changer — the diverter switch unit, are maintenance-free. — the diverter switch oil compart- ment and The parts o f the tap changer which — the tap selector. are subject t o inspection are mark- e d i n colour i n f i g.3. Fig. 3 Principal parts of the on-load tap a) Model with centric arrangement b) Model with eccentric arrange- changer of the upper gear unit on the tap ment of the upper gear unit on changer head cover. the tap changer head cover. 13 Gasket for tap changer head 14 Position indicator 15 Inspection window 16 Driving shaft for position indicator 21 Tap changer head 22 Cover bolt 23 t tap changer head cover G a s k efor 24 Cover of tap changer head 25 Upper gear unit with drive shaft 25a 26 Pipe connection R for protective relay 27 Pipe connection S for suction pipe 28 Pipe connection Q for return pipe (with oil filter unit only) 29a Bleeder screw of tap changer head cover 29b Pipe connection for transformer oil —_— 29c Bleeder screw for suction pipe 31 Diverter switch oil compartment, inside 32 Bottom of oil compartment 33 Grading rings 34 Terminal of diverter switch oil compart- ment 35 Tap changer take-off terminal 36 Suction pipe 41 Suspension of tap selector 42 Tap selector gear 43 Fine tap selector 44 Change-over selector 45 Tap selector terminal 51 Diverter switch unit 52 Suspension bar 53 Supporting plate 54 Fixing bolt 55 Lifting lug 56 Transition resistors 57 Spring energy accumulator n o Inspection - ~g¢————— F-Y E 1.4 Inspection intervals The user should regularly test the If inspection should not be done by. transformer insulating oil. The MR-personnel, please give u s your We recommend inspection of the dielectric strength and the water report for data collecting purposes tap changing equipment at regular content o f the oil (oil temperature that we can give you possibly fur- intervals t o maintain a high level o f during sample taking also t o be ther recommendations for your operating reliability. recorded) must comply with the next inspection. respective standards such as IEC In general, the inspection can be publication 422 (1973), DIN 57370 carried out by qualified and trained Teil 2/VDE 0370 Teil 2/12.78. personnel within one day provided good preparation and organisation. Standard values for oil testing ac- cording t o CIGRE report 12-13 The number of tap change opera- (1982): tions indicated i n table | as inspec- t i o n intervals are figures based o n experience with oil qualities nor- Water content *) Dielectric strength * * ) mally used. Regardless of the number of operations we recom- Neutral-end tap changers 40 ppm 30kV/25 mm mend inspection after 6 t o 7 years Single-pole tap changers 30 ppm 40 kV /2. 5 m m of service or after 4 years of service respectively if the tap changer operating voltage i s =220kV. *) measured according t o the Karl Fischer method **) measured according t o DIN 57 370 Teil 1/VDE 0370 Teil 1/12.78. If the number of operations per year i s 20000 or higher, the use of our oil filter plant type 51 (see operating instructions no. 18) i s On-load tap Operating Number ot tap change operations recommended. Filtering of swit- changer through-current without oil filter with oil filter ching oil allows t o extend the in- plant plant spection and oil change intervals for all type T models regardless o f their operating current. Continuous T I l l 600 = 600A 80.000 —] filtering also increases the T 1111000 = 600A 80.000 mechanical life of the diverter = 1000 A 60.000 switch since the metal particles T 1 601/600 = 600A 80.000 causing the mechanical wear are 100. for the most part filtered out im- T11001/1000 = 600A 80.000 00.000 mediately. = 1000 A 60.000 T 1 1502/1500 = 1000 A 60.000 =1500 A 50.000 — T 1 2002/2000 = 2mm), replacement o f — Set the diverter switch t o the single contact tips is permissi- other position, e.g. t o the left, ble. In this case the contact by means of the operating key. layer thicknes must be matched according t o the criteria explain- — Determine the value X o n a and ed i n section 5.3. a l i n all diverter switch sectors a n d enter t h e values i n t o t a b l e ii. 5.5 Removing the sectorial contact shells — Set the diverter switch t o the in- termediate position according t o section 5.5 by releasing the For removing the sectorial contact spring energy accumulator and shelis the diverter switch must be simultaneously actuating the set t o the intermediate position. In operating key. this position the two transition con- t a c t s 2 (a2, b2) o f e a c h diverter — Determine the value X on a2 switch sector are closed. Therefore, and b2 i n all sectors (see fig. 22) release the spring energy ac- and enter the values into cumulator and turn the drive shaft table l l l of appendix, section b y means of t h e operating key until 9.1. winding-up and cocking slide have reached a balanced intermediate — Evaluate the measured values position (fig. 23, 24). in t a b l e l l l according t o the criteria explained i n section 5.3. The sectorial contact shells are m a r k e d w i t h L1, L2, L3. Correspon- Replacement or matching o f con- ding marks are o n the top of the tacts i s necessary when the limit " guide plate. When reinstalling the values specified i n section 5.3 sectorial contact shells make sure have been reached. t o mount them in their original place. F o r replacement o f contacts, i f necessary, see appendix, section 9.2. Loosen the connections t o the tran- sition resistors (the leads remain Normally t h e c o n t a c t wear (c) o f with the sectorial contact shells): 9 the upper and lower contact tips screws M 5 , 1 n u t M 6 (w.s. 10), as well as of the stationary and (fig. 25). movable contact tips of a pair of Unlock and unscrew the fixing c o n t a c t s i s e q u a l. However, i t i s screws of the sectorial contact advisable t o check each pair o f shell: c o n t a c t s for equal wear. 13 First, unscrew the lateral 3 screws M 6 x 1 6 (w.s. 4), 1 screw M6x 20 (w.s. 4) with centering block, and then the interior ones: 1 screw M 6 x 16 and 1 screw M 6 x 20 (with centering block). When removing the sectorial con- tact shell (fig. 26) note the position of the arc chutes (fig. 27). Withdraw the arc chutes. 5.6 Cleaning the diverter switch Thoroughly clean the diverter switch, i.e. supporting bars, sec- torial contact shells, movable con- tact system and transition resistors, with transformer oil. Take special care t o clean all in- sulating paris. Finally flush all parts thoroughly with new oil. 5.7 Cleaning the diverter switch insulating shaft The interior of the diverter switch insulating shaft should be cleaned only in case of tubular design of shaft (see fig. 28a). For detaching the drive shaft, the upper part of the diverter switch unit has t o be dismounted from the spring energy accumulator case at the four sup- porting bars (each supporting bar: 2 =a bolts M 8 x 40 (w.s. 13) with self- wT locking nuts and cup springs). To l remove the bolts, the spring energy accumulator must be actuated t o one side for clearance. Mind not t o Fig. 28a until 1981 Fig. 28b from 1981 let any cup springs fall into the diverter switch. Always check their Designs of the diverter switch insulating shaft correct number (6 c u p springs per bolt). Clean the interior of the insulating shaft by thoroughly flushing i t with new oil. The reassembly i s t o be made i n the reverse order of the disassembly. 14 Note: The diverter switch insulating shaft must be mounted on the drive shaft i n such a way that the mark- ing of the insulating shaft matches the marking on the eccentric. The suspension bars must be put on the spring energy accumulator case in such a way that the triangular markings of the suppor- ting plate (fig. 29) and spring energy accumulator case (fig. 30) face the same suspension bar. The bolts are mounted according t o fig. 31, tor- que 22 Nm. 5.8 Reinstalling the sectorial con- t a c t shells Install each sectorial contact shell in its original place. To facilitate fastening of the shells, press back the transition contacts 2 and insert tensioning bolts (e.g. 2 bolts M 5 x 70) i n t o t h e t w o h o l e s o f t h e top guide plate. Thus the spring pressure of the movable contact system t o the out- Fig. 31 side i s counterbalanced (fig. 32). Attachment o f suspension bar Reinstall a l l s e p a r a t i n g walls. These are of different design; make sure that they are correctly posi- tioned (long and short walls i n alternate arrangement, fig. 33). Use a piece of string for provisional fixing the separating walls (fig. 34). Fix the sectorial contact shell with the two central screws. Check the separating walls as t o correct posi- tion in the grooves of the sectorial contact shell. Remove the string. Then reinstall and lock all screws: 6 s c r e w s M 6 (w.s. 10) w i t h l o c k tabs, torque 9 Nm. Remove the tension- ing bolts (fig. 35). Attach the resistor connecting leads (6 screws M5, 1 nut M6, w.s. 7, torque 9 Nm). W h e n a l l sectorial c o n t a c t s h e l l s have been reinstalled, the spring energy accumulator must b e reset and locked i n a definite diverter switch position. Insert a screwdriver between winding-up and cocking slide of the. » spring energy accumulator (fig. 36). Actuate the eccentric b y means of the operating key until the pawl has locked i n (fig. 37, 38). For checking the mechanical func- tion, operate the diverter switch several times between its two posi- tion. Finally measure the transition resistors once more as described i n section 5.2. Before reinstalling the diverter switch unit, set the diverter switch to its removal position (see section 5.1). 5.9 Checking the protective cir- cuitry (if installed) The function of the protective cir- cuitry of the diverter switch (as shown in fig. 39) i s to limit transient overvoltages occurring between the Fig. 37 Fig. 38 diverter switch contacts (i.e. bet- Pawl u nlocked ween selected and preselected taps). The protective circuitry consists of voltage-sensitive resistors (varistor elements) and, for the most recent designs, of additional linear ceramic resistors connected i n series (fig. 40). Checking comprises: a) A visual inspection Check the general condition of the assembly, of the resistor elements and of the electrical connections. Fig. 39 Protective circuitry of the diverter switch R1, R2 — transition resistors R — stack of varistor elements and linear resistors 16 b) Measuring the linear resistors by ‘means of an. ohmmeter (see fig. 41) The resistance value of a single linear resistor element is either 8 o h m s *+20% o r 1 0 o h m s 2 0 %. Enter the total resistance value i n t o table V of appendix, section 9.3. ¢) Measuring the varistor elements (see appendix, section 9.3) Measure the voltage drop on each varistor element (see fig. 42) at1mAd.c. Since a d.c. voltage of 7... 10kV is required, the diverter switch unit must be put o n a n insulated base. The feet of the diverter switch unit are made of insulating material. Current and voltage measurements on varistor elements should be car- ried out with an accuracy of less than 1.5% error (for possible measuring equipment see appendix, section 9.3). Enter the measured voltage values into table V of appendix, section 9.3. If t h e measurements were n o t car- : tM ried out within the temperature els QE range from + 15°C to + 26°C (tem- Cand 5 0 perature measured on the varistor Rey element), the values have to be ad- justed w i t h the corrective factors listed in table IV (section 9.3). Compare the measured voltages in kV against the original values shown on the varistor elements. Dif- ferences of = 6 % are permissible. In the event of larger differences contact Maschinenfabrik Reinhausen since replacement of the protective circuitry might Please advise a l l m e a s u r e d values become necessary. If no original for statistical purposes to: values are indicated on the varistor MASCHINENFABRIK REINHAUSEN elements, use the values measured Gebr. Scheubeck GmbH & Co K during the initial inspection as Kundendienst reference values. Postfach 120360 D-8400 Regensburg Telex: 65881 17  Centric arrangement Eccentric arrangement o f t h e upper gear unit o f t h e upper gear unit 6. REINSTALLING THE DIVER- TER SWITCH UNIT Remove the tap changer head cover (24 screws M10 (w.s. 17) with lock washers). Lower the diverter switch unit carefully into the oil compartment. Take care that the markings on the oil compartment and supporting plate correspond (fig. 43a,b). Fix the diverter switch unit (7 screws M 8 or 15 screws M 8 (w.s. 13), max. torque 22Nm, locked by spring washers). Remount the position indicating disc (coupling plate and fixing screw M 5 (w.s. 8), max. torque SNm, fig. 44 a,b). 7. FILLING IN THE OIL Fill new oil into the oil compartment up to the level of the supporting plate. Shut the tap changer head by its cover, see fig.45 a,b (24 screws M10, w.s. 17, max. torque 34 Nm, spring washers). Make sure that the gasket is in good condition (if not, replace ring gasket). Open the stop valve between pro- tective relay and oil conservator. Vent the tap changer head through the bleeder screw on the tap changer head cover, and also the suction pipe (cap nut M16 (w.s. 22), slotted head screw). I n case-of stationary oil filter: vent the oil filter unit. Fill up the oil conservator t o its original level with new oil. 18 8. FINAL CHECKS the protective relay should, therefore, include checking of the 8.1 Drive shafts proper function o f the circuit breakers. Perform coupling between upper gear unit and bevel gear by drive Make sure that the transformer shaft (6 screws M6, w.s. 10, max. cannot b e energized and its ground torque 9Nm, lock tabs). connections cannot be removed during the test. Furthermore, make Check the horizontal and vertical sure that the fire-extinguishing drive shafts, especially o n points of equipment, if any, coupled with the coupling, grease coupling bolts and tripping of the protective relay can- O-rings if necessary (e.g. with not operate. SHELL 6432),adjust axial clearance t o 3mm. Proceed a s follows: In case of spécial design with ball 1. Close the circuit breakers with joints, check bellows as well as isolating switches open and grease contents of ball joints. transformer terminals grounded. Check the upper gear unit o n the tap changer head cover and the 2. Open the hood of the test push- bevel gear (replenish grease if buttons (3 screws M 6 , w.s. 10). necessary). Press the test push-button »Transformer off«. The circuit 8.2 Functional test of tap changer breakers must open. an motor drive 3. With the protective relay i n the Check the symmetrical coupling of »Transformer off« position it the motor drive with the tap must be impossible t o close the changer. The lag of the motor drive circuit breakers. This i s t o be must be equal i n both directions checked. (equalize if necessary, see appen- dix, section 9.4). 4. Reset the protective relay t o the »Transformer i n service« posi- Run the tap changer through the en- tion and lock the hood (3 screws tire operating range t o check its M6, max. torque 5 Nm). function. Note: In case that the protective Check i n all service positions relay has been energized, the whether the position indicators of diverter switch unit must be ex- tap changer and motor drive show amined and the local MR agent the same position. or directly the Maschinenfabrik Reinhausen be informed. Check the electrical and mechanical position limitation of 8.4 Voltage regulator (see operat- the motor drive (see operating in- ing instructions no. 66 for vol- structions no. 40 for motor drive tage regulator M K 20) MA7). I f the tap changer i s controlled by a Inspection of the motor drive is to ° voltage regulator: be done according t o our inspection Check settings of voltage level, instructions no. 68. sensitivity (bandwidth), and delay time according t o the operating in- 8.3 Protective relay RS 2001 (see structions in order t o avoid un- operating instructions no. 59) necessary tap change operations. The transformer must immediately be switched off by the circuit breakers when the protective relay i s energized. The functional test of 19 9. APPENDIX 9.1 Evaluation of Measuring thecontactwear.............. c c ii iiiiinnnnnn.. 895 053 contact wear Contact positions o f the diverter switch unit when measuring the contactwear -.......................... 894 594 Determining the contactwear................... c c iin... Table Ili a Zam ——— N a n I~ ao or ~- nn M» om P| 0 —. LLL S O N N N NNNN 1 J LL I LL LL LLL LLL TOTALCONTACT WEAR 2¢=34 -X fmm) 2cmax =12mm REFERENCE DIMENSION S=31Imm MASCHINENFABRIK. MR rewiaisen On-load tap changer type T 895 053: OE Measuring the contact wear 20  RIGHT DIVERTER SWITCH SIDE SWITCHED ON: MEASUREMENT OFCONTACT WEAR ON MAIN ARCING CONTACT b RESISTOR CONTACT b1 DIVERTER SWITCHIN INTERMEDIATE POSITION: MEASUREMENT OF CONTACT WEAR ON RESISTOR CONTACT b2 RESISTOR CONTACT a2 il DIVERTER SWITCH Z SIDE SWITCHED ON: ) MEASUREMENT OFCONTACT WEAR ON RESISTOR CONTACT a1 MAIN ARCING CONTACTa MASCHINENFABRIK On-load t a p changer type T 894 594 : 2E REINHAUSEN Contact positions of the diverter switch unit when measuring the contact wear 21  On-load tap changer: Serial no.: Date: Operation counter reading:.............. Plant/transformer: Measurement of wear Evaluation and check Total Single 2c,—2c,, 2¢c,—2¢,, 20,1—2c,; Diverter wear wear 2¢;,—2¢y,4 2c, —2¢y,, 2c),=2Cyy Kon- switch | Contact | Value X| 2c=34—X |c=2c/2| Check | (=A2c) Check (=A2c) Check ( = A2c) trolle sector | function mm mm mm c