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On-load tap-changer, type UCG

Maintenance guide

1ZSE 5492-124 en, Rev. 6

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Summary of Contents for UC Series

Page 1: ...On load tap changer type UCG Maintenance guide 1ZSE 5492 124 en Rev 6 ...

Page 2: ...entative ABB makes no warranty or representation and assumes no liability for the accuracy of the information in this document or for the use of such information All information in this document is subject to change without notice This document must not be copied without our written permission and the contents thereof must not be imparted to a third party nor be used for any unauthorized purpose C...

Page 3: ...l information to assist in carrying out the work described and to provide trouble free operation Safety precautions WARNING The Maintenance guide should be read and understood before any work is started and the procedures in this document should be followed at all times WARNING Before any work is carried out on the tap changer Make sure that the transformer is disconnected and that grounding is pr...

Page 4: ...ter long and repeated contact with transformer oil skin becomes very dry Used tap changer oil from diverter switch housings and selector switch housings contains harmful substances Fumes are irritating to the respiratory organs and the eyes and are highly flammable Used transformer oil may well be carcinogenic Avoid contact with the oil and use oil tight protective gloves when handling the oil Fir...

Page 5: ...fill the diverter switch housing with oil if the transformer tank is under vacuum and the on load tap changer is not CAUTION Do not fill the transformer tank with oil if the on load tap changer is under vacuum and the transformer tank is not CAUTION Leave a gas cushion on top of the oil in the diverter switch housing After oil filling CAUTION Do not energize the transformer earlier than three hour...

Page 6: ...housing 17 3 6 2 Cleaning the oil filter in the conservator pipe if any 17 3 7 Oil filtration 17 3 8 Checking of the breathing device 17 3 9 Checking the contact positions 18 3 10 Checking the contact wear 20 3 11 Checking the transition resistors 20 3 12 Checking before closing 20 3 13 Installation of the diverter switch 20 3 14 Checking and replacing supervisory equipment 21 3 15 Lubrication of ...

Page 7: ...32 4 5 Mounting the moving main contacts 33 4 6 Replacing the fixed main contacts 34 4 7 Replacing the fixed transition contacts 34 4 8 Mounting the boards with transition resistors and fixed contacts 34 5 Specification of materials 35 5 1 General 35 5 2 Diverter switch housing 35 5 3 Diverter switch 35 5 4 Tap selectors 35 5 5 Conductors 35 5 6 Gearing mechanism 35 5 7 Drive shaft systems 35 ...

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Page 9: ...inspection and maintenance quick and simple The on load tap changer type UCG is housed in the transformer tank The motor drive mechanism is attached to the transformer tank and connected to the on load tap changer by means of drive shafts and a bevel gear see Fig 1 Fig 1 On load tap changer and motor drive mechanism Hood and screws Shielding ring when impulse withstand voltage to earth exceeds 380...

Page 10: ...on the rating plate normally 7 years Fig 2 shows the general arrangement of an on load tap changer type UC The main components are the spring operated diverter switch and the tap selector with sliding contacts For maintenance the diverter switch is lifted The contacts are then immediately accessible and can be inspected for wear The drive shafts should not be dismantled when lifting the diverter s...

Page 11: ...ning tube Guide pins Current terminal Transition resistors Fixed and moving contacts Intermediate gear Insulating shaft Bevel gear Position indicator Earthing terminal Serial No Diverter switch housing Serial No Connection flange for gas operated relay Shielding ring 2 Shielding ring 1 1 Only at impulse withstand voltage to earth of 650 kV and 1050 kV 2 Not on UCG of the short type Tap selector Mo...

Page 12: ...per day which means that replacement of the contacts is not normally necessary during the life of the transformer In case of on load tap changers on furnace transformers the frequency of operations may be considerably higher CAUTION The number of operations must in no case exceed 500 000 due to weakening spring tension of the contacts 1 3 Tightening torque The following tightening torques are reco...

Page 13: ...SC000498 ABH for information about the procedure On the conservator the following are to be checked Oil level Breather WARNING The breathers and the tube from the conservator contains explosive gases No open fire hot surfaces or sparks may be present when loosening the breather CAUTION Approval should be given for inspection as well as for operating the on load tap changer 1 Check the breathers ac...

Page 14: ... parts list Brass shims according to Fig 7 12 pcs New O ring for the cover 435x8 When restoring the gas cushion section 3 17 5 Small oil pump with connection to the oil valve Empty and clean barrel for transformer oil 15 l Box wrench 6 mm 3 Overhaul When measuring contact timing add this equipment See section 3 18 When replacing contacts chapter 4 add this equipment Universal pliers Pipe wrench 4 ...

Page 15: ...tch available during the overhaul see the spare parts list for ordering 3 4 Oil testing and oil draining The diverter switch housing is equipped with an oil valve placed on the top section For connection dimensions see the dimension drawing for the on load tap changer WARNING The oil in the diverter switch housing may be hot Be cautious Take an oil sample from the oil valve and carry out the diele...

Page 16: ...Drain the remaining oil in the bottom of the housing by using a hose 3 5 Lifting and cleaning the diverter switch The weight of the diverter switch is approximately 90 kg Lift the diverter switch partly so you can flush it with oil After careful flushing lift the diverter switch from the housing and wipe it with rags Lift according to Fig 4 WARNING Make sure the lifting equipment is properly fixed...

Page 17: ...ering the oil conservator An oil filter is therefore mounted in the pipe The filter which is mounted in a flange pipe on the top of the diverter switch housing is screwed from the inside It can easily be screwed out for inspection and cleaning The oil filter does not need to be replaced nor cleaned in any other way than by washing with oil 3 7 Oil filtration The drained oil should be filtered unti...

Page 18: ...g a shim of brass between the board and the current bar The shims are included in the spare parts set The shim dimensions are also shown in Fig 5 Operate the diverter switch to the opposite side when mounting the shims Operate the diverter switch back to the first side and check the clearance again If still too small put in a shim more and test again CAUTION Never mount more than three shims on ea...

Page 19: ...UCG 19 0 5 2 mm 20 14 14 Ø6 4 26 Fig 5 Fixed and moving contacts clearance Copper part Moving main switching contact Fixed main switching contact Fixed main contact Moving main contact Thickness 1 mm Current bar Board Fig 6 Transition contacts ...

Page 20: ...ed main contact and the other cable to a fixed transition contact Measure the resistance Measure the resistance of each resistor branch across the open switch Operate the diverter switch to the other side as described in section 3 9 and measure the resistance with open contacts Check that the resistors are undamaged and compare with the value on the rating plate The values must not differ by more ...

Page 21: ...ould be carried out proceed with that according to section 3 19 before mounting the cover Insert a new O ring for the cover in the upper flange Mount the on load tap changer cover Turn the cover so the guiding pin in the housing is facing the guiding hole in the cover The cover has to be pressed down in order to overcome the spring force of the springs which hold the diverter switch pressed in pla...

Page 22: ...cushion should remain on the top of the oil in the diverter switch housing The connection to the oil conservator is designed to automatically give a gas cushion when filling at atmospheric pressure If new oil especially degassed oil is filled into the diverter switch housing and the number of operations is low the gas cushion may be dissolved in the oil The oil level in the oil conservator should ...

Page 23: ...a too small or no gas cushion means a risk for a trip of the pressure relay Procedure 1 Close the valve in the tube to the conservator 2 Connect the oil pump to the oil valve For connection dimensions see the dimension drawing for the on load tap changer see Fig 10 3 Open the oil valve and the air release valve 4 Start the oil pump and drain approximately 15 litres of oil into a clean and dry cont...

Page 24: ...n The operation is then performed by means of the diverter switch only When testing the operation must be carried out in the same direction as the previous operation The test is to be made on all three phases and is to be carried out as follows Find the exact position of the on load tap changer by adjusting the disc brake as shown in the maintenance guide for motor drive mechanisms 1 Note the numb...

Page 25: ...1ZSE 5492 124 en Rev 6 Maintenance guide UCG 25 y u Fig 11 Indicator lamp connection during contact timing test x contacts v contacts Fig 12 The diverter switch outlet marking ...

Page 26: ...ing diagram BUE Position Min 3 turns Position Contact closed Turns of the hand crank of the mechanism H x u V V y Min 2 turns Turns of the hand crank of the mechanism Position Min 2 turns Position Contact Position Fig 14 Example of contact timing diagram BUL Position Min 3 turns ...

Page 27: ...red It is not necessary to replace both main switching contacts and transition contacts if for instance only the main switching contacts are worn out CAUTION Fixed contacts and its corresponding moving contacts should always be replaced at the same time Also replace contacts which are assumed to wear out before the next overhaul Replacement of contacts is described in the following sections 4 Cont...

Page 28: ...r Plain washer Connection for transition resistor Nut Guide pin Moving main switching contact Fixed transition contact Conical spring washer Moving transition contact Conical spring washer Fixed transition contact Fig 15 Diverter switch contact design Plain washer Locking washer mounted vertically on some types ...

Page 29: ...gs Locking washer Guide pin Screw Board Fig 16 Contact replacement dismantling the boards 4 2 Dismantling the moving main contacts Dismantle the moving main contacts according to Figs 18 and 19 Take away split pins washers and springs in both ends of shafts 1 3 There is one shaft for each pair of contacts Notice that the outer end of the outer phase have washers with a larger diameter see Fig 18 D...

Page 30: ...enance guide UCG 1ZSE 5492 124 en Rev 6 Fig 19 Contact replacement pulling out shaft Shaft 3 Shaft 2 Contact Shaft 1 Fig 18 Contact replacement taking away split pins Contact Shaft 1 Washer with larger diameter ...

Page 31: ...1 Remove the split pins and punch out the shaft with a 5 mm mandrel of brass and take care of the springs washers and contacts when the mandrel is pulled out The springs in view A A are loosened in the following way Punch out the locking pin in one end of the pin with a 2 mm mandrel Thereafter the spring holder can be loosened and the contacts with springs can be removed Take care of the pin Repea...

Page 32: ...with the next phase Finally lock it with new split pins Mount the springs by means of the pin and new locking pins Fig 21 Transition contact construction Shaft Split pins Spring Contact Proceed with the other side of the diverter switch Put a ruler on the linings of the tran sition contacts No lining should lie more than 1 mm from the ruler If any lining does adjust these contacts closer to the bo...

Page 33: ...the shaft Mount washers springs and split pins Steel washer Insulating washer Split pin Silver washers Spring Contact Contact View A A Spring Washer with larger diameter Fig 22 Moving main contacts with tips of copper tungsten washers and springs Proceed with the outer phases Put the outermost silver washer and contact on the shaft and punch the shaft into the bearing hole Put the next silver wash...

Page 34: ...e lowered put one side of the mechanism on an approximately 50 mm high piece of wood to make the fixed and moving contacts free from each other Fig 23 The boards should be fixed with new guide pins 4 x 30 mm spring type straight pin slotted Guide by inserting a 6 mm mandrel into an adjacent screw hole Put in and tighten all screws Secure the screws with new locking washers Fig 18 The plain washers...

Page 35: ... alloys with small amounts of aluminium and manganese 5 50 kg 5 4 Tap selectors Material Tap selector C Approx amount Tap selector III Approx amount Steel 5 kg 10 kg Aluminium 15 kg 40 kg Copper and alloys 20 kg 50 kg Silver 70 g 10 g Polyester resin 5 kg 10 kg Epoxy resin 15 kg 20 kg 5 Specification of materials 5 5 Conductors Material Approx amount Copper 5 10 kg Cellulose 5 6 Gearing mechanism ...

Page 36: ...Copyright 2015 ABB All rights reserved 1ZSE 5492 124 en Rev 6 2015 09 15 ABB AB Components SE 771 80 Ludvika Sweden Phone 46 240 78 20 00 Fax 46 240 121 57 E Mail sales se abb com www abb com electricalcomponents ...

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