Type VRLTC load tap changerInstallation and maintenance guide
Recommended practicesABB recommends careful consideration of the following factorsfor installation and maintenance work on load tap changers. ABB recommends that only service personnel withappropriate skills regarding load tap changers carry outinstallation, maintenance, and repairs of any sort. Before you start any work, make sure that the personneldoing the job have read and fully understood the installationand maintenance documents provided with the unit. To avoid damaging the unit, never exceed the operating limitsstated in delivery documents and on rating plates. Do not alter or modify a unit without first consulting ABB. Follow local and international wiring regulations at all times. Use only factory authorized replacement parts andprocedures. Approval should be given for inspections as well as foroperating the load tap changer (LTC).General cautions The LTC must not be included in the vapor phase dryingprocess of the transformer. The transformer tank and the LTC tank must besimultaneously under vacuum when filling either tank with oil. Avoid ingestion of moist air into the LTC when draining oil.Let incoming air pass through a dehydrating breather withslow air flow to obtain proper dehydration in case the air ismoist. The oil level of the transformer should always be higher thanthe oil level of the LTC. Sealing surfaces and gaskets must be clean and undamaged.Safety notationsThe following is a definition of danger, warning, caution, andnotice and a description of how each will be shown.PrecautionsThe following is a list of general warnings and cautions thatpertain to this document: Before any work is carried out on the LTC, make sure that thetransformer is de-energized and properly grounded. Before starting any work on the LTC, the mode switch of themotor drive must be set to the OFF position. Before starting any work inside the motor drive, the auxiliarypower must be switched off. The motor drive, contacts, andheating elements may be energized from separate sources. The motor drive must not be installed in any explosiveatmosphere. The electrical equipment creates sparks, whichcan cause an explosion. The oil in the tap changer may be hot. There may be a cushion of explosive gases over the oilsurface. No open fire, hot surfaces, or sparks may be presentwhen the front cover is opened. Small amounts of explosive gases may be exhaled by thebreathing devices (dehydrating breather or one-way breather).Make sure that no open fire, hot surfaces, or sparks occur inthe immediate surroundings of the breathing devices. Never insert the hand crank during electrical operation. When oil that has been used in the tap changer compartmentis pumped out, conducting tubes and hoses that aregrounded should be used to avoid the risk of explosion due tothe gases that may be present in the LTC compartment.Oil handlingAnyone who handles oil should consult a MSDS for the type ofoil used prior to handling. Consider rags and other disposableswhich you use during service as hazardous waste. Avoidcontact with oil as much as possible and use oil tight protectivegloves when handling the oil. Should contact with oil occurfollow the procedures described in the MSDS.DANGERA DANGER symbol indicates a hazardous situation which, ifnot avoided, will result in death or serious injury.WARNINGA WARNING symbol indicates a hazardous situation which, ifnot avoided, could result in death or serious injury.CAUTIONA CAUTION symbol indicates a hazardous situation which, ifnot avoided, could result in minor or moderate injury.NOTICEA NOTICE addresses practices not related to personal injury.Rev. 5, Jul 17, 2014 VRLTC installation and maintenance guide i
General informationThe VRLTC load tap changer is manufactured exclusively atthe ABB facility in Alamo, Tennessee. The LTC meets all of therequired specifications according to IEEE C57.131-1995 andIEC 60214-1. The LTC is an on-tank, vacuum reactance loadtap changer for either automatic or manual control.Three major components make up the LTC: the tap changingcomponents, the driving components, and the decision making/monitoring components. The tap changing components arecontained in an oil-filled steel tank. The transformer’s tap leadsand preventive autotransformer (PA or switching reactor) leadsare connected to the back of the LTC terminal board. Thedriving and decision-making components are contained in aseparate steel air compartment mounted below the oil-filledtank with a drive shaft connecting it to the tap changer.The drive motor is a digitally controlled servo motor whichprecisely responds to the commands from the digital drive.Cam switches and electromechanical relays are not used in thismotor drive. The entire system is monitored and controlled bythe Tap Logic Monitoring System (TLMS) mounted in the motorcompartment.1 VRLTC installation and maintenance guide Rev. 5, Jul 17, 2014The components of the tap changing circuit are: The preventive autotransformer - a separate device mountedinside the transformer which provides the transition impedance The tap changing module - consists of the tap selector andchange-over selector The load switching module - consists of the by-pass switches andthe vacuum interrupter (VI)These components work together so that the transformer loadis not interrupted at any time during a tap change operation.Oil qualityThe oil quality should meet the standards according to IEEEC57.106-2006. The oil should have an electrical withstand of atleast 35 kV, measured in a 1 mm gap. The water content mustbe below 10 ppm.VRLTC characteristicsThe VRLTC tap changer is a 3-phase, preventiveautotransformer design with vacuum interruption. It canbe configured in plus/minus, coarse/fine or linear tappingarrangements. The maximum number of positions is 33 withnine (eight effective) winding sections. Table 1 contains theelectrical and mechanical characteristics of the tap changer.
Electrical characteristicsTap changer typeVRLTC 1500-200VRLTC 1500-150-N1VRLTC 2000-150-N1VRLTC 2000-20038 / 35 kV28 / 27.5 kV28 / 27.5 kV38 / 35 kV1500 A1500 A2000 A2000 A200 kV150 kV150 kV200 kV275 kV200 kV200 kV275 kV70 kV50 kV50 kV70 kV75 kV75 kV75 kV75 kV34 kV26 kV26 kV26 kV45 kV45 kV45 kV45 kV15 kV15 kV15 kV15 kV500/1000 V250/500 V250/500 V500/1000 V20 kV20 kV20 kV20 kVmediumsmallsmallmediumMaximum continuous operatingvoltage line-to-line (IEEE/CSA)Rated through currentImpulse withstand voltage (fullwave) phase-to-phase and togroundTransformer test floor maximumimpulse withstandPower frequency withstand,phase-to-phase and to ground(rms)Impulse withstand voltage (fullwave) across tap range (VR)Power frequency withstandacross tap range (VR) (rms)Impulse withstand voltage (fullwave) tap-to-tap (VT)Power frequency withstand tapto-tap (VT) (rms)Step voltage / tap voltage, tapto tap (rms)Maximum change-over selectorrecovery voltageTank sizePhysical characteristicsSmall tankStandard number of positions33339 (8 effective)9 (8 effective)Withstand full vacuum ( 18 psi)Withstand full vacuum ( 18 psi)60 x 46 x 2967 x 50 x 3244605350Regulating winding sectionsTankMedium tankApproximate LTC tank dimensions 2 (W x H x D) (in.)Total weight excluding motordrive (pounds)Volume of oil (gallons)2Duration of tap change 3123270350Less than 2 secondsLess than 2 secondsOnly rated for application at the neutral end of Wye. P must be connected to Neutral.Approximate parameters — check outline drawing for exact details.Less than 1 second available as a special order.Table 1 — VRLTC characteristicsFigure 1 — LTC configurationRev. 5, Jul 17, 2014 VRLTC installation and maintenance guide 2
Receiving and handlingUpon receipt of the VRLTC from ABB, it should be inspectedfor any signs of shipping damage. Open the door of the motordrive enclosure. Inspect the components in the compartmentfor any obvious signs of shipping damage. If any damage issuspected, file a claim with the transport company and notifyABB.Check that the quantity delivered, the type designation andthe serial numbers agree with the delivery documents. Thenameplate of the tap changer and motor drive compartmentswill each contain a serial number (see Figure 2). Verify that bothnameplates have matching serial numbers. The serial numberof the tank will end with an “L” and the motor drive will end witha “M”. Contact ABB if the nameplates do not match.Remove any drying agents before commissioning the LTC. Ifthe packing material appears to be wet, the LTC must be driedfor at least 24 hours at a maximum temperature of 158 F(70 C) before it is fitted to the transformer.CAUTIONLoosen the 1” vent plug on the LTC cover to relieve the gaspressure in the LTC oil compartment before opening the frontinspection door.NameplateFigure 2 — Nameplate locations on motor drive and LTC3 VRLTC installation and maintenance guide Rev. 5, Jul 17, 2014StorageABB ships the tap changer filled with helium under positivepressure. If the LTC is to be stored for a period of time and thetank was opened prior to storage, the LTC must be refilled withan inert gas. The pressure within the tap changer compartmentshould not exceed 4.0 psi. If you intend to store the LTC inan unheated space or outdoors, you must do the following toprotect the LTC from weather: Fill the LTC tank with clean, dry oil and fill the gas space withan inert gas. If outdoors, provide weather protection for the exteriorsurfaces of the LTC tank and the operating mechanism.The primer paint coating is not rated for long term outdoorexposure. Provide heat within the motor drive compartment by providingpower to the internal heaters in the compartment.Tightening torqueThe following table lists the recommended tightening torques.SizeTorque N-m (lbf-ft)M610 (7.5)M824.5 (18)M1049 (36)M1284 (62)Table 2 — Recommended tightening torques
Attaching the VRLTC to the transformerWeldingVerify that the LTC opening in the transformer tank is compliantwith the specifications on the outline drawings furnishedwith the LTC. Weld the LTC compartment to the transformermain tank. This weld must be oil tight, pressure and vacuumresistant.CAUTIONWelding adjacent to the epoxy terminal board may distort itsmounting surface and cause damage to the terminal board orits oil seal.Mounting the motor drive compartmentABB ships the LTC and motor drive in the service positionwith a locking plate secured to the LTC mounting flange and alocking pin located in the motor drive (see figure 3). The serviceposition is determined by the connection configuration of thetap changer. Plus / minus and course / fine configurations areshipped on the neutral position and the linear configurationis shipped on position 17. The locking mechanism shouldnot be removed until the motor drive compartment is readyto be installed onto the LTC. Before installing the motor driveenclosure, check the position indicator to confirm that the motordrive is in the service position according to the nameplate.Open the motor drive and verify that the locking pin is in place.WARNINGThe transformer tank wall must be braced to withstand a 15psi pressure test. A 0.25” oil-tight weld is required around theoutside perimeter of the LTC mounting flange. Welding on thetransformer side of the LTC is not required.BoltingA one piece cork neoprene gasket is provided to seal againstthe transformer tank. Gaskets should not be cemented attemperatures below 32 F (0 C). The required amount ofcement (ABB 1 3401-608) is 1.0 lb. When you install the LTC,the gasket should be cemented as described below: Ensure that the surfaces in contact with the gaskets are cleanand free from grease and oil. After cleaning the contact surfaces, attach the gaskets to thetransformer tank flange with ABB cement 1 3401-608, bybrushing cement on both the gasket and the flange. Allow the cement to dry for a minimum of 10 minutes and amaximum of 30 minutes. Keep the gaskets in the correct position by using clampingblocks for a minimum of 3 hours. Set the LTC in its place on the transformer and tighten thebolts to approximately 65 lb-ft (90 N-m) torque. Tighten the dome nuts with 31 lb-ft (42 N-m) before oil filling.NOTICEDo not energize the transformer before the LTC compartmentis filled with oil. Do not fill the compartment with oil untilthe motor drive is correctly assembled to the oil-filledcompartment.Direct mount Ensure the motor drive is locked in the service position(figure 3) Remove the locking plate secured to the LTC drive flangeby removing the six bolts. Be careful not to rotate the LTCcoupling pin. Please note the orientation of the LTC couplingpin. On the motor drive enclosure, remove the packing tapecovering the hole and verify the o-ring is installed in themounting groove (figure 4). Apply a thin layer of grease (GULF-718EP synthetic grease,Mobil grease 28 or SHELL Aero Shell Grease 22) to theo-ring, drive shaft upper slot, and the motor drive couplingpin. (see figures 4 and 7) Attach the mounting brackets to the motor drive enclosure asshown and hand tighten the four horizontal bolts.Locking pinWhen a gasket is subjected to the force from the flange boltsit will change its shape and settle. This reduces the forceson the bolts, making them loose. The settling effect willincrease at higher temperatures. For this reason, retighteningis required. Retighten one day after assembly and again afterthe transformer has been in service for two weeks to let thegaskets settle at service temperature.Figure 3 — Motor drive secured in service position by lockingpinRev. 5, Jul 17, 2014 VRLTC installation and maintenance guide 4
O-ring and grooveFigure 4 — O-ring placementFigure 5 — Left side mountinghardwareCAUTIONDo not attempt to install the drive shaft assembly before liftingthe motor drive into place. Doing so could result in damageto the LTC or motor drive Lift the motor drive enclosure up to the LTC compartmentbeing sure to keep the LTC drive flange and motor drivemounting boss aligned. Attach the motor drive to the LTC by installing the hardwareas indicated (figures 5 and 6). Tighten the vertical bolts in a crisscross pattern to the propertorque (table 2) Using a crisscross pattern tighten the horizontal bolts to theproper torque (table 2) Open the motor drive door and the swing panel. Ensure that the swing panel is aligned with the alignmentpin (figure 15) by opening and closing the swing panel andmotor drive door while verifying minimum interference. Ifthe alignment pin is not aligning with the swing panel or themotor drive door will not properly latch, loosen the bolts inthe mounting brackets adjusting the orientation of the motordrive enclosure. Be sure to re-tighten the bolts to the propertorque once the motor drive has been squared.Drive shaftCouplinghalfCouplingpinFigure 7 — Exploded view of coupling inside motor drive5 VRLTC installation and m
IEC 60214-1. The LTC is an on-tank, vacuum reactance load tap changer for either automatic or manual control. Three major components make up the LTC: the tap changing components, the driving components, and the decision making/ monitoring components. The tap changing components are contained in an oil-filled steel tank. The transformer’s tap ...