On-load tap-changers, type UBB Technical guide Manufacturer’s declaration The m

On-load tap-changers, type UBB Technical guide Manufacturer’s declaration The manufacturer ABB Components AB SE-771 80 LUDVIKA Sweden Hereby declares that The products On-load tap-changers type UB with motor-drive mechanisms types BUE and BUL comply with the following requirements: By design, the machine, considered as component on a mineral oil filled power transformer, complies with the requirements of • Machinery Directive 89/392/EEC (amended 91/368/EEC and 93/44/EEC) and 93/68/EEC (marking) provided that the installation and the electrical connection be correctly realized by the manufacturer of the transformer (e.g. in compliance with our Installation Instructions) and • EMC Directive 89/336/EEC regarding the intrinsic characteristics to emission and immunity levels and • Low Voltage Directive 73/23/EEC (modified by Directive 93/68/EEC) concerning the built-in motor and apparatus in the control circuits. Certificate of Incorporation: The machines above must not be put into service until the machinery into which they have been incorporated have been declared in conformity with the Machinery Directive. Date 1997-02-10 Signed by ......................................................................... Olof Heyman Title Manager of Division for tap-changers This Technical Guide has been produced to allow transformer manufacturers, and their designers and engineers, access to all the technical information required to assist them in their selection of the appropriate on-load tap-changer and motor-drive mechanism. The guide should be used in conjunction with the Selection Guide and the Design Guides, to allow the optimum selection to be made. The technical information pertaining to on-load tap-changers and motor-drive mechanisms manufactured by ABB Components has been divided and is contained in separate documents, with one document for each type. The information provided in this document is intended to be general and does not cover all possible applications. Any specific application not covered should be referred directly to ABB Components AB, or its authorized representative. ABB Components AB 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. ABB Components also manufactures the following products: Transformer bushings Wall bushings GIS bushings Transformer cooling equipment General Information_____________ 4 Design Principles ______________ 6 On-Load Tap-Changer _____________________ 6 Selector Switch __________________________ 6 Transition Resistors ____________________ 7 Change-over Selector __________________ 7 Geneva Gear _________________________ 7 Selector Switch Housing ________________ 8 Oil Conservator _______________________ 8 Motor-Drive Mechanism ____________________ 9 Type BUL ____________________________ 9 Type BUE ____________________________ 9 Special Applications ____________________ 9 Accessories __________________________ 9 Principles of Operation __________ 10 On-Load Tap-Changer _____________________ 10 Switching Sequence ____________________ 10 Selector Switch _______________________ 10 Change-over Selector for Plus/Minus Switching ___________________ 11 Change-over Selector for Coarse/Fine Switching __________________ 11 Characteristics and Technical Data _____________ 12 On-Load Tap-Changer _____________________ 12 Type Designation ______________________ 12 Rated Phase Step Voltage _______________ 12 Standards and Testing __________________ 12 Rating Plate __________________________ 12 Contact Life __________________________ 13 Mechanical Life _______________________ 13 Table of Contents Insulation Levels_______________________ 13 Short Circuit Current Strength ____________ 14 Highest Phase Service Voltage Across the Regulating Winding _________________ 14 Tie-in Resistors _______________________ 14 Rated Through Current _________________ 14 Maximum Rated Through Current _________ 14 Occasional Overloading _________________ 14 Oil Temperature _______________________ 14 Conductors from the Windings ____________ 14 Design, Installation and Maintenance _______________ 15 On-Load Tap-Changer Schematic Diagrams ___________________ 15 Drying _______________________________ 19 Painting _____________________________ 19 Weights _____________________________ 19 Oil Filling_____________________________ 19 Installation ___________________________ 19 Maintenance __________________________ 19 Oul Filter Unit ____________________________ 19 Pressure Relay ________________________ 20 General Description _________________ 20 Design ____________________________ 20 Operation _________________________ 20 Function Pressure ___________________ 20 Testing ___________________________ 20 Dimensions, On-Load Tap-Changer Type UBB ____________________________ 21 Motor-Drive Mechanism____________________ 21 Design ______________________________ 21 Installation ___________________________ 21 Maintenance __________________________ 21 Dimensions, Drive Shaft System and Motor-Drive Mechanism _________________ 22 General Information When the on-load tap-changer operates, arcing occurs in the tap-changer. To avoid contamination of the trans- former oil, the tap-changer is housed in its own oil compartment separated from the transformer oil. All components that make or break the current during the operation of the tap-changer are located in the tap- changer compartment. The UB range of on-load tap- changers operates according to the selector switch principle, that is, the tap selector and diverter switch functions are combined in one. The UB type of on-load tap-changer is mounted on the inside of the transformer tank. Both cover-mounting and yoke-mounting may be specified. The tap-changer comes ready for mounting on the inside of the transfor- mer tank, which simplifies installation procedures. All of the equipment necessary to operate the tap- changer is contained in a cylinder of glass fibre reinforced plastic, the selector switch housing. Driving is from a separate motor-drive mechanism, fitted to the side of the transformer tank, and connected by means of drive shafts and bevel gears. 4 Fig. 1. On-load tap-changer type UBBRT L037164 5 Fig. 2. On-load tap-changer type UBBRT Pressure relay Position indicator window Air release valves Oil valve Shielding rings Transition resistor Current collector terminal Bevel gear Top-cover Flange Cylinder Connection to oil conservator Moving contacts Change-over selector: Fixed contacts Fixed contacts Selector switch: Moving contacts Selector switch shaft Bottom valve drain screw Bottom Fig. 3. Moving and fixed contacts 6 On-Load Tap-Changer The tap-changer is built-up by using three single-phase units, mutually identical, mounted in the selector switch housing. Each single-phase unit consists of a selector switch and transition contacts. When plus/minus or coarse/fine switching there is also a change-over selector. Selector Switch The selector switch consists of fixed contacts and a moving contact system. The fixed contacts are mounted on bushings which are inserted through the cylinder wall of the selector switch housing. Each fixed contact has two contact paths on each side, one for the moving main contact and one for the moving switching contacts. The moving contact system for a single-phase consists of the main contact, the main switching contact and two transition contacts. The system is built as a rigid unit rotated by a common insulated drive shaft. In the service position the load current is carried by the moving main contact, which consists of two fingers, pressed on the fixed contact by springs. The moving switching contact and the transition contacts are made as rollers, which move over the knife-like fixed contacts. See Fig. 3. The making and breaking take place between the fixed and moving switching contacts. The switching contacts are made of copper/tungsten or, in the case of tap-changers for lower currents, the contacts are made of copper. In service position the current is carried by clean surfaces of copper or silver, which are not subjected to arcing. Design Principles Fixed contacts Moving contacts 7 Transition Resistors The resistors are made from spirally wound wire moun- ted on insulating bobbins. They are connected between the moving main contact and the transition contacts. Change-over Selector The change-over selector is used for reversing the regulating winding or for changing connection in the coarse/fine regulation. One phase of the change-over selector consists of a moving contact and three fixed contacts. The moving contact is fixed to an insulated cylinder pivoted on the top of the drive shaft, see Fig. 4. The current is carried by the four contact fingers of the moving contact. The contact surfaces consist of silver and copper. The change-over selector does not make or break the current during operation. Fig. 4. Change-over selector Geneva Gear The Geneva gear principle is used to change a rotary motion into a stepping motion. Drive is transmitted via a shaft system and bevel gears from the motor-drive mechanism. A spring energy accumulator actuates the Geneva gear. The Geneva gear operates the selector switch and the change-over selector. The Geneva gear is also used to lock the moving contact system into position. The gearing mechanism is maintenance-free. Moving contacts Fixed contacts Fig 5. On-Load tap-changer system 8 Selector Switch Housing The tap-changer oil compartment is separated from the transformer oil by a vacuum-proof cylinder, designed to withstand a test pressure of 100 kPa or full vacuum. The cylinder is made of glass fibre reinforced plastic, which on its upper end has attached a metal flange and on the lower end a closed metal bottom. The bottom, the flange, the top-cover and the accessories mounted on the cover are made from casted aluminium. The cylinder and the gasket are designed to be oil-tight, and the tightness is routinely tested with a vacuum/helium-method. This safety guarantees the contaminated tap-changer oil to remain separated from the transformer oil. The top-cover is provided with connecting flanges for pipes to the oil conservator and the pressure relay. The connections are stepless orientable. Oil Conservator The tap-changer shall be connected to a separate oil conservator, preferably placed at the same height or just below the conservator for the transformer. Horizontal drive-shaft and protection cover Bevel gear Hand crank Bevel gear Motor-Drive Mechanism On-Load Tap-Changer Vertical drive-shaft and protection cover Motor-Drive Mechanism The motor-drive mechanism provides the drive to allow the tap-changer to operate. As the name implies, drive is provided from a motor through a series of gears and out through a drive shaft. Several features are incorporated within uploads/s3/ technical-guide 1 .pdf

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Administrationcontact tap-changer selector on-load switching
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