Power Transformers - Tamini

DESIGN AND FEATURES OF POWER TRANSFORMERSMAGNETIC CIRCUITSTERMINAL OUTLETSThe core is composed of silicon magnetic steelHV and LV outlets are carried out through bushingssheets, insulated by inorganic “carlite” with highfor connection to the external lines.chemical resistance to hot oil.The bushings are of different types, accordingPressboard insulation is interposed betweento the specified design: they can be eitherpackages of sheets. The joints columns-yokesof the oil/air type or oil/oil, in case of connectionsare usually of the interleaved step-lap type.to cables in oil filled terminal boxes,The core columns are strongly fastened utilisingor also oil/SF6 for connection to SF6 filledonly highly resistant clamping tape; no through boltsbus-bar ducts.are used. The yokes are clamped by a strong steelHV bushings are usually of the condenser type withPhase Shifting Transformer (PST) 160 MVA - 230000/155000 kV165 MVAr - 400 kV Shunt Reactorstructure tightened by rods.oil impregnated paper or epoxy resin insulation,250 MVA - 400/155 kV Power Transformerwhile MV or LV bushings are of the solid type.WINDINGS AND CONNECTIONSUsually the bushings are fitted with externalThe windings are made of electrolytic copper,porcelain insulators, however for the oil/air bushingsinsulated with pure cellulose paper.for outdoor installation, they can also be equippedStronger insulation is used on the terminal outlets.with silicon fins.Oil circulation through the windings is granted byFor LV and MV bushings the external connectionshorizontal and vertical channels, according to thecan be achieved through multi-contact elbowtype of winding. The winding type is designedbushings.according the voltage value.For installation in polluted areas the bushingsUsually HV windingsare designed with extended creepage distance320 MVA - 230 and 400 kV GSU Transformer for Turbogas Power Plant 320 MVA - 230 kV Power Transformerare of interleaved continuous disk type, whileLV windings are of transposed cable helical type.and special surface treatment.Winding Press EquipmentRegulating and tertiary windings, when installed,are also of helical type.The internal connections from the windingsto the bushing terminals and to the tap-changersare made by solid conductors or copper plaitsstrongly insulated and clamped to wooden supports.Special care is paid to winding stabilization,which is achieved through a process sequenceof drying, in hot air oven, and tightening by tie-rod,550 MVA – 400 kV Step Up Transformer under TestingOne of two 553/338/215 MVA - 403/19/15.75 kV Step-up Transformers for a 800 MWcombined-cycle power plantFinal Setting of Active Parts after Vapour-phase Treatmentboth on the single winding columns and on thewhole of each phase windings.9