MANUFACTURING PROCESS OF 500 MWTURBO GENERTOR STATOR WINDING BAR AT BHEL HARIDWARHARSHIT AGARWAL08070105022
INTRODUCTIONIn 1956 India took a major step towards the establishment of itsheavy engineering industry when BHEL, the first heavy electricalManufacturing unit of the country was set up at Bhopal. BHELs Heavy Electrical Equipment Plant (HEEP) was set up in technical collaboration with USSR, for the manufacturing of power plant equipment. In 1976, BHEL entered into a collaboration agreement with M/s Kraftwerk Union, AG of Germany for design, manufacturing, erection and commissioning of large size steam turbines. More than 40 percent of the countrys electrical energy is generated from the power equipment supplied by BHEL, Haridwar.
MANUFACTURING BLOCKS:BLOCK I: ELECTRICAL MACHINE BLOCK, IS DESIGNED TO MANUFACTURING OF TURBOGENERATORSBLOCK II: FABRICATION BLOCKBLOCK III: TURBINE BLADE BLOCKBLOCK IV: COIL & INSULATION MANUFACTURING & APPARATUS & CONTROL GEAR MANUFACTURING BLOCKBLOCK V: FEEDER BLOCK AND KNOWN AS FABRICATION AND FORGE BLOCKBLOCK VI: STAMPING AND DIES MANUFACTURING BLOCKBLOCK VII: WOODWORKING BLOCKBLOCK VIII: HEAT EXCHANGER BLOCK, IS DESIGNED TO . MANUFACTURE HEAT EXCHANGER UNIT FOR STEAM TURBINES.
COIL & INSULATION MANUFACTURING SHOP (BLOCK-IV)Block-4 is a feeder block for insulatingitems, winding with class-B Bituminous insulation andsheet metal components for all the products of Block-1 i.e. Turbo-generators, Hydro-generators, A.C. andD.C. machinesThere are three BAYS in this block each baymanufactures stator bars and coils for differentmachines
BAY-I: Bar winding shop: manufacturing of stator windingbars of generatorBAY-II: Manufacturing of heavy duty generator stator barswith New CNC M/cBAY-III: Insulation detail shop: Manufacturing of hardinsulation & machining of hares insulation part (Glass Textolite)such as packing, washer, insulation box, wedges etcBar Shop: This shop is meant for manufacturing of statorwinding coils of turbo-generator and hydro generator
Sections in Block IV 1) Assembly Section 2) Stator Bar Winding SectionIt is equipped with small size It is equipped with• Drilling machines •Conductor cutting, insulation and• Welding sets transposition section.• Hydraulic testing equipment •Stack consolidation section,for manufacturing turbo- forming and lug brazing sections.generator mechanical •Insulation taping sections withassemblies. automatic taping facilities in air- conditioned 3) Impregnation Section It is equipped with • Impregnation tank • Ovens for impregnation of DC pole coils.
4) Armature Winding, Rotor coil and Stator bar SectionIt is equipped with• Conductors cutting.• U- bending and terminal conductor cutting machines.• Semi-automatic winding machine.• Planking, boat pulling and diamond pulling machine.• Insulation and pressing of AC coils. 5) Insulation Section It is equipped with • Small size lathes. • Milling and radial drilling machines. • Jet cutting saw. • Electrical ovens & Hydraulic presses. •Plastic Molding Section
Types of GeneratorsThe generator may be classified based upon the coolingsystem used in the generators such as: THRI, TARI, THDI,THDD, THDF, THFF, and THW Stands for Stands for the Stands for the Stands for typeStands for type cooling media cooling media type of cooling of cooling for of generator used for Stator for Rotor for Rotor Stator coil• T- Turbo • H- Hydrogen • R- Radial • I- Indirect • W- Water Generator gas • D- Direct • D- Direct• H- Hydro • A- Air • F- Forced • F- Forced Generator • I- Indirect
Why do we call it bar?It is quite difficult (rather impossible) to manufacture, handleand wind in the stator slot of generator of higher generationcapacity because of its bigger size and heavy weight. That iswhy we make coil in two parts. One part its bottom part of coilcalled bottom or lower bar and other part of coil is called topbar or upper bar.
No. of Bars in current productsSet Type Upper Upper Lower Lower Total No. of Ordinary Terminal Ordinary Terminal Bars Bus Bars500MW 42 6 42 6 96 6 THDF210MW 54 6 54 6 120 9 THW250MW 48 12 48 12 120 9 THRI
Resin System: Rich Resin or Thermo-reactive insulation system:In this type of insulation system the bond content in resin is35 – 37 %. The raw materials are ready to use and requirepreservation and working on temperature 20 – 250C. Its shelflife is one year when kept at a temperature of 200C whichcould be increased when kept at temperature of 50C. Poor Resin or Micalastic insulation systemIn this type of insulation the bond content in the resin is 5 – 7%and insulating material is prepared with accelerator treatment.The temperature control need is not required. The insulatingmaterial is applied on job and then same is impregnated (fullydipped) in the resin.
INSULATION CLASSIFICATION: • Upto 90 °C Class Y • Cotton, Silk, or Paper. • Upto 105 °C Class A • Reinforced Class-Y materials with impregnated varnish. • Upto 120 °C Class E • Cotton lamination & Paper lamination. • Upto 130 °C Class B • Inorganic material is hardened with adhesives. • Upto 150 °C Class F • Class-B materials that are upgraded with adhesives. • Upto 180 °C Class H • Made of inorganic material glued with silicone resin. • > 180 °C Upto 220 °C Class C • Made of 100% inorganic material
TranspositionTransposition means changing/shifting of position of eachconductor in active core (slot) part.•After cutting the required number of conductors•The conductors are arranged on the comb in staggeredmanner and then bends are given to the conductors with thehelp of bending die at required distance.•Then the conductors are taken out from the comb and die andplaced with their ends in a line and transposition is carried out.•This process is repeated for making another half of the barwhich would be mirror image of the first half.•The two halves of the bar are overlapped over each other anda spacer is placed between the two halves.
Transposition is done in two ways:Half Pitch Transposition: In this transposition, the firstconductor at one end of the bar becomes the last conductor atthe other end of the bar.Full Pitch Transposition: In this method of transposition, thefirst conductor at one end of the bar becomes the lastconductor in the mid of the bar and then again becomes thefirst conductor at the other end of the bar. Need of transposition.1. To reduce eddy current losses.2. Equalize the voltage generator.3. To minimize skin effect of ac current.
Testing Tan δ test:•This test is carried out to ensure the healthiness of dielectric(Insulation) i.e. dense or rare & measured the capacitance loss.•Bar will act as capacitor when it is laid in the stator of thegenerator.•Schearing Bridge which works on the principle of wheat-stonebridge is used to find the unknown capacitance of the bar.•For good efficiency, capacitance of the bar should be high but wenever approach pure capacitance.•Bar is wrapped with aluminum to make the bar conductivethroughout the outer surface of the bar. The two conductingmaterial i.e. the aluminum sheet and the conductors of the bar actas two plates of the capacitor and the insulation on the bar act asdielectric medium for the capacitor thus the capacitance is found.•Of angle of deviation due to impurity in the insulation is obtainedfrom the formula: C4 * R4 * 10^-4 = tan δ
H.V. Test:•Each bar is tested momentary at high voltage increased graduallyto three times higher than rated voltage.•This test is also known as insulation test because this test isperformed to check the insulation of the bar.•For 500 MW the working voltage of the bar is 64.5 KV & for 210MW the working voltage of the bar is 63 KV.•In this test the bar which is already wrapped with aluminum isused.•High voltage is applied to the bar using auto-transformer and it isincreased in steps according to the working voltage of thegenerator. If the insulation is weak the bar will puncture at theplace of weaker insulation.•If any of the bar fails this test i.e. bar is punctured at any pointthen the bar is sent back for re-insulation and all the processesare repeated again
500 MW Turbo generators at a glance 2-Pole machine with the following features:Direct cooling of stator winding with water.Direct hydrogen cooling for rotor.Micalastic insulation system.Spring mounted core housing for effective transmission ofvibrations.Brushless Excitation system.Vertical hydrogen coolers
Salient technical data:Rated output: 588 MVA , 500 MWTerminal voltage: 21 KVRated stator current: 16 KARated frequency: 50 HzRated power factor: 0.85 LagEfficiency: 98.55% Important dimensions & weights:Heaviest lift of generator stator : 255 TonsRotor weight : 68 TonsOverall stator dimensions [L*B*H] : 8.83m*4.lm*4.02mRotor dimensions(Dia. and length) : 1.15m and 12.11mTotal weight of turbo generator : 428 Tons