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A SUMMER TRAINING PRESENTATION ON “ASSEMBLY OF POWER TRANSFORMER ” Under the guidance of: MR. Prabhat Katiyar (Sr. Engineer) TRM Bay 9 BHEL JHANSI Submitted By: Abhishek Khare EE 1204320002 BIET JHANSI Head Of the Dept. Dr. Deepak Nagaria Electrical Engineering Dept. BIET JHANSI




BHEL JHANSI This unit of Jhansi was established around 14 km from the city on the N.H. No 26 on Jhansi Lalitpur road. It is called second-generation plant of BHEL set up in 1974 at an estimated cost of Rs 16.22 crores inclusive of Rs 2.1 crores for township. Its foundation was laid by late Mrs. Indira Gandhi the prime minister on 9th Jan. 1974. The commercial production of the unit began in 1976-77.


Product Profile TRANSFORMER TYPE RANGE Power Transformer upto 220 kV 315 MVA Voltage Transformer upto 220 kV Current Transformer upto 400 kV Traction Transformers Single Phase Freight Loco Three Phase Freight Loco upto 25 kV 5400 kVA upto 25 kV 7475 kVA Transformer for ACEMU upto 25 kV 1550 kVA Cast Resin Dry type Transformer upto 33 kV 3150KVA


MANUFACTURING UNIT DEPARTMENTS STORE : Whatever material coming from anywhere as ordered by the purchase department first comes to central store. The supervisor looks upon all documents and decide whether material is to be unloaded at central store or at shop directly. FABRICATION ( BAY 0,1,2): Fabrication is nothing but production. This shop deals with the manufacturing of transformer and locomotive components such as tanks, plates and nuts & bolts. It comprises of three bays i.e. Bay 0, Bay 1 and Bay 2. MACHINE (BAY 3): The operations to form small components of Power & Traction Transformers are done in section. The shop consists of machines like lathe machine, radial arm drilling machine etc. WINDING SECTION (BAY 4): The different types of windings for core of transformers is done in this shop. There are four types of coils fixed in a transformer. 1) Low voltage coil (LV) 2) High voltage coil (HV) 3) Tertiary coil. 4) Tap coil.


CORE SECTION (BAY 5): In this shop cutting of CRGO and is done in form of trapezium for legs and pentagon for yoke for the further assembly of the core. TRACTION TRANSFORMER (BAY 6): Traction transformer for AC locomotives is assembled in this section. These Freight locomotive transformers are used where there is frequent change in speed. They are basically used in locomotives. INSULATION SHOP (BAY 7): Various types of insulation which are to be used in transformers are cut into its shape in this bay. The insulation materials are like press board paper, permawood etc. ESP and IT SHOP (BAY 8): In this shop ESPs and Instrument transformers (ct and pt) of different ratings are assembled. TRANSFORMER ASSEMBLY ( BAY 9) : Various types of insulation which are to be used in transformers are prepared in this bay. The steps involved in assembly are: Core building, core lifting, unlacing, relacing, HVTG and LVTG, Vapour phase and soaking, servicing and tanking.


OTHER DEPARTMNETS Apart from the manufacturing departments, other departments involved in the production of a transformer are Transformer Engineering (TRE), Technology, Transformer Commercial (TRC). The LOCOMOTIVE DEPARTMENT consists of various departments like Locomotive Manufacturing (LMM), Locomotive Engineering (LME) and Locomotive Commercial (LMC).


POWER TRANSFORMERS Power transformers are available for step-up operation, primarily used at the generator and referred to as generator step-up (GSU) transformers; step-down operation, mainly used end to feed distribution circuits and to connect grids operating at different voltage levels through interconnecting transformers. Power transformers are available as single-phase or three-phase apparatus. Power transformers have been loosely grouped into three market segments based on size ranges. These three segments are: Small power transformers 500 to 7500 kVA 2. Medium power transformers 7.5 MVA to 100 MVA 3. Large power transformers 100 MVA and above .


WORKING PRINCIPLE The working principle of transformer depends upon Faraday's law of electromagnetic induction. The physical basis of a transformer is mutual inductance between two circuits linked by a common magnetic flux through a path of low reluctance. If one winding is excited by a supply, an emf is induced in the secondary winding following the Lenz’s law given by expression: e=d φ ̸ dt e= induced emf Φ = linked flux


MAIN CONSTRUCTIONAL PARTS Primary Winding of transformer - which produces magnetic flux when it is connected to source. Magnetic Core of transformer - the magnetic flux produced by the primary winding, will pass through low reluctance path linked with secondary winding and creates a closed magneticcircuit. Secondary Winding of transformer - the flux, produced by primary winding, passes through the core, will link with the secondary winding. This winding is also wound on the same core and gives the desired output.


WINDINGS USED R-S Coil : reverse section winding. Helical coil : winded in shape of spring. Spiral coil : simply wounded on the base. Interleaved coil : the hv and lv windings are interleaved within each other.


. Helical winding Interleaved winding


CORE MATERIAL CRGO : Cold rolled grain oriented silicon steel is used to build the core. Purpose of using CRGO is to reduce the Hysteresis losses. Laminations of these sheets minimizes eddy current loss. The sheets used are as thick as 0.3 mm.


ASSEMBLY OF POWER TRANSFORMER The various steps involved are: 1. Core building : In this shop the core of a transformer is built using the ballets of CRGO sheets.


. 2. Unlacing & Relacing: The yoke of this core is removed using crane. This process is called unlacing. The coil are then lowered primary, secondary, tertiary & tap in that sequences.. After that end frames are bolted back. This is called relacing of the core.


. 3 . H.V.T.G. & L.V.T.G: In this the terminals of sections of coils are connected as per drawing and the process is called terminal gear assembly.


. 4. Vapour Phasing & Oil Soaking : The process of moisture removal from transformer is called vapour phasing. The job is put in dummy tank and place in a vacuum vessel. A solvent vessel is released is the chamber which enters all transformer parts and insulations. It absorbs water rapidly. The job is heated in vacuum.


. 5. Final Servicing & Tanking: After taking the job out of dummy tank all the parts retightened any other defects are rectified and the job is retimed in mild steel tank. After this the tanking oil is filled. Case Fitting: The accessories are fixed and final touches given the job. The accessories included tank cover, fixing bushing, fixing valves etc. The terminals are marked and R and D (rating and diagram) plate is fixed.


. 7. Testing: TYPE TESTS: Impulse test: This test is made to prove that the transformer insulation will withstand voltage surges which may be caused by lightning or switching; this includes insulation to ground, insulation between turns and windings, and the flashover value of the associated bushings.


. The other type tests are temperature rise test, noise level test, dielectric test etc. ROUTINE TEST: IR Test: Insulation resistance tests are made to determine insulation resistance from individual windings to ground or between individual windings. The recommended practice in measuring insulation resistance is to always ground the tank (and the core). Short circuit each winding of the transformer at the bushing terminals. Resistance measurements are then made between each winding and all other windings grounded. The other routine test includes ratio test, magnetic balance etc . 8. Dispatch: When a transformer leaves the factory, it is shipped by heavy haul trucks, rail and/or seaway vessel to site. The tank of transformer is filled with N 2 O gas to avoid moisture.


CONCLUSION To conclude power transformers are extensive device in today’s world for transmission and distribution systems. Power transformer undergoes several stages for manufacturing process. Tests are done to ensure the status and reliability of the power transformer during as well as after manufacturing. Transformer design and manufacturing techniques have remained similar for many years. Over time, improvements have been made in materials, design programs and testing techniques to allow for lighter and more efficient units to be produced. This training period helped me a lot in gaining the knowledge of power transformer. It helped me to learn the manufacturing process of power transformer.



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