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MANUFACTURING OF 500/600MW STATOR WINDING BAR (BHEL)
SUBMITTED TO:-
Mr. A.K DHIMAN (MGR-CIM)
SUBMITTED BY:-
AVINASH KUMAR
K.N.G.D MEC (EEE)
ROLL NO.- 495
introduction
It is quit difficult to manufacture, handle and wind in the stator slot of generator of higher generation capacity because of its bigger size and heavy weight called BAR.
Bar is make in to two partUpper BarLower Bar
Bottom part of the bar is called lower bar. Top part of the bar is called upper bar.
PROCESS OF BAR FINISHING
1) CONDUCTOR CUTTING SECTION It is equipped with Conductor cutting (Robal machine). Insulation and transposition section. Stack consolidation section, forming and lug brazing
sections. Insulation taping sections with automatic taping.
2) INSULATION SECTIONIt is equipped with Small size lathes. Milling and radial drilling machines.
Jet cutting saw.Electrical ovens & Hydraulic presses.Plastic Molding Section.
3) IMPREGNATION SECTION It is equipped with
Impregnation tank.Ovens for impregnation of DC pole coils.
4) Assembly Section It is equipped with small size
Drilling machines.Welding sets.Hydraulic testing equipment for
manufacturing turbo-generator mechanical assemblies.
SIZE OF CONDUCTOR
For Lower Bar CONDUCTOR SIZE
LENGTH NO. OF CONDUCTOR
For Lower Bar 8*4.6*1.5*mm 10200mm 20 (Hollow)
For Lower Bar 8*2.8*mm 10200mm 20 (Solid)
For Upper Bar CONDUCTOR SIZE
LENGTH NO. OF CONDUCTOR
For Upper Bar 8*4.6*1.5*mm 10050mm 20 (Hollow)
For Upper Bar 8*1.3*mm 10050mm 40 (Solid)
NUMBERS OF BAR
TYPES OF BAR
UPPER ORDINARY
UPPER TERMINAL
LOWER ORDINARY
LOWER TERMINAL
TOTAL BARS
NO. OF BUS BAR
600MW THDF
42 6 42 6 96 6
500MW THDF
42 6 42 6 96 6
250MW THRI
48 12 48 12 120 9
COIL & INSULATION OF BAR’S
High voltage insulation is provided with thermosetting system .
A voltage insulation obtained by vaccum press impregnation is particularly void free with excellent electrical, mechanical and thermal properties.
To prevent corona discharge between the insulation and slot wall, a final layer of conductive tape is applied to the surface of all bars with in the slot range.
INSULATION CLASSIFICATION
Class-A Upto-105˚cReinforced Class-Y
materials with impregnated varnish.
Class-B Upto-130˚cInorganic material is
hardened with adhesives.
Class-C >180˚c & <220˚cMade of 100%
inorganic material.
INSULATION CLASSIFICATION
Class-E Upto-120˚cCotton lamination
& paper lamination.
Class-F Upto-150˚c Class-B materials that are upgraded with adhesives.
Class-Y Upto-90˚cCotton, Silk, or
Paper.
Transposition means changing/shifting of position of each conductor in active core (slot) part.
After cutting the required number of conductors. The conductors are arranged on the comb in
staggered manner and then bends are given to the conductors with the help of bending die at required distance.
Then the conductors are taken out from the comb and placed with their ends in a line and transposition is carried out.
TRANSPOSITION
TRANSPOSITION PROCESS
Half Pitch Transposition: In this transposition, the first conductor at one end of the bar because the last conductor at the other end of the bar.
Full Pitch Transposition: In this method of transposition, the first conductor at one end of the bar because the last conductor in the mid of the bar and then again becomes the first 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.
RESIN SYSTEM
Rich Resin or Thermo-reactive insulation system
In this type of insulation system the bond content in resin is 35-37%. The raw materials are ready to use and require preservation and working on temperature 20-25˚c. Its shelf life is one year when kept at a temperature of 20˚c which could be increased when kept at temperature of 5˚c.
Poor Resin or Micalastic insulation system
In this type of insulation the bond content in the resin is 5-7% and insulation material is prepared with accelerator treatment.
The temperature control need is not required. The insulating material is applied on job and then same impregnated (fully dipped) in the resin.
TESTING֎ TAN TEST
This test is carried out to ensure the healthiness of dielectric (Insulation) i.e. dense rare & measured the capacitance loss.
Bar will act as capacitor when it is laid in the stator of the generator.
Schearing Bridge which works on the principal oh wheat-stone bridge is used to find the unknown capacitance of the bar.
For good efficiency, capacitance of the bar should be high but never approach pure capacitance.
֎ TAN TEST
Bar is wrapped with aluminum to make the bar conduction throughout the outer surface of the bar. The two conduction material i.e. the aluminum sheet and the conductors of the bar as two parts of the capacitor and the bar insulation on the act dielectric medium for the capacitor thus as found.
Of angle of deviation to impurity in the insulation is obtained from the formula C4*R4*10˄-4=tanδ
Tan Test
Loss Angle Test Loss Angle Test
H.V. TEST
Each bar is tested momentary at high voltage increased gradully to three times higher than rated voltage.
This test is also known as insulation test because this test is performed to check the insulation of the bar.
For 600 MW the working voltage of the bar is 64.5 KV & for 210 MW the working voltage of the bar is 63 KV.
In this test the bar which is already wrapped with aluminum is used.
H.V. TEST
High voltage is applied to the bar using auto-transformer and it is increased in steps according to the working voltage of the generator. If the insulation is weak the bar will puncture at the place of weaker insulation.
If any of the bar fails this test i.e. bar is punctured at any point then the bar is sent back for re-insulation and the processes are repeated again.
Formulae for H.V Test 1Up=2Un+1 ;Un=21kw for 500MW
600 MW Turbo Generators At a Glance
2 Pole Machine Features
Direct cooling of stator winding with water. Direct hydrogen cooling for rotor. Micalastic insulation system. Spring mounted core housing for effective
transmission of vibrations. Brushless excitation system. Vertical hydrogen coolers.
Ratings of 600MW Generators
Rated output :- 588 MVA , 600MW Terminal voltage :- 21 KV Rated stator current :- 16 KA Rated frequency :- 50 Hz Rated power factor :- 0.85 Lag Efficiency :- 98.55 %
DIMENSION & WEIGHT Stator weight :- 255 Tons Rotor weight :- 68 Tons Stator dimension :- 8.83*4.1*4.02*m Rotor dimension :- 1.15*m & 12.11*m (Dia. &
Len.)
Stator Bar
CONCLUSION
This training has proved to be quite faithful.This gave me , a chance to have an encounter with such heavy machines like turbo generator 500/600MW.The architecture of BHEL the way the various units are linked and the way the working of whole plant controlled , makes the student realize that engineering is not just the structural description but more of planning and management .It has provide an opportunity to learn that optimization of technology used at proper place and time can save a lot of labour.
The training has proved to be immensely helpful as it has helped me to have an exposure of the practical implementation of the theoretical knowledge.
THANK YOU