TRAINING REPORTON

INSULATION AND MANUFACTURING PROCESS OF 500MW TURBO GENERATOR

BARS

Under the Guidance of Mr. A.K Dhiman

(DGM)BHEL, HARIDWAR

SUBMITTED BY-

Gaurav Panchal (EN-2RD YEAR)

H.C.T.M.TECHNICAL CAMPUS(KAITHAL)

KAITHAL(HARYANA)-136027

ACKNOWLEDGEMENT

An engineer with the theoretical knowledge is not a complete engineer. Practical knowledge is very important to develop and apply engineering skills. It gives me a great pleasure to have an opportunity to acknowledge an to express my gratitude to those who are associated with me during my training at BHEL, Haridwar.

Special thanks to Mr. A.K. Dhiman for providing me with an opportunity to undertraining under his able guidance and offering me a very deep knowledge of practical aspects of industrial work culture...

I express my sincere thanks and gratitude to BHEL authorities for allowing me to undergo the training in this prestigious organization. I will always be indebted to them for their constant interest and excellent guidance in my training work, moreover for providing me with an opportunity to work and gain experience.

GAURAV PANCHAL

H.C.T.M. TECHONICAL CAMPOUS,

KAITHAL(HARYANA)

BHEL- AN OVERVIEW

BHEL is the largest engineering and manufacturing enterprise in India in the energy related / infrastructure sector. BHEL was established more than 55 years ago, ushering in the indigenous Heavy Electrical Equipment industry in India, a dream which has been more than released with a well-recognized track record of performance. It has been earning profits continuously since 1971-72 and achieved a sales turnover of Rs. (check bhel.com for current status) crore.

BHEL caters to core sectors of the India economy viz. Power Generation and Transmission, Renewable Energy, Defense etc. The wide network of BHEL’s 14 manufacturing divisions, 4 power sector regional centers, 8 service centers, 15 regional offices and a large number of Projects sites spread all over India and abroad enables the company to promptly serve its customer and provide them with suitable products, systems and services- efficiently and at competitive prices. 2006.

BHEL has attained ISO 9001 certification for quality management and all the manufacturing units/divisions of BHEL have been upgraded to the latest ISO 9001:2000 version. All the major units/divisions of BHEL have been awarded ISO 14001 certification for Environmental Management System and OHSAS-18001 certification for Occupational Health and Safety management System. BHEL become the first Public Sector Company in the country to win the coveted “PRIZE” for its Haridwar unit under the CII Exim Award for business excellence as per the globally

recognized model of European Foundation for Quality Management. BHEL is the only PSU among the 12 Indian Companies to figure in “Forbes Asia Fabulous 50” list. It has also won the “Business Standard Star Public Sector Company Award 2006”. The company received MoU Excellence Award for 2004-2005 and Merit Certificate for MoU Excellence for 2005-

Power Generation

Power generation Sector comprises Thermal, Gas, Hydrogen Nuclear power plant business. Asof 31.3.2007. BHEL supplied sets accounts for 80,781 MW or nearly 65% of the total install capacity of 1, 25,414 MW in the country. Significantly these sets contribute 73% of the total power generated in the county.

BHEL has proven turnkey capabilities for executing power projects from Concept to Commissioning. It possesses the technology and capability to produce Thermal sets with super critical parameters upto 1000MW unit rating and gas turbine generator sets of upto 300MW units rating. Co-generating and Combined cycle plants have been introduce to achieve higher plant efficiencies. To make efficient use of the high-ash-content coal available in India. BHEL also supplies circulating Fluidized Bed Combustion (CFBC) boilers for Thermal plants.

The company has proven expertise in Plant Performance Improvement through Renovation, Modernization and Uprating of a variety of Power plant equipment, besides specialized know-how of residual life assessment health diagnostics and life extension of plants. Overall, BHEL built Thermal sets achieved the highest ever PLF of 78.3% in 2006-2007 which is 1.5% higher than the National average. The combined operating availability of these sets was 84.7%.

BRIEF SUMMARY OF CIM SHOP (BLOCK – IV)

BAY-1: Bar winding shop: Manufacturing of stator winding bars of generator, Micalastic Tank & Oven

BAY-2: Heavy duty generator stator bars with New CNC M/c No, 3-464 i.e. Roebel bar centre, TIG Welding

BAY-3: Insulation detail shop: Manufacturing of hard insulation & machining of hares insulation part (Glass textolite) such as packing, washer, insulation box, wedges etc. & CNC Taping Machine

Bar Shop: This shop is meant for manufacturing of stator winding coils of generator that may be turbo-generator or hydro-generator.

Why do we call it bar: It is quite difficult (rather impossible) to manufacture, handle and wind the coil in stator slot of generator of higher generation capacity because of its bigger size and heavy weight. That is why we make coil in two parts. One part is Bottom part of coil called bottom or tower bar and other part of coil is called top bar or upper bar.

TURBO-GENERATORS: The manufacturing of bars of standard capacity such as: 100MW, 130MW, 150Mw, 210/235MW, 500MW

No. of Bars in current products:

Set TypeUpper

OrdinaryUpper

Terminal

Lower

Ordinary

Lower Terminal

Total Bars

No of

Bus Bars

500MW THDF

42 6 42 6 96 6

210MW THW

54 6 54 6 120 9

250MW THRI

48 12 48 12 120 9

The plant has capacity and technology to manufacture 660MW, 800MW and 1000MW generators.

MFG. PROCESS FLOW CHART OF 500MW TG STATOR BAR

1. Conductor Draw from Store.

2. Conductor cutting and end cleaning.

3. Transposition of conductor.

4. Assembly of all conductors to be used in stator Bars.

5. Cross over insulation.

6. Consolidation if slot portion of Bar.

7. IS Test (i.e. inter strand

15. Top part brazing with nipple by induction machine (2mm) on ES & TS Side (Connection Socket)

16. Mounting water box leakage test.

17. Internal-pickling (Variant)

18. Number Punching

test).

8. Forming or Bar (to shape overhang portion).

9. 0 Pickling of E/S or T/S ends

10 Mounting of Contact sleeve & bottom part with details.

11. Brazing of Contact sleeve & bottom part by induction machine with brazing alloy (3mm)

12. Milling & Debarring T/S or E/S by M/C

13. 2nd pickling of bar ends E/S or T/S

14. Main brazing leakage test (ES & TS)

according to variant

19. Water flow and N2 test.

20. Thermal Shock Application.

21. Helium Leak Test.

22. Reforming of Bar.(i.e. overhang portion).

23. Insulation of bar on CNC machine.

24. Impregnation & curing of bar insulation.

25. Surface finishing of stator bar.

26. OCP on stator Bar.

27. Preparation of bar for HV and Tan∆ Test.

28. If O.K. Dispatch to Bicck-1 for lying in the generator.

INSULATION CLASSIFICATION:

Thermal classification of insulation depends upon the temperature withstand capability of the insulation.

Class – Y upto 90 C

Class – A upto 105 C

Class – E upto 120 C

Class – B upto 130 C

Class – F upto 155 C

Class – H upto 180 C

Class – C >180 C.

TYPES OF GENERATORS:

The generator may be classified based upon the cooling system used in the generators such as-THRI, TARI, THDI, THDD, THDF, THFF, THW.

T-> First alphabet signifies the type of generator i.e. turbo-generator or Hydro-generator.

H/A-> Second alphabet stands for the coding media used for the cooling of rotor i.e. hydrogen gas or air.

R/D/F/I-> Third alphabet signifies the type of cooling or rotor e.g. radial, indirect, forced, direct etc.

I/D/F-> Last alphabet stands for the type of cooling of stator e.g. indirect cooling, direct cooling, forced cooling.

W-> Cooling media used for cooling of stator coil e.g. water.

Resin system:

a) Rich Resin or Thermo-reactive insulation system: In this type of insulation system the bond content in resin 36-37%. 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 temperature 20 C which could be increased when kept at temperature of 5 C.

b) Poor resin or Micalastic insulation system: In 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 not required. The insulating material is applied on job and then the same is impregnated (fully dipped) in the resin.

MANUFACTURING PROCESS OF BARS:

Some Points of Manufacturing Process are in brief as below:-

1.Conductor Cutting : (Please Visit Preparatory Section)

This process is done by automatic CNC machine. In this process the pre-insulated copper conductor is cut into number of required length. Insulation is removed from both ends of the conductor cut.

Lower Bar:

Conductor size Length Number of conductors

8*4.6*1.5mm(Hollow) 8*2.8 mm (Solid)

10200 mm Hollow- 20 Solid - 20

Upper Bar:

Conductor size Length Number of conductors

8*4.6*1.5mm(Hollow) 8*1.3 mm (Solid)

10050 mm Hollow- 20 Solid - 40

2. Transposition:

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 die and placed with their ends in a line and transposition is carried out. This process is repeated for making another half of the bar which would be mirror image of the first half. The two halves of the bar are overlapped over each other and a spacer is placed between the two -halves.

1. To reduce eddy current losses. 2. 2.Equalize the voltage generator

3. To minimize skin effect of ac current, small cross section of conductor is used and also hollow conductors are used to effect cooling by D.M. water.

3. Crossover Insulation:

The pre insulation of the copper conductor may get damaged due to mechanical bending in die during transposition, hence the insulating spacers are provided at the crossover portion of the conductors. A filler material (insulating putty or molding micanite) is provided along the height of the bar to maintain the rectangular shape and to cover the difference of level of conductors. To eliminate inter turn short at bends during edges wise bending and leveling of bars in slots portion for proper stack pressing.

4. Stack Consolidation:

The core part of the bar stack is pressed in press (closed box) under pressure (varies from product to product) and temperature of 1600 C for a given period. The consolidated stack is withdrawn from the press and the dimensions are checked.

5. Inter Strand Short Test :

The consolidated oar stack is tested for the short between any two conductors in the bar, if found then it has to be rectified. This is done to ensure that no local current is flowing due to short circuit between conductors. (300V A/C supply)

6. Forming:

The straight bar stack is formed as per overhang profile (as per design), the overhang portion is consolidated after forming.

7. Brazing of coil lugs:

For water cooled generator bars, the electrical connection contact and water box for inlet and outlet of water are brazed.

8. Thermal shock test:

26 cycles of hot (800C) and cold (30°C) water are flown through the bar to ensure the thermal expansion and contraction of the joints.

9. Helium leakage test:

After thermal shock test bar is tested for any leakage with the help of helium gas.

10. Insulation:

The bar is insulated with the given number of layers to build the wall thickness of insulation subjected to the generating voltage of the machine.

11. Impregnation and baking:

a) Thermoreactive system: In case of rich resin insulation the bar is pressed in closed box in heated condition and baked under pressure and temperature as per requirement for a given period.

b) Micalastic system: In case of poor resin system the insulated bars are heated under vacuum and the impregnated (dipped) in heated resin so that all the air gaps are filled, layer by layer, with resin. Then extra resin is drained out and bars are heated and baked under pressed condition in closed box fixture.

VPI Micalastic system: The bars already laid in closed fixture and full fixture is impregnated (dipped) in resin and then fixture with box is baked under given temperature for given duration.

VIP Micalstic system: The individual (separate) bar is heated in vacuum and impregnated in resin. Then bar is taken out and pressed in closed box fixture and then baked at given temperature for given duration.

12. Finishing:

The baked and dimensionally correct bars are sanded-off to smooth the edges and the surface is calibrated, if required, for the dimension.

13. Conducting varnish coating:

i) OCP (Outer Corona Protection) coating: The black semi-conducting varnish coating is applied on the bar surface on the core length.

ii) ECP (End Corona Protection) coating : The grey semi-conducting varnish is applied at the bend outside core end of bars in gradient to prevent from discharge and minimize the end corona.

14. Testing:

a) Tan∆ test: This test is carried out to ensure the healthiness of dielectric (Insulation) i.e. dense or rare and measured the capacitance loss.

b) H.V. Test: (High Voltage Test) each bar is tested momentary at high voltage increased gradually to three times higher than rated voltage.

15. Dispatched for Winding:

The bars preserved with polythene sleeves to protect from dust, dirt, oil, rain etc are send to Block-I (Electric Machines Production Block – I, Turbo Generators and Hydro Generators) for winding.

500MW Generator characteristics

Rating 500MW Gen Self Excitation 340V, 4040A

Rating MVA 588MVA Generator Voltage 21KV

Cooling H2 and primary water

H.V. Test Voltage / Duration of test for 500MW stator bars:

Formula for HV test =1.5 Up 1 Up = 2Un+1

Un = working voltage of generator.

Working voltage of 500 mw generator = 21kw

HV testing voltage of 500mw generator = 64.5kw

Maximum Tan∆ limit for 500MW stator bar:-

Tan Delta is measured al 0.2 Un , 0.4 Un,0.6 Un,0.8 Un, 1.0 Un,01.2 Un,1.2 Un, 1.4 Un

The difference of tan delta between two adjacent values should not be more than 1x10-3 up to 1.0Un

i.e. ………..

a) 0.4Un -0.2 Un </ 1x10-3

b) 0.6Un – 0.4 Un </ 1x10-3

c) 0.8Un – 0.6 Un </ 1x10-3

d) 1.0Un – 0.8 Un </ 1x10-3

CONTENT

1.