report on transformers

Bharat Heavy Electricals, Limited Bhopal

A Training report submitted to HRDC, BHEL, BHOPAL (M.P.)

Project report on

Transformers , Capacitor & Bushing

In partial fulfillment of the requirement for the awarded of the degree of

BECHLOR OF ENGINEERING in electrical and electronics engineering

2009-2013

Guided by: Passed by: Submitted by:

Mr. S. PATEL(Sr.Eng.) H.O.D. ABHISHEK SHUKLA

Dept. of FTX division Dept. of E.X. B.E.(EX)

BHEL (BHOPAL) SIRTS, BHOPAL SIRTS, BHOPAL

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Study Report On:

DECLARATION

I ABHISHEK SHUKLA declare that this project

report entitled report on a original piece of work

and submitted by me to words partial fulfillment of

my B.E. (ELECTRICAL ENGNEERNG) graduate

program (industrial training), under the guidance of

Mr. S.PATEL (Sr.Eng.) FTX division BHEL, BHOPAL.

DATE – 11 July 2012

ABHISHEK SHUKLAB.E. (ELECTRICAL ENGG)SIRTS, BHOPALUNIV. - RGPV, BHOPAL (M.P.)

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ACKNOWLEDGEMENT

WE WOULD LIKE TO THANK ALL, WHO’S HELP WAS INEVITABLE IN THE SUCCESSFUL COMPLETION OF THIS REPORT.

FIRST OF ALL, WE WOULD LIKE TO THANK THE HR DEPARTMENT, BHEL, BHOPAL FOR GIVING US THIS OPPORTUNITY. IT DIRECTLY HELPED US TO LEARN RIGHT FROM THE BASICS, AND TO OBSERVE THINGS ACTUALLY HAPPENING.

WE WOULD ALSO LIKE TO THANK MR. ASEEM DHAMEEJA (AGM, CAPACITOR & BUSHING, BLOCK 3); UNDER WHOSE SKILFUL GUIDANCE WE HAVE LEARNED ALL WE COULD. ALSO FOR ALLOCATING US THE DIFFERENT SECTIONS OF BLOCK SO AS TO MAKE US UNDERSTAND THE WHOLE PROCESS.

MR. S. A. DANI (MANAGER, TRM) FOR SCHEDULING OUR STUDY AT THE SHOP FLOOR TO UNDERSTAND THINGS PRACTICALLY.

THE EMPLOYEES ON SHOP FLOOR WHO HELPED US EVERY NOW AND THEN TO UNDERSTAND EVERY BIT OF PROCESS; AND TO ABSORB EVERYTHING.

MR. R. K. PHADNIS(PRODUCTION ENGINEER), MR. RAMJI VERMA (DY. ENGG., INSULATION SHOP, TRM), MR. SUDHIR SHUKLA (ENGINEER, COIL WINDING), MR. P. MAHTO (ENGG., CORE COIL ASSLY., TRM), MR. YASHWANT CHAUHAN (TECH. DEV., TRM), MR. LALIT PATIDAR (BCM) AND MR. R. K. SHARMA (CPM). THEY HAVE BEEN ON THEIR TOES IN MAKING US UNDERSTAND THE HUGE COMPLEXITIES OF THE PROCESS, AND, PATIENTLY ANSWERING EVEN THE STUPIDEST OF OUR QUESTIONS. WE WOULD LIKE TO THANK THEM FROM THE BOTTOM OF OUR HEART AND WISH THEM ALL SUCCESS.

A SPECIAL THANKS TO MR. UTTAM SINGH (COIL CORE ASSLY., TRM).

THANKING BHEL AGAIN FOR SUCH AN OPPORTUNITY.

Abhishek shukla

TABLE OF CONTENTS

SR. NO. SECTION PAGE

CHAPTER 1TRM

01. INTRODUCTION

02. CORE PUNCH

03. INSULATION

04. WINDING

05. COIL AND POWER ASSLY

06. TECHNICAL DIVISION

07. INSTRUMENT

CHAPTER 2 08. BCM

CHAPTER 3 09. CPM

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TCB

Transformer Capacitor Bushing

TRANSFORMERS

Power Transformers upto 420kV class, 50/60 Hz 930 MVA, 3-phase Bank. Power Transformers upto 420kV class, 50/60 Hz 400 MVA, 3-phase Unit. HVDC Converter Transformers and Smoothing Reactors. 500 MVA, ± 500kVDC, 3 winding, 1- Phase. Convertor Transformer.

254 MVAR, 360mH, 1568A, ±500 kVDC 1 –Phase Smoothing Reactor.

INSTRUMENTS TRANSFORMERS

Current transformers up to 400 kV. Capacitor voltage Transformer up to 420 kV.

REACTORS Gapped core Shunt Reactors up to 420 kV class, 125 MVAR 3 Phase Unit. Series and Neutral Grounding Reactors.

Controlled Shunt Reactor up to 420 kV class, 80 MVAR 3 Phase Unit.

Major Consumers of BHEL:

National International

NTPC TNB, Malaysia

PGCIL PPC, Greece

NJPC MEW, Oman

NHPC OCC, Oman

NLC GECOL, Libya

NPCIL Trinidad & Tobago

NEEPCO New Zealand

APTRANSCO Tanzania etc

APGENCO

JPPCL

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ALL State Electricity Boards

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CORE PUNCH

Ferrous M/C AssembledMaterial Comp Core

CRGO Lamination Core To Next Process Preparation Building

B.O. InsulationComponent

In HouseInsul. Comp.

FabricationComponent

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Core Manufacturing Process:

CRGO Imported

Slitting Machine

Cropping Machine

Stacking / Arranging

Setting (Job)

Core Building

Clamping

Lifting

Tapping

Curing

Test (2KV / 10KV)

Shift to Assembly / Tank

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Types of CRGO Silicon Steel UsedCRGO Type Lamination Size Losses (Watts per Kg)

M4 0.27 mm 1.00 W/Kg

MOH 0.27 mm 1.00 W/Kg

ZDKH 90 0.27 mm 0.90 W/Kg

ZDKH 85 0.23 mm 0.85 W/Kg

CRGO Imported from:1) Nippon Steel Corporation, Yawata Works (Japan)2) VIZ-Stal Ltd., Etakerinburg (Russia)3) POSCO

Slitting Machine (Sequence of operation):- Drawing / Q plan- Size / Grade CRGO- Burr Level 20 micron- Steel width within tolerance- Every 500m width check Burr Gauge- Scrap and Buckling

Cropping Machine (Sequence of operation):- Revised drawing / QA Plan checked- Every 100 sheet parameter check

After completion of assembly of core including curing of resin glass tape,10 KV AC test between- Core and End-Frame- Core and Yoke-Bolts- End-Frame and Yoke-Bolts

Current CRGO grades used in various projects:

Core Building Project CRGO Grade Used

BINA Power ZDKH - 85

TATA Mundra MOH

PG Sujalpur MOH

INSULATION SHOP

Materials Used:i. Press Board (1mm – 50mm)ii. Perma Woodiii. Bakelite (2mm – 25mm)iv. Fiber Glass (0.5mm – 4mm)v. Card Sheet / Gasket (for tanking) (3mm – 12.5mm)vi. GUM –Fevicol & Dendroid

List of machines used in Insulation Shop:i. Power Press (T-Block)ii. Crepe Paper Cuttingiii. Embossing m/c iv. Plate Bending m/cv. Cylinder Gumming m/cvi. Scraffing m/cvii. Press Board Impregnation Equipmentviii. Shield Ring Milling m/cix. Guillitone m/cx. RM62 / Drill m/cxi. Lissing m/cxii. Weighing Drill m/cxiii. Bend Saw –Cutting m/cxiv. Angle Hot Pressxv. Circular Sawxvi. Hydraulic Press m/c (300T / 500T)xvii. Pneumatic Platform - 4xviii. Structural Platform – 8xix. Steam Oven – 2xx. Vacuum Drying Vessel – 2xxi. EOT Cranes (50/10 T, 25/5 T)

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COIL WINDING

PICC / CTC Wound Coil

Moulded Comp. Coil To ProcessWinding

B.O. Insul. Component

In HouseInsul. Comp.

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Copper imported from:

Sr. No. M/S From Dimension

01. Precision Wires Ltd. Silvassa 7.00 x 2.05 mm

02. Bhandari Power Lines Pvt. Ltd. Manipal 10.05 x 1.40 mm

03. BPCL Conductors Pvt. Ltd. Mandideep 1.90 x 7.50 mm

04. Sam Dong Co. Ltd. Japan 2.05 x 9.60 mm

05. Chandra Proteco (CP Transco) 2.00 x 4.15 mm

Coil Pre-Heating:- 100 oC (min 95 oC oven temperature)- Duration 3 Hours

Types of Winding:- Disc and Interleaved- Helical, Spiral and Inter-Wound Helical

Copper Conductors:- PICC - Bunched

- Glued

- CTC - Glued

COIL ASSEMBLY AND POWER ASSEMBLY

Wound Coil

Coil Assembled Coil Moulded Comp. Assembly

To Process 4 B.O. Insul Comonent.

In House Insul. Comp.

General Winding Arrangement:TAP LV HV

LV TAP HV

LV HV TAP

Transformer Oil Properties – (Ascoryl / OM 16 / Pyroclor)

- High insulating- Low Viscosity- Low Surface Tension- Optimum Cooling Point- Low Decomposition

Material used: SRBP – Synthetic Resin Best Paper

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TECHNICAL DIVISION(VAPOR PHASE DYING PLANT)

Capacity : 430 KWAutoclave Size : 12500 x 6000 x 6000Max Loading : 450 TonTransformer Rating : 750 MVA, 765 KV

Process:It is a process of proper drying of insulation of transformer by a perfectly

controlled automatic process, with lowest possible paper de-polymerization and energy consumption.

Basic Equipment of Vapor Phase Drying (VPD) plant:

a. Evaporator system.b. Condensation system.c. Autoclave.d. Vacuum system.e. Solvent Pumping system.f. Heating system for evaporator and autoclave.g. Heat recovery system.h. Distillation equipment.i. Special water extraction measuring equipment.j. Computer aided process.

The whole process is carried out in % stages, which is as explained below:

R1: Preparation:In this first stage, the oven is prepared for the process. The job is let

inside the chamber by means of crane. All the instruments and devices are checked for correct operation. The oil filling pipe is placed in position. Thermocouple is attached to the core of the transformer for temperature monitoring; drain plug is connected by steel pipe, etc... Finally, the door is closed and clamped by hydraulic pump.

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H1: Heating Up:The heating process is started after initial preparation. Pressure of

7mBar is maintained within the autoclave. The capacity of solvent tank is 12,000 L and a minimum of 5,000-6,000L is maintained during the process. The heating cycle is of 48-60 Hrs and 2-3 intermediate pressure lowering (IPL) of 1.5-2 Hrs is applied in between.

The job temperature is maintained between 105oC – 125oC.

P1: Fine Pressure Reduction:

V1: Fine Vacuum:When water is obtained at 50mL/hour is obtained for three hours in

three simultaneous reading at 105oC – 125oC temperature and 0.2 Torr pressure, the solvent is closed down through valves.

The job is flooded with oil and it is soaked for a minimum of 12Hrs.

A1: Aeration:The vacuum inside the clave is broken down and air is let inside. Oil

is drained from the job and it is sent to the assembly unit for servicing.

Post servicing, the job is let in for P2 process. This is generally carried out by conventional process only. The ob is heated to 100 +/- 5oC 0.2 torr vacuum pressure. When simultaneous 3 reading of 50mL/hour of water is obtained for 3 hours, the job is sent to Testing department for further process in oil-filled condition.

Transformer Oil Properties – (Ascoryl / OM 16 / Pyroclor)

- High insulating- Low Viscosity- Low Surface Tension- Optimum Cooling Point- Low Decomposition

Advantages of VPD:

01.Fast, uniform heating up of the material to be dried.02.Substantial reduction in the drying cycle of the transformer compared to

conventional process.

Sr. Conventional Process VPD Process

1st Process 12 to 15 days 5 days

2nd Process 07 to 08 days 3 days

03.Little de-polymerization of insulating material.04.Optimum and homogeneous dring quality, since the heating process takes

place in practically air free atmosphere, i.e. NO2.

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Following are the products of Bushing Manufacturing Division:

52KV TO 525 KV OIP condenser Bushings up to 3150 amps. Rating 25 kV, up to 300 amps. Bushing for Indian Railways. Bushing for miscellaneous applications such as bushings, roof

bushings, T.G. bushings etc. To suit customer requirements. SRBP cylinders for transformer application up to 1400 mm I/D, up to

2400 mm long.

Bushing Core Winding

Assembly

Processing

Leakage Test

Testing

Pinking

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Bushing Core Winding:The Core of bushing is hollow copper conductor. It is wrapped up with a

layer of insulation and aluminum foil, alternatively, to form parallel capacitors. This is done so as to reduce the electrical field stress, which would otherwise occur and cause breakdown.

A center terminal is then taken out from aluminum foil for testing purposes (2KV test). This ready core is then treated in oven to remove moisture content for 48 hours at around 100oC. It is then delivered to the Assembly Line for further process.

Assembly:Following materials are generally installed in a complete assembly of

bushing, in order from bottom to top:

Bottom End Nut

Bottom Sealing Plate

Bottom PorcelainO - Ring

FlangeO - Ring

Top PorcelainO - Ring

Top Cap

Top Cover

The top cover consists of pack assembly which accommodated washer / stud. Force is applied by compressor and nut is tightened to hold the complete bushing.

Entire assembly is carried out in five stages, which are explained below:Stage 01: Assembly of bushing in horizontal position

- Top Porcelain.- Core condenser bushing.- Top cap.- Bottom porcelain.- Sealing item.

Stage 02: Assembly of bushing in Vertical position

- Spring pack.- Top cap setting / adjustment.

Stage 03: Vacuum & Impregnation processing

- Quality of oil according to specified parameters.- Impregnation of bushing for specified time / temperature / vacuum.- Moisture in bushing according to specified vacuum / temperature.- Correct filling of oil.- Minimum 12hrs of soaking in plant.- Top-up of oil in case of low oil level.- Minimum 5 days of soaking.- Protection from dust.

Stage 04: Post-Processing Checks

- Mounting in upright position in fixture.- Gauge mounting.- N2 pressure- Stabilization of pressure at specified oil level.- Rectification of oil, if any.

Stage 05: Assembly of extra items according to design for dispatch

- Check Lead / Lead length.

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- Cable thumble.- Terminal stand.- Painting- Checking of oil in bushing in vertical position.

In N2 pressure test, the bushing is filled up with N2 gas at 1.5 Kg/cm2 and kept under observation for 12 hours. If any leakage exists, there’s a fall in the inside pressure, it is then identified and rectified. The bushing is then sent to the processing plant for moisture removal and oil filling.

Bushing Processing Plant:

The processing of bushings is carried out in two forms: Full process and Short process. The Full process is carried out over bushings which come for processing for the first time, and the short process takes place for those bushings which have been already treated once.

For a 420 KV bushing, the typical Full process is:

Oven 100oC /96 hours minimum

Start vacuum 0.005 mBar pressure /48 hours

Temperature 60oC24 hours

Start oil fillingDrop by Drop18 – 20 hours

Stop Heating

Soaking 24 hours

For a 420 KV bushing, the typical short process is:




Stop Heating

Soaking 24 hours

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For 245 KV / 145 KV / 72 KV / 52.5 KV bushing, the typical full process is:

Oven 100oC /72 hours minimum




Stop Heating

Soaking 24 hours

For 245 KV / 145 KV / 72 KV / 52.5 KV bushing, the typical short process is:

Temperature 60oC - 65oC12 hours

Vacuum48 hours


Stop Heating

Soaking 24 hours

Soaking Duration:

Rating Duration

420 KV Bushing 16 Hours minimum



72.5 KV Bushing 04 Hours minimum


Bushing Testing:

Routine and type tests are carried out on bushing according to the requirement and customers demand. A typical routine test observation on 420 KV bushing is shown below. The basic device for testing is Schering Bridge, and the parameters C3 and R3 are measured:

Parameter KV 10 122 255 364 420 364 255 122 10Capacitance C3Tan deltaPartial Discharge (internal)

The applied voltage on bushing is increased from 0-420 KV and reduced to zero again, and readings are taken as shown above. Upon reaching 420 KV, an overvoltage of 630 KV is maintained for a period of one minute and the same parameter readings are taken.

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Following Products are manufactured at the CPM Division:

Sr. No. Product Rating Purpose01. Shunt Capacitors 6.6 KV - 500 KV improvement of power

factor02. Series Capacitors 33 KV - 400 KV reactive compensation

and voltage regulation03. Filter Capacitors up - 500 KV different types of

harmonics filtering (HVDC)

04. Surge Capacitors up - 40 KV protection of generator & transformers

05. CVTs 33 KV - 1200 KV measuring line metering & power line carrier communication

06. Motor Capacitors 3.3 KV - 11 KV improving power factor07. Roof Capacitors 2000 volts dc traction locomotive

Shunt Capacitor banks with all film dielectric impregnated with non PCB Impregnate of desired ratings from 6.6 to 400 kV complete with manual / automatic control equipment for Industrial and power system application.

Pole mounted Capacitors for mounting in line with Rural Electrification scheme up to 11 KV

Roof Capacitor in Traction Motor application: 4 microfarad, 2 KV DC Series capacitors for Reactive compensation and voltage regulation in power

system from 33kV to 400 KV Capacitor to improve power factor of traction substations suitable for Railway

Electrification. Surge Capacitor for protection of Rotating Machine and Generator transformers

winding 15 kV and 40 kV, 0.125 micro farad. AC filter Capacitor for Harmonic filtering suitable for HVDC application up to

500 kV. Coupling capacitors / CVT up to 800 kV class for Power line carrier

communication application, meeting and protection.

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Manufacturing Process of Power Capacitor:

Element Winding

Testing 4.5 KVElement Stack Assembly

Pack Testing Testing at 4 KV

Soldering and Wiring

Boxing

VP Plant

Rack / Dispatch

Major raw materials:

Sr. No. Material Purpose / Dimension

01. Polypropylene film as a dielectric- 9 to 18 microns

02. Aluminum Foil 5 microns

03. PXE (Phenyl Xylyl Ethane) oil as liquid dielectric

04. Bushing -

Capacitor consists of electrode made of 5 microns Aluminum Foil. The dielectric used is of Polypropylene film having thickness 9 microns to 18 microns. Three layer dielectrics are used between two electrodes of 5 microns Al Foil.

All these layers of Polypropylene film and Aluminum Foil are wound on a Semi Automatic winding machine. And then it is pressed to get the capacitor element. This complete process is done in a dust proof air-conditioned winding room.

All the elements are then tested using element-testing machine. If faulty elements are detected then they are at once rejected and are separated from the manufacturing process.

For Power Capacitors, the elements are arranged in an appropriate series or parallel combination, so as to get desired capacitor rating. The arrangement of the elements is called a stack. The stacks are again tested in a pack-testing machine. These stacks are boxed in a steel container of suitable dimensions. This box can be referred as a Capacitor can. The Can is welded and the appropriate terminals are taken out through the bushings.

The box is then impregnated by PXE (Phenyl Xylyl Ethane) oil under fine vacuum and temperature.

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Each unit is then routine tested as per relevant IS/IEC. Once the unit passes in the entire test it is then painted and assembled into a rack. The rack when completed is then dispatched to the customer.

Testing:

Well Equipped Capacitor test & ultra high voltage laboratory to cope up with routine & type test requirements as per latest Indian & International for Power capacitor & coupling capacitor.

ROUTINE TEST as per IS 13925 (1998)Sr. TEST PROCEDURE

1. Measurement of Capacitance.

Capacitance is measured at rated voltage.

2. Capacitor Loss tangent measurement at rated voltage.

Capacitor Loss tangent is measured after 48 hrs of stabilization or at the end of Thermal Stability Test.

3. Voltage test between terminals.

4 times the rated voltage in DC is applied between the terminal for 10 sec.

4. Ac test terminals and container.

An Ac Voltage depending on the BIL level of the unit is applied between shorted terminals and container for 10 sec. this is applied only for units having all terminals insulated.

5. Test of Discharge device.

Discharge resistance shall be measured. The DR shall be suitable discharge to less than 50 volts from an initial peak voltage of sqrt of 2 times the rated voltage after disconnecting from supply. The maximum discharge time shall be 10 min.

6. Sealing test A sealing test shall be carried out to demonstrate that the impregnate does not leak from the capacitor. The test shall be carried out at 80`c for a period of 4 hours after attaining container temperature of 80`c.

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TYPE TESTS as per IS 13925(1998)Sr. TEST PROCEDURE

1. Thermal Stability Test a. Capacitor units are placed inside the oven having 55+- 2`c.

b. An AC voltage equal to 1.2 Un is applied for 48 hrs.

c. Te value of tan delta measured during last 10 hrs shall not increase by 1x 10-4 Capacitance is measured at rated voltage.

2. Capacitor loss tangent measurement at elevated temperature

Capacitor Loss tangent is measured after 48 hrs of stabilization or at the end of thermal stability test.

3. Ac test terminals and container.

An Ac Voltage depending on the BIL level of the unit is applied between shorted terminals and container for 1 min. this is applied only for units having all terminals insulated.

4. Lighting impulse voltage test between shorted terminals and container.

An Impulse Voltage depending on the BIL level of the unit is applied between shorted terminals and container. this test is applicable only for units having all terminals insulated.

5. Shorted Circuit Discharge Test.

a. 2.5 times the rated voltage in DC is applied between the terminals & then discharged through a gap situated as close as possible to the capacitor. The unit shall be subjected to give 5 such discharge within 10 min.

b. Within 5 min after this test, the unit shall be subjected to 4.3 times the rated voltage between terminals for 10 sec.

THANK YOU

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report on transformers

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