pgcil engg lecture
Post on 28-Oct-2014
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WEL-COME
TO
POWER GRID OFFICIALS
DESIGN & DEVELOPMENT OF POWER TRANSFOMERS
Presented by-
J.K.JAIN – Sr.DGM(TRE)
Special Characteristic Features of Transformer Designs
• Tailor made designs to suit customer requirements.
• Design Problems – Two fold.
> Associated with high voltages (Dielectric design,
behaviour under transient voltages, PD).
> Associated with high currents (Electromagnetic.
problems related to stray losses and hot spots,
thermal design, mechanical short circuit forces).
• High cost of losses demand low loss designs with high material content (Transport and handling problems), better methods of stray loss control.
• No two designs of same MVA and Voltage rating are comparable in terms of weights and losses owing to different capitalization, Impedance, Tapping range, Limiting current densities, Flux density etc.
Constituents of a Transformer
• Windings
• Core
• Insulation Structure
• Tank
• Cover
• Core clamping Structure
• Pipe Work
• Cooling Equipment
• Bushings
• Leads (Terminal Gear)
• Fittings
• Control Equipments
• Oil
Type of Windings
• SPIRAL WINDING
• HELICAL WINDING
• CONTINUOUS DISC WINDING
• PARTIALLY OR FULLY INTERLEAVED DISC WINDING
• SHIELDED LAYER WINDING
Type of Windings
Spiral winding Helical winding
(No radial duct)
(a) cross-section (b) connections
SINGLE LAYER DISC COIL
INTERLEAVED DISC WINDING
INTERLEAVED DISC WINDING
(4 discs per group)
Transposition
Transposition at each cross-over in
Continuous Disc Winding
Transposition in Spiral/Helical Winding
(a) Complete Transposition
(b) Partial Transposition
Directed Oil Flow Arrangement
WINDING
• USE OF SPECIAL TYPE OF COPPER CONDUCTORS (BUNCHED PICC, GLUED PICC, WORK HARDENED etc.)
• OPTIMUM WINDING PLACEMENT• USE OF GUIDED OIL FLOW AND FORCED
DIRECTED OIL FLOW IN WINDINGS FOR CONTROL OF HOT SPOTS
• USE OF YOKE SHUNT/WALL SHUNTS/FLUX TRAP TO CONTROL STRAY LOSSES
DESIGN TRENDS IN RECENT YEARS
• USE OF INTERLEAVED/PARTIALLY
INTERLEAVED DISC WINDING (LAYER WINDING, IN SPECIFIC CASES)
• OPTIMISATION OF RADIAL CLEARANCES BY STRESS DISTRIBUTION CONCEPT INCLUDING TG & BUSHING CLEARANCES
• OPTIMISATION OF AXIAL CLEARANCES AND USE OF INSULATION MOULDINGS
• REDUCTION IN SOLID PRESS BOARD INSULATION BY SUB-DIVIDED BARRIER ARRANGEMENT
Insulating Area
A: Vertical Area B: Horizontal Area C: Area between A&B
Core Nomenclature
• L= Leg Length• C= Distance
between leg centres
• W=Main leg width
Top Yoke
Bottom YokeAuxiliary
Limb
WA AL
C C
D= Max. core diameter
Section through ‘A-A’
Cooling Duct
D
W
Type of core forms
Single Phase, Core type 2 legs wound
SC
W
WL
Single Phase, core type middle leg wound
SM
W
W/2
W/2
Single Phase, core type 2 middle legs wound
SMC
W W
W/2
W/2
Three Phase, core type
TC
W
W
W W
Three phase, core type, 5 limb
TCF
0.43 W
0.57 W
Inside Yoke Length
W W W
Core ConstructionsA. Three phase- 3 limb core
INTERLEAVED THREE QUARTER MITRED
FULLY MITRED FULLY MITRED SPLIT WITH DIAMOND INSERT
Three phase, five limb coreB: Three phase, five limb core
FULL WIDTH
SPLIT WIDTH
CORE:
USE OF BUTTON SPACERS IN CORE FOR BETTER SPACEFACTOR AND OIL FLOW
USE OF HI-B GRADES OF STEEL FOR REDUCTION OF NO LOADLOSSES
USE OF LASER SCRIBED CORE STEEL FOR FURTHER LOSSREDUCTION
USE OF NON-MAGNETIC STEEL FOR CLAMP PLATE FORHIGHER CAPACITY TRANSFORMER FOR STRAY LOSSCONTROL AND IMPROVED OVERFLUXING CAPABILITY
ELIMINATION OF YOKE BOLTS REDUCED NO. OF PACKETS IN YOKE FOR IMPROVED
PRODUCTIVITY
DESIGN TRENDS IN RECENT YEARS
Radial Short Circuit Stress
Short Circuit Stress in Core Type Transformers with cylindrical windings
Internal sketch of Transformer
PLAN VIEW
ELEVATION VIEW
Types of Transformer Tank
1) Conventional Tank
- Bolted Tank
- Welded Tank
2) Bell Type
Conventional Tank
Tank Cover Turret
Tank Body
Stiffner
Core Clamping structure
ResiglassTape
Clamp Plate
End
Frame
Leakage Flux
Flux entering the tank
Flux enters the Shunt
Clearance between Windings and YokeAngle rings and Caps with Field
Fittings and Accessories• Buchholz Relay• conservator• Breather• Magnetic Oil Level gauge• Winding Temperature Indicator• Oil Temperature Indicator• Fans• Radiators• Pressure relief Device• Thermometer• Oil Preservation System
• Marshalling Box
• Bushings
• Post Insulator
• Current Transformer
• On Load Tap Changer
Oil Preservation System
Breather
Air cell
Typical Outline General Arrangement
A: ELEVATION
B: PLAN
Thanks
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