thermal management of transformers

Transformer Technology Symposium 2016

Dr S Shamasundar

ProSIM R&D Pvt Ltd

Thermal Management of Transformers

Thermal & Flow Analysis


Design Tool

Design Verification, Analysis and Optimisation

Virtual Prototyping and

Testing

Inputs

Inputs

OK

NO

Design

OK

Release control mfg drawings

A framework of integrated software for Transformer Design and Optimisation

Physical Prototype

Physical Test and Type Approval

OK

Fine Tune??

NO


Inputs

Design Requirements / Specifications

Material

DESIGN TOOL Formulae

Transformer design

calculations

Assumptions

Output

Geometry

Mass Ratios, BOM, design

details

A customised design tool can be developed. ProSIM has network who can such design automation tools for Power and transmission transformer design.


Design Verification and Optimisation tool

Inputs - All design details - Geometry of core,

tank, cooling circuit, joinery, etc

- Input / output current / voltage

- Material of core, and mechanical structures

- Connection details

Outputs Stray Loss Short circuit forces Impulse distribution Tank stresses No Load losses Load Losses Impedance Temperature rise Mode shapes / Vibration Stresses / pressure

JMAG software will take the design inputs and analyse the entire transformer.

JMAG is also used as a virtual prototyping and virtual testing tool.


Design Calculations

• Geometry

• Winding details

• Materials

• Circuit details

• Performance estimate

EMAG

• Losses

• Magnetic Flux

• Current Density

• Temp Rise due to loss

Thermal

• Conduction

• Convection

• Steady State

• Transient Thermal

Mechanical • Vibration

• Noise

• Stress, Pressure

Other Studies

• Transportation

• Seismic

• Failure Analysis

• Life Assessment

Abaqus


Thermal Management

• Standard rating and overload capacity

• Temperature Rise and efficiency

• Transformer Life

• Overload Capacity

• Confined spaces

• Designing Transformers for Low Temperature Rise


Efficient Transformers =

Lower Temp Rise

Source of Heat


Transformer Thermal Management

Mitigation of Losses –

Enhancement of Cooling


Types of cooling techniques

Air Natural / Self Air Cooled Transformer Shell type.

Oil Natural Air Natural.

Oil Natural Air Forced.

Oil Forced Water Forced.

Note: Images are taken from Open source


• Used in small transformers (up to 3 MVA).

• Transformer cooling by natural air convection

• No external cooling is used.

Air Natural Cooling

Note: Images are taken from Open source


• Oil immersed transformers.

• Heat generated in the core and winding is transferred to the oil.

• Used for transformers up to about 30MVA.

Oil Natural Air Natural.

References: http://www.google.com/ electricaleasy.com


• The heat dissipation can be improved further by applying forced air on the dissipating surface.

• This transformer cooling method is generally used for large transformers up to about 60 MVA.

Oil Natural Air Forced



• Oil is circulated by a pump.

• The oil circulation is forced through the heat exchangers.

• This type of cooling is provided for higher

Oil Forced Water Forced


.


What Codes Say

• Standards / Codes such as IEC 354 (loading guide for oil immersed transformers)

• IEEE C57.91

• IEEE 1538 guide for determination of maximum temperature rise in liquid filled transformers etc…


Relationship Between Physical Phenomena and Analysis Models


Hot spot Temperature identification

Temperature distribution in tank

Temperature distribution in core

Temperature distribution in Core


Velocity and temperature distribution in disc windings


Case study 2: Hot Spot Temperature Analysis in Transformers

Objective: To investigate Solenoid-type windings transformer from simulation of a 3 phases 10 MVA transformer.

Design parameters of the transformer The primary and secondary windings have 16 layers and each layer 45 turns. The main parameters of the transformer are: Rating:10MVA, Voltage: 63/20 kV, Current: 90/290A, Frequency: 50 Hz, Phase: three-phase

Magnetic field distribution in typical transformer

Thermal field distribution in typical transformer

References: “Hot Spot Temperature Analysis in 3 Phase Transformers Using FEM Method”, ISSN: 2249-6645, Vol.1, Issue.2, pp-425-429, Published at International Journal of Modern Engineering Research (IJMER)


Case study 3: Distribution Transformer Cooling System Improvement

Objective: To evaluate the proper cooling for the existed design of electrical transformer (160KVA).

Electrical transformer active part and typical transformer oil tank

The transformer active part thermal distribution Active part contours used for the visualization of the temperature distribution results

References: “Distribution Transformer Cooling System Improvement by Innovative Tank Panel Geometries”, Vol. 19, No. 3, Published by IEEE Transactions on Dielectrics and Electrical Insulation in June 2012


Case study 5: Temperature distribution in geometry

Velocity distribution of oil in the transformer by FEA

Objective : To study the velocity distribution of oil flowing inside the transformer.

The FE analysis is carried out by considering the partial section of electrical transformer and analyze the velocity distribution at each point in that section. This velocity distribution will help to know the temperature carrying capability of that oil at each point.



Dr S Shamasundar

ProSIM R&D Pvt Ltd

Vibration & Stress Analysis of Transformers


Sources of Vibration

• Winding Vibrations

• Core Vibrations

– Forces for excitation are • Magnetostriction

• Electro-magnetic force

• Lorentz force


Possible domain structures, showing large magnetostatic energy associated with isolated domain (a), and successively lower energies associated with (b), (c) and (d). The last represents the kind of domain structure actually observed. In (c) and (d) the 90 degrees Bloch Walls are clearly visible at the top and bottom.

Magneto-Acoustic Emission (MAE)


THANK YOU