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Design of the winding–bushing interconnections in large power transformers

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Abstract

The paper presents the improvement in design of the conductor connecting the windings and bushings in oil power transformers. This is a sensitive part of large transformers and there is a need to optimise its manufacturing time and costs. The thermal problem of the heating of this conductor with increased insulation thickness on a part of it is treated using a non-linear two-dimensional thermal model. The experiments performed made determining of some problematic parameters (heat resistance of oil-paper insulation and the paper to oil convection heat transfer coefficient) of the thermal model feasible. The results obtained are of practical interest in the design practice of interconnections, but also affect the important parameters of heat transfer by devices with oil immersed paper insulation.

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Abbreviations

Δx (m):

Length of a finite conductor element (0.1 m)

a×b (m2):

Copper cross-section dimensions (17×22 mm)

δp (m):

Paper insulation thickness

Subscript *:

With normal insulation

Subscript **:

With additional insulation (equivalent value Eq. 14)

δa (m):

Thickness of the additional manually wrapped insulation

ϑO (°C):

Oil temperature

ϑa (°C):

Ambient (air) temperature

qCui (W):

Power losses in the ith finite element

ϑCui (°C):

Conductor temperature of the ith finite element

ϑPi (°C):

Insulation temperature of the ith finite element

RλPi (K W−1):

Thermal resistance of conduction through paper insulation

Rαi (K W−1):

Thermal resistance of convection from the paper’s insulation outer surface to the surrounding oil

RλCu (K W−1):

Thermal resistance of conductive heat transfer through the copper

k s :

Skin and proximity effect coefficient

SCu (m2):

Total conductor cross section (263.25 mm2)

ρCu20 (Ω m):

Specific electrical copper resistance at 20°C (1.7×10−8 Ω m)

αCu20 (°C−1):

Thermal coefficient of resistance (3.9×10−3°C−1)

I (A):

Current

λCu (W m−1 K−1):

Thermal conductivity of copper (401 W m−1 K−1)

αi (W m−2 K−1):

Convection heat transfer coefficient

Spo (m2):

Convection heat transfer surface

Ra:

Rayleigh number

Nu:

Nusselt number

D (m):

Cylinder diameter, i.e. equivalent diameter of the conductor

ϑs (°C):

Cylinder surface temperature

ϑf (°C):

Fluid temperature

g (m s−2):

Gravitational acceleration (9.81 m s−2)

β (K−1):

Oil volumetric thermal expansion coefficient

ν (m s−2):

Oil kinematic viscosity

a (m2 s−1):

Oil thermal diffusivity

λ (W m−1 K−1):

Oil thermal conductivity

Pr:

Oil Prandtl number

ϑpar (°C):

Average surface and oil temperature

λP (W m−1 K−1):

Thermal conductivity of the oil-paper insulation (0.0015 W m−1 K−1)

SP (m2):

Cross section of heat conduction through the paper area

ϑsi (°C):

Temperature measured by the sensor at position i (i=0,1,2,...,28)

ϑ (°C):

Temperature

J (A mm−2):

Current density

ϑac (°C):

Calculated mean winding temperature

ϑam (°C):

Measured mean winding temperature

Δ ϑa (K):

Deviation of calculated from measured mean winding temperature

ϑOa (°C):

Average oil temperature

Δ ϑsi (K):

Difference between calculated and measured temperature values at measuring positions in the insulation

References

  1. Bejan FP (1994) Convective heat transfer, 2nd edn. Wiley, New York

    Google Scholar 

  2. Churchill SW, Chu HS (1975) Correlating equations for laminar and turbulent free convection from a horizontal cylinder. Int J Heat Mass Transfer 18:1049–1053

    Google Scholar 

  3. Morgan VT (1975) The overall convective heat transfer from smooth circular cylinder. Adv Heat Transfer 11:199–264

    Google Scholar 

  4. Gotter G (1954) Erwärmung und Kühlung elektrischer Maschinen. Springer, Berlin Heidelberg New York

    Google Scholar 

  5. Incropera FP, Dewitt DP (1996) Fundamentals of heat and mass transfer, 4th edn. Wiley, New York

    Google Scholar 

  6. IEC (1991) Loading guide for oil immersed transformers, 2nd edn. IEC Standard, Publication 60354

  7. Seip GG (2000) Electrical installations handbook, 4th edn. Publicis MCD Verlag, Erlangen

    Google Scholar 

  8. Schaefer M, Feser K (1999) Thermal monitoring of large power transformers. In: Proceedings of the IEEE power tech 1999 conference, Budapest, paper nr. BPT99-072-30

  9. Pradhan MK, Ramu TS (2003) Prediction of hottest spot temperature (HST) in power and station transformers. IEEE Trans Power Deliv 18:1275–1283

    Google Scholar 

  10. Radakovic Z, Feser K (2003) A new method for the calculation of the hot-spot temperature in power transformers with ONAN cooling. IEEE Trans Power Deliv 18:1284–1292

    Google Scholar 

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Author information

Authors and Affiliations

  1. Siemens AG PTD T TI, Katzwanger Strasse 150, 90461, Nuernberg, Germany

    Z. Radakovic

  2. Institute of Power Transmission and High Voltage Technology (IEH), Pfaffenwaldring 47, 70569, Stuttgart-Vaihingen, Germany

    E. Cardillo & K. Feser

  3. Siemens AG PTD T PN O, Katzwanger Strasse 150, 90461, Nuernberg, Germany

    M. Schaefer

Authors
  1. Z. Radakovic
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  2. E. Cardillo
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  3. M. Schaefer
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  4. K. Feser
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Corresponding author

Correspondence to Z. Radakovic.

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Radakovic, Z., Cardillo, E., Schaefer, M. et al. Design of the winding–bushing interconnections in large power transformers. Electr Eng 88, 183–190 (2006). https://doi.org/10.1007/s00202-004-0275-x

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  • DOI: https://doi.org/10.1007/s00202-004-0275-x

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