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DEVELOPMENT OF A PROGRAM FOR THE DETERMINATION OF THE TEMPERATURE AT TRANSFORMERS COPPER BUS BARS BY CALCULATING THEIR DIMENSIONLESS NUMBERS

Wilerson Calil ; ABB Ltda
Vinicius Rubio ; ABB Ltda
Jorge Inhasz ; ABB Ltda

Sažetak

The present technical study aims to demonstrate how to make the determination of the
temperature at Transformers Copper Bus Bars by calculating their dimensionless numbers its will explain
about the development of a thermal software that represents a viable and cost-effective to dimensioning
the transformers Bus Bars due the temperature rise generate by the current. In this environment, the
program is basically a virtual lab where is only necessary the cost of specialized engineering analysis and
the critical time analysis.
This program allows to be done a large number of tests with different types of Bus Bars and
different positions of this Bus Bars with the main objective of loss and temperature reduction, material and
final cost of the equipment it can also be used to avoid a possible re-work, non-acceptance or disapproval
in heating tests, improving the overall performance of the equipment.
To find the temperature at the Bus Bar was necessary to calculate the losses at the Bus Bars and
the dimensionless numbers of Prandtl which is the ratio of momentum diffusivity (kinematic viscosity) to
thermal diffusivity, Grashof which is a dimensionless number in fluid dynamics and heat transfer which
approximates the ratio of the buoyancy to viscous force acting on a fluid, Rayleigh which is associated
with buoyancy driven flow (also known as free convection or natural convection) and is the product of the
Grashof number and the Prandtl number also and finally Nusselt which is the ratio of convective to
conductive heat transfer across (normal to) the boundary. The conductive component is measured under
the same conditions as the heat convection but with a (hypothetically) stagnant (or motionless) fluid. All
dimensionless numbers were considered for natural convection.
To do this calculation an analytical program using Visual Basic at MSExcel was created. To find
this temperature some variables are dependent. In that case, this variables need to be fixed after the first
temperature found at copper Bus Bars. Some iterations must be done using the program starting from
this first temperature to find the correct final temperature.
After this procedure is possible to determinate the temperature considering the paper layer of the
copper Bus Bars when it exists.
The measured results show the reliability of the proposed model by calculating the dimensionless
numbers for the determination of the temperature at Transformers copper Bus Bars.

Ključne riječi

Losses; Prandtl; Nusselt; Rayleigh; Temperature; Program

Hrčak ID:

199032

URI

https://hrcak.srce.hr/199032

Datum izdavanja:

15.7.2017.

Posjeta: 633 *