Use of Alternative Fluids in Very High-Power Transformers: Experimental and Numerical Thermal Studies

Ramazan Altay,Carlos J Renedo,Agustin Santisteban,Cristian Olmo,Alfredo Ortiz Fernandez,Fernando Delgado,Felix Ortiz

doi:10.1109/access.2020.3037672

Ramazan Altay, Carlos J Renedo + Show 5 more

Open Access

https://doi.org/10.1109/access.2020.3037672

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Journal: IEEE Access	Publication Date: Jan 1, 2020
Citations: 24	License type: CC BY 4.0

Affiliation: Universidad de Cantabria, Balıkesir University

Abstract

The very high-power transformer lifespan depends mainly on the temperature that cellulose insulation reaches during its operation. Traditionally, its cooling has been carried out using mineral oil as coolant. Nowadays, alternative ester-based liquids are under study as substitutes due to their better environmental and fire-safety properties. This paper compares the cooling capacity of two ester-based fluids with that of a mineral oil using a 3D numerical model of a 100 MVA low voltage winding of a power transformer with axial cooling system and ONAN cooling mode. Heat-run test results with mineral oil have been used to validate this model. As a first approximation, according to the comparison developed, ester-based fluids could replace mineral oils in this type of transformers when they are going to work in a range of powers close to the rated one.

Highlights

High power transformers (HPT) are one of the most expensive equipment of electricity Transmission Systems (TS)
MODEL VALIDATION The validity of the Computational Fluid Dynamics (CFD) model developed was carried out by comparison of the average temperatures measured by the Fiber Optic Sensors (FOSs) in the test with that obtained in the same position of the model with mineral oil
This way, the CFD model is validated and it will be used to compare the thermal-hydraulic behavior of the mineral oil with those of the ester-based oils

Summary

Introduction

High power transformers (HPT) are one of the most expensive equipment of electricity Transmission Systems (TS). Any proposed improvement of these electrical machines that could affect to these evaluation criteria (cost and reliability) must be deeply tested before their final implementation. These static electrical machines are usually cooled by mineral oil. The replacement of this type of liquid by others with better environmental and fire safety properties is currently being studied. These alternative liquids are ester-based and are produced from harvest products such

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