Performance analysis of natural, synthetic and mineral oil in a 100 MVA power transformer

R Altay,A Santisteban,Carlos J Renedo,A.Kerem Koseoglu,C Olmo,F Delgado,A Ortiz

doi:10.1109/icd46958.2020.9341919

Abstract

The power transformer lifespan depends on the dielectric capacity of its insulation system, mainly of the paper. Integrity of this material depends significantly on the cooling capacity of the oil used to cool it. Currently, ester-based fluids are being researched with the intention to substitute the traditional cooling liquid in power transformers, the mineral oil. Here, cooling capacity of two different ester-based fluids, a synthetic and anatural esters, is compared with that of a mineral oil. To carry out this task, CFD results of a low voltage winding of a 100 MVA power transformer jointly with the experimental ones get from a heat-run test done in this transformer are used. This winding has an axial cooling system in ON regime. As a result of this study, it can be inferred that alternative liquids could be used with high load levels (rated power or higher) since no significant changes in the temperatures distribution of the winding cooled with these fluids in comparison with that get with mineral oil are appreciated.

Highlights

High power transformers are one of the most expensive equipments of the Transmission Systems (TS)
A temperature-rise test has been carried out according [7] to get the temperatures inside the Low Voltage Windig (LVW) of a phase of a three-phase power transformer (100 MVA, 170/36 kV, ONAN/ONAF)
Short-circuit method was used to determine whether the coolant and winding temperatures were in accordance with the specifications of the standard when the total losses are supplied

Summary

Introduction

High power transformers are one of the most expensive equipments of the Transmission Systems (TS). The reliability of these systems depends importantly on these equipment’s working correctly. Any improvement applied to these machines must be very tested before their final implementation. The transformer fleets of the TS use habitually mineral oil as a coolant due to its proven reliability from the dielectric and cooling standpoint, [1]. The replacement of this type of liquid by others with better environmental and fire safety properties is currently being studied. Several studies can be found in the scientific literature analyzing different aspects of these new dielectric ester-based liquids. Dielectric behavior of these fluids has been studied, [2], [3]

Methods

Results

Conclusion