Reduced model for the thermo-fluid dynamic analysis of a power transformer radiator working in ONAF mode

Garelli, Luciano; Rodriguez, Giselle; Storti, Mario A.; Granata, Daniel; Amadei, Mauro; Rossetti, Marcelo

doi:10.1016/j.applthermaleng.2017.06.098

Cited by 25 publications

(11 citation statements)

References 17 publications

(27 reference statements)

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“…This aim was accomplished. An extension of this work was presented the same year with the goal of analysing the thermal-fluid dynamic behaviour of the radiator working in ONAF mode with vertical blowing of the fans [23]. The results obtained, which were validated with experimental and CFD results, showed that the semi-analytical model they proposed was a useful tool for radiator design processes.…”

Section: Radiator Modellingmentioning

confidence: 83%

Thermal Modelling of Electrical Insulation System in Power Transformers

Santisteban¹,

Delgado²,

Ortiz³

et al. 2018

Simulation and Modelling of Electrical Insulation Weaknesses in Electrical Equipment

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Temperature is one of the limiting factors in the application of power transformers. According to IEC 60076-7 standard, a temperature increase of 6 C doubles the insulation ageing rate, reducing the expected lifetime of the device. Power losses of the transformer behave as a heating source, and the insulating liquids act as a coolant circulating through the windings and dissipating heat. For these reasons, thermal modelling becomes an important fact of transformer design, and both manufacturers and utilities consider it. Different techniques for thermal modelling have been developed and used for determining the hot-spot temperature, which is the highest temperature in the winding, and it is related with the degradation rate of the solid insulation. First models were developed as a first estimation for modelling the hot-spot temperature and the top-oil temperature. These models were based on thermal-electric analogy and are known as dynamic models. Other two different kinds of models are widely used for thermal modelling, known as Computational Fluid Dynamics (CFD) and Thermal Hydraulic Network Models (THNMs). These two techniques determine the temperature and velocity fields in the winding and in the insulating fluid. In this chapter, the different techniques for transformer thermal modelling will be introduced and described.

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Section: Radiator Modellingmentioning

confidence: 83%

Thermal Modelling of Electrical Insulation System in Power Transformers

Santisteban¹,

Delgado²,

Ortiz³

et al. 2018

Simulation and Modelling of Electrical Insulation Weaknesses in Electrical Equipment

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“…Considering the difference between the convective heat transfer coefficient in natural convection and that in forced convection, the average convective heat transfer coefficient on the air side of radiator h airF is selected to characterize the cooling capacity after installing cooling fans. Assuming T 1 fins are working in forced convection and T 2 fins are working in natural convection, the h airF after installing cooling fans can be calculated by the following equation [47][48]:…”

Section: Calculation Methodsmentioning

confidence: 99%

Thermal evaluation optimization analysis for non‐rated load oil‐natural air‐natural transformer with auxiliary cooling equipment

Zhang

Liu

Lin

et al. 2022

IET Generation Trans & Dist

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Obtaining an accurate hot-spot temperature of oil-natural air-natural (ONAN) transformer is important for evaluating its operation status and load capacity. To meet the overload requirement, the cooling fan is usually added to the operating ONAN transformer as the auxiliary cooling equipment. However, the hot-spot temperature evaluation methods in this case lacked discussion currently. To address this issue, an improved hot-spot temperature evaluation method for the ONAN transformer considering the thermal resistance on the air side of radiator was proposed in this paper. Subsequently, the calculation method for the key parameter of the improved method (the convective heat transfer coefficient on the air side of radiator) was conducted. The accuracy and superiority of the improved method compared with the IEEE loading guides were verified by the manufacturer's software. Finally, the maximum steady-state load of the ONAN transformer with cooling fan was achieved by the improved method. The results indicate that for the case of non-rated load, the improved method can provide a more accurate thermal evaluation of ONAN transformer under different cooling modes than the IEEE loading guides. The method proposed in this paper can provide a reference for selecting the cooling fan parameters and formulating the load control strategy of the ONAN transformer.

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“…The semi-analytical reduced model of a power transformer radiator with the aim of analyzing the thermo-fluid dynamic behavior in ONAF mode is proposed in Garelli et al., 1 considering vertical blowing of the fans. In Kim et al., 2 the power transformer radiators conjugate heat transfer and fluid flow are analyzed to investigate the cooling performance.…”

Section: Introductionmentioning

confidence: 99%

Fans arrangement analysis in oil forced air natural cooling method of power transformer radiator

Taghikhani

Afshar

2020

Proceedings of the Institution of Mechanical Engineers, Part A:

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The cooling of radiators in power transformers employing natural oil-air forced method is the purpose of this study. Two modes used for cooling fans, namely vertical and horizontal placement, will be compared as well. Four sets of radiators have been studied in this research, and in each set, 14 fins and three fans with a diameter of half a meter have been used. The fans will be arranged such that three of them will be placed under the radiator (in vertical position) in the first case, while in the second case, they will be located in one side of the radiator (in horizontal position). The results derived from the comparisons indicate the superiority of the horizontal mode in heat transfer against the vertical mode. Furthermore, it is notable that if the internal fan is disconnected, the cooling can be enhanced with the help of some existing points in the vertical mode. The improvement in heat transfer rate can be observed through locating the vertical fans optimally, once compared to the horizontal placement. The lower reliability of the vertical mode can be detected once the side fans are disconnected, while in any cases, the heat transfer superiority is achievable for horizontal mode. That is because, the disconnection of one of the fans, leads to the negligence of the radiators major parts in the vertical mode.

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Reduced model for the thermo-fluid dynamic analysis of a power transformer radiator working in ONAF mode

Cited by 25 publications

References 17 publications

Thermal Modelling of Electrical Insulation System in Power Transformers

Thermal Modelling of Electrical Insulation System in Power Transformers

Thermal evaluation optimization analysis for non‐rated load oil‐natural air‐natural transformer with auxiliary cooling equipment

Fans arrangement analysis in oil forced air natural cooling method of power transformer radiator

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