Thermal modelling of power transformer

Bouhaddiche, Rafik; Bouazabia, S.; Fofana, I.

doi:10.1109/icdl.2017.8124676

Cited by 10 publications

(4 citation statements)

References 4 publications

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“…Table 6 presents the technical data for the modeled transformer [ 40 ]. Based on that, the building of an accurate model of the transformer is very difficult, so some simplifications were considered in this work: Only one winding was considered, and the tank in the model was considered to be a perfect cylinder equivalent to one-third of the real transformer tank [ 41 ]. Moreover, an approximately 10% voltage drop across transformer windings was considered due to the copper resistance of these windings that can slightly change the electric field stress along the winding [ 40 ].…”

Section: Electrostatic Modelling Of Oil-filled Transformermentioning

confidence: 99%

Condition Assessment of Natural Ester–Mineral Oil Mixture Due to Transformer Retrofilling via Sensing Dielectric Properties

Karaman

Mansour

Lehtonen

et al. 2023

Sensors

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Mineral oil (MO) is the most popular insulating liquid that is used as an insulating and cooling medium in electrical power transformers. Indeed, for green energy and environmental protection requirements, many researchers introduced other oil types to study the various characteristics of alternative insulating oils using advanced diagnostic tools. In this regard, natural ester oil (NEO) can be considered an attractive substitute for MO. Although NEO has a high viscosity and high dielectric loss, it presents fire safety and environmental advantages over mineral oil. Therefore, the retrofilling of aged MO with fresh NEO is highly recommended for power transformers from an environmental viewpoint. In this study, two accelerated aging processes were applied to MO for 6 and 12 days to simulate MO in service for 6 and 12 years. Moreover, these aged oils were mixed with 80% and 90% fresh NEO. The dielectric strength, relative permittivity, and dissipation factor were sensed using a LCR meter and oil tester devices for all prepared samples to support the condition assessment performance of the oil mixtures. In addition, the electric field distribution was analyzed for a power transformer using the oil mixtures. Furthermore, the dynamic viscosity was measured for all insulating oil samples at different temperatures. From the obtained results, the sample obtained by mixing 90% natural ester oil with 10% mineral oil aged for 6 days is considered superior and achieves an improvement in dielectric strength and relative permittivity by approximately 43% and 48%, respectively, compared to fresh mineral oil. However, the dissipation factor was increased by approximately 20% but was at an acceptable limit. On the other hand, for the same oil sample, due to the higher molecular weight of the NEO, the viscosities of all mixtures were at a higher level than the mineral oil.

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Section: Electrostatic Modelling Of Oil-filled Transformermentioning

confidence: 99%

Condition Assessment of Natural Ester–Mineral Oil Mixture Due to Transformer Retrofilling via Sensing Dielectric Properties

Karaman

Mansour

Lehtonen

et al. 2023

Sensors

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“…This study is based on the numerical solution of the momentum and continuity equations in laminar regime, (1) and (2), respectively. It also solves the heat transfer equation, (3).…”

Section: A Governing Equationsmentioning

confidence: 99%

“…The symbols ρ, u, p, I, μ, F, C p T and q of (1), (2) and 3are density, velocity vector, pressure, identity matrix, dynamic viscosity, body force vector (buoyancy forces), specific heat capacity, temperature and unitary heat transfer, respectively.…”

Section: A Governing Equationsmentioning

confidence: 99%

“…In fact, according to IEC 60076-7 standard, an increase of 6 ºC doubles the insulation ageing rate, reducing the lifespan of the device, [1]. For this reason, several theoretical and experimental techniques have been traditionally used by manufacturers and customers to determine the oil flow pattern, temperatures distribution and the location and value of the hot-spots in the windings, [2]. Among the former, Computational Fluid Dynamics (CFD) modelling is relatively recent in comparison with other such as Thermal-Hydraulic Network Modelling (THNM).…”

Section: Introductionmentioning

confidence: 99%

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The aging impact on the cooling capacity of a natural ester used in power transformers

Ortiz

Delgado

Fernández

et al. 2018

Applied Thermal Engineering

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In this paper, an experimental and numerical research was conducted to study the aging effect on the cooling performance of a natural ester habitually used in power transformers. A monitored experimental platform has been used to observe the temperature increases with the aging of the ester. Three samples with three aging levels (fresh oil, aged oil and aged oil with paper) were tested at three load levels, C=0.72, C=1 and C=1.3 (9 tests). The two aged samples (6 liters each) were aged in an accelerated way within an oven: 1 week at 150 ºC. Also, some physicochemical properties of the insulation system were determined. In the case of the liquid, viscosity, moisture, acidity, dissipation factor (90ºC) were measured. The degree of polymerization and the moisture were measured in paper samples. A 2D numerical model has been developed with COMSOL Multiphysics to replicate the thermal-hydraulic behavior of the samples in the platform. That is, the idea is to determine the temperature and velocity distributions of the different samples in order to analyze their differences and to compare their cooling capacity. At first sight, the aging affects negatively to the cooling capacity of the new alternative liquid based on natural esters.

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Thermo-magnetic-fluid dynamics analysis of an ONAN distribution transformer cooled with mineral oil and biodegradable esters

Garelli

Rodriguez

Kubiczek

et al. 2021

Thermal Science and Engineering Progress

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Thermal modelling of power transformer

Cited by 10 publications

References 4 publications

Condition Assessment of Natural Ester–Mineral Oil Mixture Due to Transformer Retrofilling via Sensing Dielectric Properties

Condition Assessment of Natural Ester–Mineral Oil Mixture Due to Transformer Retrofilling via Sensing Dielectric Properties

The aging impact on the cooling capacity of a natural ester used in power transformers

Thermo-magnetic-fluid dynamics analysis of an ONAN distribution transformer cooled with mineral oil and biodegradable esters

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