DOI: https://doi.org/10.61435/ijred.2025.60959

An electro-thermal modeling of distribution transformer for hottest spot evaluation under photovoltaic-induced harmonics

1Centre of Electrical Energy Systems, Institute of Future Energy, Universiti Teknologi Malaysia, Skudai, Malaysia

2Faculty of Electrical Engineering, Universiti Teknologi Malaysia, Skudai, Malaysia

3Electrical Engineering Branch, Public Works Departments of Malaysia, Kuala Lumpur, Malaysia

4 School of Engineering and Computing, Mila University, Nilai, Malaysia

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Received: 24 Dec 2024; Revised: 27 Feb 2025; Accepted: 18 Mar 2025; Available online: 25 Mar 2025; Published: 1 May 2025.
Editor(s): H Hadiyanto
Open Access Copyright (c) 2025 The Author(s). Published by Centre of Biomass and Renewable Energy (CBIORE)
Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

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Abstract
Elevated winding insulation temperature, driven by harmonic distortions, is a key factor in transformer lifespan reduction. Conventional models often oversimplify the effect of combined current and voltage harmonics. This paper proposes an electro-thermal modeling approach, incorporating dual heat sources from core and winding domains, to enhance HST estimation in distribution transformers affected by photovoltaic-induced (PV)-induced harmonic losses. A sophisticated numerical approach, Finite Element Analysis (FEA), is employed using COMSOL Multiphysics software, with a 250-minute time-dependent study assessing thermal effects. The results, verified against a mathematical model approach based on IEEE C57.110-2018 guidance, demonstrate that higher levels of harmonics lead to a rapid increase in HST, accelerating the time to reach the aging factor temperature and consequently diminishing the transformer’s operational lifespan. Specifically, the per-unit life of the transformer decreases from 0.219 in Case 1 to 0.154 in Case 2 and 0.027 in Case 3, while the aging acceleration factor increases from 4.310 to 5.683 and 21.7, respectively. The methods showed over 95% alignment with the mathematical modeling approach, confirming the model’s precision in its predictive capability. The novelty of this study lies in its enhanced electro-thermal framework, which overcomes the limitations of conventional methods by integrating dual heat sources and providing a refined assessment of transformer aging under harmonic distortions. This advancement offers a more precise and computationally efficient approach for assessing transformer thermal stress under harmonic distortions.
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Keywords: Distribution transformer; harmonics; hotspot temperature; photovoltaic systems; winding insulation

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Section: Original Research Article
Language : EN
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