Open Access

Bushings are one of the most important components of electrical equipment such as power transformers, reactors, capacitors. Most of the installed bushings have Oil-Immersed Paper (OIP) insulation structure. Bushing failure is caused by various reasons such as poor manufacturing process, overloading and also poor installation process, but moisture ingress is one of the main reasons of OIP bushing defect during its operation. In this paper, the electric field distribution of OIP bushings in multiple situations are simulated and effects of moisture distribution are analyzed. The simulations are stablished in polluted and clean surfaces of the studied bushing and done by COMSOL Multiphysics Software. The results show that non-uniform moisture distribution has a significant effect on electric fields of OIP insulation. This effect strongly increases with increasing the pollution on the external insulator of the bushing. © 2025, Iran University of Science and Technology. All rights reserved.

Bushings are one of the most important and essential equipment of power transformers. Statistics show that one of the main causes of transformer failures is due to bushing problems. One of the main reasons for bushing failures is the penetration of moisture into its internal insulation system. The moisture affects the dielectric properties and leads to an increase in its leakage current. These effects lead to changes in the electric field of the inner insulating layers of the bushings, so it is necessary to investigate these effects. In this paper, the changes of the electric field in the insulating layers of a sample bushing have been investigated with considering the different moisture distribution between the layers. This evaluation has been done during the moisture diffusion time, from the start of penetration to the time of uniformity of moisture in all layers. Also, the moisture effects on the bushing leakage current under above conditions have been studied. For this purpose, an OIP bushing is modeled in COMSOL Multiphysics software and the simulations are carried out based on Finite Element Method (FEM) and finally the obtained results are analyzed. The results show that the moisture distribution in the bushing can have an important effect on the internal electric fields. Also, according to the results, the moisture distribution inside the bushing does not have a great effect on the leakage current and this current is only affected by the volume of the moisture penetrated inside the bushing.

The transformer industry faces critical challenges, such as maintaining reliable production while meeting rising sustainability requirements. This paper introduces a significant advancement in the design and optimization of a transformer dedicated to a photovoltaic power plant, which exhibits a unique loading cycle distinct from standard power and distribution transformers. The main aim is to minimize the carbon footprint by enhancing the design process to improve operational performance, efficiency, and functional reliability. Such upgrades are essential for transitioning to a zero-emission electricity system and developing green energy projects. In this paper, a transformer has been studied using a combination of electrical design and 3D finite element method simulation to evaluate various design parameters. An optimization study has been conducted using an innovative multi-objective genetic algorithm utilizing a cost function that factors in size and material costs to identify the most efficient and cost-effective design solutions. The proposed design method was then validated through thermal model simulations and experimental tests based on the photovoltaic load cycle. A comparison of critical thermal parameters directly affecting the transformer’s lifetime and reliability was also drawn. The results were consistent with the expected outcomes, confirming the effectiveness and reliability of the proposed design methodology.