Work

Study of Transformer Insulation Life Under Distributed Generation Insertion and Harmonic Distortions: Technical, Economic, and Environmental Assessment

Year: 2026

Type: article

Abstract: This study investigates transformer insulation life (TIL) under distributed generation (DG) insertion and harmonic distortion, particularly photovoltaic (PV) systems, considering technical, economic, and environmental dimensions. While DG can reduce transformer loading, inverter-based generation and nonlinear loads introduce harmonic distortions that modify loss mechanisms and thermal behavior. Unlike conventional approaches that evaluate loading, harmonic effects, and thermal aging separately, this study integrates these aspects by explicitly linking DG penetration levels to harmonic spectra, transformer loss components, thermal response, and insulation degradation. Harmonic losses were evaluated in accordance with IEEE Std C57.110 and combined with thermal-aging models primarily based on IEEE Std C57.91, consistent with IEC 60076-7, to estimate the hot-spot temperature and TIL under non-sinusoidal operating conditions. The analysis was conducted on a representative distribution feeder modeled in OpenDSS and automated in PyCharm using measurement-based load profiles and harmonic data over a 24-hour operating cycle across multiple DG penetration levels. Economic and environmental impacts were incorporated through Net Present Value (NPV) and life-cycle emission analyses associated with transformer losses. The results revealed a non-monotonic relationship between DG penetration and TIL. Moderate DG levels reduced loading and extended TIL, whereas higher penetration levels increased harmonic-related losses and progressively accelerated insulation aging beyond an intermediate DG penetration range. A decomposition-based analysis was used to assess the relative influence of load reduction and harmonic-induced losses. An intermediate range of DG penetration was identified in which the transformer lifetime, life-cycle cost, and emissions were jointly improved.

Source: IEEE Access

DOI: 10.1109/access.2026.3729126

Authors: Fabio de Oliveira Carvalho, Andre Gifalli, Andre Nunes de Souza, Welson Bassi

Institutions: Federal Institute of São Paulo, Universidade de Marília, Universidade Estadual Paulista (Unesp), Universidade de São Paulo

Language: English

Topic: Power Transformer Diagnostics and Insulation

Subfield: Electrical and Electronic Engineering

Field: Engineering

Domain: Physical Sciences

SDGs: Industry, innovation and infrastructure, Affordable and clean energy

Open Access status: gold

Estimated APC paid: $2,075