What question did this study set out to answer?

The aim is to assess the insulation resistance of low voltage distribution transformers and predict their remaining life.

June 19, 2026

Data-Driven Condition Assessment and Remaining Life Prediction of Low-Voltage Distribution Transformers Using Insulation Resistance Measurements: A Case Study of Ajayi Crowther University Distribution Network

JAJohnson Gbadebo AdenleAjayi Crowther University OAOpakunle James Akinpelu OOOluwole Oladele ObanisolaAjayi Crowther University

Key Points

The aim is to assess the insulation resistance of low voltage distribution transformers and predict their remaining life.
Conducted insulation resistance measurements using a Megger MIT1025 tester.
Tested four distribution transformers in three configurations: Line-to-Earth, Neutral-to-Earth, and Line-to-Neutral.
Used statistical analysis to evaluate results, corrected to a standard temperature of 20°C.
Overall mean corrected insulation resistance was 137.5 MΩ with a standard deviation of 21.46 MΩ.
Transformers T1, T3, and T4 showed healthy insulation with values between 100 to 160 MΩ.
Transformer T2 failed the L-N test with a corrected IR of 90 MΩ, requiring immediate maintenance.

Abstract

This paper presents a comprehensive insulation resistance (IR) assessment of low voltage distribution transformers at Ajayi Crowther University (ACU), Oyo, Nigeria. The study evaluates the safety, reliability, and operational efficiency of four distribution transformers (three 500 kVA units and one 750 kVA unit) through systematic IR testing using a Megger MIT1025 insulation tester. Testing was conducted in three configurations: Line-to-Earth (L-E), Neutral-to-Earth (N-E), and Line-to-Neutral (L-N), with results corrected to a standard temperature of 20°C and benchmarked against IEEE standards. Statistical analysis revealed an overall mean corrected IR of 137.5 MΩ with a standard deviation of 21.46 MΩ. Three transformers (T1, T3, and T4) demonstrated healthy insulation with corrected IR values ranging from 100 to 160 MΩ. However, transformer T2 exhibited localized insulation degradation, failing the L-N test with a corrected IR of 90 MΩ, below the IEEE minimum threshold of 100 MΩ. The findings indicate that while the university's electrical distribution system is largely in satisfactory condition, immediate corrective maintenance is required for T2.

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