Diagnostics of Transformers Condition by Polarisation Current and Oil Conductivity Measurements

Student: Jools Chih-Chieh Chen

Supervisor: Dr. Tapan Saha

Category: Electrical Engineering Thesis Project

Trouble free transformers play an important role in the electricity industry. Due to the increasing demand for electric energy, it is crucial to ensure that transformers operate efficiently. The condition of insulation materials within the transformer determines its operational reliability. Since increasing numbers of transformers in electrical industries around the world are approaching their design life, condition monitoring of the insulation of transformers has become an ever more important necessity.

Transformer insulation degrades with time especially in the presence of moisture. The degradation of transformer insulation is one of the major causes of transformer breakdown. Condition monitoring can be utilized to attempt predicting the insulation condition and the remaining lifetime of a transformer. One of the non-destructive monitoring methods is the Interfacial Polarization Spectra (IPS) measurement by Polarization and Depolarization Current Measurements, and Recovery (or Return) Voltage Measurement (RVM).

In this thesis, IPS measurement by polarization and depolarization current measurements is used to study both the ageing and non-ageing conditions of transformer paper insulated samples under the effect of different moisture contents. The experimental work of this thesis is mainly based on conditioning samples of paper insulated conductors with 2% and 5% moisture content, ageing them at 95 degrees celsius, and testing both aged and non-aged samples for polarization and depolarization current using IPS measurement. Aged samples for 2%, 4% and 5% moisture content aged for 125 days at 115 degrees Celsius are also tested. Modeling and analysis of the experimental data are presented in this thesis.

Poster Presentation (PDF)

Thesis Document (PDF)

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