Dissolved Gas Analysis of Transformer Oil Due to Thermal Effect

Abstract

The ageing or chemical decomposition of transformer oil and silicon oil occurs due to thermal effect is shown in this thesis. Since the transformer plays a key role in transmission and distribution in electrical network of power system. Transformers are subjected to thermal and electrical stresses during its huge time span of its operation which causes degradation of transformer oil. This degraded transformer oil leads to faults of the transformer. So, the health of the transformer oil should be monitored. The degradation of the transformer oil and silicon oil are detected by the renowned methods such as Ultra Violet (UV) Spectroscopy, Breakdown Voltage Test and Refractive Index Test. The UV spectral responses have great capability to analyse the oil quantitatively and qualitatively. The values of Breakdown Voltage (BDV) determine the dielectric strength of the oils, so BDV test is the standard test of oils. Refractive Index (RI) test shows that aged transformer has the higher values of RI. So, these three methods has great capability to determine the types of faults occurred on transformer and to determine the health conditions of the oils.