Condition Monitoring of Power Transformer Insulation by Return Voltage Measurement

Due to ageing, insulation of the power transformers degrade. Ageing occurs mainly due to moisture content and oxygen in the oil-paper insulation of the power transformer. The ageing process causes an increase in the dissipation factor. To evaluate the service life of an in-situ transformer, condition monitoring of the insulation is essential. Researchers recently developed new techniques for condition assessment of power transformers' insulation based on dielectric response measurement. However, the instruments used for those techniques are costly. In the present work, the return voltage measurement technique is used to estimate the high voltage insulation degradation; the data was obtained using a low-cost instrument. This paper reports the relationship between the initial rate of rising of RVM with variation in operational age and dielectric loss.