ANALYSIS EXAMPLES
Online Analysis – water in cellulose diagnosis
Before water is removed from the transformer, analyse online using either the portable Analysis System or the Dry-Out System. The water in oil / temperature Sensor records the water activity in the oil over the temperature load cycle. Temperature, relative saturation and water in oil ppm are recorded. This allows us to accurately diagnose the water in cellulose content, and creates an accurate starting point.
The Technical Centre provides a section on measuring the water in old oxidised oils. It provides clear evidence that the Sensor only reads only the dissolved water in both new and oxidised oils. New oil Equilibrium Charts can be used.
We analyse and remove water from a lot of transformers and find that the best approach is to keep the analytical process consistent. Simply analyse the water activity online with a relative saturation Sensor with new oil ppm settings, and use a proven new oil equilibrium chart to calculate the water in cellulose. There is no need for extended oil sampling to measure solubility, or equilibrium software with fuzzy logic. The Altmann / Bukvis chart for download below was created using a sensor in both new and used oils.
Equilibrium charts
Altmann / Bukvis (2003) – Sensor accurate 
Oommen (1984) – closest to Altmann / Bukvis
Trojan Analysis Examples
Example 1
15 Mva 3 ph transmission transformer analysed over 17 days to record the water activity prior to water removal. Two methods of calculating the water in cellulose are used to provide a quick cross check. An overlay of the oil dielectric profile based on relative saturation is provided.
Example 2
20 Mva, 3 ph transmission transformer was analysed over a 7 day period. Two methods are explored to calculate the water in cellulose from the Analysis data. 1 – the total data averaged, and 2 – the peak temperatures on each day.