DRY-OUT EXAMPLES
Water reduction will take several weeks depending on the size and oil volume of the transformer, the volume of water in the cellulose insulation, the operating load temperature. The examples should provide a good indication. The TTAS example gives a Filter cost for water volume removed.
Data recorded allows a detailed understanding of the water migration rates from cellulose at various temperature profiles. Examples show the total water removed over the filtering time, and the water from cellulose migration trends. Both TTA1 and TTP1 have been re-analysed following the water reduction and the improvements detailed.
Analysis and water reduction on a group of seven 40yr old 10 mva transmission transformers at one utility. The summary compares the water from cellulose migration rates at various load temperatures:
TTA S – Summary of seven identical 10 Mva transformers- TTA 1 – 10 mva 3 ph Network transformer over 23 days
- TTA 4 – 10 mva 3 ph Network transformer over 40 days
- TTA 7 – 10 mva 3 ph Network transformer over 52 days
Two 40yr old water cooled generation transformers, with similar design but different oil volumes. Both show the superior water from oil removal performance of the Trojan
- GTC 1 – 13.33 mva single phase, 15,230 litres oil
- GTT 2 – 13.33 mva single phase, 4500 litres oil
Before and after Analysis, 5.25 litres of water was removed from a 40yr old 15 mva transmission transformer with significant improvement.