Temperature rise in Power Transformer

[atheistrical]

The following transformer gets overheated and I was looking for most probable the causes associated with it.

1. Rating : 7.5 MVA, 0.85 power factor, Power Transformer (Manufacturer - Kirloskar)
2. Connected Load : Upto 6 MW
3. Oil Natural Cooling System
4. Normal Atmospheric Temperature : 25 C
5. Clauses : The transformer performs well most of the times and at peak load that occurs mostly at 0600 hrs and 1800-2100 hrs. However, on a hot day the temperature of the transformer exceeds the permissible limits. The reading are as follows: Oil Temperature : 50 C, Winding Temperature : 73 C. The connected load at this time was noted to be upto 4 MW and the atmospheric temperature was noted to be about 30 C. This should, practically, never cause the transformer to overheat.
6. Observation : The transformer's vent-pipe seemed to be missing, or perhaps this transformer never used one. Also, this is a pretty new transformer, installed in 2001.
7. My assessment : I thought that the dielectric strength of the oil has deteriorated and/or sludge formation within the tank has occurred. I am planning to filter the oil in the tank.

What are your recommendations/feedback?

 

[russ_watters]

This is too expensive of a problem to trust to a message board. Hire an engineer to evaluate the transformer. He'll want to physically examine the transformer and read the submittal information.

 

[oswaler]

Based on the information provided, it seems that the most probable cause of the temperature rise in the power transformer is the lack of proper ventilation. The missing or non-functioning vent-pipe could be preventing the heat from escaping the transformer, leading to overheating. This is especially concerning since the transformer is operating at a high load during peak hours and in hot weather conditions.

I would recommend checking the dielectric strength of the oil and conducting a thorough inspection of the transformer to ensure there is no sludge formation or other issues. Additionally, installing a vent-pipe or ensuring that the existing one is functioning properly is crucial to prevent future overheating.

It is also important to regularly monitor and maintain the transformer to prevent any potential issues. This includes regular oil filtration and ensuring proper ventilation. I would also suggest consulting with the manufacturer, Kirloskar, for any specific recommendations or guidelines for maintaining their transformers.

Overall, it is important to address the issue of overheating as it can lead to further damage and potential power outages. Taking proactive measures such as regular maintenance and proper ventilation can help prevent such issues in the future.