Mike Dolt Enterprises
Mike Dolt Enterprises
User: wirenut1980, Location: Plainfield, IN
Asked on: Thursday, June 2, 2011 at 11:18 am EDT
Answered on: Tuesday, May 14, 2024 at 6:07 am EDT
Question: Hello! I work for a utility and one of our customers had IR images taken of internal equipment and utility equipment in the area. One image brought to my attention was of a primary (12kV) elbow on a pad mount transformer that is loop fed. The image showed "A" phase elbow at 84.4 degrees F, "B" phase elbow at about 73 degrees F, and "C" phase elbow at about 70 degrees F.Is there some kind of standard or document that speaks to how high is too high for the temperature? Or is it more just about one phase being hotter than the others, indicating a bad connection?Thanks in advance guys and gals!
Temperature Standards IEEE Std C57.12.01-2020, IEEE Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers
Specifies a maximum allowable hotspot temperature of
110°C (230°F) for non-load tap-changer transformers and 120°C (248°F) for load tap-changer transformers. ANSI C84.1-1995, American National Standard for Electric Power Substations
Provides guidance on typical operating temperatures for electrical equipment, including transformers: Normal operating temperature: 35-55°C (95-131°F) Maximum ambient temperature: 40°C (104°F)
Analysis of IR Image Phase Temperature Difference
A significant temperature difference between phases (e.g., >5-10°F) can indicate a poor connection or other fault.
Hottest Phase
The "A" phase elbow in the IR image is significantly hotter than the other two phases, indicating a potential problem.
Possible Causes of High Temperature Loose connections Corrosion Overloading Internal arcing Failed insulationNext Steps Inspect the Elbow
Visually inspect the "A" phase elbow for any signs of damage or loose connections.
Perform Electrical Testing
Perform electrical testing, such as resistance or impedance measurements, to verify the integrity of the connection.
Consider Temperature Monitoring
If the problem persists, consider installing a temperature monitoring device to track the elbow's temperature over time.*
Consult with a Manufacturer or Experienced Engineer
Seek professional advice if the issue cannot be easily resolved.
Conclusion
The temperature of the "A" phase elbow on the pad mount transformer appears to be elevated, indicating a potential issue. While there is no specific standard for maximum operating temperature, a significant temperature difference between phases can be a concern. Further investigation and testing are recommended to determine the cause of the high temperature and ensure the safe operation of the transformer. Flag for review