Infrared thermography, Standards and Set Limits for Power Transformer and HV Switchgears.

Hi All,

I have been doing thermography for a while now and on substations to be particular, last year, I carried out one, and on looking at the final verdicts I gave on some of the switchgears, I believe I may have gone for higher severity levels during analysis than is necessary but this was based on the following standards/ guidance I could get at the time:

1. Thermographic analysis is in accordance with IEEE Std 242-2001Tm - IEEE Recommended Practice
for Protection and Coordination of Industrial and Commercial Power Systems (Buff Book)
regulation 16.11.3.2, NFPA 70B regulation 11.17.5.6 & ATS table 100.18.
2. Even though BS 7671 does not recognize thermographic surveying equipment as a test instrument,
it’s importance is elaborated in IET Guidance Note 3 – Inspection & Testing updated to BS
7671:2018+A2:2022 Page 144.
3. It was observed that the Transformers within the compact stations were operating at high
temperatures between 63 - 70°C while they were rated for optimum operation at 40°C at a system
loading of over 60%, at the same system loading, the power transformers were operating at
temperatures of 44-45°C.

could someone point me to some guidance codes or standards on how to go about doing analysis on HV, it's a little easy and straight forward on LV systems but not so where transformers are involved, thanks in advance.

Parents
  • Hi Owaga

    My understanding is that there are no specific guidelines other than comparative severity. I however would be more concerned as to the method of measurement, taking into consideration for example, convection and distance.

    Regards

    Rod 

  • Actually found the IEEE C57.152-2013 clause 7.3.5 helpful, I was more concerned on the analysis of the measurement, convention and distance is something that is taken care depending on the settings and type of equipment you are using, of course there are other factors to take care of, including field of view, focus, emissivity settings and all.

    My main concern was on the analysis of power transformer readings, and in addition to the severity levels indicated in that guidance, I think for oil transformers WTI/ OTI set points should be part of the consideration while undertaking the analysis, for example if a transformer is an ONAF, then their is a set point for the start of the radiator fans, before this temperature setting is reached then it would be difficult to put this in category of moderate/severe even if the temperature difference above the ambient temperature is within this categories.

    For HV switchgear it is straight forward and using the table on above standard seemed to make sense to me.

Reply
  • Actually found the IEEE C57.152-2013 clause 7.3.5 helpful, I was more concerned on the analysis of the measurement, convention and distance is something that is taken care depending on the settings and type of equipment you are using, of course there are other factors to take care of, including field of view, focus, emissivity settings and all.

    My main concern was on the analysis of power transformer readings, and in addition to the severity levels indicated in that guidance, I think for oil transformers WTI/ OTI set points should be part of the consideration while undertaking the analysis, for example if a transformer is an ONAF, then their is a set point for the start of the radiator fans, before this temperature setting is reached then it would be difficult to put this in category of moderate/severe even if the temperature difference above the ambient temperature is within this categories.

    For HV switchgear it is straight forward and using the table on above standard seemed to make sense to me.

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