Permissible Winding and Oil Temperature Indicator values
Permissible Winding and Oil Temperature Indicator values
(OP)
Hello,
We have recently installed a 15MVA , 66/11kv, Dyn11 transformer of which cooling is ONAN. Unfortunately we lost its manual from our station. When it was fully loaded we found that the Winding Temperature and Oil Temperature is compared other generator transformers in the same station. Which are ONAF and of different make. When we checked the name plate details we found the following details:
Maximum permissible Ambient Temperature: 50 degree Centigrade
Maximum Temperature rise above Ambient Temeprature for Oil/Winding: 50/55 degree Centigrade.
When we checked maximum Ambient temperature, we found that it was 34 degree.
Also we found that Winding Temperature is about 18 degree higher than Oil Temeperature.
My doubt is: Which is permissible maximum Winding Temperature Indicator reading? Is it 105 (=50+55)degree centigrade or 89 (=34+55) degree centigrade? Similarly which is maximum permissible Oil Temperature Indicator , 100 or 84 degree centigrade?
We have to set the alarm and trip settings to both Oil Temperature Indicator and Winding Temperature Indicator of the transformer. Please provide some suggestions in this regard too.
Thanks in advance,
zkz
We have recently installed a 15MVA , 66/11kv, Dyn11 transformer of which cooling is ONAN. Unfortunately we lost its manual from our station. When it was fully loaded we found that the Winding Temperature and Oil Temperature is compared other generator transformers in the same station. Which are ONAF and of different make. When we checked the name plate details we found the following details:
Maximum permissible Ambient Temperature: 50 degree Centigrade
Maximum Temperature rise above Ambient Temeprature for Oil/Winding: 50/55 degree Centigrade.
When we checked maximum Ambient temperature, we found that it was 34 degree.
Also we found that Winding Temperature is about 18 degree higher than Oil Temeperature.
My doubt is: Which is permissible maximum Winding Temperature Indicator reading? Is it 105 (=50+55)degree centigrade or 89 (=34+55) degree centigrade? Similarly which is maximum permissible Oil Temperature Indicator , 100 or 84 degree centigrade?
We have to set the alarm and trip settings to both Oil Temperature Indicator and Winding Temperature Indicator of the transformer. Please provide some suggestions in this regard too.
Thanks in advance,
zkz






RE: Permissible Winding and Oil Temperature Indicator values
Alarm - I would set 10 C above your normal observed values to give you enough early warning.
Muthu
www.edison.co.in
RE: Permissible Winding and Oil Temperature Indicator values
------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: Permissible Winding and Oil Temperature Indicator values
So in your case,assuming no overload ever at max ambient condition, take max ambient (T),top oil(to),average wdg rise(tw),drop across cooler (tc)from temperature rise report.
Then Winding hot spot setting is T+ to + 1.3[tw-(to-1/2 tc)]Make sure that WTI is calibrated for this hot spot gradient corresponding to rated load current.Top oil setting will be T+to.While selecting setting, some may take + 5C margin over those maximum attainable temperatures.
RE: Permissible Winding and Oil Temperature Indicator values
Thanks for all who gave me advices. As per your suggestion, we do not have to consider actual ambient temperature(which was 34 C) but to consider max.permissible temp. indicated in name plate (which is 55 C). Please correct me if I am wrong.
Let me ask one (perhaps silly) question then. If we are setting everything based on the name plate details, why should the name plate indicate maximum permissible ambient temperature, max. permissible oil temperature rise and max. permissible winding temperature rise separately? Why do not the name plates be displayed like the ones given below?
Maximum permissible oil temperature: 100 C
Maximum permissible winding temperature: 105 C.
Thanks in advance.
regads,
zkz
RE: Permissible Winding and Oil Temperature Indicator values
------------------------------------------------------------------------
If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: Permissible Winding and Oil Temperature Indicator values
RE: Permissible Winding and Oil Temperature Indicator values
regards,
zkz