- Joined Jan 16, 2015
That is a darn good question and quite frankly I am stumped!
I win. I found it! The driving factor for insulation credibility is temperature exposure, since at high temperatures insulation can lose its insulation properties. For this reason, it is necessary to establish the hottest-spot winding temperature.I am thinking how to corelate that with the insulation class?
Thanks so much, I am doing my calculations now and trying to fit my curve according to the b and a value, wishing myself luck!I win. I found it! The driving factor for insulation credibility is temperature exposure, since at high temperatures insulation can lose its insulation properties. For this reason, it is necessary to establish the hottest-spot winding temperature.
If you know the maximum hottest-spot temperature to which the insulation is exposed, we know how much life is lost, allowing you to limit the overload.
According to the IEEE C57.12.00-2000 standard, power transformer are rated on a maximum ambient
temperature of 40° C, and the average ambient
temperature shall not exceed 30° C in a 24-hour period. This standard also states that an average winding rise of 65° C
shall not be exceeded when the transformer is operated at its rated load (KVA), voltage (V), and frequency (Hz).
In other words.As Mr. @LowQCab stated , it is in the context ,based on the ambient temperature criteria, the average temperature of the winding cannot exceed 65° C above ambient,when operated at rated
conditions. Maximum hottest-spot winding temperature cannot exceed a value of 80° C above ambient.
The IEEE C57.91-1995 states that under a continuous ambient temperature of 30° C, the maximum hottest-spot winding temperature should not exceed 110° C.
If the transformer is operated continuously at this temperature, the normal life expectancy of the transformer is 20.55 years,ambient temperature, the average winding temperature,and the maximum winding hottest-spot temperature.
The IEEE Guide of Loading of Mineral Oil-Immerse Transformers C57.91-1995 aids you in calculating the effect of aging
insulation and its exposure to high temperatures. But you know of course they use a microprocessor protective relay that can perform the algorithm calculations.
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