IEEE C57.100-1986 pdf free.IEEE Standard Test Procedure for Thermal Evaluation of Oil-Immersed Distribution Transformers.
This test procedure is intended to give a direct evaluation of the composite insulation system of an oil-immerseddistribution transformer, tested as an integral unit. It is to be noted that the oil in which the transformer is immersed isto be considered a part of the insulation system.
lt is intent of the procedure to provide that each component of the insulation structure operate during the test underconditions that are, as nearly as possible, the same as those that it would encounter in service. Thus, it is intended thateach component be evaluated in accordance with its actual function.
The object of this test procedure is to establish a uniform method for investigating the effect of operating temperatureon the life expectancy of oil-immersed distribution transformers. The results may be used, for example, to:
1) Provide data for selection of a limiting hottest-spot temperature for rating purposes，which will provide reasonable life expectancy under normal operating conditions
2)Provide data that may serve as the basis of a guide for loading
3) Permit the comparative evaluation of a proposed insulation system, with reference to a system that has proven to be acceptable in service
The primary aging factors employed in this procedure are temperature and time.Since few distribution transformersoperate for extended periods at constant temperature, and since thermal cycling may have an adverse effect on lifeexpectancy of some insulation, provision is made for thermal cycling in the test procedure.
lt is recognized that environmental conditions, such as corrosive atmosphere and excessive vibration, may affect actualservice life. It seems appropriate, however, to evaluate such extraneous influences separately from the effects oftemperature, and they are not included in this procedure.
The load on most distribution transformers is cyclic, with both daily and annual cycles. For this reason, the peakthermal loading (that which develops the highest temperature in the transformer windings) occurs on relatively fewdays during the year, and for a relatively mall portion of each of these days. Thus the cumulative time at or above therated hottest-spot temperature is considerably less than the total elapsed time.Further, it is generally agreed thatthermal degradation of insulation is a function of both temperature and time at that temperature.Consequently, the lifeexpectancy (elapsed time) in actual service should be very much greater than the life determined by the essentiallycontinuous loading procedure prescribed in this specification.
Experience and experimental evidence indicate that an insulation system capable of operating 60 000 h (approximately7 yr) at rated temperature should give satisfactory life expectancy under the normal operating conditions described inthe preceding paragraph. Therefore, in the absence of other criteria, acceptable thermal aging performance may beassumed if the hottest-spot temperature at rated load as defined in IEEE Std 1-1969[5] does not exceed thatcorresponding to a minimum life expectancy of 60 000 h, as determined by this test procedure. It is anticipated thatspecific minimum life expectancy criteria for transformers with standard average temperature rises at rated load will beincorporated in the appropriate transformer standards.IEEE C57.100 pdf download.