IEEE Std C57.12.60-2020 pdf free download

IEEE Std C57.12.60-2020 pdf free download.IEEE Standard for Thermal Evaluation of Insulation Systems for Dry-Type Power and Distribution Transformers.
The means for making small adjustments to the current through individual samples may be provided to aid in achieving the desired temperatures. Individual enclosures for the test models may be used to maintain test temperatures. However, the physical arrangement of the prototype coils with respect to each other shall be such as to promote equality of temperature in all samples.
Any suitabic method may be used for monitoring the temperature of the prototype coils during the temperature exposure. Annex 11 provides detailed information that may provide useful information related to this testing. The following method is recommended: one prototype coil in a group shall be equipped with thermocouples and shall be used for temperature monitoring purposes only. The number and location of thermocouples shall be such as to give an accurate indication of the hottest-spot temperature and an adequate knowledge of the temperature distribution within the prototype coil to satisfy the conditions specified below. This prototype coil is also referred to as an instrumented control coil.
The temperatures in all prototype coils shall be monitored by one or more thermometers or thermocouples located on each sample. The relative position of the thermometers or thermocouples shall be the same for all samples, including the control sample. The monitored temperatures on individual test and control samples shall have a degree of uniformity of ±2 °C at temperatures up to I 0 °C and ±3 °C for temperatures from greater than I X0 °C to 300 o’, for the same monitored locations. The tolerance for aging temperatures above 300 °C shall be determined by the involved parties.
The intent is to maintain constant test temperatures at the hottest spots within the sample as measured by the monitoring thermocouples. Thus, the hottest-spot temperature of each winding shall be nearly the same.
For solid cast designs. the heat-up rate of the prototype coils should be controlled and monitored to prevent premature coil cracking. It should be cautioned, however, that an excessive heat-up time adds aging time to the samples that is not to be included in the total aging time.
The aging cycle begins only when the monitored control sample has reached the prescribed aging temperature. The aging cycle terminates at the point in time when the control sample drops more than 3 °C below the aging temperature Should the aging cycle be interrupted for any reason, including a power outage, only the time within this temperature band shall be counted for calculation of aging time. Depending on when the aging cycle is interrupted. the aging cycle can either be restarted or terminated to conduct the diagnostic test cycle as if a full cycle had been conducted.IEEE Std C57.12.60-2020 pdf free download.