IEEE P1538-D3-2015 pdf free.Draft IEEE Guide for Determination of Maximum Winding Temperature Rise in Liquid-Immersed Transformers Amendment #1.
Fiber optic temperature detectors may be used to measure temperatures in power transfijrmers. The main application of fiber optic probes has been the measurement of local temperatures in the windings. and particularly the hottest-spot temperature in the windings. The probes have usually remained in the windings. and in some cases thcy have been used for thc measurement of temperatures under operating conditions.
There are fiber optic probes on the market with embedded sensors at cetlain intervals along their length. Such probes could measure the local temperatures along the whole length of the conductor. For use in power transformers such probes are, however, not very practical. One reason is that the probe has to be embedded in a slot in a single strand. This creates complications for example at the transposition of parallel strands. Another reason is that the current distribution is not completely balanced between parallel conductors, in spite of a proper transposition scheme. Furthermore, at the design stage it is not obvious which one of the parallel conductors carries the highest current. This makes selection of the proper conductor for probe installation uncertain, because probes would have to be installed in all of the parallel conductors, which would be both expensive and time consuming. Consequently. point sensors are more likely to be used in most transformer applications.
When using point sensors then, choosing the best installation locations is crucial to determining the hottest- spot temperature with reasonable accuracy. The term “reasonable accuracy” is used here to mean that the measured maximum temperature is close enough to the real hottest-spot temperature, such that it can be used as a reference for safe operation of the transformer and for the estimation of consumed transtbrmer life. The probable location of the hottest-spot is usually determined by analysis of the eddy loss distribution, the liquid flow distribution, and the heat transfer characteristics of the winding. Unfortunately. large thermal scatter often overrides the theoretical predictions. Thus, a certain minimum number of probes are needed. The following sub-clauses recommend numbers and locations of probes in core type transformers. It is then assumed that the windings are of approximately equal length. are designed with axial or zig-zag liquid circulation. that the load current is sinusoidal and that the transformer is ON-, OF-. or OD-cooled. These recommendations arc based on a CIGRF brochure [24a].
Thermal tests may be conducted at rated load in accordance with lElE Std C57.l2.’k). Thermal data. including the hottest fiber optic probe recordings may be used to verify the hottest-spot temperature performance of the transformer. Such data arc also useful to verify thermal models to be used to calculate the hottest-spot temperature of other designs. Data from tests at loads above and below rating assists further in the development of thermal models to predict the performance of the transformer at diflerent loads and also to predict the performance of other designs.IEEE P1538-D3 pdf free download.