Prediction Of Hottest Spot Temperature And Temperature Measurement With Opticical Fiber In Oil-Immersed Transformer Windings

One of the most important parameters governing transformer's safety,economicoperation and life expectancy is the hottest spot temperature value. The insulating materialsaging because of overheating in winding's hottest spot maybe lead to overall damage of thetransformer. Consequently, investigation for the hottest spot in transformer windings hasattracted particular attention from both manufactures and user sectors; accordingly,IEEEstandard C57.12.00-2000 requires that the hottest spot temperature and its location can bedetermined.The most direct and accurate way of accurately monitoring the hot spot is to directlymeasure the hot temperatures. Directly measurement of hot spot temperature must firstlypredict the location of hot spot by calculation method, that is ,need to accurately calculate theoverall winding's temperature distribution. In this article, based on the original temperaturefield calculation software, the calculation model is further improved, then a more exacttemperature distribution is given, thus the location of hottest pot is precisely predicted.Bottom on above research, a set of technology process that temperature measurement withoptical fiber is formed.When the previous software of temperature field dealing with eddy loss, approximatemethod is used, this may result in the final calculated temperature field and the actual valueserror. In this paper an accurate analytic method for calculating eddy losses is presented, andthe exact winding eddy loss distribution is obtained. In addition, we also study internal heatconduction model of the winding and boundary hydraulic model in particular, and furtherimprove calculation accuracy by coupling the two models. Thus the hottest spot position ispredicted through precisely calculating the windings'temperature field. Since hottest spot is accurately predicted, the process of temperature-rise test withoptical fiber is proposed, and a complete and mature program of temperature-rise test withoptical fiber is formed in this article. The mean temperature-rise value or hottest spottemperature obtained through test and the predictions values calculated by software oftemperature field are in good agreement, it not only indicate that the temperature fieldcalculation software which predict hottest spot is reliable; but also indirectly proved that thedeviation of the hottest spot's location determined in this experiment is in a reasonable range.Therefore, measuring the windings'hottest spot temperature with the fiber-optic probe in thetemperature-rise test is feasible. The gained experience have reference value to the unitswhich using optical fiber probe for online monitoring of transformer windings'hottest spottemperature in the future .