CALCULATION OF CFD-THERMAL MODELS OF OIL-COOLED TRANSFORMER EQUIPMENT

Abstract

The purpose of the study is to ensure designing of full-function and stable CFD-simulation procedure for integrated thermal models of the transformers and the reactors, as well as to receive the approval of method of quality and abilities using the calculation examples of full-scale models of the equipment, along with autonomous models of coil-type windings having various design versions of heat-transfer intensification. Research Methods. Computational Fluid Dynamics (CFD) method of mathematical simulation of nonlinear processes as concerns hydrodynamics and heat transfer in the transformer equipment using finite-element analysis is employed. The results obtained. The paper presents the main elements of technique for creation of mathematical models; it also contains the examples of CFD-calculations as referred to axisymmetrical integrated models of furnace transformer and gapped-core shunt reactor, as well as the models of windings having design approaches of heat exchange intensification owing to «labyrinth» (partitions) and «alternation» (of number and locations) of axial cooling ducts. Scientific novelty. Scientific value of applied methodological approach lies in the fact that the developed models are the integrated ones, i.e., they consider geometry, loss, thermal parameters not only of the windings, but also of the main structural elements and cooling system. This ensures the quality and the accuracy of simulation of heat-and-mass transfer processes in complex structure of oil ducts and coils in the windings, enables to avoid erroneous «zigzag» oil flow movement through the groups of coil regular structures (without labyrinth and «alternation» of number and locations of axial ducts under conditions of transformer oil natural cooling as was deduced in the certain studies. Practical significance. Integrated models ensure calculation of oil temperature distribution within active part, including winding fields, oil temperature field between the tank and the windings, temperatures at oil outlet from the tank (top) and oil inlet into the tank (bottom). Calculations allow estimation of mean temperature distribution over the crosssection of winding coils, mean winding temperatures by means of averaging of the temperatures within the coils, detection of location and maximum temperature on the surface of conductors relevant to the most heated coil. The latter is treated as winding hot spot temperature (HST) and used to evaluate the aging of the contacting insulation. Determination of winding hot spot locations and temperatures (HST) is used as support data for installation areas of fiber optic probes for measurement during type testing, as well as in operational monitoring systems of the equipment. The results presented above are practically applied for industrial designing and testing of transformers and reactors.