Simplified transient model of transformer based on geometrical dimensions used in power network analysis and fault detection studies

Abstract

Various models have been presented for evaluation and study of transformers, but a model including all the following properties has not been given in literature by now: 1- The parameters of the model can be calculated through geometrical dimensions, so investigation of a fault effect on the model is possible and it needs no costly measurements. 2- The accuracy of the model in the medium transient frequency domain is satisfactory. 3- The model is simple, so simulation of this model is easy and fast. 4- It is feasible to use the model as a two-port element in network analysis. Such a model is proposed in this paper as simplified transient model (STM). Accuracy and validity of the model is verified using a 2.5 MVA and 6300/420 V three-phase transformer as a test object. This transformer consists of a disk-type high-voltage winding and a layer-type low-voltage winding. Finally, analysis of some important faults in transformers using this model is discussed.