Study On Online Monitoring Of Transformer Windings Deformation

Power transformer is an important part of power system, and the failure of the power system will cause significant economic losses and even serious consequences. Transformer windings deformation is an important factor affecting the safe operation of the transformer. Therefore, the operation reliability can be improved by the test and diagnosis of the winding deformation. In this thesis, the transfer function characteristics of transformer windings is studied, which lay a theoretical foundation for on-line monitoring development of transformer winding deformation.Taking into consideration the mutual inductance and the loss of transformer winding, the simulation model of transformer winding is established. Taking a continuous single winding transformer as an example, the transformer winding inductance and capacitance parameter calculation method of the equivalent circuit model are introduced in this thesis. The changes of the winding structure and size caused by deformation in different forms and degrees are studied by the structural parameters method. And parameters of the equivalent circuit according to the deformation situation are calculated.The basic principle of transformer winding deformation diagnosis based on transfer function method is studied. A criterion of the winding deformation diagnosis is proposed by using the correlation coefficient and the root mean square of the spectrum difference in different time.The simulation of different types and degree transformer winding deformation are used to analyze the influence of the transfer function. The correlation coefficient and the root mean square value of the transfer function curves are demonstrated, which can be used as a characteristic parameter for winding deformation degree diagnosis. And the corresponding judging threshold between mild, moderate and severe deformation are given. The transfer function curve can be divided into low frequency, intermediate frequency and high frequency according to the pole number. We should calculate the value of the corresponding segments to judge winding condition. The simulation model is verified by the experiment, and it provides theoretical basis and algorithm for the on-line monitoring of winding deformation.The on-line monitoring method of transformer winding deformation is proposed. And the online monitoring of winding deformation is realized through continuous online comparing winding transfer function curve. If the two transfer function curves correlation have obvious drop, the winding deformation can be judged. The method based on the high frequency components of transformer working current is proposed for the on-line monitoring to construct the transfer function. The actual transformer online experiments was used to verify the feasibility of using the high frequency components of transformer working current to construct the transfer function, and it provides a theoretical support for on-line monitoring of transformer winding deformation.The online monitoring system of transformer winding deformation was designed based on LabVIEW software platform. It has continuous real-time monitoring capabilities under the condition of without changing primary equipment connection mode. Due to the transformer winding deformation generally occurs in exports after short circuit, the online monitoring system provides the transformer working current monitoring. The system can automatically strengthen monitor density in the event of short circuit or overload phenomenon, so it has certain intelligence.