Research On On-line Detection Technology Of Transformer Winding Deformation

Transformer is one of core equipment in the power grid transmission.Winding deformation failure is a common fault of transformer,especially in the event of a short circuit.Power civilization development requires us to decrease the times of blackout for winding deformation,we pursue to realize online detectionAfter the winding deformation,reflected in the winding equivalent network transfer function is the change of the pole and the zero.The frequency response method is one of the main methods to detect the deformation defects of the transformer winding off-line.When applied to the on-line situation,there are two most important questions,one is to solve how to inject signal into transformer winding and then how to get the detection signal,the other one is how to eliminate the influence of external devices connected to the transformer winding directly.In this thesis,to the wye connected transformers with neutral points the principle of magnetic field coupling is proposed,and the swept voltage signal is injected into the winding by the Rogowski coil,and the current response signal is measured by the Rogowski coil in the root of the high pressure casing.The required Rogowski coil is designed,and the test was done to verify the feasibility of the magnetic field coupling method.The experiment indicates that the method of magnetic field coupling is feasible,and the frequency response curve of winding frequency is obtained when the transformer is online.When the amplitude-frequency response function of a winding equivalent network is obtained by the excitation of the voltage signal and the response of the current signal,the influence of the external device and how to eliminate it are studied theoretically.It is found that the zero of the transfer function of the equivalent network of the winding is not affected by the external device.The simulation results verify the correctness of this method and verify that the minimum point frequency position is not affected by the external device when the off-line test is carried out to verify whether the transformer winding is deformed.The point corresponding to Zero on the amplitude-frequency response curve is put forward to use as a criterion of the winding deformation.The simulation results validate the correctness of th is method,and the experiments indicate that the zero point is not affected by external devices.