Transformer winding deformation tester detection principle

Under the action of higher frequency voltage, each winding of the transformer can be regarded as a passive linear two-port network composed of linear resistance, inductance (mutual inductance), capacitance, and other distribution parameters, and its internal characteristics can be transmitted through the transfer function H ( Jω) description, as shown in Figure 1. If the winding is deformed, the parameters such as distributed inductance and capacitance inside the winding will inevitably change, which will cause the zero point and pole of the equivalent network transfer function H(jω) to change, which will change the frequency response characteristics of the network.

The frequency response analysis method is used to detect the deformation of the transformer windings by detecting the amplitude-frequency response characteristics of each winding of the transformer and comparing the detection results in the longitudinal or transverse direction. According to the difference of the amplitude-frequency response characteristics, the transformer winding deformation may be determined.

The amplitude-frequency response characteristics of the transformer windings are obtained using the frequency sweeping method shown in Figure 1. Continuously change the frequency f of the externally applied sine wave excitation source VS (angular frequency ω=2πf), measure the ratio of the amplitudes of the response terminal voltage V2 and the excitation terminal voltage V1 at different frequencies, and obtain the designated excitation end and response end The frequency response curve of the lower winding. In the figure, L, K and C represent the distributed inductance, distributed capacitance and distributed capacitance of the winding unit length respectively. V1 and V2 are the excitation terminal voltage and response terminal voltage of the equivalent network, respectively, and VS is the sine wave excitation signal source voltage. RS is the signal source output impedance, and R is the matching resistor.