Propagation Characteristics Of Partial Discharge Pulses In Dry-Type Transformer Windings

The transient model of SCR-500/10 dry-type transformer winding is studied and used for locating PD. Based on the theory of linear time-invariant and transfer function, a method for locating PD is establish.Based on the structure of windings, the multi-conductor transmission model of partial discharge pulse propagating in single phase transformer is established. The parameters of capacity, Inductance, resistance and conductivity are calculated and the math expression of the model is obtained. Transient analysis of different equivalent circuit of dry-type transformer windings is carried on using the model. It is obtained that the affection of various equivalent components to the transient process and the equivalent components for locating PD is established.The transfer function of voltage-subparagraph is calculated based on the theory of linear time-invariant and transfer function. Because the FFT and IFFT computing are used at the same time in the process of transfer function solution, there is aliasing phenomenon. The frequency and the damping ratio of signal are going to change when the aliasing phenomenon happen. The frequency will decreases and the damping ratio will rise. In order to overcome the aliasing of FFT and IFFT, vector fitting method is used in this paper to fit the Weilite of the transfer function.The method for locating PD is analyzed based on the theory of transfer function. Two kinds of PD signal of dry-type transformer are simulated, and it is analyzed that the PD signal at the different location of windings. Then the Euclidean distance of signal is computed, and the position of PD is located.The calculated result is meaningful for detecting and diagnosing PD in Dry-type transformer.