Simulation Analysis of Transformer Winding Deformation on Winding Voltage Distribution

Author： GOZ Electric Time：2024-09-29 09:29:34 Read：24

Figure 1

1. Axial deformation of high-voltage winding

This section analyzes the maximum voltage distribution of the winding when the front, middle and rear sections of the high-voltage winding are deformed to different degrees. Since the longitudinal capacitance between the coils in the front section of the high-voltage winding is greater than that in the middle and rear sections, it can be seen from the formula that the axial deformation of the coils in the front section of the high-voltage winding will increase the space factor of the winding, increase the maximum voltage of the coils in the front section, and increase the maximum voltage of the coils in the middle and rear sections; the axial deformation of the coils in the middle section will reduce the space factor of the winding, reduce the maximum voltage of the coils in the middle section, and reduce the maximum voltage of the coils in the rear section; the axial deformation of the coils in the rear section will reduce the space factor of the winding, and reduce the maximum voltage of the coils in the rear section.

The reduction of the ground capacitance of the high-voltage winding on the deformed side will reduce the ground shunt of the winding, so that more energy of the lightning wave is concentrated on the winding, thereby improving the maximum voltage distribution of the high-voltage winding on the non-deformed side. Since the energy of the lightning wave flowing through the front section of the winding is greater than that of the middle and rear sections, the energy lost when the front section of the high-voltage winding undergoes axial deformation is less, and the maximum voltage distribution of the non-deformed side winding is larger at this time. Similarly, when the middle section of the high-voltage winding undergoes axial deformation, the maximum voltage distribution of the non-deformed side winding is greater than the maximum voltage of the non-deformed side winding when the rear section undergoes axial deformation. The greater the degree of deformation of the winding, the greater the increase or decrease of the above maximum voltage. It can be seen from the formula that the maximum voltage distribution of the medium-voltage winding is less affected by the axial deformation of the high-voltage winding.

2. Axial deformation of medium-voltage winding

This section analyzes the maximum voltage distribution of the winding when the front, middle and rear sections of the medium-voltage winding undergo different degrees of axial deformation. Since the capacitance of a single medium-voltage winding to ground is much greater than the mutual capacitance between the opposite parts of the single high-voltage and medium-voltage windings, according to the formula, it can be found that the axial deformation of part of the medium-voltage winding has almost no effect on the voltage transfer ratio, so the maximum voltage distribution of the medium-voltage winding remains almost unchanged. Similarly, the reduction of the capacitance of the medium-voltage winding to the ground will increase the maximum voltage distribution of the high-voltage winding coil. The greater the deformation, the greater the amplitude of the maximum voltage.

3. Radial deformation of high-voltage winding

This section analyzes the maximum voltage distribution of the winding when the front, middle and rear sections of the high-voltage winding are radially deformed to different degrees. It can be seen from the formula that the radial deformation of the coil of the front section of the high-voltage winding will reduce the space factor of the winding, reduce the maximum voltage of the coil of the front section, and reduce the maximum voltage of the coil of the middle and rear sections. The greater the deformation, the more obvious the voltage change.

Due to the energy loss of the wave during propagation, when it is transmitted to the middle and rear sections of the winding, the steepness of the rising edge of the wave head will decrease, and the value of the operator p in the formula will no longer be infinite. At this time, the influence of the winding inductance on the space factor needs to be considered. Therefore, when the coil of the middle and rear sections of the high-voltage winding undergoes radial deformation, the space factor and the maximum voltage distribution no longer change monotonically with the change of the degree of winding deformation. It can be seen from the formula that the influence of radial deformation of high-voltage winding on the maximum voltage distribution of medium-voltage winding can be ignored.

4. Radial deformation of medium-voltage winding

This section analyzes the maximum voltage distribution of the winding when the front, middle and rear sections of the medium-voltage winding undergo different degrees of radial deformation. It can be seen from the formula that radial deformation of the medium-voltage winding will reduce the voltage transfer ratio, reduce the maximum voltage at the deformed position of the medium-voltage winding, and thus reduce the maximum potential of the relative position of the high-voltage winding. When radial deformation occurs in the front and rear sections of the medium-voltage winding, the energy attenuation caused by the reduction of the maximum voltage of the front and rear sections of the high-voltage winding is greater than the energy loss caused by the increase in the capacitance of the medium-voltage winding to the ground, so the maximum voltage of the non-relative position of the high-voltage winding will increase accordingly. The greater the degree of deformation, the greater the increase or decrease in the above-mentioned maximum voltage.

5. Comparative analysis

By comparing various situations of axial deformation and radial deformation, the following rules can be drawn:

① The greater the degree of winding deformation, the greater the change of concentrated parameters such as capacitance and inductance in the equivalent circuit, and the greater the impact on the maximum voltage distribution of the winding;

② Since the inter-pancake capacitance and ground capacitance of the deformed winding are reduced at the same time during axial deformation, only the ground capacitance of the deformed winding changes during radial deformation, and the inter-pancake capacitance does not change. According to formula (1), it can be found that the parameter change caused by radial deformation has a greater impact on the space factor. Therefore, compared with axial deformation, radial deformation has a more obvious impact on the maximum voltage distribution of the winding;

③ After the lightning wave invades, First, it flows through the front section of the high-voltage winding. The front section of the winding collects the most energy. The change of the parameters of the front section also has the greatest change on the energy of the intrusion wave. Therefore, the deformation of the front section of the high-voltage winding has the greatest impact on the maximum voltage distribution of the winding; ④ The axial (radial) deformation of the high-voltage winding will increase (reduce) the maximum voltage of the high-voltage winding on the deformed side, reduce (increase) the maximum voltage of the winding on the non-deformed side, and have almost no effect on the maximum voltage distribution of the medium-voltage winding; ⑤ The axial deformation of the medium-voltage winding has no obvious effect on the maximum voltage distribution of the high (medium) voltage winding. The radial deformation will reduce the maximum voltage of the medium-voltage winding deformation position and the high-voltage winding directly opposite position, and increase the maximum voltage of other positions of the high-voltage winding.