Simulation Analysis of Transformer Impact Deformation Overvoltage Characteristics

Author： GOZ Electric Time：2024-09-23 09:45:03 Read：10

When the transformer is subjected to lightning impulse, the winding will deform, which can be divided into axial deformation and radial deformation of the winding. The deformation of the winding will affect the capacitance, inductance and other parameters of the transformer equivalent circuit, thereby affecting the overvoltage characteristics of the transformer. When the winding is axially deformed, the inter-winding capacitance and the capacitance to ground are reduced; when the winding is radially deformed, only the capacitance to ground is changed, and the inter-winding capacitance does not change; radial deformation has a greater impact on the maximum voltage of the transformer winding. In the analysis process, only the radial deformation of the winding caused by lightning impulse is analyzed.

1. Simulation analysis of radial deformation of high-voltage winding

When subjected to lightning impulse, the front, middle and rear sections of the high-voltage winding will produce different degrees of radial deformation. Among them, the radial deformation of the front section of the high-voltage winding will cause the reduction of the winding space factor, which will reduce the maximum voltage value of the front section of the winding, and cause the maximum voltage values of the middle and rear sections to decrease accordingly. The distribution of the voltage of the front section of the high-voltage winding is shown in the figure.

Figure 1

It can be seen from the figure that when radial deformation occurs in the front section of the high-voltage winding, the distribution trend of the changes in different high-voltage and medium-voltage deformations is consistent. The maximum voltage change of the transformer when different high-voltage values are applied is quite different. As the high-voltage value increases, the maximum voltage value generated also gradually increases; the maximum voltage of the transformer also changes to a certain extent when different medium-voltage values are applied, but the difference is not large, which shows that when the high-voltage winding produces radial deformation under lightning impulse, the voltage of the medium-voltage winding has little effect. It can also be seen in Figure 3 that the curvature of the voltage fluctuation in the front section is greater than that in the middle and rear sections. This is because there is a certain amount of energy loss in the voltage waveform during the transmission process, which causes the curvature of the maximum voltage to decrease when it is transmitted to the middle and rear sections, making the space factor of the middle and rear sections of the coil and the distribution change of the maximum voltage nonlinear with the deformation of the winding, and there is a certain compound change effect.

2. Simulation analysis of radial deformation of medium voltage winding

When subjected to lightning impact, the front, middle and rear sections of the medium voltage winding will produce different degrees of radial deformation. The radial deformation of the medium voltage winding will reduce the voltage transfer ratio between the high and medium voltage windings of the transformer, so that the maximum voltage value of the medium voltage winding deformation position is reduced, thereby reducing the maximum voltage of the relative position of the high voltage winding. Taking the voltage distribution when the middle section of the medium voltage winding is deformed as an example for analysis, the distribution of the voltage in the middle section of the medium voltage winding is shown in Figure 4. It can be seen from Figure 4 that when different deformation effects occur in the middle section of the medium voltage winding, the change distribution trend of different high and medium voltage values is consistent, among which the difference in the maximum voltage change of the transformer when different high voltage values act is smaller than the change of the medium voltage value; when the medium voltage value changes, as the medium voltage value increases, the maximum voltage at different positions gradually decreases. This is because when the middle section of the transformer undergoes radial deformation, the energy loss caused by the increase in the capacitance of the medium voltage winding to the ground is smaller, resulting in a larger proportion of energy consumption when a smaller voltage value acts, thereby increasing the maximum voltage of the transformer. The greater the degree of deformation, the greater the change in voltage.

Figure 2

Conclusion

1) When the transformer is in use, it will be subjected to lightning impact, which will cause the deformation of the winding, thereby affecting the overvoltage characteristics of the transformer and affecting the use of the transformer. EMTP is used to simulate and analyze the winding deformation caused by lightning impact, and an equivalent circuit of transformer concentrated parameters is established. Different deformation effects are simulated by adjusting parameters to analyze the transformer overvoltage characteristics caused by winding deformation.

2) The radial deformation of the transformer high-voltage winding has a greater impact on the voltage distribution, and the radial deformation of the high-voltage winding has a greater impact on the high-voltage winding, and has a smaller impact on the voltage of the medium-voltage winding; the deformation of the middle section of the transformer radial medium-voltage winding has a smaller impact on the voltage change of the high-voltage winding, which can reduce the maximum voltage of the medium-voltage winding and increase the voltage of the relative position of the high-voltage winding.

3) The deformation of the transformer winding has a greater impact on the overvoltage characteristics of the transformer. During use, the insulation protection of the transformer winding should be improved, especially the radial insulation protection, to avoid voltage changes caused by deformation during lightning impact.