Analysis On Electric Field Under Polarity Reversal Voltage For Converter Transformer Valve Side With Considering The Temperature Influence

Due to converter transformer own characteristics, its irreplaceable in high-voltage direct current transmission system, played a key role in connection with the coordination of the DC and AC conversion transmission system, to achieve better power transmission. Insulation failure is the main reason for converter transformer fault occurs during operation. When the converter transformer in a strong electric field environment, it will lead to local field strength is too high, lead to its internal dielectric insulation and even cause electrical breakdown damage. Therefore, the calculation and analysis of electric field distribution of the converter transformer operation in different conditions. To find out the maximum electric field strength point and then find the root cause of breakdown and insulation damage.Due to its special operating environment, withstand voltage excitation is different from common transformers, which under the special polarity reversal voltage of the electric field distribution is the focus of research on its insulating properties. This paper will take ± 500 kV converter transformers as the research object. Using the finite element method(fem) analyses converter transformer valve side winding under polarity reversal voltage model, we can get the internal electric field distribution, and analyze its insulating property. First without considering the effects of temperature, analyze the electric field distribution under polarity reversal voltage for converter transformer value side winding. Under DC voltage the internal electric field distribution is resistance, and relatively concentrated in insulation board. Under DC electric field, in the insulation material accumulation of free charge will distort the electric field distribution during the process of polarity reversal, Which may cause high threat to its internal insulation.During the converter transformer operation process, under the continuing high voltage, the internal temperature is bound to arise. It is necessary to consider the issue of its internal thermal insulation. This paper, by using Ansys finite element analysis software analyze the 2D model of transformer leakage magnetic field, to calculate the loss then apply to load on the converter transformer core and winding as the heat load. Get the converter transformer 2D temperature field distribution, providing the theory basis for the analysis of electric field distribution under polarity reversal voltage when considering temperature gradient effect. Effect of temperature will change the converter transformer insulation resistivity, by considering the resistivity change in case of temperature change to the impact of the electric field distribution, to take the converter transformer insulation design and overall development, as well as for HVDC technology development and progress has important significance.