496 / 2022-03-21 13:53:18

Simulation study of high voltage insulation prevention test without disconnection for 220 kV converter transformer

transformer, simulation, prevention test, disconnetction

Converter transformer is the main device of direct current power transmission system, and the maintenance of converter transformer is indispensable for its safe and stable operation. Neverthless, disconnecting the lead of converter transformer takes up 73 percent of total working time according to the statistic. To reduce the time of maintenance for converter transformer, it is necessary to study the feasibility of high voltage insulation prevention test without disconnection for 220 kV converter transformer by simulation method.Based on matlab simulink toolbox, a lumped parameter model of converter transformer according to actual operation and designed parameter is established, which is a resistance and capacitance equivalent model of transformer and connected equipment; Then, three calculation conditions (disconnection of both sides, disconnection of network side and non-disconnection) are setted; After that, the capacitance, dielectric loss and insulation resistance test under direct current and power frequency alternating power with fixed step size method based on Kirchhoff’s law are simulated; At last, the simulation results under three different calculation conditions are compared to choose the best test strategy.For direct current resistance, dielectric loss and capacitance, the difference of simulation result of three calculation conditions is negligible. While the insulation resistance simulated without disconnection of both sides is the smallest, and that with disconnection is the largest. When the lead of converter is connected, the test of insulation resistance includes not only the resistance of converter transformer, but also the resistance of connected devices in parallal connection with the transformer, leading to the reduction of insulation resistance.