Study on Factors Affecting Residual Magnetism of Phase Selection of Extreme High Voltage Transformer and Its Calculation Method

Abstract

As one of the core components in the extreme high voltage power grid, the extreme high voltage transformer has a large rated capacity, and the level of magnetizing inrush current generated by the air-to-air transformer is high. At the same time, a large amount of harmonics are injected into the power grid. In severe cases, a long duration and a slow decay can be generated. The voltage has an adverse effect on the near-area grid and equipment (especially power electronics). In order to further improve the safety and reliability of systems and equipment, effective measures need to be taken to suppress them. At present, the measures that can be used to limit the main transformer closing current include the circuit breaker installation closing resistor and the phase selection closing technology. However, since the closing resistance does not exceed 10 ms, it limits the main transformer closing excitation current, harmonics and over The effect of voltage is relatively limited, and the conventional phase-selection closing technology cannot consider the influence of transformer remanence, and its limiting effect is also not ideal. Foreign research and the use of phase-selection closing technology that takes residual magnetism in some ultra-high-pressure projects to solve the problem of air-to-air inrush current has gained some experience. In theory, this measure is expected to solve the extreme high voltage large-capacity transformer very ideally. Inrush current, harmonics, waveform distortion and overvoltage caused by closing. In this paper, the influencing factors of remanence of extreme high voltage transformers in phase-selective switching technology are studied. According to the research results, the specific scheme of voltage integral to measure residual magnetism is established.