Overvoltage protection device for variable impedance transformer

Abstract

The invention relates to an overvoltage protection device for a variable impedance transformer. The overvoltage protection device is characterized by comprising a resistance-capacitance absorption device connected with a selector switch (K) and an air reactor in parallel, wherein the resistance-capacitance absorption device comprises a resistor R and a capacitor C1 connected in series, and arresters (MOV) are connected with two ends of the capacitor (C1) in parallel. When in use, the air reactor is placed in the box of a transformer, and a high-speed switch is positioned on the outer side of an oil tank and connected between the high-voltage winding and the neutral point of the transformer in series. When the variable impedance transformer works normally, the high-speed switch is closed, a current-limiting reactor is short-circuited, and the reactor is prevented from causing energy loss; when the system is short-circuited, the high-speed switch is open, the current-limiting reactor is available, then the transformer is equal to a high impedance transformer at the moment, and the short circuit current is inhibited to a certain extent. The device provided by the invention is compact in structure and small in size, and can effectively reduce overvoltage amplitude and gradient caused during an impedance conversion process of the variable impedance transformer.

Description

technical field [0001] The invention relates to an overvoltage protection device for variable impedance transformers. Background technique [0002] The power transformer is one of the important power transmission and transformation equipment in the power system. It connects multiple voltage levels of power grids and plays a pivotal role in the power grid. When the windings of power transformers are short-circuited, especially when the load is short-circuited, the huge electromagnetic force generated by the fault current will do great harm to the windings of the transformer. It is an urgent technical problem to adopt economical, effective, compact, convenient and efficient technical measures to reduce the impact of short-circuit current on transformers and improve the operation reliability of large transformers. At present, high-impedance transformers and fault current limiters are mainly used to limit the short-circuit current flowing into the transformer. However, high-imp...

AI Technical Summary

Problems solved by technology

[0004] The commonly used protection devices are surge arresters or resistance-capacity absorption devices. Due to the influence of high-frequency response characteristics, the protection effect of surge arresters is poor.

The resistance-capacitance absorption device has a good protection effect, but the capacitance value of the absorption capacitor is large, and the power of the absorption resistance is also very high, making the device difficult to manufacture

Therefore, these two protection devices have not been widely used in shunt reactor cut-off overvoltage protection.

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