Main transformer neutral point overvoltage protection device

Abstract

The invention relates to a main transformer neutral point overvoltage protection device. The main transformer neutral point overvoltage protection device is characterized in that the main transformer neutral point overvoltage protection device comprises a base, a transient high-frequency overvoltage absorption protection unit and a rod gap power frequency overvoltage protection unit, wherein the transient high-frequency overvoltage absorption protection unit and the rod gap power frequency overvoltage protection unit are installed on the base and connected in parallel. In the transient high-frequency overvoltage absorption protection unit, a lightning arrester and a capacitor are combined, the neutral point lightning arrester is divided into an upper segment and a lower segment which are connected in series, the lower segment of the lightning arrester is connected with the capacitor in parallel, and due to the bypass absorption capacity of the capacitor for high-frequency transient overvoltage, lightning and operation residual voltage is 40% lower than that of an existing common neutral point lightning arrester on the premise that the work frequency residual voltage of the lightning arrester is kept higher than the upper limit of rod gap power frequency discharge voltage. Compared with an existing commonly-used neutral point protection product with a rod gap and a lightning arrester connected in parallel, the situation that because the rod gap discharges frequently when lightning invades, abnormal action occurs in relay protection and a main transformer is cut off can be remarkably improved.

Description

technical field [0001] The invention relates to a transformer protection device, in particular to a main transformer neutral point overvoltage protection device. Background technique [0002] 110kV and 220kV are the main voltage levels of the power supply network. Due to the requirements of relay protection setting configuration and prevention of communication interference, in order to limit the single-phase short-circuit current, some transformers adopt the neutral point ungrounded method. In this mode of operation, the overvoltage at the neutral point will be caused by lightning strikes, single-phase grounding short-circuit faults, etc., and most of the transformers are graded insulation, so the overvoltage poses a great threat to the insulation of the neutral point, and protection must be provided for it. device to prevent accidents. [0003] The 110kV and 220kV systems are effectively grounded systems during normal operation, some main transformers are not grounded, and...

AI Technical Summary

Problems solved by technology

[0008] In order to avoid frequent discharge in the gap, some operating units adjust the gap distance too large, only considering the requirements of the insulation coordination of the neutral point of the main transformer, but ignoring the requirements of the insulation coordination of the line ends. Once a ground loss occurs, the line end arrester may be aging Even damaged, insulation coordination is leaky

When the 220kV neutral point uses the rod gap alone, the current general information recommends 275mm, and the power frequency discharge voltage is 99~120kV, which meets the insulation coordination requirements, but without the arrester, the lightning overvoltage wave will be totally reflected at the neutral point, and the overvoltage amplitude The value is higher, the discharge probability of the rod gap is also higher, so the parallel arrester is necessary

After searching the relevant literature, there are some reports about the main transformer neutral point overvoltage protection device, but no similar or identical technical solution to this patent has been found

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