Transformer neutral point capacitive DC blocking device

Abstract

The invention provides a transformer neutral point capacitive DC blocking device adopting a high-capacity high-voltage capacitor and BOD protection. The device comprises an isolating switch, the high-capacity high-voltage capacitor, a voltage divider, a resistor, a discharging gap, a current mutual inductor and a current sensor. The isolating switch, the high-capacity high-voltage capacitor, the current sensor and the current mutual inductor are connected in series and connected between the neutral point of a transformer and the ground. The voltage divider, the resistor and the discharging gap are respectively connected in parallel with the high-capacity high-voltage capacitor. After the device is connected in series with the neutral point of the transformer, DC current entering the neutral point of the transformer can be effectively eliminated without influencing normal grounding of an AC system or passing of AC zero sequence current so that safe operation of the system can be ensured. The device is easy and convenient to operate, compact in structure, small in size and convenient to transport without influencing the overall layout of intra-station equipment after installation. Besides, the high-capacity high-voltage capacitor is high in withstand voltage, high in current withstand capacity and also high in safety and reliability.

Description

technical field [0001] The invention relates to high-voltage power transmission technology, in particular to a transformer neutral-point capacitive direct-blocking device that adopts large-capacity high-voltage capacitors and BOD protection. Background technique [0002] Since the implementation of the strategy of "power transmission from west to east, mutual supply from north to south, and national networking" in China, many DC transmission lines of ±500kV ~ ±800kV have been built and put into operation. When the high-voltage direct current transmission line operates in a single-pole ground loop mode, there may be a DC current of up to several thousand amperes flowing from the ground electrode to the ground. The AC transmission lines with a voltage level of 110kV and above are usually directly grounded systems with neutral points, so part of the DC current can enter equipment such as power transformers with grounded neutral points, and form a loop in the AC transmission lin...

AI Technical Summary

Problems solved by technology

The AC transmission lines with a voltage level of 110kV and above are usually directly grounded systems with neutral points, so part of the DC current can enter equipment such as power transformers with grounded neutral points, and form a loop in the AC transmission lines, so that the power transformers are in DC. The abnormal operation state of the magnetic bias will cause the transformer to increase its operating noise, violent vibration, excessive temperature rise, shorten the service life of the transformer, and even damage the transformer

The DC current entering the AC system may also cause protection malfunctions, affecting the safe operation of power equipment and power systems

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