A strategy to deal with the risk of conversion failure of three-terminal DC earth metal return line

Abstract

The invention discloses a risk response strategy for the failure risk of three-terminal DC earth metal loop conversion. When the earth metal loop is converted, if the current flowing through the transfer switch is lower than the set protection value for the first time, the control system cannot recognize Whether the transfer branch is effectively established, which leads to the interruption of the transfer, by adjusting the current setting value of the converter station to make the transfer switch pass current, after satisfying the effective establishment criterion of the transfer branch, the subsequent transfer operation can be successfully completed, and then the stations can be restored current setting. The risk coping strategy for the conversion failure risk of the three-terminal direct current ground metal loop of the present invention is to adjust the current setting value of the converter station to make the transfer switch flow, satisfy the effective establishment criteria of the transfer branch, and successfully complete the conversion operation.

Description

technical field [0001] The invention relates to direct current transmission technology, in particular to a risk response strategy for conversion failure of a three-terminal direct current earth metal loop. Background technique [0002] In order to improve equipment availability and reduce transmission line investment, long-distance DC transmission projects mostly adopt the "true bipolar + grounding pole" architecture. Taking DC at both ends as an example, under normal circumstances, the two stations operate with a double-pole ground return line. When the poles are balanced, the grounding current can be ignored. Under single-pole fault conditions, as the faulty pole exits, the grounding pole will flow through Rated current, in order to avoid the impact of large ground current on the oil and gas pipeline network, it is necessary to switch the operating pole to a single-pole metal loop operation in time. In addition, after the faulty pole is recovered, it is necessary to switc...

AI Technical Summary

Problems solved by technology

In the existing DC project, in order to prevent the operation overvoltage caused by breaking the earth loop or metal loop when the transfer branch is not effectively established, the protection function of the transfer switch is integrated in the control and protection system, that is, during the conversion process of the earth metal loop, If the current flowing through MRTB or MRS is less than the protection setting value Iset after closing, it is determined that the transfer branch has not been effectively established, and subsequent operations are prohibited. Therefore, the above working conditions will cause the earth metal circuit to fail to transfer

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