Line longitudinal differential protection method applicable to three-terminal conventional DC transmission system

Abstract

The invention discloses a line longitudinal differential protection method applicable to a three-terminal conventional DC transmission system, and relates to the technical field of emergency protection circuit devices. The method comprises the following steps: Step 1, reading the operation state of a converter station B and judging whether the converter station B is in a rectification mode or an inverter mode; Step 2, judging the input situation of each pole of each station in the three-terminal conventional DC transmission system; and Step 3, distinguishing the longitudinal differential protection of the same DC line at each pole of each station in the three-terminal conventional DC transmission system. When the longitudinal differential protection input current at both ends of the same DC line meets the following criteria and meets the set delay conditions, a protection device of the three-terminal conventional DC transmission system outputs the protection action. By the line longitudinal differential protection method applicable to the three-terminal conventional DC transmission system, the longitudinal differential protection of DC lines can effectively play a role under various operation modes of the three-terminal DC transmission system by judging the put-into-operation state of each converter station.

Description

technical field [0001] The invention relates to the technical field of emergency protection circuit devices, in particular to a line differential protection method suitable for a three-terminal conventional direct current transmission system. Background technique [0002] Longitudinal differential protection, that is, the longitudinal differential protection of the transmission line, is to use some kind of communication channel to longitudinally connect the protection devices at both ends of the transmission line, and transmit the electrical quantity at each end, such as the direction of current and power, to the opposite end. Compare the electrical quantities at both ends to judge whether the fault is within the range of the line or outside the range of the line, so as to decide whether to cut off the protected line. The conventional DC transmission projects currently in operation are DC at both ends, using bipolar wiring, such as figure 1 shown. In the conventional DC po...

AI Technical Summary

Problems solved by technology

[0005] 1) During inverter operation of converter station B, the second pole protection of converter station B compares the current at both ends of the second pole line, but the actual second pole is connected to the first pole line. The second pole of converter station B loses the protection of the first pole line

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