High-sensitivity traveling-wave protection method for high-voltage direct current power transmission line

Abstract

The invention discloses a high-sensitivity traveling-wave protection method for a high-voltage direct current power transmission line. The method sequentially comprises the steps of powering on a relay protection device; assigning values to traveling-wave protection fixed values Delta initial, Delta u, Delta T, Delta i and Delta du / dt; measuring the voltage u and current i of the line, and calculating a voltage change rate du / dt; judging whether du / dt is greater than Delta initial or not, entering the next step if du / dt is greater than Delta initial, otherwise repeating the step; calculating a voltage change rate calculation value du / dtAVG, an average current change value iAVG and duration T meeting the condition that u is smaller than Delta u; judging whether iAVG at a point is greater than Delta i or not, whether du / dtAVG at the point is greater than Delta du / dt or not and whether T more than or equal to Delta T exists in a time period t1 or not if du / dt is greater than Delta initial, starting protection if the three conditions are met, otherwise continuing judging whether du / dt is greater than Delta initial or not. According to the method, the addition of converter station communication is avoided, and the method is quick in response and high in sensitivity.

Description

technical field [0001] The invention relates to the field of direct current transmission in electric power systems, in particular to a high-sensitivity traveling wave protection method for high-voltage direct current transmission lines. Background technique [0002] In recent years, my country's direct current transmission has developed rapidly, and a large number of direct current transmission projects are about to be put into production or operation. Therefore, direct current transmission will play a vital role in the safety and stability of my country's power grid and the optimal allocation of resources in the future. However, the line protection of existing DC transmission projects has a low correct action rate for line faults, which is concentrated in the fact that the main protection traveling wave protection of the line protection has a low ability to withstand transition resistance, and the ability to withstand transition resistance at weak points is lower than 100 o...

AI Technical Summary

Problems solved by technology

[0004] (1) Increase the communication between converter stations: the actual application of traveling wave protection does not use communication, and the line and system need to be modified, which increases the difficulty of application and reduces the reliability of protection actions; and the existing converter station The communication time is greater than 10ms, which will affect the action time of the protection

[0005] (2) Some studies are more theoretical and lack engineering applicability: the sampling frequency of the new principle of traveling wave protection proposed by some documents is relatively high, up to 1MHz, but the sampling frequency of the current DC system is 6kHz or 10kHz, so a higher sampling frequency is adopted. The sampling frequency of the traveling wave protection principle has limited practical value

However, this traveling wave protection method only uses the maximum value or extreme value of the voltage change rate, voltage change amount, and current change amount to judge the fault, but this method cannot really distinguish the high-resistance fault inside the zone and the fault outside the zone, and ignores a large number of faults. The transient characteristics of the fault

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