A differential protection algorithm for two-terminal HVDC transmission lines

Abstract

The invention discloses a differential protection method for double-terminal high-voltage direct current transmission lines. The specific steps are as follows: 1, constructing equivalent line models of out-of-zone and in-zone fault DC power transmission lines; 2: describing the voltage and current of the two measuring terminals of each pole DC line and the mathematical expressions in time domain related to the voltage and current; 3, describing a time domain mathematical expression of the integral expression of the voltage difference and the integral expression of the current sum, constructinga calculation term of the integral expression of the longitudinal impedance based on the fault component and the total fault quantity, and qualitatively analyzing the fault state result according tothe longitudinal impedance protection idea; 4, construct an improved criterion of current differential protection according to that qualitative analysis result. The method of the invention overcomes the problems that the traditional DC line differential protection lacks a relatively stable braking amount and is susceptible to high-frequency harmonic interference generated by line distributed capacitance, operation of power electronic devices and the like.

Description

technical field [0001] The invention belongs to the technical field of relay protection for direct current transmission lines, and relates to a differential protection method for double-terminal high-voltage direct current transmission lines. Background technique [0002] The high-voltage DC transmission line is the main artery of my country's energy allocation pattern. Its safety and stability will not only affect the operation safety of the entire DC system, but also have an impact on the AC power grid at both ends of the DC system. Due to the long high-voltage direct current transmission line, the geographical environment and climate environment along the line are complex and changeable, and the probability of failure is high. Therefore, in-depth analysis and research on the problems existing in the protection of HVDC transmission lines, and the optimization and improvement of their protection are very important to strengthen the ability of the line to resist risks and im...

AI Technical Summary

Problems solved by technology

[0009] The purpose of the present invention is to provide a differential protection method for double-ended HVDC transmission lines, which overcomes the lack of relatively stable braking capacity of traditional DC line differential protection and is susceptible to high-frequency harmonics generated by line distributed capacitance and power electronic device operation. wave interference etc.

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