A companion impedance protection method for half-wavelength transmission lines

Abstract

The invention relates to an accompanying impedance protection method for a half-wavelength transmission line, which includes: separately obtaining the three-phase current and the three-phase current at the installation place of the M-side relay protection device and the N-side relay protection device of the half-wavelength transmission line. voltage; determine whether the start-up quantity on the M side and the N side meets the start-up condition; determine the fault point F according to the time difference between the start-up quantity on the M-side and the N-side to meet the start-up condition; open the relay of the half-wavelength transmission line according to the accompanying impedance of the half-wavelength transmission line protective action. The method provided by the invention can locate the fault by using the time difference method according to the characteristics of the fault period, construct the accompanying impedance by compensating the voltage and current on both sides of the line, and correctly reflect the fault inside and outside the line area, because the accompanying impedance protection effectively utilizes Double-terminal electrical information, so faults within the line area can be quickly and reliably activated, and faults outside the line area will not malfunction, and the protection has high sensitivity.

Description

technical field [0001] The invention relates to the field of relay protection of electric power systems, in particular to an accompanying impedance protection method for half-wavelength transmission lines. Background technique [0002] The half-wavelength AC transmission system is a new type of power transmission system, and its transmission distance is 3000 kilometers (50Hz) or 2600 kilometers (60Hz). Compared with conventional AC power transmission, half-wavelength power transmission has the advantages of no need to install reactive power compensation equipment, excellent economy, and no need to install intermediate switching stations, so it is a very potential power transmission method. [0003] On traditional transmission lines, due to the relatively simple principle of distance protection, the obtained impedance can correctly reflect the characteristics of the line after a fault, and can act quickly and reliably after a fault, so it is widely used as a fast protection i...

AI Technical Summary

Problems solved by technology

[0004] However, the transmission distance of the half-wavelength transmission line is extremely long, the distributed capacitance is large, and reactive power compensation equipment is not installed on the line, the voltage along the line changes greatly, and the impedance obtained according to the conventional distance protection principle cannot reflect the fault characteristics of the line at all. The formed distance protection cannot operate correctly when a fault occurs inside or outside the line area, so the existing conventional distance protection cannot be applied to half-wavelength transmission lines.

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