Concomitant impedance protection method for half-wavelength transmission line

Abstract

The invention relates to a concomitant impedance protection method for a half-wavelength transmission line. The method comprises the following steps of obtaining three-phase currents and three-phase voltages of the location of a relay protection device at an M side of the half-wavelength transmission line and the location of a relay protection device at an N side of the half-wavelength transmission line separately; judging whether the starting quantities of the M side and the N side meet the starting conditions or not; determining a fault point F according to a time difference that the starting quantities of the M side and the N side meet the starting conditions; and opening the relay protection action of the half-wavelength transmission line according to a concomitant impedance of the half-wavelength transmission line. The method provided by the invention can position the fault by a time-difference method according to the characteristics of a failure period, construct the concomitant impedance by compensating the voltages and the currents at two sides of the line, and correctly reflect an internal fault and an external fault of a line region. Two-terminal electric information is effectively utilized by the concomitant impedance protection, so that the protection can quickly and reliably act after the internal fault of the line region happens; the protection does not move by mistake after the external fault of the line region happens; and the protection has relatively 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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