A single-ended self-accompanying impedance protection method suitable for half-wavelength transmission lines

Abstract

The invention relates to a non-unit self-adjoint impedance protection method applicable to a half-wavelength power transmission line. The method comprises the following steps of acquiring a three-phase current and a three-phase voltage of a relay protection device installation side of the half-wavelength power transmission line; judging whether starting quantity of the half-wavelength power transmission line conforms to a starting condition or not; determining variable quantity impedance of the half-wavelength power transmission line; combining steady-state quantity impedance and variable quantity impedance of the half-wavelength power transmission line into self-adjoint impedance of the half-wavelength power transmission line; and opening relay protection action of the half-wavelength power transmission line according to the self-adjoint impedance of the half-wavelength power transmission line. According to the method provided by the invention, relay protection action is very rapidly and reliably carried out when a fault occurs in a circuit by means of non-unit electrical quantity of the half-wavelength power transmission line, false action of the fault outside a circuit region can be prevented, and the reliability and the sensitivity of relay protection of the half-wavelength power transmission line are improved.

Description

technical field [0001] The invention relates to the field of relay protection of power systems, in particular to a single-ended self-accompanying impedance protection method suitable 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 the protection only requires a single-ended electrical quantity, and i...

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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 can no longer reflect the fault characteristics of the line. The 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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