Under-range fast protection system and method for half-wavelength line

Abstract

The invention discloses an under-range fast protection system for a half-wavelength line. The system comprises a distance I-segment protection unit for sending an action signal to a control unit whenan I-segment protection action condition is satisfied, a zero negative sequence time difference protection unit for sending an action signal to the control unit when a zero negative sequence time difference protection action condition is satisfied, and the control unit used for rapidly removing a fault near a half-wavelength line outlet when the action signals sent by the distance I-segment protection unit and the zero negative sequence time difference protection unit are received at the same time. The invention also discloses an under-range fast protection method for a half-wavelength line. Distance I-segment protection and zero negative sequence time difference protection are arranged for the half-wavelength line at the same time, and the fault near a half-wavelength line exit is quicklyremoved when the I-segment protection action condition and the zero negative sequence time difference protection action condition are satisfied at the same time. According to the technical scheme, the collection of single end single-end electrical quantity is only needed, the protection delay is small, and the fault near the half-wavelength line exit is quickly removed.

Description

technical field [0001] The invention belongs to the field of relay protection of electric power systems, and in particular relates to a system and method for short-range rapid protection of half-wavelength lines. Background technique [0002] Half-wavelength AC transmission (HWACT) refers to the ultra-long-distance three-phase AC transmission whose electrical distance is close to a power frequency half-wave, that is, 3000km (50Hz). With the construction of Energy Internet, half-wavelength AC power transmission, as an efficient long-distance intercontinental power transmission method, has a good application prospect. [0003] UHV half-wavelength transmission lines have long transmission distances, and their electrical characteristics are quite different from existing UHV lines. Some enterprises and scholars have conducted research on the relay protection principle of half-wavelength AC transmission lines. [0004] Chinese patent application number CN201610866926.8, applicat...

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Problems solved by technology

[0004] Chinese patent application number CN201610866926.8, application date September 29, 2016, publication number CN106356821A, publication date January 25, 2017, the title of the invention is "a half-wavelength line protection method based on three reference point Berillon differential currents "; Chinese patent application number CN201610058603.6, application date January 28, 2016, publication number CN105552863A, publication date May 4, 2016, the title of the invention is "A method for accompanying impedance protection for half-wavelength transmission lines" , the half-wavelength line protection methods of these two patents need to collect the three-phase voltage and three-phase current on both sides of the line, and the protection is not fast enough.

However, the half-wavelength line has brought a new problem to the protection of the distance I section: when a three-phase short-circuit fault occurs at F1 point x kilometers away from the M side in the area, the measured impedance is Z m = Z c tanh(γx); when a three-phase short circuit occurs at point F2 at a distance of L+x kilometers from side M outside the area, the measured impedance is also Z m = Z c tanh(γx); distance I section protection cannot distinguish F1 and F2 point faults, such as figure 1 shown

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