A transmission line current differential protection system and method with enhanced robustness

Abstract

The invention discloses an enhanced-robustness differential protection system for a transmission line. The differential protection system comprises an acquisition module for collecting an electrical quantity and sending the electrical quantity to a single-ended quantity protection module, the single-ended quantity protection module for performing single-ended quantity protection operation according to the electric quantity data collected by the acquisition module, a differential adjustment module for adjusting a differential threshold and a braking coefficient according to a calculation result of the single-ended quantity protection module, a differential protection module for latching a differential relay or performing differential protection operation according to the calculation result of the single-ended quantity protection module. With the protection system disclosed by the invention, when a CT line breaking phenomenon occurs at a certain side of a line and an external fault occurs, misoperation of differential protection can be avoided. Besides, while the reliability of differential protection is guaranteed, the anti-transition resistance capability of the differential protection is improved. In addition, the invention also discloses an enhanced-robustness differential protection method for transmission line.

Description

technical field [0001] The invention belongs to the technical field of power grid relay protection, and in particular relates to a transmission line current differential protection system and a protection method. Background technique [0002] Transmission line current differential protection is a kind of transmission line main protection, and its theoretical basis is Kirchhoff's current theorem. When the transmission line is working normally or there is a fault outside the area, ignoring the influence of the distributed capacitance of the line, the current flowing into the line is equal to the current flowing out, the differential current is zero, and the differential relay does not operate. When the transmission line internal fault, ignoring the influence of line distributed capacitance, the differential current is equal to the fault current flowing into the line, and the differential relay operates. The principle of current differential protection is simple, reliable and ...

AI Technical Summary

Problems solved by technology

However, when the CT is disconnected and a large fault current out-of-area fault occurs at the same time, the differential protection will still malfunction

[0004] In addition, the differential protection is greatly affected by the load current. When a high-resistance fault occurs in the area under heavy load, the differential protection has the risk of refusing to operate.

At present, the method to improve the anti-transition resistance ability of differential protection is to reduce the differential current threshold and braking coefficient, but this method increases the possibility of out-of-area faults, differential protection misoperation, and reduces the reliability of differential protection.

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