A method for checking the sensitivity of the distance protection setting value suitable for single-circuit series connection double-circuit transmission lines

Abstract

The invention discloses a constant value sensitivity check method applicable to single-return-wire tandem-connection double-return transmission line distance protection. According to the working mode, for a single-return-wire interval, a measured impedance calculation expression in fault of the single-return-wire interval is formed on the basis of the characteristic that measured impedance in fault and fault distance are in direct proportion according to a full-line circuit and system impedance parameters; for a double-return-wire interval, according to a grid structure, a circuit and system impedance parameters of a transmission line, circuits and system impedance outside a double return wire are merged to form a typical system layout of power sources at the two ends of the double return wire, then, the calculation mode with which measured impedance changes according to positions of fault points is formed according to the impedance parameters, and different calculation expressions are adopted for one-phase grounding and phase-to-phase faults; all the results are combined, the calculation expression of full-line measured impedance in one-phase grounding and phase-to-phase faults according to the positions of the fault positions is formed, the maximum value of the measured impedance in full-line fault is acquired, and the maximum value is compared with a distance protection element constant value so that the sensitivity of the distance protection element constant value can be checked.

Description

technical field [0001] The invention relates to a power grid relay protection fixed value checking technology, in particular to a technology for checking the sensitivity of a distance protection element in a special mode in which a single-circuit line is connected in series with a double-circuit transmission line. Background technique [0002] With the increasing demand for industrial and residential electricity and the rapid growth of the installed capacity of the power system, the transmission capacity of the original transmission line is close to the limit, and the cost of the new transmission line is getting higher and higher. In order to make the best use of the existing transmission corridor, A new mode of transmission lines in which double-circuit lines are connected in series in the middle of single-circuit lines has emerged. [0003] The current calibration method for the sensitivity of the distance protection element is usually to measure the impedance when a singl...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a calibration method for the fixed value of distance protection for a single-circuit line connected in series with a double-circuit transmission line, so as to solve the problem that the fixed value of the distance protection cannot be calibrated due to the non-monotonic change of the measured impedance with the fault location under the system. test question

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