A fault line selection method for double-circuit DC transmission lines on the same tower based on unipolar information

Abstract

The invention discloses a fault line selection method of double-circuit direct current transmission lines on the same tower based on unipolar information, which comprises the following steps: 1. Calculating the voltage variation of four pole lines; Step 3, if the lower polar line meets the conditions, go to step 4; 3, if the low-frequency harmonic amplitude meets the minimum value requirement, continue to calculate the low-frequency and high-frequency harmonic amplitude ratio, if the ratio is greater than 1, it is judged that the local polar line is faulty , otherwise block the traveling wave protection of this pole; 4. Delay the voltage change to sample, if only one abrupt wave head is detected within the data processing time window, go to step 3; if at least Two abrupt wave heads, compare the relationship between the polarity and amplitude of two consecutive wave heads, if the polarities are both positive and the amplitude relationship satisfies a certain multiple condition, it is judged that the local line is not a near-end fault, otherwise, block the local Polar traveling wave protection. It has the advantages of high sensitivity, strong quick movement, and is not easy to misjudgment.

Description

technical field [0001] The invention relates to a direct current transmission technology of a power system, in particular to a fault line selection method of a double-circuit direct current transmission line on the same tower based on unipolar information. Background technique [0002] The uneven distribution of natural energy in China and the asymmetric distribution of energy and population make HVDC transmission technology have broad application prospects in China. Compared with high-voltage AC transmission technology, high-voltage direct current transmission technology has the advantages of low unit cost, large transmission power, no need for synchronous operation of AC at both ends, and rapid control and adjustment. Therefore, the use of high-voltage direct current transmission technology is conducive to improving the economic and technical indicators of the power system , operational reliability and scheduling flexibility. [0003] In order to ensure the safe and relia...

AI Technical Summary

Problems solved by technology

However, since the double-circuit DC transmission lines on the same tower do not perform transposition, the polarities and amplitudes of the line-mode and ground-mode traveling wave components coupled out when different polar lines are grounded are different on each polar line, and the wave velocity It is not the same, which greatly increases the difficulty of identifying faulty polar lines in existing traveling wave protection schemes based on unipolar line information

If the above problems are solved only by increasing the setting value, the sensitivity of the protection will be affected. Therefore, it is necessary to make full use of the fault traveling wave propagation characteristics of the double-circuit DC line on the same tower to solve the problem.

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