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

Abstract

The invention discloses a fault line selection method for a same-tower double-circuit direct current transmission line. The fault line selection method comprises the following steps: calculating linear modal wave and ground modal wave of the current circuit of the double-circuit according to the polar line voltage and current of the current circuit; calculating ground modal wave change rate; judging whether the ground modal wave change rate is larger than a minimum setting valve or not, if yes, obtaining squared value of the linear modal wave and the ground modal wave respectively, then performing integration, and calculating the integral ratio of the linear modal wave and the ground modal wave, and if not, continuing to judge; distinguishing the fault circuit and the non-fault circuit according to the ratio; distinguishing the fault polar and the non-fault polar in the fault circuit according to the integral value of the ground modal wave. The method has the advantages of high sensitivity, small operation amount, requirement of current circuit information, no communication between different circuits, short determining time, low influence by transition resistance, capability of quickly determining the fault circuit of the same-tower double direct current transmission line without misjudgement and the like.

Description

technical field [0001] The invention relates to a direct current transmission technology of an electric power system, in particular to a fault line selection method of a double-circuit direct current transmission line on the same tower. 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 reliable operation of the...

AI Technical Summary

Problems solved by technology

The double-circuit line on the same tower has two circuits, and each circuit has a positive pole and a negative pole. If the pole line of one circuit fails, the fault electric quantity will be induced at the positive pole and negative pole of the other circuit during the traveling wave propagation process. It is unfavorable to the traveling wave protection based on single-circuit line or single-pole line, and may cause non-faulty circuit protection misoperation

In order to ensure the reliability of transmission line selection, the line setting value must be increased, but because the fault characteristics of electrical quantities such as voltage and current are not obvious during high-impedance ground faults, the fault line selection method is also prone to refusal

After the traditional modulus traveling wave protection based on single-circuit line design is applied to the double-circuit DC transmission line on the same tower, although the line-mode wave coupled to the non-fault is very small, because there are three different lines on the double-circuit line on the same tower Mode component, the line mode wave induced by non-fault echo changes with the transition resistance and fault distance, which may cause the line mode wave change rate and line mode wave change amplitude to be greater than the setting value and cause malfunction

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