Protection method of DC transmission line transverse difference based on DC filter branch current

Abstract

The invention discloses a transverse differential protection method for a DC power transmission line based on a DC filter branch current, and the method comprises the steps: 1, measuring current instantaneous values, passing through an I-pole DC filter branch circuit and an II-pole DC filter branch circuit, of a rectification side of a DC power transmission system, and recording the current instantaneous values as i(t) and i<II>(t); 2, calculating a transverse differential protection current instantaneous value according to a formula: i<hc>(t) = i(t) + i<II>(t), taking 10 ms as a data window, calculating a transverse differential current, the root-mean-square value of the I-pole DC filter branch circuit and the root-mean-square value of the II-pole DC filter branch circuit, and respectively recording the transverse differential current, the root-mean-square value of the I-pole DC filter branch circuit and the root-mean-square value of the II-pole DC filter branch circuit as I<hc>, I, and I<II>; 3, carrying out the fault discrimination: start timing from zero when I<hc> is greater than I<set>, and recording a timing result as t; setting a mark flag = 1 if t is greater than t<set>, judging that a DC power transmission line region has a fault at this moment, and executing step 4, wherein I<set> is a current operation set value, and t<set> is a time delay set value; 4, carrying out the discrimination of a fault region: judging that the fault happens in a I-pole line region if I / I<II> is greater than one, or else, judging that the fault happens in an II-pole line region.

Description

technical field [0001] The invention relates to the technical field of relay protection and automatic control of a power system, in particular to a method for protecting DC transmission line transverse differences based on DC filter branch current. Background technique [0002] With the rapid development of DC transmission technology in my country in recent years, a large number of EHV and UHV DC transmission projects have been put into operation, and the AC-DC hybrid grid has gradually replaced the traditional AC grid and has become an important feature of the current domestic grid. [0003] In the DC transmission system, the working conditions of the DC transmission line are harsh and the probability of failure is high. Therefore, configuring a high-performance relay protection system is an important prerequisite to ensure the safe and reliable operation of the DC transmission system. At present, most DC transmission lines use traveling wave protection and differential und...

AI Technical Summary

Problems solved by technology

The main protection has low sensitivity and lack of setting basis. At the same time, the sampling frequency and processing capacity of the device are extremely high; the current differential protection action speed is too slow, it is difficult to quickly remove the fault, and the sensitivity to the high-impedance ground fault of the DC transmission line is insufficient. As a result, the protection performance cannot fully meet the actual needs of the project

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