Pilot protection method for direct current line current abrupt change of multi-terminal direct current transmission system

Abstract

The invention provides a pilot protection method for the direct current line current abrupt change of a multi-terminal direct current transmission system. The method comprises the following steps of: 1, acquiring fault transient state current amperage; 2, calculating the current abrupt change in one period of time by using the acquired fault transient state current amperage, comparing the current abrupt change with a setting value according to the value of the current abrupt change and judging the direction of faults; and 3, distinguishing inside-area and outside-area faults by the cooperation of the current abrupt change directional elements at the terminals of a line; and if the directional element at each terminal is judged to have a forward directional fault, the fault is judged as the inside-area fault, and if at least one directional element is judged to have a reverse directional fault, the fault is judged as the outside-area fault. The method has the advantages that only current data is used, the required sampling rate is low, the current abrupt change is easy to calculate, the communication amount is small, and line faults can be rapidly detected; all energy information but a high frequency signal in a fault transient state is used, the signal energy is strong, and the protection is safety and reliable; and the method is applied to a parallel, a serial and a hybrid multi-terminal direct current system.

Description

【Technical field】 [0001] The invention relates to a relay protection method for a power system line, in particular to a longitudinal protection method for a sudden change in the current of a direct current transmission line in a multi-terminal direct current transmission system. 【Background technique】 [0002] my country's energy distribution and power grid structure determine that HVDC transmission has broad application prospects. Traditional two-terminal DC can only realize point-to-point DC power transmission. When DC interconnection is used between multiple AC systems, multiple DC transmission lines are required, which will greatly increase investment costs and operating costs. With the development of economy and the construction of power grid, it is inevitable that the power grid can realize multi-source power supply and multi-drop power receiving. Therefore, multi-terminal DC transmission system has attracted more and more attention because of its economical, flexible ...

AI Technical Summary

Problems solved by technology

However, the traveling wave protection currently in operation at home and abroad generally has the problem of low reliability and is prone to misoperation. According to the analysis of statistical data, the current transmission line failure is still the main reason for the outage of the DC transmission system. The protection of DC lines Reliability needs to be improved

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