A method and system for fault detection of a DC transmission line

Abstract

The invention relates to a fault detection method and system for a direct current transmission line, belonging to the field of power system relay protection. The method firstly collects the single-ended electrical quantity data of the DC line in real time, and obtains the spatial modulus signal of the single-ended electrical quantity; calculates and obtains the accumulated quantity of the power transformation of the variation of the spatial modulus signal of the single-ended electrical quantity within the set time window, Construct a fault detection signal; continuously judge at least three adjacent fault detection signals, and judge whether they are all greater than the set detection threshold, if not, return to continue to collect and calculate the single-ended electrical quantity, if so, then the line is faulty and a protection is issued start signal. The invention also provides a DC line fault detection system. The method proposed in the invention detects line faults quickly and reliably, and takes into account sensitivity, reliability and quickness.

Description

technical field [0001] The invention relates to a fault detection method and system for a direct current transmission line, belonging to the field of power system relay protection. Background technique [0002] With the rapid development of my country's economy, AC transmission has been unable to meet the electricity demand of our residents. As my country's energy distribution and electricity load demand distribution are in reverse phase, DC transmission lines have become the main direction of my country's power transmission development in the future due to their large capacity, long transmission distance, and convenient grid interconnection. After the failure of the DC transmission line, due to the malfunction of the protection, the DC system will be blocked, resulting in unnecessary shutdown of the DC transmission system. In addition, most of the DC lines are arranged in remote mountainous areas, the natural environment is relatively harsh, and the maintenance is extremel...

AI Technical Summary

Problems solved by technology

Among them, the traveling wave protection is the main protection of the DC line, and its advantage is to determine the fault line quickly and accurately; the differential undervoltage protection is not only the main protection of the DC line, but also the backup protection of the traveling wave protection. For traveling wave protection, the protection speed is slow but the sensitivity and reliability are high, but the above two protections have the technical problem that the protection will malfunction in high-impedance faults, which has not been resolved.

Low voltage protection is the backup protection of traveling wave protection and differential undervoltage protection. This protection is divided into line low voltage protection and pole control line voltage protection. Its advantage is that high resistance faults that cannot be cut off by traveling wave protection and differential undervoltage protection , but there is a problem that it is impossible to distinguish what is an internal fault and what is an external fault

The longitudinal differential protection is the backup protection of the DC transmission line. Its advantage is that it can reliably cut off the high-resistance fault, but there is a problem that any voltage change may cause the protection to malfunction without considering the capacitive current.

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