A method and system for distance protection of instantaneous value variation based on coordinate transformation

Abstract

The invention discloses a distance protection method and system for instantaneous value variation based on coordinate transformation, and belongs to the field of relay protection of electric power systems. The present invention introduces the key technical means of coordinate change, and transforms the AC flow into a DC flow through coordinate transformation. The introduced coordinate transformation is only applicable to the three-phase symmetrical system, and if it is used directly, it is only applicable to the three-phase symmetrical fault in the power system. The virtual three-phase system realizes the response to different types of faults in the power system. The present invention determines whether an in-zone fault occurs by comparing the variation of the instantaneous voltage value at the setting point with the variation of the instantaneous voltage value at the fault point, without extracting the power frequency phasor, and has faster action speed, simple criterion, and short required data window. It can effectively improve the action speed of AC line distance protection and improve the safety and stability of the system.

Description

technical field [0001] The invention belongs to the field of relay protection of electric power systems, and more specifically relates to a method and system for distance protection of instantaneous value variation based on coordinate transformation. Background technique [0002] At this stage, my country has formed the world's largest and highest voltage level AC-DC hybrid power grid. High-voltage AC transmission lines are the main arteries of power transmission, and their operation safety is particularly important for the safety and stability of the entire power system. The cutting speed puts forward higher requirements. The distance protection has the advantages of being basically not affected by the system operation mode, and the setting calculation is relatively simple, so it has been widely used in the AC transmission system. Therefore, improving the action speed of distance protection is of great significance to ensure the safe and stable operation of the power grid. ...

AI Technical Summary

Problems solved by technology

[0003] At present, the traditional distance protection is generally based on the power frequency phasor. By comparing the magnitude of the voltage phasor change at the setting point and the voltage phasor change at the fault point to determine whether an internal fault occurs, the action speed will be extracted by the power frequency phasor. The time window of the algorithm is limited, and the speed of action is facing a bottleneck

[0004] To solve this problem, patent CN112039036A discloses a distance protection method and system for the instantaneous value variation of AC lines, using the three-phase voltage and three-phase current collected by the relay protection device, combined with the transmission line model, to calculate the set point voltage; according to the fault time and The three-phase voltage and three-phase current collected by the relay protection device, combined with the transmission line model, constructs the virtual fault point voltage; uses the set point voltage processed by the digital low-pass filter to calculate the change of the set point voltage; uses the digital low-pass The voltage at the virtual fault point processed by the filter is used to calculate the voltage change at the virtual fault point; the absolute value of the voltage change at the set point and the virtual fault point voltage change within a preset time after the fault is compared to determine whether an internal fault occurs. This method exists The problem of invalidation of zero-crossing criterion

In addition, in the AC-DC hybrid power grid with large-scale new energy access, it is difficult to accurately extract the power frequency phasor.

Images