Instantaneous value variation distance protection method and system based on coordinate transformation

Abstract

The invention discloses an instantaneous value variation distance protection method and system based on coordinate transformation, and belongs to the field of power system relay protection. According to the invention, a key technical means of coordinate change is introduced, and an alternating current quantity is converted into a direct current quantity through coordinate transformation. The introduced coordinate transformation is only suitable for a three-phase symmetric system, if the coordinate transformation is directly used, the coordinate transformation is only suitable for a three-phase symmetric fault in a power system, in order to deal with a single-phase earth fault, an interphase short-circuit earth fault and an interphase fault, a virtual three-phase system is constructed based on single-phase information, and different types of faults in the power system are dealt with. According to the method, whether the internal fault occurs or not is determined by comparing the variable quantity of the voltage instantaneous value at the setting point and the variable quantity of the voltage instantaneous value at the fault point, power frequency phasors do not need to be extracted, the action speed is higher, the criterion is simple, the required data window is short, the distance protection action speed of the alternating-current line can be effectively increased, and the safety and stability of the system are improved.

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.

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