Pilot protection of high-voltage direct-current transmission line based on measurement wave impedance under tuning frequency

Abstract

The invention relates to a pilot protection method for a high-voltage direct-current transmission line based on measurement wave impedance under tuning frequency. The pilot protection method comprises the following steps: determining internal and external fault identification criteria; determining a fault starting criterion; determining a fault pole selection criterion; determining a protection scheme; continuously collecting current and voltage data at two sides of the line and extracting tuning frequency components of the current and voltage data, if the current at the protection installation position of the DC line at a certain end meets a fault starting criterion, starting a protection starting element at the end, and calculating the measurement wave impedance at the tuning frequency of the end; when the measured wave impedance under the tuning frequency at the two ends of the rectification side and the inversion side is smaller than a threshold value, an internal fault is judged; otherwise, the fault is an external fault; and if the internal fault is determined, calculating a pole selection function by using the voltage fault component to realize fault pole selection. The method can quickly and reliably identify internal and external faults of the DC line area, reliably protects the overall length of the line, is high in transition resistance resistance, does not need real-time synchronization of data at two ends of the line, and is higher in action speed than traditional current differential protection.

Description

technical field [0001] The invention belongs to the technical field of power system protection and control, and relates to a high-voltage direct current transmission line longitudinal protection based on measuring wave impedance at a tuning frequency. Background technique [0002] High voltage direct current (HVDC) is widely used in asynchronous grid interconnection and long-distance large-capacity power transmission. The HVDC transmission distance generally exceeds 1 000 km, the geographical / climatic conditions along the route are complex and harsh, and the possibility of line failure is high, so reliable DC line protection is urgently needed. At present, DC lines generally adopt traveling wave protection as the main protection, and differential undervoltage protection and current differential protection as backup protection. Traveling wave protection operates quickly, but it is difficult to detect the wave head in the event of a high-resistance grounding fault; differenti...

AI Technical Summary

Problems solved by technology

However, this type of protection mostly ignores the attenuation effect of the DC line on the high frequency

For long UHV DC transmission lines, when there is a fault in the line end area, especially when the high-resistance ground fault is in the end area, the high frequency measured by the protection element at the head end of the line may be smaller than that when the metal ground fault near the rectifier side is outside the area. The high-frequency quantity measured by the protection element makes it difficult to set the value of the single-ended transient quantity protection, and even causes the protection to fail to protect the entire length of the line.

In order to solve this problem, some literature proposes to use the fault current and DC reactor voltage drop to form a direction discrimination element, and cooperate with the boundary element to realize full-line protection. However, the protection quickness and reliability of this method have declined.

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