A single-ended protection method for HVDC transmission lines based on the second-order current gradient

Abstract

The invention discloses a current second-order gradient-based single-ended data protection method for a high-voltage direct-current transmission line. The method comprises the steps of measuring the current at each end of the line, calculating the second-order gradient integral value of the current, and recognizing troubles inside the sample space through comparing the second-order gradient integral value of the current with a starting threshold. The method is simple in principle, and can be realized only by adopting the whole content of a single-ended current. Meanwhile, the filtering is not needed, and the method is easy in implementation. In viewing from the principle, a most serious external fault is guaranteed. That means, the method is free of maloperation and good in selectively during the external metallic grounding fault of a smoothing reactor. Based on the cooperation of existing fault pole selection elements, the correct pole selection action can be achieved. The method is fast in action speed and realizes the complete setting principle. The full-line high speed can be realized. Compared with traveling wave protection, the method is not influenced by noises and is high in reliability. Compared with break variable protection, the method is not influenced by the most serious external fault and is good in selectively. The method can be used for the main protection of the high-voltage direct-current transmission line.

Description

technical field [0001] The invention relates to the field of direct current transmission relay protection in electric power systems, in particular to the fast protection of current single-ended quantity of super / ultra-high voltage direct current transmission lines. Background technique [0002] High-voltage direct current (HVDC) transmission technology has the advantages of large transmission power, low line cost, low converter cost and loss, simple control, and high reliability. It is still the main means of high-voltage, long-distance, and high-power transmission in my country. [0003] The HVDC transmission line is long and has a high probability of failure, while the current source converter lacks a hard control method for the voltage. The DC line fault cannot be removed quickly, and the DC system will rely on the slow adjustment characteristics of VDCOL (low voltage current limiting) to limit the fault current. While a large amount of DC power is lost, it will also impa...

AI Technical Summary

Problems solved by technology

[0004] In the high-voltage DC line protection configurations that have been put into operation, the traveling wave transient protection is mainly used as the fast main protection. However, the existing traveling wave protection principle has disadvantages such as poor resistance to transition resistance, susceptibility to noise interference, and dependence on simulation for setting.

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