High-voltage transmission line distance protection method based on parametric recognition

Abstract

The invention provides a high-voltage transmission line distance protection method based on parametric recognition. The method comprises the following steps: collecting a three-phase voltage and a current; performing low-pass filtering, sampling holding and A/D (Analog to Digital) conversion on the sampled three-phase voltage and current, thereby acquiring a three-phase sampling value; performing phase-to-analog conversion on the three-phase sampling value, using a compensation algorithm which takes a line frequency-changing parameter characteristic into account to compensate till reaching the tail end of the line, and acquiring the three-phase voltage and the current of a compensation point by performing the phase-to-analog conversion; and utilizing three-coefficient differential equation algorithms of corresponding phases to calculate three phases, combining with a fault phase element result, and confirming a fault position according to a fault phase calculated result when a single-phase grounding fault occurs. The high-voltage transmission line distance protection method based on parametric recognition has the advantages that the influences of a long-line distributed parameter and a fault transient state are overcome; the influence of line parameter frequency change is overcome; the transition resistance resisting capability of distance protection is greatly promoted, especially the transition resistance resisting capability close to the tail end of the line; and when fault occurs at the tail end of the line, the method is used for greatly promoting the transition resistance resisting capability under the condition of ensuring the protection being free from exceeding.

Description

【Technical field】 [0001] The invention relates to the field of relay protection of power system transmission lines, in particular to a method for distance protection of high-voltage transmission lines of power systems. 【Background technique】 [0002] Distance protection is widely used in high voltage transmission lines. The shortcomings of traditional distance protection, such as low resistance to transition resistance and insufficient speed of action, limit its further application. In high-voltage transmission lines, single-phase ground faults are the most common faults. Single-phase ground faults are often accompanied by high transition resistance. If such faults cannot be removed quickly, it will cause greater harm to system stability and safety. [0003] At present, when the traditional microcomputer distance protection considers the influence of grounding resistance in the equation, it generally treats the current distribution coefficient of the system on both sides of...

AI Technical Summary

Problems solved by technology

With this assumption method, when the fault occurs near the beginning of the protection range, the error introduced is very small, and the protection operates reliably; when the fault occurs at the end of the protection range, especially after a high transition resistance fault, the calculation distance of the protection will be greatly increased. error, resulting in protection overriding or refusal to move

When the traditional distance protection has a fault at the end of the line, its resistance to transition resistance is very low

Under the 500kV system, the maximum transition resistance can reach 300Ω, while the transition resistance of traditional distance protection at the end of the line is less than 20Ω, which is far from meeting the requirements of the system

The protection method based on the power frequency quantity is limited by the power frequency quantity extraction, the protection action speed is limited, and the short data window is greatly affected by the transient component

The fundamental problem of the above two methods is that after calculating the voltage and current of the compensation point, the traditional distance protection equation is still used, that is, based on the assumption that the system current distribution coefficient on both sides of the fault point is a real number, which leads to the transition resistance of the two methods The capacity is not high, and when a high-resistance grounding fault occurs at the end of the line, there will be problems of overshooting or refusal to move

[0005] The distributed parameter characteristics of long ultra-high voltage lines make the measured impedance of traditional distance protection not proportional to the fault distance. During the fault transient period, the voltage and current contain a large number of harmonics, and the line parameters have frequency-varying characteristics. The model is not accurate enough, and the influence of frequency variable parameters should be taken into account to further obtain accurate compensation voltage and current

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