A Method for Identifying Faults in Grounding Electrode Lines of HVDC Transmission System

Abstract

A method for identifying ground electrode line faults in HVDC transmission systems. The main steps are: A. data acquisition, the electrical measuring device at the neutral bus measurement point of the grounding electrode system collects the voltage signal at the head end of the grounding electrode line and the current signal of the two grounding electrode lines in real time; B. data processing, through the full-wave The Fourier algorithm extracts the characteristic harmonic components of the voltage signal at the head end of the ground electrode line and the current signal of the earth electrode line; C, the calculation of the impedance amplitude ratio of the characteristic harmonic measurement, using the characteristic harmonic voltage amplitude and The characteristic harmonic current amplitudes of the two grounding electrode lines are respectively calculated for the characteristic harmonic measurement impedance amplitudes of the two grounding electrode lines, and then the characteristic harmonic measurement impedance amplitude ratio is obtained; D. Line short-circuit fault identification, characteristic harmonic If the measured impedance amplitude ratio is less than or equal to the set threshold, it is determined that the grounding electrode line is faulty. The method has strong resistance to transition resistance, high detection sensitivity, low implementation cost and easy engineering realization.

Description

technical field [0001] The invention relates to a fault identification method in relay protection of an electric power system, in particular to a fault identification method for a ground electrode line of a high-voltage direct current transmission system. Background technique [0002] The grounding electrode is an important part of the HVDC transmission system, which plays the role of providing a path for the unbalanced current and clamping the neutral point voltage. In order to avoid the impact of DC bias on the converter station equipment, the grounding pole is usually not grounded at the nearest converter station equipment, but connects the neutral point of the converter station equipment to a remote place through two parallel overhead lines of hundreds of kilometers grounding. Its ground electrode line is long and the environment experienced is complex, resulting in a high failure rate. In actual engineering, there are many incidents where ground electrode line faults ...

AI Technical Summary

Problems solved by technology

For example: Since Xing’an DC Transmission Project was put into operation in 2007, there have been too many unbalanced ground electrode lines (the current deviation on the two parallel lines is large) protection actions, resulting in bipolar or unipolar blocking events

In July 2015, when Binjin DC was operating at full load, pole 2 was blocked, and the current of Binjin and Fufeng DC's common grounding pole line increased instantaneously, causing the grounding pole lead 1 to break due to overload

When a short-circuit ground fault occurs at the back of the protective ground electrode line, the current deviation of the two ground electrode lines is small enough to determine that the fault has occurred; and the transition resistance of the short-circuit ground fault (the resistance formed by various debris between the short-circuit point and the ground) ) will also reduce the current deviation of the two grounding electrode lines, resulting in low protection sensitivity, and the grounding electrode line may run with "disease" for a long time, posing safety hazards

In order to solve the problem of low protection sensitivity when a high-resistance, remote grounding fault occurs in the grounding electrode line of the HVDC power transmission system, high-frequency signals can be injected into the grounding electrode line to monitor the high-frequency impedance or electrical quantity of the line to identify the fault

However, the drift and deviation of the parameters of the ground electrode line in the high-frequency signal environment will seriously affect the impedance monitoring value, which objectively brings difficulties to the setting of such criteria; at the same time, this method requires accurate high-frequency signal injection equipment and sensitive The high-frequency signal detection device has high requirements on hardware and is difficult to implement in engineering

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