Current differential protection method based on fault component current amplitudes and phase differences

Abstract

The invention relates to a current differential protection method based on fault component current amplitudes and phase differences. The current differential protection method is characterized in that: a differential protection criterion is formed by the adoption of the current fault component amplitudes at two sides of a protected line and the phase differences at the two sides of the protected line, wherein the differential current value (Icd) is equal to the sum of the current fault component amplitude (the absolute value of [delta]IM) at one side and the product of the current fault component amplitude (the absolute value of [delta]IN) at the opposite side and a cosine function of the phase difference ([phi]) between the absolute value of [delta]IM and the absolute value of [delta]IN, i.e. Icd= (the absolute value of [delta]IM)+(the absolute value of [delta]IN)cos[phi]; and the braking current (Ir) is equal to the difference between the absolute value of [delta]IM and the product of the absolute value of [delta]IN and the cos[phi], i.e. Ir= (the absolute value of [delta]IM)-(the absolute value of [delta]IN)cos[phi], and the differential protection criterion is the following inequation: Icd-KIr>= Idz, wherein K is a braking coefficient and Idz is an action current threshold. If the differential protection criterion is satisfied, an internal fault is determined and the differential protection acts; if the differential protection criterion is not satisfied, an external fault is determined and the differential protection does not act. The current differential protection method related to the invention has the advantages of higher sensitivity for internal faults, higher safety for external faults, fewer effects subjected from the factors, such as the transition resistance, the distributed capacitance, the TA saturation and the like, and good performances.

Description

technical field [0001] The invention relates to a current differential protection method in the field of electric power system relay protection, in particular to a current differential protection method based on fault component current amplitude and phase difference. Background technique [0002] The principle of current differential protection is implemented according to Kirchhoff's first law. By calculating whether the current flowing into and out of the protected object is equal, it can be judged whether an internal fault has occurred in the protected object. The principle of current differential protection has a strong ability to extract internal fault information and does not require voltage. It has been widely used in power systems. Most equipment and lines are preferentially using current differential protection as the main protection. According to the different currents used, the current differential protection can be divided into the principle of full current differ...

AI Technical Summary

Problems solved by technology

Compared with the traditional method, this invention has greatly improved the reliability and sensitivity of fault judgment, but the performance in dealing with unbalanced current needs to be improved

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