Research On The Influence Of Missing Information On Line Differential Protection And Countermeasures

The intelligent substation is based on the IEC 61850 standard to complete functions such as data collection and transmission of equipment in the station.In the transmission process of analog sampled data of the substation,due to communication network failures and other reasons,the sampled data may be lost or even a data transmission link failure.The loss of sampled data will affect the accuracy of the phasor calculation,which will have a serious impact on the reliability of various types of protection in the substation,especially the differential main protection.Since there are multiple scenarios for the number and types of sampled data loss,the error analysis of the information reconstruction method after data loss has certain limitations.Based on the information entropy theory and the residual valid information in the missing data packets,this paper proposes a method for evaluating the effectiveness of information reconstruction scheme based on singular entropy.This method directly measures the error magnitude of the reconstructed signal phasor by sampling data.According to the evaluation method,countermeasures for differential protection in the absence of sampling information are proposed,which is of great value to ensure the normal operation of differential protection and maintain the safety of intelligent substations.This article first classifies the scenarios where sampled data is lost based on the number and location of data points lost.The full-cycle Fourier algorithm used in line differential protection phasor calculation is introduced,and the error caused by the loss of sampling data to the phasor calculation using full-cycle Fourier algorithm is quantitatively analyzed.This article introduces several mathematical interpolation reconstruction methods after the sampled data is lost.At the same time,this paper proposes an interpolation reconstruction method based on the orthogonal characteristics of the filter,and compares it with the commonly used zero-filling interpolation and linear Lagrange interpolation methods in different sampled data loss scenarios.In addition to the interpolation reconstruction method,this paper also proposes a reconstruction method based on adjacent channel information,analyzes the basic principles of the reconstruction of adjacent channel information and the main factors that cause the reconstruction error of the method,and quantitatively analyzes the method in different scenarios Phasor calculation error.Based on the information entropy theory,this paper constructs the sampled data into a state space matrix and calculates the singular entropy of its eigenvalues,and proposes a method for evaluating the reconstruction effect of the sampled data based on singular entropy.The correlation between the reconstruction error of the sampled data and the singular entropy value is quantitatively analyzed.This evaluation method can be applied to various scenarios where the sampled data is lost,and the phasor calculation error generated by the reconstruction method can be effectively judged,and the differential is proposed based on this method.The countermeasures for missing protection sampling data,by adaptively changing the setting value and braking coefficient of differential protection through singular entropy value,can avoid the influence of the lack of sampling information on the reliability of differential protection,and verify the difference proposed in this paper by simulation analysis The correctness of the response measures for automatic protection.