New Principle of Fault Data Synchronization for Intelligent Protection Based on Wavelet Analysis

Abstract

In order to eliminate the influence of the delay error of the sampled value in the data link on the longitudinal differential protection device, this paper proposes a protection data self-healing synchronization algorithm based on wavelet transform to calculate the moment of sudden change. First, calculate the mutation amount of the sampled data at each end in real time. When the mutation amount threshold is exceeded, it is determined that the multi-terminal system has a short-circuit fault. Then, according to the sudden change characteristics of the collected current waveform, the wavelet modulus maximum value is used to extract the fault sudden change time of each end data, based on the fault time at one terminal, the automatic compensation for the time differences between this terminal and others are realized, thus a new sampling sequence is formed. The resynchronized sampling sequences are used to calculate the differential current and braking current after fault to ensure the correct action of the protective device. Through theoretical analysis and simulations, the correctness and effectiveness of the proposed algorithm is verified; in addition, it is shown that this algorithm can improve the reliability of actions by the intelligent protection device, thus realizing protections such as multi-terminal differential, wide-area differential, etc.