Özet:

In this paper a wavelet packet transform (WPT)-based algorithm is proposed to develop and improve the backup wide area protection for power systems equipped with phasor measurement units (PMUs). Faults on power systems such as high impedance faults (HIFs) have specific characteristics that include high frequency components that can be extracted using the WPT, which is one of the important methods in signal processing. The proposed idea uses power system voltage and current, measured by voltage and current transformers, respectively, and calculates high frequency information of voltage and current waveforms. Afterwards, the differences of voltage coefficients of each phase at each bus with remote buses are compared with a threshold value to detect HIFs in a power system. In addition, differences of current coefficients of each phase of transmission lines in local and remote terminals are compared with a threshold value for discovering the faulted line. The sum of the current coefficients of all feeders connected to the same bus, for each phase, is compared with a threshold value for discriminating the faulted bus. This algorithm is able to detect the regular fault types. It should be noted that for using PMUs and their time-synchronized systems with high-speed GPS communication links, it is necessary to access the power system's real-time data at local and remote terminals. The presented method is simulated by MATLAB software on the New England Power Network. Simulation results show that the algorithm has sufficient security and dependability.

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