The current conventional oscillatory search algorithm for relay protection logic diagram is prone to fall into local optimum due to the late population diversity reduction, which leads to poor search results. In this regard, a sequential traversal-based oscillation search method for relay protection logic diagrams is proposed. The oscillation search algorithm is optimized by finding the second-order oscillation factor, optimizing the topology of the algorithm, and constructing the relay protection logic diagram model to obtain a library of graph elements. The experimental results show that the proposed oscillation search algorithm converges faster and has a more desirable search effect.

Savitzky-Golay (SG) filter is an effective and convenient gradient calculation method employed for full-field strain measurement in digital image correlation (DIC). Currently, the strain field can be conveniently obtained by moving smoothing filtering with SG filters. This is a way of spatial filtering, which offers the advantages of easy implementation and high accuracy. This study proposed a strain calculation method based on frequency domain SG (FD-SG) filtering. Prior to performing FD-SG filtering, data extension operations involving outer-boundary padding and zero-padding were performed on the displacement field data. Similarly, the SG filters template was extended with zero-padding and circularly shift operations. Subsequently, FD-SG filters were generated by applying the fast Fourier transform (FFT) to the expanded SG template. Thereafter, FD-SG filtering was implemented through the multiplication of the displacement in the Fourier-domain by an FD-SG filter. Finally, the strain field was obtained via inverse fast Fourier transform (IFFT) and valid data interception operation. The simulation and practical experiments confirmed the equivalent accuracy exhibited by FD-SG and spatial domain SG (SD-SG) filtering. Thus, the proposed FD-SG filtering method has great potential for real-time strain measurement in DIC.