Measurement of intensity ratio of anodic peak pairs with method of symmetrical wave form in internal standard cyclic voltammetry to determine ethanol in wine was presented in this paper.

Differential protection based on waveform symmetry is furtherly studied and analyzed through a mal-operation incident when the unloaded power transformer is connected to the power system.

In consideration of the frequent mal-operation of transformer differential protection based on the principle of waveform symmetry, this paper analyzes the internal relationship of the waveform symmetry principle and the secondary harmonic restraint principle based on the generating mechanism of the magnetic inrush current of the three-phase transformer.

In connection with analyzing operation of two differential protections for transformer, The criterias for exciting current of differential protection were compared,and further explanation for the principle of waveform symmetry.

De-noising algorithm in multi-scale products based on symmetry wavelet transform;