Phase identification for space charge measurement under periodic stress of an arbitrary waveform based on the Hilbert transform

• Published in: Measurement science & technology 2016-04, Vol.27 (4), p.45004
• Main Authors: Wu, Jiandong, Huang, Ruodong, Wan, Jiadong, Chen, Yading, Yin, Yi, Chen, George
• Format: Article
• Language: English
• Subjects: Fourier transform; Hilbert transform; periodic electric field; phase identification; space charge
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/27/4/045004

Data processing (i.e. phase identification) using the instantaneous phase ′(t) defined by the Hilbert transform is discussed to confirm the detecting phase of the space charge observed by the pulsed electroacoustic method under the periodic wave Va(t). The discrete voltage Va(i) of the periodic wave at the detecting phase (i) is used for phase identification, and (i) is equally distributed to obtain Np divisions for the phase within one period. The accuracy of the discrete instantaneous phase ′(i) is significantly determined by the number of samples N for the discrete voltage Va(i). The instantaneous phase is consistent with the real phase of pure sine and cosine waves, and this phase linearly varies with time. However, the instantaneous phase non-linearly varies with time under the periodic stress of arbitrary waveforms. This limitation can be resolved using the base wave component, i.e. sine or cosine wave of Va(t), which is acquired by the Fourier transform. Finally, the space charge behaviour in low-density polyethylene under square and sine waves with offset is detected to verify the accuracy and effectiveness of the proposed method.