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Detection and analysis of series arcs is significantly meaningful for preventing arc-caused electrical fires in advance. However, the improvement of arc detection sensitivity and the discrimination of arc conditions are still challenges when developing an arc fault detector. In this paper, arc signals in various loads with three major incomplete connection states were detected and further analyzed using the discrete wavelet transform. It was verified that the db13 was the optimal mother wavelet to analyze the arc pulses and the decomposed signals in the detail components of D5, D6, D7, and D8 were related with arc phenomena. Therefore, a band pass filter with a frequency from 2.4 to 39 kHz was designed, which can extract arc signals while eliminating the AC mains current and noise generated in loads. By investigating the arc signal energy as well as the arc pulse counts that were important parameters of arc occurrence, an arc diagnosis algorithm was developed based on LabVIEW program for electrical fire prevention.

A novel design of a simple microstrip‐fed monopole antenna for wireless local‐area network/worldwide interoperability of microwave access (WLAN/WiMAX) band operation is proposed in this article. The proposed antenna consists of two branch strip, an asymmetrical ground plane, and a rectangular‐slit ground plane. The proposed antenna is capable of generating two separate resonant modes with good impedance‐matching conditions. Prototypes of the proposed antenna were fabricated and experimentally measured. Acceptable agreement between the measurement and simulation results was achieved. The numerical and experiment results demonstrate that the proposed antenna satisfies the return loss −10 dB (VSWR < 1:2) impedance bandwidth requirement while simultaneously covering the WLAN and WiMAX bands. Meanwhile, the two‐dimensional radiation pattern and three‐dimensional gain performance of the antenna in the operation bands were also observed and discussed. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1559–1566, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26875

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With the increasing demand for precise condition monitoring and diagnosis of gas-insulated switchgears (GISs), it has become a challenge to improve the detection sensitivity of partial discharge (PD) induced in the GIS spacer. This paper deals with the elimination of the capacitive component from the phase-resolved partial discharge (PRPD) signal generated in GIS spacers based on discrete wavelet transform (WT). Three types of typical insulation defects were simulated using PD cells. The single PD pulses were detected and were further used to determine the optimal mother wavelet. As a result, the bior6.8 was selected to decompose the PD signal into 8 levels and the signal energy at each level was calculated. The decomposed components related with capacitive disturbance were discarded, whereas those associated with PD were de-noised by a threshold and a thresholding function. Finally, the PRPD signals were reconstructed using the de-noised components.