We focus on the high frequency current method which is widely applied in the partial discharge(PD)detection of cables.Aiming at guaranteeing the accuracy of this method,we study an innovative time-domain technology fo...We focus on the high frequency current method which is widely applied in the partial discharge(PD)detection of cables.Aiming at guaranteeing the accuracy of this method,we study an innovative time-domain technology for effectively measuring the transfer impedance of the high frequency current transformers(HFCTs).The proposed technology called pulse injection method obtains the system response under the excitation of the wide-band instantaneous pulse signal.Firstly,by studying the working principle of HFCTs,we summarize that the bandwidth of the selected signal acquisition device should be at least 100 MHz to ensure measurement accuracy.Secondly,Gauss pulse and square wave pulse are generated to determine the effects of different sources.The measurement results indicate that Gauss pulse is more suitable for pulse injection method,and the rise time should be under 10 ns to improve the starting frequency of oscillation distortion.Finally,the transfer impedance curves of five types of HFCTs are acquired by both pulse injection and traditional point-frequency methods.The measurement results show a remarkable consistency between two methods.However,pulse injection method requires the simpler operation and lias a higher resolution,obviously improving the measurement efficiency and bet ter displaying the details of the transfer impedance curves.展开更多
A new algorithm was developed for arcing fault detection based on high-frequency current transients analyzed with wavelet transforms to avoid automatic reclosing on permanent faults. The characteristics of arc curren...A new algorithm was developed for arcing fault detection based on high-frequency current transients analyzed with wavelet transforms to avoid automatic reclosing on permanent faults. The characteristics of arc currents during transient faults were investigated. The current curves of transient and permanent faults are quite similar since current variation from the fault arc is much less than the voltage variation. However, the fault current details are quite different because of the arc extinguishing and reigniting. Dyadic wavelet transforms were used to identify the current variation since wavelet transform has time-frequency localization ability. Many electric magnetic transient program (EMTP) simulations have verified the feasibility of the algorithm.展开更多
文摘We focus on the high frequency current method which is widely applied in the partial discharge(PD)detection of cables.Aiming at guaranteeing the accuracy of this method,we study an innovative time-domain technology for effectively measuring the transfer impedance of the high frequency current transformers(HFCTs).The proposed technology called pulse injection method obtains the system response under the excitation of the wide-band instantaneous pulse signal.Firstly,by studying the working principle of HFCTs,we summarize that the bandwidth of the selected signal acquisition device should be at least 100 MHz to ensure measurement accuracy.Secondly,Gauss pulse and square wave pulse are generated to determine the effects of different sources.The measurement results indicate that Gauss pulse is more suitable for pulse injection method,and the rise time should be under 10 ns to improve the starting frequency of oscillation distortion.Finally,the transfer impedance curves of five types of HFCTs are acquired by both pulse injection and traditional point-frequency methods.The measurement results show a remarkable consistency between two methods.However,pulse injection method requires the simpler operation and lias a higher resolution,obviously improving the measurement efficiency and bet ter displaying the details of the transfer impedance curves.
基金the National Natural Science Foundationof China(No.5 0 0 770 11)
文摘A new algorithm was developed for arcing fault detection based on high-frequency current transients analyzed with wavelet transforms to avoid automatic reclosing on permanent faults. The characteristics of arc currents during transient faults were investigated. The current curves of transient and permanent faults are quite similar since current variation from the fault arc is much less than the voltage variation. However, the fault current details are quite different because of the arc extinguishing and reigniting. Dyadic wavelet transforms were used to identify the current variation since wavelet transform has time-frequency localization ability. Many electric magnetic transient program (EMTP) simulations have verified the feasibility of the algorithm.
