中压电缆早期故障多物理场仿真及时频特征分析OA

Incipient faults in cables are often accompanied by intermittent arcing,with self-extinuishing of the arc occuring near the current zero-crossinng point,manifesting as self fault clearanc.However,the physical changes du-rig this process are still not well understood.Due to the very short duration of intermittent arc discharge,it is diffi-cult for traditional relay protection equipment to identify incipient faults and appropriate features need to be extract-ed to identify incipient fault signals.In this paper,based on the magneto hydro dynamics theory(MHD),the multi-physical field simulation of medium voltage cables is performed to analyze the variation of current density,magnetic field intensity and temperature distribution during a quarter cycle of intermittent arcing.Short-time Fourier trans-form(STFT)is performed on the simulation waveform so to obtain the frequency domain characteristics of the incipi-ent fault.The results show that in case of incipient fault in cables there is a high frequency component,which is ob-viously different from the normal operation under the 5 kHz frequency treated by Hanning window,and the ampli-tude difference can be up to 85 dB.While,the Hamming window has a weak processing effect,so it is necessary to select or combine appropriate features for identification.