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Reference: ISH2015_434

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Steep rise time properties of PD Current Pulse Waveform in gaseous and oil insulations measured with the SHF_PDPW system



Since a number of high-voltage electrical power apparatuses such as GIS, power transformer and so on, it is important for precise evaluation of insulation condition to detect a partial discharge (PD) that could occur as an early signal of insulation degradation or formation of high electric field. From this background, UHF method that measures the PD-emitted electromagnetic (EM) waves with UHF band components is focused on as an insulation diagnosis technique of high-voltage electrical power apparatus. To sophisticate the UHF method, accurate measurement of PD current pulse is quite important because the PD current pulse is a radiation source of the EM wave. Also, in theory at the far field, the amplitude of EM wave is proportional to the current changing rate di/dt. So far, we have developed the SHF_PDPW (super high frequency wideband PD current pulse waveform measurement) system that enables us to obtain accurately waveforms up to SHF band (3-30GHz). Using this system, we have investigated PD current pulse waveforms in SF6 gas, and the SF6 substitute gases as well as oil insulations. As a result, we showed that the negative PD current pulse waveforms in the mineral oil, silicon oil and SF6 gas had the very steeped rise time as a few tens pico seconds. In this study, we investigated the steep rise time properties of the negative PD current pulse waveforms in oil insulations and SF6 gas. Then, we discussed the rise times of these PD current pulse waveforms based on the movement of electrons and ions in the critical electric field region. As a result, it could be confirmed that the rise time relates to the electron movement time in the critical electric field and the effectiveness of the super high frequency measurement of PD current pulse waveform even in the discussion on discharge physics.

File Size: 407,6 KB

Year: 2015

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