为了通过空间电荷脱陷行为反映电缆XLPE绝缘老化程度,提出了一种从XLPE绝缘介质的极化-去极化电流(polarization and depolarization current,PDC)中提取出脱陷电流ide-trap的方法与相应的陷阱电荷密度Anτn和陷阱深度τn的计算方法。...为了通过空间电荷脱陷行为反映电缆XLPE绝缘老化程度,提出了一种从XLPE绝缘介质的极化-去极化电流(polarization and depolarization current,PDC)中提取出脱陷电流ide-trap的方法与相应的陷阱电荷密度Anτn和陷阱深度τn的计算方法。通过从脱陷电流中提取出参数τn和Anτn,并利用脱陷电流曲线作出ide-trapt~lnt曲线(t为时间),表征了XLPE中陷阱电荷密度与陷阱深度。在分别改变PDC测试时的极化场强、空间电荷注入时长和试样热老化程度后计算试样中陷阱电荷密度和陷阱深度,结果表明:PDC测试中较高的极化场强更能促进深陷阱中电荷逃逸;随着空间电荷注入时长增加,中等深度陷阱相较于浅陷阱和深陷阱更容易积聚电荷;XLPE的热老化首先经历重结晶阶段,后进入热氧老化阶段,结晶度变化导致XLPE中陷阱数量先增加后减少,而在整个热老化过程中陷阱深度逐渐加深。研究结果表明,基于极化-去极化电流测试可对XLPE中陷阱电荷的脱陷特性进行分析,通过参数τn、Anτn和ide-trapt~lnt曲线可反映XLPE中陷阱电荷密度及陷阱深度并表征XLPE绝缘的老化程度。展开更多
In recent years,haze has posed a serious threat to the global climate change,ecological balance and human health.In this study,the laboratory experiments and field observations were performed and a possible charging m...In recent years,haze has posed a serious threat to the global climate change,ecological balance and human health.In this study,the laboratory experiments and field observations were performed and a possible charging mechanism was proposed to investigate the space charge properties in haze events.The laboratory experiments showed that the charge polarity of primary aerosol is determined by species of combustion fuels while the magnitude is dependent on the combustion completeness.The field observations revealed that the space charge of atmosphere aerosol in haze events differs from that of fair weather and is closely related to PM2.5 concentration when Relative Humidity(RH)<60%,with 1 to 2 orders of magnitude less than the case when RH≥60%.The analysis of equivalent chargeto-mass ratio(ECTM)suggested that in haze events the space charge is governed by primary aerosol emitted by combustion of fossil fuel in a low relative humidity,whereas it is manipulated by the secondary chemical reaction of atmosphere aerosol in a high relative humidity.And we can identify the main pollutants in haze events according to the polarity of atmosphere aerosol and quickly take measures when RH<60%.Accordingly,the dusthaze of RH<80% can be divided into dry-dust-haze when RH<60%and wet-dust-haze when 60%≤RH<80%.Our study firstly elucidated the space charge properties of atmosphere aerosol in haze events and can provide a new perspective for the prevention and control of air pollution.展开更多
文摘为了通过空间电荷脱陷行为反映电缆XLPE绝缘老化程度,提出了一种从XLPE绝缘介质的极化-去极化电流(polarization and depolarization current,PDC)中提取出脱陷电流ide-trap的方法与相应的陷阱电荷密度Anτn和陷阱深度τn的计算方法。通过从脱陷电流中提取出参数τn和Anτn,并利用脱陷电流曲线作出ide-trapt~lnt曲线(t为时间),表征了XLPE中陷阱电荷密度与陷阱深度。在分别改变PDC测试时的极化场强、空间电荷注入时长和试样热老化程度后计算试样中陷阱电荷密度和陷阱深度,结果表明:PDC测试中较高的极化场强更能促进深陷阱中电荷逃逸;随着空间电荷注入时长增加,中等深度陷阱相较于浅陷阱和深陷阱更容易积聚电荷;XLPE的热老化首先经历重结晶阶段,后进入热氧老化阶段,结晶度变化导致XLPE中陷阱数量先增加后减少,而在整个热老化过程中陷阱深度逐渐加深。研究结果表明,基于极化-去极化电流测试可对XLPE中陷阱电荷的脱陷特性进行分析,通过参数τn、Anτn和ide-trapt~lnt曲线可反映XLPE中陷阱电荷密度及陷阱深度并表征XLPE绝缘的老化程度。
基金supported by a grant from the National Natural Science Foundation of China(Nos.11490551)。
文摘In recent years,haze has posed a serious threat to the global climate change,ecological balance and human health.In this study,the laboratory experiments and field observations were performed and a possible charging mechanism was proposed to investigate the space charge properties in haze events.The laboratory experiments showed that the charge polarity of primary aerosol is determined by species of combustion fuels while the magnitude is dependent on the combustion completeness.The field observations revealed that the space charge of atmosphere aerosol in haze events differs from that of fair weather and is closely related to PM2.5 concentration when Relative Humidity(RH)<60%,with 1 to 2 orders of magnitude less than the case when RH≥60%.The analysis of equivalent chargeto-mass ratio(ECTM)suggested that in haze events the space charge is governed by primary aerosol emitted by combustion of fossil fuel in a low relative humidity,whereas it is manipulated by the secondary chemical reaction of atmosphere aerosol in a high relative humidity.And we can identify the main pollutants in haze events according to the polarity of atmosphere aerosol and quickly take measures when RH<60%.Accordingly,the dusthaze of RH<80% can be divided into dry-dust-haze when RH<60%and wet-dust-haze when 60%≤RH<80%.Our study firstly elucidated the space charge properties of atmosphere aerosol in haze events and can provide a new perspective for the prevention and control of air pollution.