Single event latch-up (SEL) is a significant issue for electronics design in space application, which would cause large currents in electronic devices, and may lead to burning out of devices. A new monitoring circuit ...Single event latch-up (SEL) is a significant issue for electronics design in space application, which would cause large currents in electronic devices, and may lead to burning out of devices. A new monitoring circuit based on current-comparing method is designed to protect the electronics away from SEL’s damage in radiation environment. The response time of protection circuit has been analyzed. The signal simulation results indicated that the operating time of the SEL protection circuit is dependent on the action time of current comparator and system application recovery time. The function of the monitoring circuit protection device away from SEL’s damage has validated through experiment at last.展开更多
In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave th...In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave threat to the power grid security.The cause of the accident and the accident process were studied for the sake of further understanding of the impact of lightning on power grid.As an example,110 kV double circuit transmission line(Xilong-line) was analyzed.At first,the system topology was given.Through the analysis on relay protection actions and the fault recorder data,over voltage on the insulator strings was calculated.Based on the analysis and the calculation,accident cause and the process were presented respectively.Secondly,it comes to the conclusion that the lightning failure was caused by counterattack.The wave of the lightning over voltage would spread to the not grounded neutral point of the transformers,and make the neutral protective gap breakdown,then cause freewheeling with the frequency of 50 Hz.As results of the relay protection,the double circuit transmission line all tripped out.Finally,the causes of the accident were proposed that included terrain features,large corner towers,strong thunderstorm weather and poor grounded contact of the tower.展开更多
为解决目前直流线路主保护不能反映高阻接地故障的问题,提出了一种检测电流首峰值时间(the first peak time of fault current,FPTFC)的直流线路保护新原理。首先,对两极直流母线上的FPTFC变化特性进行解析与仿真研究,得到其在区内、区...为解决目前直流线路主保护不能反映高阻接地故障的问题,提出了一种检测电流首峰值时间(the first peak time of fault current,FPTFC)的直流线路保护新原理。首先,对两极直流母线上的FPTFC变化特性进行解析与仿真研究,得到其在区内、区外故障情况下的一般变化规律。根据所得规律,安装于一极上的新型保护,以本端换流站另外一极直流母线上的FPTFC作为保护特征量,从而消除了过渡电阻对保护性能的影响。保护功能分两段实现,I段用于区内故障识别,约可以保护本极线路全长的70%;II段用于本极线路末端故障与区外故障的辨识,与I段共同保护线路全长。PSCAD/EMTDC环境下的相关仿真结果验证了新型保护的可行性与实用性。展开更多
文摘Single event latch-up (SEL) is a significant issue for electronics design in space application, which would cause large currents in electronic devices, and may lead to burning out of devices. A new monitoring circuit based on current-comparing method is designed to protect the electronics away from SEL’s damage in radiation environment. The response time of protection circuit has been analyzed. The signal simulation results indicated that the operating time of the SEL protection circuit is dependent on the action time of current comparator and system application recovery time. The function of the monitoring circuit protection device away from SEL’s damage has validated through experiment at last.
文摘In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave threat to the power grid security.The cause of the accident and the accident process were studied for the sake of further understanding of the impact of lightning on power grid.As an example,110 kV double circuit transmission line(Xilong-line) was analyzed.At first,the system topology was given.Through the analysis on relay protection actions and the fault recorder data,over voltage on the insulator strings was calculated.Based on the analysis and the calculation,accident cause and the process were presented respectively.Secondly,it comes to the conclusion that the lightning failure was caused by counterattack.The wave of the lightning over voltage would spread to the not grounded neutral point of the transformers,and make the neutral protective gap breakdown,then cause freewheeling with the frequency of 50 Hz.As results of the relay protection,the double circuit transmission line all tripped out.Finally,the causes of the accident were proposed that included terrain features,large corner towers,strong thunderstorm weather and poor grounded contact of the tower.
文摘为解决目前直流线路主保护不能反映高阻接地故障的问题,提出了一种检测电流首峰值时间(the first peak time of fault current,FPTFC)的直流线路保护新原理。首先,对两极直流母线上的FPTFC变化特性进行解析与仿真研究,得到其在区内、区外故障情况下的一般变化规律。根据所得规律,安装于一极上的新型保护,以本端换流站另外一极直流母线上的FPTFC作为保护特征量,从而消除了过渡电阻对保护性能的影响。保护功能分两段实现,I段用于区内故障识别,约可以保护本极线路全长的70%;II段用于本极线路末端故障与区外故障的辨识,与I段共同保护线路全长。PSCAD/EMTDC环境下的相关仿真结果验证了新型保护的可行性与实用性。
