In order to veritably measure the first peak of hydration heat evolution that has been illustrated important in indicating cement behavior in early hydration, an improved way of water addition into cement in isotherma...In order to veritably measure the first peak of hydration heat evolution that has been illustrated important in indicating cement behavior in early hydration, an improved way of water addition into cement in isothermally calorimetric experiment is put forward. The experimental results indicated that: the magnitude of first peak of heat evolution varies from sample to sample, correlation between heat evolution during first peak of heat evolution and initial (as well as final) setting time is unsatisfactory when samples are not classified; while groups of sample classified based on strength grade represent satisfactory correlations, which indicating the existence of close relation between hydration heat evolution in much earlier hydration age and setting property of cement in rather later age. Importance of first peak in hydration heat evolution for understanding cement setting property and reasons for sample classification are also discussed in this paper.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
基金Funded by Guangxi Science Foundation(No. 0639006)
文摘In order to veritably measure the first peak of hydration heat evolution that has been illustrated important in indicating cement behavior in early hydration, an improved way of water addition into cement in isothermally calorimetric experiment is put forward. The experimental results indicated that: the magnitude of first peak of heat evolution varies from sample to sample, correlation between heat evolution during first peak of heat evolution and initial (as well as final) setting time is unsatisfactory when samples are not classified; while groups of sample classified based on strength grade represent satisfactory correlations, which indicating the existence of close relation between hydration heat evolution in much earlier hydration age and setting property of cement in rather later age. Importance of first peak in hydration heat evolution for understanding cement setting property and reasons for sample classification are also discussed in this paper.
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。
