10kV有机避雷器短路试验研究

对额定电压10 kV的设计B类有机避雷器进行了预击穿短路试验,验证了IEC60099-4Ed2.2:2009和GB11032-2010中的预击穿短路试验程序。试验表明:电压源法预击穿电压的范围为避雷器参考额定电压的1.08~1.13倍,击穿时间为2~8 min。并且,短路大电流试验时,试品电流波形延后其电压波形约1个周波,而标准中规定的预击穿试验与短路电流试验之间时间间隔及再击穿试验等对短路试验的结果影响不大。     

浪涌信号发生器的校准方法

介绍了浪涌来源于雷电瞬态和开关瞬态,给出了模拟雷电瞬态和开关瞬态的浪涌信号发生器的主要性能指标及工作原理。根据浪涌信号发生器的性能指标及工作原理,提出了一种简单可行的校准方法,给出了详细的测试数据,并应用到了实际工作中。     

无吸程变频恒压设备用于二次供水

二次加压供水设备使用于自来水管网压力不足的场合.在二次加压供水中采用无吸程变频恒压供水设备,既能利用自来水管道的原有压力,又能利用足够的储存水量缓解高峰用水,不会对自来水管道产生吸力,达到节能效果.     

新型压缩机防喘振控制在气压机改造中的应用

通过新型压缩机防喘振控制在机组改造中的成功应用 ,介绍了新型防喘振控制算法 ,并以该控制算法精确建立了压缩机通用防喘振性能图。防喘振控制器根据压缩机通用防喘振性能图上喘振控制线进行PI控制 ,并通过备用控制线阶跃输出 ,给定值迁移和浮动比例控制 ,完成防喘振控制     

离心式压缩机防喘振控制系统设计探讨

离心式压缩机是石油化工生产中的关键设备，必须保证它安全运行。分析了离心式压缩机喘振的原因、现象及危害．介绍了防喘振控制的原理及典型的防喘振控制系统，并结合具体的工程设计、组态，给出防喘振控制的工程设计方法。     

潮汐河口闸下风暴潮特征模拟

潮汐河口闸下风暴潮水位对于河道防洪排水至关重要。以苏北里下河主要入海通道射阳河、黄沙河、新洋河和斗龙河等建闸河口为例,采用模型嵌套的方法,以平面二维数学模型模拟了里下河地区“9711”台风风暴潮期间闸下河段的潮汐水流和风暴潮运动过程,研究了闸下风暴潮水位相对河口风暴潮水位的变化特征。模拟结果显示,底摩擦、浅水变形、边界反射等相互作用影响,闸下风暴潮水位和潮汐水位存在一致的变化特性,即高潮位抬升,低潮位下降,潮差(增水)增加;涨潮历时缩短,落潮历时延长;风暴潮水位的变化幅度大于同时期的潮汐水位,风暴潮过程对于闸下排水具有显著影响。在与闸顶高程一致的上游水位条件下,相比天文潮过程,“9711”风暴潮过程可减少闸门过流流量的20%~25%。     

大水量急涌降水井封堵技术优化

以南京医科大学第四附属医院项目为例,研究深基坑高水位地区项目,在实际施工过程中遇到大水量急涌降水井的有效封堵方式。设计了一种带水封堵的操作工艺,在进行封井施工时,边降水边进行钢盖板的焊接。由于在封堵时用抽水泵同步降水,因此降水井的水位一直保持在钢盖板焊接作业面以下,从而创造了带水封堵的作业条件。该工艺有效解决了大水量急涌降水井封堵困难的问题,保证了封堵质量,避免了封井后出现地下水渗漏的隐患。在此基础之上,提出了一种在地下水丰富地区应如何提前布置降水井封堵措施的设想,以期为类似工程施工提供借鉴。     

Analytical study on water hammer pressure in pressurized conduits with a throttled surge chamber for slow closure

This paper presents an analytical investigation of water hammer in a hydraulic pressurized pipe system with a throttled surge chamber located at the junction between a tunnel and a penstock,and a valve positioned at the downstream end of the penstock.Analytical formulas of maximum water hammer pressures at the downstream end of the tunnel and the valve were derived for a system subjected to linear and slow valve closure.The analytical results were then compared with numerical ones obtained using the method of characteristics.There is agreement between them.The formulas can be applied to estimating water hammer pressure at the valve and transmission of water hammer pressure through the surge chamber at the junction for a hydraulic pipe system with a surge chamber.     

基于全固态调频发射机的调频发射系统

介绍了重新构建基于意大利RVRTX5KPSS／V1全固态调频发射机调频发射系统的基本过程,简要分析了新旧调频系统之间各种实测数据。基于全固态调频发射机的调频发射系统正式投入使用后．不但大大扩展了信号场强覆盖范围,系统的指标和安全可靠性都有了大幅度提高,而且广播接收质量也获得质的飞跃,更重要的是进一步确保了信号的安全优质播出。     

Water hammer protection for diversion systems in front of pumps in long-distance water supply projects

For a water supply system with long-distance diversion pipelines, in addition to the water hammer problems that occur beyond pumps, the safety of the water diversion pipeline in front of pumps also deserves attention. In this study, a water hammer protection scheme combined with an overflow surge tank and a regulating valve was developed. A mathematical model of the overflow surge tank was developed, and an analytical formula for the height of the overflow surge tank was derived. Furthermore, a practical water supply project was used to evaluate the feasibility of the combined protection scheme and analyze the sensitivity of valve regulation rules. The results showed that the combined protection scheme effectively reduced the height of the surge tank, lessened the difficulties related to construction, and reduced the necessary financial investment for the project. The two-stage closing rule articulated as fast first and then slow could minimize the overflow volume of the surge tank when the power failure occurred, while the two-stage opening rule articulated as slow first and then fast could be more conducive to the safety of the water supply system when the pump started up.