Priority analysis for risk factors of equipment in a hydraulic turbine generator unit

Ensuring the safe operation of hydropower stations is one of the key challenges for electric generation. Clearly the safe operation of such systems can only be archived with proper and effective maintenance scheduling. The objective of this study is to analyze, rank and prioritize the risk factors responsible for equipment failures of a hydraulic turbine generator unit (HTGU) based on operating data and expert elicitation. Here a simple qualitative risk evaluation model is proposed able to consider seven typical failures in HTGU. The proposed tool is applied for the risk prioritization of equipment failures, e.g. shaft torsion, misalignment, rotating fault, axis bend, runner fault, water guide, and wicket gate of a hydropower station in China. The obtained results have been compared against the actual statistics of equipment failures of a hydropower station in China, considered showing good agreement. All of these results provide theoretical guidance for digitalization realization of equipment failures.     

A coordinated control strategy using supercapacitor energy storage and series dynamic resistor for enhancement of fault ride-through of doubly fed induction generator

Power fluctuation and fault-related complication are the two major issues for doubly fed induction generator (DFIG)-based wind energy conversion system (WECS). The occurrence of fault leads to the rotor over current, stator over current, and DC-link overvoltage as well. These uncertainties may damage the rotor circuit, converter circuit and force the disconnection of wind system from the grid. To get rid of these issues, a supercapacitor energy storage element along with a passive series dynamic resistor (SDR) is suggested in this paper. Supercapacitor energy storage system (SCESS) is located across the DC-link, which able to handle the power fluctuation and the SDR is placed in rotor circuit, which will reduce the overcurrent possibility. Simulation is carried for a DFIG-based WECS for three phase to ground fault and two phase to ground fault. During symmetrical fault as well as asymmetrical fault, various operational disorders appeared such as rotor overcurrent, stator overcurrent and DC-Link overvoltage are found to be within their permissible limits. The results reveal the effectiveness of the proposed strategy over the conventional vector control scheme and SCESS as well.     

4×250 kW发电机组低温环境适应性试验研究

目的研究某大功率发电机组的低温环境适应性。方法将发电机组放置于高低温综合环境模拟试验室,室温降至–55℃,保温48 h,而后升温至–40℃,保温12 h,恢复常温。结果经检查,机组用时11′20″低温启动成功,其低温持续工作的稳态电压调整率为–0.880%,稳态频率调整率为–0.036%,稳态电压波动率为0.175%,稳态频率波动率为0.080%。试验过程中,样机塑料件、橡胶件、金属件未出现故障。结论该发电机组的启动性能、电气性能、结构材料等满足低温环境适应性要求,也为其他发电机组的低温环境适应性考核提供了指导方法。     

曲壁薄管的滚压成形工艺及模具

在现代的生产、生活中 ,板金零件的应用越来越广泛 ,零件的形状更具特色 ,而零件的成形工艺则越来越多样化。以仿古铜鼓为例 ,介绍了曲壁管在车床上滚压成形的工艺技术及其模具结构 ,并分析了工艺特点和应用中应注意的问题     

一种高效的圆盘板式臭氧发生器

本文介绍臭氧的应用领域及其作用机理 ,对一种新型臭氧发生器的结构、原理及其技术参数进行了系统分析     

The influence of melt composition,liquidus temperature and solidus temperature on vapour explosions in melt droplet impingement experiments

For the investigation of vapour explosions, droplet impingement experiments were performed with the binary system Pb–Sn and the pseudo-binary system PbS–Cu₂S. The experiments were performed with a melt at 600 °C (Pb–Sn) or 700 °C (PbS–Cu₂S) and a water bath at ambient temperature and pressure. A hydrophone and a high-speed camera were used to study the interaction and from this data, the explosion probability and intensity were determined.The explosion probability had a single minimum around 70 wt% Sn, close to the eutectic composition. Moreover, the explosion probability increased approximately linearly with changing composition towards the pure melts, and was similar for pure tin and pure lead. On the other hand, the explosion intensity was comparable for tin and the eutectic alloy while clearly lower for lead. Almost all intermediate alloys had a reduced explosion intensity.Based on the variation in composition, the effects of the liquidus or solidus temperature and the liquidus-solidus gap on the explosion behaviour were also investigated. The explosion probability in both systems increased with increasing liquidus temperature. Also, the maximum explosion intensity in the Pb–Sn system increased with increasing liquidus temperature. Both could be related to easier triggering due to (partial) solidification. On the other hand, the explosion intensity was found to decrease with increasing gap between liquidus and solidus temperature, as was also found in literature. No significant trends for the explosion intensity were found for experiments with PbS–Cu₂S.     

Hg-CEMS系统中元素汞发生器的溯源和质控方法研究

参考借鉴美国IEMGTP元素汞溯源协议中规定的4个溯源传递层级以及4种常用的成熟溯源质控方法,研究了在中国现有技术条件下,各种质控方法针对Hg-CEMS中元素汞发生器User generator进行质控的适用性。通过对不同质控方法的测试,显示通过可吸附元素汞的活性炭吸附管采样分析（美国EPA 30B方法）和通过汞渗透源两种对元素汞发生器进行质控的方法在中国目前是可行且科学、可靠的。同时对建立和完善中国的元素汞溯源协议和元素汞发生器质控方法提出了建议。     

The proton exchange membrane fuel cell systems using methanolysis of sodium borohydride as a hydrogen source with cobalt catalysts

Constant hydrogen generation via a hydrogen generator is evaluated from the methanolysis of sodium borohydride (NaBH₄) using Co/Al₂O₃ and MnO_x/Al₂O₃ catalysts. Chemical borohydrides coupled with catalysts can be used for compact storage and to create efficient generation systems. Thus, we first report the catalytic activity of MnO_x/Al₂O₃, which is synthesized using the simple wet-impregnation method, for the methanolysis reaction. The results indicate that both catalysts can effectively accelerate the methanolysis reaction and provide constant hydrogen generation rates. Thus, we integrate this hydrogen generation system into a proton exchange membrane fuel cell stack (PEMFC) to determine whether it can be used as a portable power supply. As a result, this fuel cell system operates at 40 W for 1 hr using the hydrogen source supplied from the catalytic methanolysis reaction.     

300MW汽轮发电机定子接地保护动作跳机原因分析及防范措施

某热电厂13号发电机定子接地保护动作跳闸,发电机组全停,依据电厂主设备的具体参数和配置情况,对故障录波图进行分析,检查了发电机及附属设备,并对发电机单元主要一次设备进行了试验,对机组跳闸原因进行了分析,提出了防范措施.