中压电阻接地系统零序保护动作行为分析

通过对4起不同电气元件接地故障时的零序保护拒动分析,提出了保护装置拒动的可能因素,在保护装置选择等方面给出了预防措施。     

进口可控硅整流装置的应急修理

通过对引进瑞士ＡＢＢ公司的可控硅整流装置损坏故障的分析，成功地采用了国内可控硅元件替代引进元件，解决了燃眉之急，同时为消化引进技术提供了现场维修经验。     

USB光电鼠标四芯线的原理与维修

我们做电子制作和设计的朋友离不开电脑，写程序，编程芯片都需要频繁使用鼠标，而光电鼠标容易出现如下故障：断线、接口芯片损坏、元件虚焊或脱焊、发光二极管损坏，光学系统脏污等。我在几年的鼠标维修过程中发现90％的故障都来自鼠标的四根芯线。本文专门讨论下USB光电鼠标四芯线的故障情况。     

武钢某变电所一段110kV母线全停电事故分析

武钢某变电所由于主变穿墙套管CT绝缘损坏和停用线路接地隐患,导致区外故障时110 kV母线差动保护动作,使一段母线全停电。通过该事故进行分析,提出加强二次回路绝缘电阻测试和检查的必要性,防止母差保护误动,并对此次事故应吸取的教训和同类事故预防提出对策。     

喷吹白云石提高电弧炉耐火材料寿命

为了更方便地对保护元件和保护性装置的性能进行仿真测试，本文建立了一种新的振荡模型，包括纯振荡模型和振荡中故障模型，能够较好地模拟纯振荡和振荡中故障时电气量的变化情况。这一模型可用以检查各种微机线路保护，有广泛的实用性。     

行车电气故障分析与处理

<正>1前言2011年炼铁A区煤棚行车故障222起,其中行车电气故障占总故障的78%。统计电气故障种类主要有:电缆故障,占电气故障的30%;电气元件损坏,占70%。说明电气元件的损坏是造成行车故障主要原因。2分析与处理2.1原因分析A区煤棚行车提升、开闭电机的调速电阻同档位的切换设计采用同一接触器来完成,在抓煤的时候,若开闭主令控制器已打到第三档,开闭电机的调速电阻切完,此时若马上操作提     

变压器保护励磁涌流探讨

变压器保护的一个主要技术问题是解决变压器励磁涌流的问题,即如何解决空投变压器于内部故障(尤其是匝间故障)时差动保护动作速度慢的问题;同时在变压器各种空投时产生的励磁涌流、区外故障切除后产生的恢复性涌流以及和应涌流等状态下差动保护不误动。这个课题一直是国内外变压器保护研究的热点。     

110kV金专线横差保护误动原因分析

介绍了110kV金专线的保护配置及故障时的情况，对横差保护误动原因充分地加以定性分析，并得出相应的合理解释。所存问题在保护复查过程中予以消除，更进一步地提出今后所采取的必要措施和建设性整改意见。     

IEC反时限曲线热效应分析及其在电机保护中的应用

对常见的三种IEC曲线进行了简单介绍，并通过可视化图表对相关曲线动作特点及保护动作时产生的热效应变化趋势进行了直观展示，揭示了该曲线在限制故障电流热效应方面存在的不足。提出了一种选取两条曲线的优化应用的方法，采用该方法通过设置合理的参数，能够避免采用单条曲线的缺点，达到有益的效果。最后，通过一台电机过电流保护工程应用实例，介绍了曲线组合应用时，相关参数的计算方法，并对采用该方法由故障电流产生的热效应进行了校验。通过工程实例计算表明，该方法能将故障电流造成的热效应限制在电机可承受的范围，避免故障电流对被保护电机造成进一步损坏，能达到良好效果。该方法在对其他的电气设备保护方面，也同样具有工程应用价值。     

电压互感器开口绕组接线错误导致电压异常的分析

对一起中性点不接地系统中电压互感器开口绕组接线错误导致故障时二次回路电压异常的故障原因进行了分析,指出开口绕组二次线接线错误可能导致系统故障时刻电压互感器保护绕组三相电压不能正确反映故障类型,可能引起保护误动或拒动。对电压互感器开口绕组的接线错误状况进行剖析,并提出了防范措施。     

Thermal expansion modular femoral head extractor for revision total hip arthroplasty

Removal of a prosthetic modular femoral head is sometimes desirable during revision hip arthroplasty. A femoral head extractor was designed to heat and expand the prosthetic femoral head, apply a gentle distraction load, and remove the femoral head without injury to the femoral neck, taper, or bone-prosthesis interface. The device was used clinically in six hip revision cases. In five hips with cobalt-chrome heads and titanium alloy tapers, femoral heads were removed successfully; femoral fixation was maintained and femoral components were not visibly damaged. In the sixth case, the female portion of the taper junction was contained in a long femoral head sleeve. Heating the ball did not adequately expand the sleeve to allow easy ball removal.     

Measuring first ray mobility with a new device

First ray hypermobility has been linked to many abnormal conditions in the foot. First metatarsal vertical displacement is proportional to the measurement of first ray dorsiflexion. A new device that measures first ray mobility has been built and tested. The device applies a dorsiflexing force to the head of the first metatarsal and measures the amount of vertical displacement that results. The design and instrumentation of the device is described. A safe and reliable testing procedure for measuring maximal first ray displacement is discussed. Clinicians could use this measure when selecting treatment options for patients who suffer foot pathologies resulting from faulty mechanics of the first ray.     

电机本机温度测量保护技术与智能自诊断保护装置的试用

中小型电机的温度监测通常采用人工测温,大型电机使用埋置的热电阻传感器测温,温度保护采取上限控制,故障时往往得不到迅速诊断与保护。介绍了电机本机全方位温度测量保护技术与智能自诊断保护装置的测试效果。     

电工钢方圈磁性测量偏差影响因素的探讨

电工钢爱泼斯坦方圈磁性能测量受到设备状态、试样制取和测量过程等因素的影响。通过对这些影响因素进行试验研究,结果表明:利用标准试样核查设备状态是不充分的,实验室应制定磁性测量设备各关键部件的检定和校准计划来确保设备准确;同时,不同的样品加工方式会导致试样断面形貌存在较大差异,应控制试样断面切断区厚度不低于试样厚度的60%;另外,测量时试样应统一至约定密度,还需关注试样磁化发热的影响,控制试样温度不能超过50℃。     

耐候钢锈层稳定化处理大气曝晒(喷淋)试验

以WSD-N耐候钢和Q345钢为基板,采用大气曝晒(喷淋)的方法,对研制的锈层稳定化表面处理剂进行了性能试验。结果表明,在喷淋1%氯化钠溶液的大气曝晒试验中,耐候钢不能形成稳定化的保护锈层,对严酷的海洋环境有较好的模拟性,可用来进行锈层稳定化处理的研究;经锈层稳定化处理剂处理的耐候钢,腐蚀率仅为耐候钢的47%,且有更好的耐局部腐蚀性能。经锈层稳定化处理剂处理的Q345钢,腐蚀率是Q345钢的82%,说明锈层稳定化剂对Q345钢有一定的保护作用,但不能在Q345钢上形成稳定化的保护锈层。     

新型钕铁硼粉末配料设备的研制

针对钕铁硼(Nd-Fe-B) 生产企业配料时出现的问题, 研制了一种适用于钕铁硼粉末在密闭气保环境下的自动配料设备。在原有CJ2000钕铁硼粉末自动称量机的基础上, 应用TRIZ (Teoriya Resheniya Izobreatatelskikh Zadatch) 理论中的功能分析、裁剪原理、物场模型、标准解并结合钕铁合金粉末硼配料工艺、用户需求对设备的关键部件进行了设计。在原料桶至给料器之间设计了新的料位检测及防护部件, 该部件能够可靠地完成胶管内部料位检测的功能, 同时防护罩能够在胶管意外破裂后起到一定的保护作用, 为操作人员争取时间, 防止事故的进一步扩大。秤斗进料口及出料口出均设有快装接头, 可与软连接相连, 确保其在密闭状态下完成物料的称量, 在秤斗的侧壁上设有振动电机, 可有效清除秤斗内部的残余物料。采用自同步原理设计的GZG103管状密闭给料器, 该给料器不但能够实现物料的定量供送, 同时能够完成给料器内部残余物料的清理, 便于下一批次产品的配料。经过对样机的试验考核, 对单支200 kg物料的称量, 其生产率可达20次/h, 精度等级达到X (0.2) 级。当给料器完成内部物料的自清理后, 其物料残留量小于1 g。该设备是针对钕铁硼粉末的配料进行研发的, 但对于其它易氧化合金粉末的分料和配料, 也具有一定的应用价值。     

电渣重熔轴承钢中的硅元素烧损的控制

以G20Cr2Ni4A轴承钢为研究对象,根据现场生产数据,对不同电极氧质量分数下的硅烧损、渣中不同SiO2质量分数下的硅烧损以及不同氩气流量下的硅烧损率进行了统计分析,研究了电渣重熔中不同保护气氛下以及不同工艺下对电渣锭硅质量分数的影响。结果表明：保护气氛电渣炉生产的电渣锭硅烧损小且成分均匀,当氧质量分数控制到0.001%下时,硅不易烧损;当采用非保护气氛冶炼G20Cr2Ni4A钢时,渣系中的SiO2质量分数在2%时能够保证硅的波动比较小,当采用保护气氛冶炼时,渣系中的SiO2质量分数在1%时对硅的控制效果良好;采用非保护气氛电渣炉,由于渣- 气界面传氧以及电极氧化增重的不断变化,硅的烧损也呈增大趋势。针对于厂内30 t保护气氛电渣炉,氩气流量增加到50 L/min时,生产的电渣锭成分均匀,经济性良好。     

Endogenous carbon monoxide in control of respiration

CASE REPORT: A patient with recurrent breast cancer was reirradiated twice on adjacent fields with a time interval of 9 months. The first time she was treated with reirradiation alone, the second time with reirradiation plus hyperthermia. The reirradiation schedule for both fields was 8 x 4 Gy in 4 weeks. Both fields overlapped partly with the field of postoperative radiotherapy, which was applied 57 and 66 months earlier to a total dose of 40.5 Gy. RESULTS: During the 52 to 61 months follow-up, a remarkable difference in telangiectasia development, between the parts of the reirradiation fields overlapping with the primary radiotherapy field, became apparent. Telangiectasia was observed 9 months after treatment with reirradiation alone and progressed to confluent in 47 months after treatment. In the reirradiation plus hyperthermia area, the maximum observed telangiectasia was slight until 52 months after treatment. DISCUSSION: The difference in the development of telangiectasia between these fields cannot be explained by differences in any of the known radiation treatment related prognostic factors. A protective effect by hyperthermia has been suggested by Haveman and coworkers, who have shown experimentally that heat treatment leads to enhanced proliferation of endothelial cells, thereby inducing a fast repopulation and replacement of X-ray damaged cells. CONCLUSION: This difference in telangiectasia formation is an interesting observation. Whether such a protective effect of hyperthermia is of general relevance has to become clear from more extensive clinical studies.     

Ketamine and nifedipine protect cultured cortical neurons against injurious effect of glutamate]

The effects of glutamate on cultured cortical neurons and the protective effect of ketamine and nifedipine were studied. On day 10 after plating of the cortical cells from 16-18 day-old fetal rats, the cultures were exposed to 50 mumol.L-1 glutamate and low glucose (1 g.L-1) for 10 min-24 h. The results showed that a release of lactate dehydrogenase (LDH) into the culture supernatant was observed as a function of time. The values of LDH efflux in culture medium was significantly lower than those of controls when the cells were pretreated with ketamine or nifedipine 10 min prior to addition of glutamate. More significant decrease of LDH activity in culture medium was observed when the two drugs were used in combination. These results demonstrate that the dissociated cultured cortical neurons from fetal rat are seriously damaged by glutamate. Such damage could be attenuated by ketamine and nifedipine, suggesting that ketamine and nifedipine may protect neurons from the glutamate toxicity, and the effect of combining ketamine and nifedipine was greater than either ketamine or nifedipine alone.     

非金属夹杂物三维形貌及其包裹的非夹杂物颗粒物来源分析

钢中非金属夹杂物的分离提取过程,需要解决外来因素的干扰问题,准确判断是否来源于钢中,是夹杂物检测与表征方法的重点。分析了在实验室环境下,以U75V重轨钢为代表,采用酸溶法和非水溶液电解法分离提取出钢中非金属夹杂物,利用扫描电镜对夹杂物的基本形貌和成分进行了系统的分析研究。结果表明,利用电磁搅拌装置的酸溶法能有效得到耐酸类的夹杂物形貌和成分,其最佳溶液配比为盐酸(1+1);采用非水溶液电解法能够得到耐酸类和不耐酸类的微米和纳米尺度的非金属夹杂物,电解时间控制在8～10 h。与此同时,U75V重轨钢的酸溶和电解法分析结果表明,夹杂物中存在大尺寸不规则状的颗粒物,经分析判断该类是外来的颗粒物,被定义为非夹杂物,主要来源于空气中、自来水、干燥箱和电解槽内等,其成分为MgO、CaO、SiO₂和Al₂O₃,与钢中的氧化物夹杂物成分接近,从而对生产过程中控制夹杂物的措施易造成不准确的指导。因此,在分离提取钢中夹杂物的过程中,需要严格的保护操作,杜绝不利因素的干扰,准确得到钢中夹杂物的三维形貌、尺寸、化学成分等详细信息,能够为工艺改进或实验研究提供有效的支持。