变压器差动保护误动作原因分析

差动保护是变压器的主保护,差动保护的正确动作与否,直接危及到变压器和电网的安全.因而,分析差动保护可能出现的不正确动作的原因,在实际施工、安装中加以防范,就能很好地避免差动保护不正确动作的情况发生,本文以典型例子对变压器差动误动的原理进行了分析.     

主变差动保护误动作的原因分析及处理

变压器差动保护的目的是在变压器内部出现故障时,无延时跳开变压器各侧断路器,保护变压器本体、各侧引线和套管,并躲开励磁涌流、区外故障引起的穿越性电流的影响.针对变压器逆相序接入引起的差动保护误动作的现象、原因,进行理论分析并提出防范措施.     

一起变压器差动保护误动事故的原因及处理

在实际生产中,有时会发生“原因不明”的变压器差动保护误动的情况,现将我公司变压器差动保护误动的原因总结如下,旨在总结自己的经验教训并与同行进行交流讨论,以便采取相应的措施,提高变压器差动保护的可靠性,避免主变压器在运行中差动保护的误动作。     

提高变压器严重故障时差动保护动作速度的方法

纵向比率制动式差动保护是变压器的主保护,它的正确动作与否关系到变压器的安全和经济效益,它的动作速度关系到变压器的安全和电网的稳定。为了防止励磁涌流导致差动保护误动,差动保护常常增加二次谐波闭锁。采用二次谐波闭锁后,对于区内严重故障,受谐波的影响,差动保护往往会延迟动作。对于大容量的变压器,为了保证空投变压器差动保护不误动,往往要降低二次谐波的制动系数（一般为15%）,二次谐波制动系数的降低更加延缓了区内严重故障差动保护的动作速度;另外,目前采用双主双后的双重化保护配置,以前用作后备保护的非TYP级互感器也要应用于差动保护,为了提高差动保护的可靠性,差动保护又增加了抗区外故障CT饱和的闭锁逻辑,这进一步延缓了变压器差动保护区内严重故障的动作时间。为了保证区内严重故障时变压器的安全和系统的稳定,必须提高变压器区内严重故障时差动保护的动作速度。     

采用SPAD346C微机型变压器差动保护装置误动作原因分析

分析电力变压器差动电流产生的原因,针对一起微机型变压器差动保护误动作原因从技术原理进行分析,找出存在的问题,采取相应的措施进行处理,对ABB生产的微机保护装置功能进一步完善提出建议.     

变压器差动保护误动原因及预防

变压器差动保护用于反映变压器绕组的相间短路,绕组的匝间短路故障,中性点接地故障及引出线的相间短路故障,中性点接地侧引出线的接地故障。在正常运行情况下,流过差动保护差动继电器的不平衡电流应为零,因此差动保护不动作,然而由于变压器种种运行引起不平衡电流,使得差动整定动作电流加大,从而降低保护灵敏度。     

变压器差动保护不正确动作原因分析及引入比率制动特性曲线的测试方法

目前变压器都安装了差动保护,对变压器差动保护不正确动作的原因进行了详细的分析及归纳。尤其对其电流互感器二次接线的错误进行了定性、定量分析,有利于现场调试人员迅速查找事故原因。并引入比率制动式差动继电器,以保障电力系统的安全运行水平。介绍变压器差动保护的制动特性曲线及现场测试方法。     

变压器差动保护及其CT接线方式探讨分析

本文主要介绍了电磁式、晶体管式、集成电路式和微机变压器差动保护的工作原理以及CT接线方式,并结合准电电除尘变压器差动保护SPAD 346C分析了微机型差动保护“相位补偿”的作用。     

氮肥企业主变压器差动保护装置监视问题

<正> 大中型氮肥企业的主变压器,其容量等级大多在1000千伏安之上,按照继电保护设计规程,应装设纵联差动保护作为变压器的主保护。差动保护有着动作迅速、选择性好、灵敏度高的优点,但如差动保护电流回路接线错误,或者运行中出现断线时,都将引起差动保护误动作,酿成主变跳闸的全厂停电事故。迄今,关于对变压器差动保护装置的监视,正如《电力工程设计手册》(2)中指出的那样:“目前尚无完善的监视方案”。这里,就我厂在主变压器差动保护装置监视问题方面的改进,作一介绍和讨论。     

试论变压器差动保护带负荷测试

针对变压器差动保护在设计、站桩、鉴定过程中可能出现各种问题,结合变压器差动保护原理,提出了带负荷测试的内容及分析、判断方法。     

新型硅铝矿物吸附剂用于废变压器油再生处理

利用天然纳米硅酸盐黏土矿物的独特层状结构与晶体表面特性制备出具有纳米三维孔道结构的新型硅铝矿物吸附剂，并对所得纳米多孔材料的性能进行相应的表征及废变压器油吸附再生应用研究，通过吸附再生条件考察确定了最佳吸附条件。对吸附前后变压器油理化性能及电气性能分析结果表明，利用上述吸附剂吸附处理废变压器油后变压器油性能明显改善，耐压性、体积电阻率、界面张力、介质损耗因素、酸值等指标完全符合国家标准，可以实现废变压器油的高效吸附及再生，显著降低了成本，并避免了环境污染及资源浪费。     

Size exclusion and adsorption column chromatographic studies on functionality distribution of HTPB

Adsorption column chromatography and size exclusion chromatography have been used to determine the functionality distribution of hydroxyl terminated polybutadiene (HTPB), a modern solid propellant binder. The resin after conversion to 3,5-dinitrobenzoyl ester was separated into various fractions on a silica column. The fractions were analysed using a dual detector (UV and differential refractive index) analytical gel permeation chromatograph. The functionality of each fraction calculated from the chromatogram showed a continuous increase with increase in the molecular weight. The adsorption chromatography method is unable to fractionate the polymer into fractions with specific functionality. All the fractions have molecules ranging from monofunctional to multifunctional ones and therefore the apportionment method followed in the conventional adsorption chromatography method yields conflicting results.     

聚乙烯醇缩丁醛包膜球形活性炭对血液模拟体系的吸附

利用聚乙烯醇缩丁醛（PVB）对球形活性炭进行包覆并分析PVB溶液质量分数及其分子量，对肌酐、VB12和溶菌酶所构成的血液模拟体系吸附性能的影响。利用吸附动力学与吸附等温线对单组分及相对差异性双组分吸附过程进行分析。采用SEM、BET、压汞法孔隙率测定及FTIR对包覆活性炭形貌、结构进行表征。结果表明：包膜前后活性炭的吸附机理均为化学吸附，PVB质量分数对吸附量及吸附速率的影响最大，且随质量分数的增大而下降显著；PVB分子量则影响较小，但对增强炭表面亲水作用意义重大。双组分体系下：溶菌酶对VB12的竞争吸附作用明显，VB12的竞争吸附强度高达30%以上；肌酐与溶菌酶体系中，两者竞争吸附强度均低于8%，竞争吸附现象不明显。     

Investigation of the state and distribution of water in poly(ethylene terephthalate)/polyethylene glycol copolymers with various molecular weight of polyethylene glycol

Poly(ethylene terephthalate)/polyethylene glycol (PETG) copolymers with molecular weight of PEG varied from 800 to 20,000 g/mol were synthesized by melt macromolecular interesterification method. The results of contact angle and water adsorption capacity reveal that the molecular weight of PEG has a positive effect on the hydrophilic behavior of PETG copolymers. The interaction between water molecule and PETG copolymer was investigated through each relaxation time component by the Carr–Purcell–Meiboom–Gill sequence of low‐field nuclear magnetic resonance. The analysis of T₂ component with different states shows that with the increase of molecular weight of PEG, the water adsorption capacity increases due to the microphase separation behavior of PETG copolymers. This result was also supported by the endothermic behavior of H₂O/PETG mixtures measured by differential scanning calorimetry (DSC). Water molecule was tightly bound with PEG flexible chains at first stage, and then water molecules could swell the PETG copolymers, additional water permeating into the swelling copolymers. POLYM. ENG. SCI., 55:2195–2204, 2015. © 2015 Society of Plastics Engineers     

基于距离分析的邓式灰关联在故障诊断中的应用

传统邓氏灰关联方法是采用等权重的形式求取关联度,其关联度带有较大的主观因素,易造成信息损失,造成错误的故障诊断。针对存在的问题,本文引入了距离分析法,利用非匀权重的形式求取关联度,体现五种油中溶解气体对判断变压器故障类型的不同程度影响。它的特点是权重的分配不受主观因素制约,完全由样本数据信息决定。将该方法用于变压器故障诊断,结果表明,该方法可行有效,有实用意义。     

用于吸附过程开发的从分子水平级开始的多尺度模拟

This article presents a multiscale simulation approach starting at the molecular level for the adsorption process development. A grand canonical Monte Carlo method is used for the prediction of adsorption isotherms of methanol on an activated carbon at the molecular level. The adsorption isotherms obtained in the linear region （or adsorption constant） are exploited as a model parameter required for the adsorption process simulation. The adsorption process model described by a set of partial differential equations （PDEs） is solved by using the conservation element and solution element method, which produces a fast and an accurate numerical solution to PDEs. The simulation results obtained from the adsorption constant estimated at the molecular level are in good agreement with the experimental results of the pulse response. The systematical multiscale simulation approach addressed in this study may be useful to accelerate the adsorption process development by reducing the number of experiments.     

A novel water‐soluble,conducting polymer composite for mild steel acid corrosion inhibition

A novel water‐soluble conducting polymer composite, poly(vinyl alcohol‐histidine) was synthesized from aqueous solution by free radical condensation using persulfate. The composite was characterized using UV–Visible, Fourier transform infrared, scanning electron microscopy, thermogravimetric analysis (TG/DTG), and differential scanning calorimetry techniques while its AC conductance was measured by LCZ analyzer. The inhibitive action of the composite on the corrosion behavior of mild steel in 1M HCl was studied by conventional weight loss method, potentiodynamic polarization studies (Tafel), linear polarization studies, and electrochemical impedance spectroscopy. The effects of inhibitor concentrations, exposure time, and temperature have been investigated. The corrosion rate, inhibition efficiency (IE), and other parameters have been evaluated for different inhibitor concentrations. The composite provided more than 95% IE at an optimum concentration of 0.6% by weight. The results showed the composite as an effective mixed type inhibitor. The adsorption of this inhibitor obeyed Temkin adsorption isotherm. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization of Mordenite-Supported Pd, Pt, and Ir Determined by CO Adsorption Microcalorimetry and the Dehydrogenation Reaction of C3 Alkanes

Techniques such as adsorption microcalorimetry and the dehydrogenation of alkenes are used to measure the differential heats of adsorption and reactivity of several catalyst surfaces. An adsorption microcalorimeter built specifically to determine adsorption heats is employed. CO was used as the probe molecule in this study and was adsorbed on the following catalysts: Pd/mordenite, Pd?CPt/mordenite, and Pd?CIr/mordenite. The results show that the differential heat of adsorption was between 50 and 150 kJ/mol. The adsorption heat decreases with an increased in CO coverage for all catalysts. The best conversion for alkene studies was seen on the Pd?CIr/mordenite, which was close to 70%.     

基于改进粒子群算法的变压器故障诊断研究

针对基本粒子群算法存在收敛慢、易陷入局部极值的缺点,分析了粒子群算法中惯性权重和加速因子的作用,对其作了修改,并用改进后的粒子群算法训练神经网络,应用在变压器故障诊断上。仿真结果表明:改进后的粒子群算法迭代次数少,收敛速度比改进的BP算法快,可以对变压器的故障类型进行区分。     

活性炭微波改性及对偏二甲肼中氧化杂质的吸附

研究了活性炭微波改性后表面性质的变化及对偏二甲肼中氧化杂质吸附的性能.结果表明:微波法改性使活性炭表面的含氧基团有明显的减少,孔隙结构更为丰富;随着微波功率的提高,吸附率有明显的提高,微波照射时间对吸附效果的影响与功率有关;微波改性后的活性炭对偏二甲肼中的氧化杂质有更大的平衡吸附量及较小的等量微分吸附热.