我酒厂变压器并联运行的条件

0　概述随着现代电力事业的发展 ,发电厂和变电所的容量日趋扩大 ,须将两台或两台以上的变压器并联运行。并联运行在现代电力网中具有重要意义。第一、保证供电的可靠性。多台变压器并联运行时 ,当有一台变压器发生故障 ,仍可保证对重要用户的供电 ,各台变压器还可以有计划地轮流检修 ,延长设备的使用寿命。第二、减少安装时的初次投资。根据负载的增长情况 ,分期安装变压器 ,既可以减少初次投资 ,又能满足负载的增长需要。第三、提高供电效率。当负载随昼夜或季节变化时 ,可以在负载较小时适当地断开一部分变压器 ,以减少一部分变压器的能…     

油厂变压器容量的计算与选择

正确选择配电变压器容量,对油厂经济运行,降低电能损失,提高利用率有直接的关系。配电变压器应选择ST或SLT型低损耗变压器,逐渐淘汰高损耗老旧系列产品。 在确定配电变压器容量时,既不要造成“大马拉小车”,又不能选得容量偏小。应首先调查负荷情况,包括用电设备的总负荷(kW);各类负荷(预榨、精炼、锅炉、浸出、修配、综合利用、照明)和用电时间;直接起动时,单台电机的最大容量(kW);变压器全年的空载和轻载(负荷率<10％)运行时间。具体选择的办法有以下两种:     

制盐配电变压器经济运行分析

变压器经济运行是通过对变压器技术参数的分析计算,结合负载的特点及容量,选择合适的变压器以降低变压器损耗率和提高其运行效率。     

平朔矿区变压器节能降耗研究与应用

平朔矿区变压器损耗要占到总用电量的3%左右,落后于国内同等级电网的变压器损耗,有很大的提升空间。对此,我们依据变压器节能降耗理论,采取了优选变压器的容量、优选变压器的运行方式、优化变压器的负载分配、加速老旧变压器的更新换代等节能降耗措施降低了变压器的总损耗,使矿区变压器损耗降低到总用电量的2%左右,取得了可观的经济效益。     

安川VS—616G5变频器在造纸机中的应用

安川VS-616G5是全数字多功能电流矢量控制变频器,具有良好的驱动性能,先进的自动控制功能和完善的保护功能。矢量控制是将异步电动机在三相坐标系下的定子交流电流Ia、Ib、Ic通过三相—二相变换,等效成两相静止坐标系下的交流电流Ia1、Ib1,再通过按转子磁场定向旋转变换,等效成同步旋转坐标系下的直流电流Im1、It1(Im1相当于直流电动机的励磁电流,It1相当于与转矩成正比的电枢电流)即将力矩电流,励磁电流分量进行解藕。使解藕的磁通与力矩控制器使二者互不影响,而使电机的速度,力矩连续可调。从而可实现在极低速状态时的平滑运行和高力…     

浅谈县级供电企业理论线损计算与典型线损分析

电能在传输的过程中经过供电线路和配电变压器等相关设备时,会产生电能损耗和功率损耗,便称为供电损耗,简称为线损。线损主要可以分为两大部分,一是可变损耗,主要指电流通过导体所产生的能量损耗;二是固定损耗,主要是变压器的铁损、现场运行的电能表内部线圈的损耗,电力电容器的内部介质损耗等,上述两部分的线损通常称为技术损耗,除此以外的其他损耗则称为管理损耗,主要是指因为供电企业管理不够完善、要求执行不严格、现场运行的计量装置存在误差无及时校验修正等因素造成的各种电能损耗。     

关于C*-代数中Bohr不等式的一个注记

利用C*-代数到B(H)中的等距*-表示,研究C*-代数中的Bohr不等式,得到了4个推广的Bohr不等式成立的一些充分必要条件.主要结论如下:设p,q∈R+,且满足1/p+1/q=1,则(V) A,B∈S(S为有单位元的C*-代数),| A-B | 2+|(1-p)A-B | 2≤p|A|2+q| B|2成立当且仅当p≤2;设α,β,u,u∈R,p,q∈R+,则|αA+βB| 2+|uA+vB| 2≤p|A|2+q | B | 2成立当且仅当p≥α2+u2,q≥β2+v2且(p-(α2+ u2))(q-(β2+v2))≥(αβ+uv)2;设a,b∈R+,c∈C,则VA,B∈S,a|A|2+b|B|2+cA*B+cB*A≥0成立当且仅当ab≥|c | 2;设α,β∈R,x,y是正数,则(V)A,B∈S,|αA+βB| 2≤x|A|2+y|B|2成立,当且仅当x≥α2,y≥β2且(x-α2)(y-β2)≥α2β2.     

制浆造纸企业配电变压器的选择和节能探讨

本文计算并分析了变压器运行的损耗,从配电变压器的选型、负荷率的选择等方面探讨了其节能降耗措施;并对制浆造纸企业配电变压器选用方法提出了建议。     

对配电变压器节能措施的研究探讨

研究探讨了影响配电变压器损耗的各种因素,主要在变压器的材质上、铁心的结构上、制作技术上和技术的发展情况等问题进行了分析,对怎样可以减少损耗进行摸索研究;制定出了降低损耗的详细手段方法,包括对变压器的经济有效的运行方式以及对电压的调整方式等。分析针对变压器的节能运行问题上,国内外的相关标准,以便在配电变压器的节能运行、生产、使用等方面给予有效的信息参考。     

矩阵的Hadamard积和Fan积的特征值的界

讨论了矩阵的Hadamard积和Fan积的最小特征值的下界问题.令Mn为所有非奇异M-矩阵的集合,(1)若A,B∈Mn,B-1=(βij),则τ( A°B-1)≥min1≤I≤n2aiiβii-τ(A)βii+(τ(A)-aii)/(τ(B));(2) 若A,B∈Mn,则τ(A*B)≥min1≤I≤n[aiiτ(A)+biiτ(A)-τ(A)τ(B)].同时又将这两结果与有关文献的结果进行比较.     

Economic values of production and functional traits,including residual feed intake,in Finnish milk production

Improving the feed efficiency of dairy cattle has a substantial effect on the economic efficiency and on the reduction of harmful environmental effects of dairy production through lower feeding costs and emissions from dairy farming. To assess the economic importance of feed efficiency in the breeding goal for dairy cattle, the economic values for the current breeding goal traits and the additional feed efficiency traits for Finnish Ayrshire cattle under production circumstances in 2011 were determined. The derivation of economic values was based on a bioeconomic model in which the profit of the production system was calculated, using the generated steady state herd structure. Considering beef production from dairy farms, 2 marketing strategies for surplus calves were investigated: (A) surplus calves were sold at a young age and (B) surplus calves were fattened on dairy farms. Both marketing strategies were unprofitable when subsidies were not included in the revenues. When subsidies were taken into account, a positive profitability was observed in both marketing strategies. The marginal economic values for residual feed intake (RFI) of breeding heifers and cows were −25.5 and −55.8 €/kg of dry matter per day per cow and year, respectively. The marginal economic value for RFI of animals in fattening was −29.5 €/kg of dry matter per day per cow and year. To compare the economic importance among traits, the standardized economic weight of each trait was calculated as the product of the marginal economic value and the genetic standard deviation; the standardized economic weight expressed as a percentage of the sum of all standardized economic weights was called relative economic weight. When not accounting for subsidies, the highest relative economic weight was found for 305-d milk yield (34% in strategy A and 29% in strategy B), which was followed by protein percentage (13% in strategy A and 11% in strategy B). The third most important traits were calving interval (9%) and mature weight of cows (11%) in strategy A and B, respectively. The sums of the relative economic weights over categories for RFI were 6 and 7% in strategy A and B, respectively. Under production conditions in 2011, the relative economic weights for the studied feed efficiency traits were low. However, it is possible that the relative importance of feed efficiency traits in the breeding goal will increase in the future due to increasing requirements to mitigate the environmental impact of milk production.     

浅谈实现自备电厂经济安全运行的途径

针对国家电力部门实施的两部制电价政策,结合制盐企业发用电实际情况,拟提出:(1)运用隔离变压器改造电网运行结构,以减少基本电费支出;(2)实施分散式低周减载,实现制盐企业发用电设备经济安全运行.     

Biological deodorization of hydrogen sulfide using porous lava as a carrier of Thiobacillus thiooxidans

Biological deodorization of hydrogen sulfide (H2S) was studied using porous lava as a carrier of Thiobacillus thiooxidans in a laboratory-scale biofilter. Three different samples of porous lava, A, B, and C, which were obtained from Cheju Island in Korea, were used. The water-holding capacities of samples A, B and C were 0.38, 0.25, and 0.47 g-H2O/g-lava, respectively. The pHs and densities of the lava samples ranged from 8.25-9.24 and 920-1190 kg/m3, respectively. The buffering capacities, expressed as the amount of sulfate added to lower the pH to 4, were 60 g-SO4(2-)/kg-lava for sample A, 50 g-SO4(2-)/kg-lava for B, and 90 g-SO4(2-)/kg-lava for C. To investigate the removal characteristics of H2S by the lava biofilters, T. thiooxidans was immobilized on the lava samples. Biofilters A and C showed a removal capacity of 428 g-S.m(-3).h(-1) when H2S was supplied with 428 g-S.m(-3).h(-1) of inlet load at a space velocity (SV) of 300 h(-1). At the same inlet load and SV, the removal capacity of biofilter B was 396 g-S.m(-3).h(-1). The H2S critical loads of biofilters A, B and C at a SV of 400 h(-1) were 396, 157 and 342 g-S.m(-3).h(-1), respectively. It is suggested that natural, porous lava is a promising candidate as a carrier of microorganisms in biofiltration.     

Novel electromagnetic-black-hole-based high-efficiency single-mode microwave liquid-phase food heating system

Microwave heating exhibits a high potential for usage in liquid food processing. Current microwave heating systems are designed for a specific load. However, when the permittivity of the load changes dynamically, the heating efficiency of these systems fluctuates considerably. We proposed a novel high-efficiency microwave liquid heating system for dynamic dielectric loads to address this limitation. In this system, an electromagnetic black hole efficiently absorbs electromagnetic waves in all directions. First, an electromagnetic black hole was realized using metamaterials (which means artificially structured dielectric materials with extraordinary physical properties) with a radially continuous refractive index distribution. Next, an electromagnetic field simulation model was established to calculate the microwave absorption of various load permittivity. To discretize and simplify the parameters of the continuous distribution in an electromagnetic black hole, a concentric layered structure and a punched structure composed of uniform isotropic dielectric materials were designed. Finally, the experimental samples were processed based on the two discrete structures. The microwave system developed for experimental verification confirmed the high efficiency of the heating system; the system is simple and usable in numerous applications. Thus, the proposed method can realize high-efficiency heating of loads over large dielectric dynamic ranges. When the dielectric constant of the load changed dynamically from 10 to 80, the microwave energy utilization rate can increase by up to 90%.     

2005—2012年宁波市食源性金黄色葡萄球菌肠毒素基因和多位点序列分型研究

目的了解宁波市食源性金黄色葡萄球菌(S.aureus)肠毒素基因分布和分子分型特征。方法收集2005—2012年宁波市食品中金黄色葡萄球菌菌株,利用聚合酶链式反应(PCR)检测肠毒素A、B、C和D基因(sea,seb,sec和sed),对肠毒素基因阳性菌株利用多位点序列分型(MLST)进行分子分型。结果 2005—2012年共分离菌株190株,肠毒素基因阳性菌株为41株,阳性率为21.58%。4种肠毒素基因阳性率分别为7.37%(14/190)、5.26%(10/190)、8.95%(17/190)和5.79%(11/190),其中13株菌株具有两个及两个以上肠毒素基因。41株菌株可分为12个序列型(ST),以ST5、ST6、ST188和ST1为主,共占75.61%(31/41),在进化树上主要形成4个分支。结论 2005—2012年宁波市食品中金黄色葡萄球菌携带肠毒素基因频率较高,需加强监测。肠毒素基因阳性菌株与中国其他地区食品株在分子分型上存在较大差异。     

响应曲面法优化母乳化结构油脂制备工艺

文中对母乳化结构油脂的制备工艺进行优化。选用Sn-2位富含棕榈酸的猪油为原料,以Sn-1,3专一性脂肪酶Lipozyme RM IM作催化剂,与游离脂肪酸进行酶促酯交换反应制备母乳化结构油脂。通过单因素试验和响应面法优化工艺参数,建立了合成产物中Sn-2棕榈酸分布与反应温度、底物比酰基供体与猪油摩尔比、反应时间、加酶量之间的二次回归模型,即Y=-2 304.15+63.75 A+129.27 B+158.19C+45.85D-0.28AB-1.21AC-0.12AD-6.02BC-0.36BD+3.62CD-0.50A2-24.64 B2-52.00C2-2.05D2。优化后的工艺条件为:反应温度60.42°C;底物酰基供体与猪油的摩尔比为2.08∶1;反应时间1.05 h,酶/底物10.15%,制得的结构油脂中棕榈酸含量为20.35%,其中71.68%位于Sn-2位,与母乳脂肪的结构基本一致。表明采用RSM优化得到的酶促酯交换工艺条件参数适合以猪油为原料,制备母乳化结构油脂,建立的模型可以进行准确可靠的预测。     

再生丝素蛋白溶液脱盐新工艺及其应用

为提高丝素蛋白溶液的脱盐效率,降低脱盐能耗,采用扩散渗析-电渗析集成膜分离技术对丝素蛋白溶液进行脱盐,并初步探索所得溶液的应用。研究了丝素蛋白溶液浓度质量分数和扩散渗析预脱盐率对脱盐效率和能耗的影响,同时将所得丝素蛋白溶液加入无水乙醇制备不溶性丝素蛋白粉,测定了产品氨基酸的组成并利用扫描电子显微镜对丝素蛋白粉进行表征。结果表明,最佳的脱盐技术参数为丝素蛋白溶液浓度为5%、扩散渗析预脱盐率为40%,在此工艺条件下脱盐时间缩短至9 h,能耗（动力能耗除外）为3.81×10-2 kw?h/L;产品中丝氨酸和甘氨酸含量接近50%,丝素蛋白粉末粒径较小且分布均匀。     

Impact of temperature on lethality and energy efficiency of apple juice pasteurization by pulsed electric fields treatment

The applicability of pulsed electric fields as a non-thermal preservation process for liquid food decontamination has been shown in several studies. However, high costs of operation due to the occurrence of a high amount of dissipated electrical energy inhibited an industrial exploitation so far. In this study the focus was put on improving energy efficiency of this process for pasteurization of apple juice inoculated with Escherichia coli by investigating the relation between achieved reduction in survivor count and electric field strength and treatment temperature. An empirical mathematical model was derived to predict the required input of electrical energy for a given inactivation. Using synergistic effects of elevated treatment temperature of 35–65 °C on microbial inactivation the energy consumption could be reduced from above 100 to less than 40 kJ kg⁻¹ for a reduction of 6 log cycles and the need to preheat the juice before treatment provided a possibility to recover the dissipated electrical energy after treatment, leading to a drastic reduction in operation costs. To evaluate the thermal load of the product the pasteurization unit (PU) and the cook value, key benchmarks for the thermal load, were used to compare PEF and conventional heat treatment.     

Increase in pladienolide D production rate using a Streptomyces strain overexpressing a cytochrome P450 gene

Pladienolide B and its 16-hydroxylated derivative (pladienolide D) are novel 12-membered macrolides produced by Streptomyces platensis Mer-11107 showing strong in vitro and in vivo antitumor activity. While pladienolide B is mainly produced by this strain, pladienolide D is produced to a lesser extent. To facilitate the production of pladienolide D by biotransformation, we found that Streptomyces bungoensis A-1544 was able to hydroxylate pladienolide B at 16-position. We identified psmA from S. bungoensis A-1544, which encoded a pladienolide B 16-hydroxylase PsmA belonging to the CYP105 family of cytochrome P450. To increase the efficiency of pladienolide D production, we constructed recombinant S. bungoensis A-1544 overexpressing psmA and performed biotransformation of pladienolide B to pladienolide D. This biotransformation achieved a production level 15-fold higher than that using the control strain S. bungoensis A-1544/pIJ702.     

Marginal emissions factors for the U.S. electricity system

There is growing interest in reducing emissions from electricity generation in the United States (U.S.). Renewable energy, energy efficiency, and energy conservation are all commonly suggested solutions. Both supply- and demand-side interventions will displace energy-and emissions-from conventional generators. Marginal emissions factors (MEFs) give a consistent metric for assessing the avoided emissions resulting from such interventions. This paper presents the first systematic calculation of MEFs for the U.S. electricity system. Using regressions of hourly generation and emissions data from 2006 through 2011, we estimate regional MEFs for CO(2), NO(x), and SO(2), as well as the share of marginal generation from coal-, gas-, and oil-fired generators. Trends in MEFs with respect to system load, time of day, and month are explored. We compare marginal and average emissions factors (AEFs), finding that AEFs may grossly misestimate the avoided emissions resulting from an intervention. We find significant regional differences in the emissions benefits of avoiding one megawatt-hour of electricity: compared to the West, an equivalent energy efficiency measure in the Midwest is expected to avoid roughly 70% more CO(2), 12 times more SO(2), and 3 times more NO(x) emissions.