35kV智能变电站集成化技术及应用

提出的35 kV智能变电站优化集成设计主要包括:在过程层设计综合智能组件实现合并单元、智能终端等功能;在间隔层设计智能站域测控保护主机实现全站的保护、测控、站域控制、故障录波、电能质量监测等功能;在站控层建立一体化信息平台,整合各系统功能,实现站控层数据与辅助系统全面共享互动。     

一种新的智能变电站继电保护架构

针对国内智能变电站继电保护现状,提出一种智能变电站继电保护架构,该架构将继电保护分为两个层次,现场就地安装的单间隔保护、MU和智能终端。预制舱安装的多间隔保护、站域级保护以及就地保护管控单元。就地安装的继电保护电缆直接采样、电缆跳闸,提高保护的安全可靠性;就地安装的MU和智能终端为站域保护、多间隔保护提供SV和GOOSE数据。保护管控单元为就地保护提供人机界面、状态监测等高级管理功能。该架构单间隔保护不依赖网络,多间隔保护数据点对点传输,站域保护依赖网络,解决了智能变电站光纤数量大、交换机多、保护环节增多导致可靠性降低的问题。     

智能变电站二次设备的整合方案

智能变电站是智能电网建设的重要节点,按照国家电网公司编制的一系列与智能变电站相关的技术规定,通过对变电站合并单元与智能终端、故障录波与网络报文分析、保护装置与测控装置等方面的分析,提出了二次系统功能整合方案,例如建设220kV及以下或者规模不大的500kV智能变电站,优先采用故障录波与网络分析一体化方案,可以解决动态和暂态报文的记录问题,同时还简化了网络配置。通过整合智能变电站二次系统的功能,在满足保护测控装置可靠性的前提下,合理配置二次系统相关设备,优化二次系统网络架构,以降低变电站的建设投资,方便变电站的运行和维护管理。     

基于分层分布的变电站跨间隔闭环检修方法

针对现有变电站跨间隔故障检修方法收敛速度慢、检修率低的问题,提出基于分层分布的跨间隔闭环检修方法。首先按照分层分布式的设计思想,将变电站故障在线检修模块细分为信息采集层、网络层、后台控制层,构建网络资源和电气间隔故障状态的实时共享,然后提出电力系统在线故障检修体系结构,设计变电站分层分布式网络总体方案。利用Matlab进行仿真分析,并与ANN方法、专家评估法的结果对比。对比仿真分析表明,该方法的迭代速度快、均方误差值低、故障检修率高,可应用于实际工程中。     

110 kV雪山智能变电站联调测试中若干问题探讨

为精确校验与考核110kV雪山智能变电站三层两网构架下各智能电子设备(IED)及通信网络系统的关联可靠性,结合系统联调测试结果,分析了合并单元(MU)时延偏差、同步性能对主变差动动作性能的影响,为智能变电站系统联调测试工程化实践积累了宝贵的经验。     

新一代智能变电站二次系统图模库一体化设计技术

针对新一代智能变电站二次系统模块化生产、设计、施工的特点与要求,研究并制定基于图模库技术的一体化设计方法及工具。介绍智能站传统的设计移交模式,在此基础上,结合新一代智能变电站的建设特点,制定新一代智能变电站的设计移交流程,提出自动化、模块化的二次系统设计技术;接着,提出1种利用关联知识库校验虚回路的静态技术手段与大容量虚回路配置动态校核和过程层数据校核技术,实现虚回路校核;最后,在工具中集成了标准化工程数据库,方案可整体调用或按间隔调用,大幅提高设计效率。     

基于智能变电站间隔层设备顺序控制功能实现

针对目前智能变电站顺序控制等高级应用功能可靠性和自动化程度不高等问题,基于智能变电站间隔层设备逻辑虚回路原理,提出了基于智能变电站间隔层设备顺序控制功能实现方法,该方法配置灵活,能可靠实现一次设备的顺序控制和全过程监控,从根本上解决制约顺序控制技术应用问题,提高电网智能化水平。     

配电网串供线路继电保护整定原则研究

解析现行配电网线路过电流保护整定规程规定,分析典型电网两段式简化整定原则存在的问题,以及部分电网三段式整定原则的局限性,提出优化的三段式整定方案,兼顾选择性和速动性,保障供电可靠性和主设备安全.     

分布式状态估计技术在智能变电站的应用

分析了智能电网研究和建设中的关键问题和需求,结合分布式状态估计技术在苏州智能变电站的实际应用情况,详细阐述实现方案和关键技术,从调度和变电站两端总结分布式状态估计技术在智能电网中的应用价值。结果表明,分布式状态估计技术在智能变电站的应用,提升了变电站基础数据的可靠性、准确性,加快了二次信息缺陷的处理,提高了变电站智能化水平,对变电站的高级智能应用有积极意义。     

基于规则推理的智能变电站操作票自动生成方法

智能变电站操作票开票系统能够有效防止误操作，实现顺序控制。目前开票系统的操作逻辑主要基于典型间隔，进行人工组态，工作量较大。提出一种基于规则推理的智能变电站操作票自动生成方法。基于“五防”规则建立基本单元模型，并生成各类典型间隔设备的操作规则函数，实现系统知识库的构建；通过解析智能变电站的SSD文件得到一次设备的状态，以此构建一次设备拓扑表，并采用基于设备状态的推理算法结合设备操作规则函数，完成推理机的构建，实现操作票的自动生成。通过算例验证，测试结果表明，文中研究的方法具有完善的知识库，针对不同接线方式下的操作任务，能高效快速地完成自动开票，通用性及准确性较强。     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法，这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Economie d'énergie en trigénération

Trigeneration is defined as the production of three useful forms of energy—heat, cold and power—from a primary source of energy such as natural gas or oil. For instance, trigeneration systems typically produce electrical power via a reciprocating engine or gas turbine and recover a large percentage of the heat energy retained in the lubricating oil, exhaust gas and coolant water systems to maximize the utilization of the primary fuel. The heat produced can be totally or partially used to fuel absorption refrigerators. Therefore, trigeneration systems enjoy an inherently high efficiency and have the potential to significantly reduce the energy-related operation costs of facilities. In this paper, we describe a model of characterization of trigeneration systems trough the condition of primary energy saving and the quality index, compared to the separate production of heat, cold and power. The study highlights the importance of the choice of the separate production reference system on the level of primary energy saving and emissions reduction.     

Mineralogical characterization of the intraseam layers of Lofoi lignite deposits in Florina basin (western Makedonia,northwest Greece)

The mineralogical composition of intraseam layers from Lofoi lignite deposits (northwest Greece) is the subject of the present study. The samples were examined by means of X-ray diffraction (XRD), thermo-gravimetric (TG/DTG) and differential thermal analysis (DTA), and Fourier transform infrared (FT-IR) spectrometry. The clay minerals prevail in most samples, with illite-muscovite being the dominant phase, and kaolinite and chlorite being the other major clay components. No smectite was found. Quartz and feldspars, dominate in two cases. The studied materials are characterized as clays to clayey sands, showing significant similarities with the intraseam layers of the adjacent Achlada lignite deposits.     

Innovative methodologies in renewable energy: A review

This paper is concerned with innovative approaches to renewable energy sources computation methodologies, which provide more refined results than the classical alternatives. Such refinements provide additional improvements especially for replacement of fossil energy usages that emit greenhouse gas (GHG) into the atmosphere leading to climate change impact. Current knowledge gap among each renewable energy source calculation is rather missing fundamentals of plausible, rational, and logical explanations for the interpretation of results. In the literature, there are rather complicated and mechanically applicable methodologies, which require input and output measurement data match with missing physical explanations. The view taken in this review paper is to concentrate on quite plausible, logical, rational, and effectively applicable innovative energy calculation methodologies with simplistic fundamentals. For this purpose, a set of renewable energy methodological approaches is revisited with their innovative structures concerning solar, wind, hydro, current, and geothermal energy resources. With the increase in the renewable energy utilizations to combat the undesirable impacts of global warming and climate change, there is a need for better models that will include physical environmental conditions and data properties in the probabilistic, statistical, stochastic, logical, and rational senses leading to refined and more reliable estimations with application examples in the text. Finally, new research directions are also recommended for more refined innovative energy system calculations.     

Decomposition of limestone in a solar reactor

The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m² parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO₂ emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.     

Constrained Optimization of Heat Transfer from an Extended Surface

Two different zero‐order optimization techniques are used to maximize the rates of heat transfer from a fin assembly of a specified cost and in the shape of several annular fins that are mounted on a central stem. The problem is formulated to account for two‐dimensional steady‐state heat transfer that is limited by several inequality constraints. The dimensionless governing equations are used to identify the relevant decision variables. The number of fins making up the assembly is treated as an input parameter. A digital computer is used to determine the required temperature distributions and to implement the optimization search algorithms. Three different fin materials are assessed—aluminum, copper and carbon steel. Design optimizations of the extended surface assembly were made over a range of operating conditions, encompassing several different convection heat transfer coefficients that are representative of free and forced convection in air, and several different overall temperature differences between the substrate surface and air. A few recommendations based on trends in the predicted results are given. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(6): 504–521, 2014; Published online 3 October 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21093