750 kV同塔双回线路对地高度取值研究

分析了750kV单、双回路对地高度取值的设计依据。结合750kV西宁-永登-白银同塔双回线路大部分处于交通困难地区的实际情况,认为该线路导线对地高度普遍可以考虑降低2．7～4．5m,可节省工程投资近1000万元,经济效益明显。     

非全线同塔双回架设的1000kV换位线路电流不平衡度研究

在地形复杂或覆冰较严重处,输电线路无法采用全线同塔双回的方式架设,而采用并行单回架设的线路段时需研究其对全线三相电流不平衡的影响。对此,在推导电流不平衡度计算方法的基础上,通过ATPEMTP仿真建模计算,研究了有一个整循环换位的1 000kV双回分段架设线路中相序排列、换位方式及单回线路段的首尾连接方式、回间距离等因素对电流不平衡度的影响,得出了较优的换位、相序排列组合方案及单回线路段连接方式,并总结了单回线路段的回间距离对线路电流不平衡度的影响规律,对改善实际非全线同塔双回架设的线路中出现的电流不平衡问题有参考意义。     

750 kV同塔双回线路电磁环境控制值研究

由于同塔双回导线排列方式不同,其电磁环境影响相对于单回路情况既有改善的可能,也有增加的风险。为合理控制工程造价和环境影响水平,通过对前期科研成果和国内外电磁环境情况的调查,结合我国对750kV单回线路电磁环境参数控制值的研究,确定了750kV同塔双回线路电磁骚扰水平,使其不突破现有单回路水平。同时结合对330kV线路的测试,依据高海拔对线路电磁环境的影响,提出了同塔双回线路无线电干扰和可听噪声的海拔修正值。     

同塔双回输电线路的雷电反击计算及仿真

由于同塔双回输电线路电感较大,将面临更加严苛的防雷保护问题,所以为了降低输电线路的跳闸率,有必要对输电线路雷电反击的影响因素进行研究。采用ATP-EMTP建立了反击仿真模型,研究了不同雷电流幅值下的绝缘子两端的电压变化情况。利用规程法计算出不同冲击接地电阻、不同杆塔高度及不同波阻抗下的线路的耐雷水平和反击跳闸率。计算结果表明:降低接地电阻或杆塔高度可以有效地降低同塔双回输电线路反击跳闸率;当波阻抗独立地变化10%时,输电线路的反击跳闸率将相应地变化约20%。     

基于多维虚拟电流差动母线保护研究与应用

[目的] 为了实现母线倒闸操作过程中母线保护在隔离刀闸出错情况下,仍然可以可靠快速地切除故障母线,提出了母线双位置刀闸配置与虚拟电流差动量互校原理,并对其进行了理论分析和动态模型仿真测试。 [方法] 基于上述需求,利用刀闸的双位置信息辅助虚拟电流差动逻辑,则可以很好地解决变电站倒闸过程中出现的问题。 [结果] 母线保护接入刀闸双位置信息从数学量化理论来说,降低了位置错误的可能性,再辅以虚拟电流差动逻辑来纠错,能很好的避免变电站倒闸操作出现问题导致母线无选择性的跳闸。 [结论] 母线保护接入双位置刀闸辅助开入,并辅以虚拟差动逻辑判据,可有效对倒闸操作过程中发生的刀闸位置异常进行纠错处理,从而确保母线保护的选择性和可靠性。     

750kV同塔双回线路电磁环境控制值研究

由于同塔双回导线排列方式不同，其电磁环境影响相对于单回路情况既有改善的可能，也有增加的风险。为合理控制工程造价和环境影响水平，通过对前期科研成果和国内外电磁环境情况的调查。结合我国对750kV单回线路电磁环境参数控制值的研究，确定了750kV同塔双回线路电磁骚扰水平，使其不突破现有单回路水平。同时结合对330kV线路的测试，依据高海拔对线路电磁环境的影响，提出了同塔双回线路无线电干扰和可听噪声的海拔修正值。     

750 kV兰州东-平凉-乾县同塔双回送电线路工程绝缘配合研究

依据现行国家标准、规程、规范、IEC标准,依托"西北电网750 kV同塔双回输电线路关键技术研究报告"第一批项目课题的研究成果和结论,结合"西北电网750 kV输变电工程关键技术研究"结论,根据兰州东-平凉-乾县750 kV同塔双回输电线路送工程的具体特点,参考国内第一条750 kV示范输电线路工程--官亭-兰州的成功设计经验,以及国外在750 kV电压等级输电线路成熟的设计运行经验,并结合国内330 kV和500 kV同塔双回输电线路的设计和运行经验进行分析研究,提出针对本工程绝缘子选型及绝缘配合的推荐数值.     

一种适用于电流差动保护的T型高压输电线路故障测距算法

针对在T型线路的T节点附近发生短路,特别是高阻短路时,常用的T型线路故障测距方法会无法正确判断故障支路而存在一个测距死区的问题,提出了一种利用过渡阻抗的纯电阻性质进行故障测距的方法,并利用反证方法判断在T节点附近发生故障的支路。PSCAD仿真结果表明,该方法原理正确,无测距死区,测距精度不受故障类型、故障距离和过渡阻抗的影响,精度较高。     

750 kV同塔双回交流输变电工程防雷保护研究

研究了750 kV线路雷电性能及750 kV变电所和开关站雷电侵入波过电压,指出造成750 kV线路雷击跳闸的主要原因是绕击。建议增加地线间距和提高绝缘子串绝缘水平以减小跳闸率。通过对兰州东变电所雷电侵入波的计算分析和变电所的特点,提出2种相应的MOA布置方案,并验证了绝缘选择的安全裕度,得出2种方案均可以满足防雷要求。     

微机差动保护中检测电流互感器接线错误的方法

分析了微机保护中电流互感器（简称CT）接线错误的几种可能性,以及每种接线错误时电流呈现的特点．并提出一种快速检测接线错误的方法．     

低压储能微网孤岛运行保护的研究

储能是微电网的核心部分,可以消减一些可再生能源发电的间歇性和波动性对发电系统的影响,保证微网安全可靠的运行。针对储能单元在低压微网孤岛运行的保护,提出了一种电压反时限保护方法,以对微网故障的检测、故障类型的判别以及故障的切除。通过MATLAB仿真分析,验证了该方法的有效性,对微网实际工程中的保护提供了理论依据。     

Distance protection of EHV long transmission lines considering compensation degree of shunt reactor

This study investigated the feasibility of distance protection in extra-high voltage (EHV) networks. In long-distance transmission lines, the distributed parameter characteristic of the EHV network is obvious. When a fault occurs far away from the measurement site, the measured impedance might not be directly proportional to the fault distance, and the protection domain of distance protection will be decreased. The detailed theory inferred and proven in this paper reveals that this phenomenon is widespread in EHV transmission lines. The results indicate that the protection domain error is greatly reduced by the application of the shunt reactor. Overall, simulation results show that the proposed method is effective for impedance relay, considering different characteristics, different lengths of lines, and compensation degrees.     

Effect of distribution system protection on voltage sags

The general relationship between distribution system protection schemes and voltage sags is presented. The definition, characteristics, and sources of sags are given. The probability of sag occurrence is studied from the three points of view: reliability assessment, historic reliability, and general tendency. General values for the reliability assessment uncertainties and facts related to the historic reliability are proposed. The general tendency is analyzed in normalized form. The reliability index appropriate for the study of the protection scheme interaction with voltage sag are described     

工厂低压无功补偿方式优化的思考

对当前大多工厂的单一低压无功补偿方式利弊关系进行了分析,提出改革优化设想,采用无功就地补偿为主,车间补偿为辅,配电房集中弥补平衡全厂无功分级相结合的补偿方式。     

Open circuit voltage durability study and model of catalyst coated membranes at different humidification levels

Fuel cell material durability is an area of extensive research today. Chemical degradation of the ionomer membrane is one important degradation mechanism leading to overall failure of fuel cells. This study examined the effects of relative humidity on the chemical degradation of the membrane during open circuit voltage testing. Five Gore™ PRIMEA^® series 5510 catalyst coated membranes were degraded at 100%, 75%, 50%, and 20% RH. Open circuit potential and cumulative fluoride release were monitored over time. Additionally scanning electron microscopy images were taken at end of the test. The results showed that with decreasing RH fluoride release rate increased as did performance degradation. This was attributed to an increase in gas crossover with a decrease in RH. Further, it is also shown that interruptions in testing may heavily influence cumulative fluoride release measurements where frequent stoppages in testing will cause fluoride release to be underestimated. SEM analysis shows that degradation occurred in the ionomer layer close to the cathode catalyst. A chemical degradation model of the ionomer membrane was used to model the results. The model was able to predict fluoride release trends, including the effects of interruptions, showing that changes in gas crossover with RH could explain the experimental results.     

Bargaining local compensation payments for the installation of new power transmission lines

This paper analyzes transmission system operator (TSO)-host community negotiations over an efficient and socially-optimal compensation payment for the installation of new electric power transmission lines. We consider that the TSO has an incentive to negotiate over a transfer that will become a function of final demand. We thus develop a bargaining game within a vertical relationship framework to include the distribution system operator (DSO) and the end-users at the downside of the bargaining problem. We determine the equilibrium of the game, for three negotiation protocols (sequential, bilateral, and multilateral) as an alternative to the non-cooperative situation. We show that when the number of municipalities involved in the process is higher than 5, the multilateral bargaining procedure is the most profitable for all agents, including the municipalities. Inversely, when the number of municipalities is lower than 5, different cases can arise. A single municipality will prefer the non-cooperative outcome while municipalities will prefer the sequential case when there are 2 or the bilateral case when there are 3 or 4. However, from the TSO standpoint and for the society, multilateral negotiations are always the best outcome.     

Transient phenomenon of step switching for current or voltage in PEMFC

The transient phenomenon of fuel cell with 5 cm² active area is investigated in this study by current density step increase and switching voltage under different conditions. It is found that there is an undershoot when the current density step increase is at the loading of 60% RH anode cathode, 3 stoic., 70 °C, 15 psi for automobile applications. The voltage is almost zero under 0.2 step increase to 1.0 A/cm² due to the H⁺ transport in membrane or H₂/O₂ in catalyst layer is almost used up. The undershoot phenomenon is more serious under gases stoichiometries of 3.0/3.0 when H₂ is fully humidified due to low gas concentration or flooding on the electrode. This phenomenon would induce the degradation of fuel cell components.     

Power output of segmented MHD Faraday generators with hall voltage compensation

Hall voltage causes a deterioration of the performance of a segmented MHD Faraday generator, and methods of compensation for this effect are studied. A simple network analogue is developed and used to analyze current flow through the generator and the effect of compensating voltages.Practical segmentation ratios are found to be <0.2. This limit is shown to be well below that required to minimize Hall effects due to electrode length. Smaller segmentation ratios, as used in larger designs therefore, are used mainly to cover inter-electrode breakdown caused by Hall voltages.Hall effect compensation is found to produce a significant increase in generator power only at the expense of a large recirculation of power and internal losses.