±800 kV Fulong-Fengxian UHVDC transmission system (XSH800 project) has successfully operated for 5 years. Its operation situation in last 5 years was analyzed, as well as the availability index and influence factors. In last 5 years, the cumulative transmission power of XSH800 was up to 895.53 billion kWh； bipolar and unipolar forced outage did not occur； single-valve group forced outage only happened five times； the unavailability of forced energy was only 0.0368%, which reached the international leading level. The practice results prove the safety and economy of UHVDC technology. The equipment problems exposed during operation, which may affect the availability, have been timely and fully corrected, and applied in the subsequent UHVDC transmission project. The successful operation of XSH800 in last 5 years has played a role in the demonstration and promotion for the large-scale construction and rapid development of UHVDC transmission project.

With the rapid development of energy storage technology, the large-scale energy storage system has gradually become a key method to ensure power system reliability and safety, of which electrochemical energy storage has been one of the directions of preferential development due to its unique performance. In order to promote the development of energy storage technology and speed up the efficient use of large-scale energy storage system, several large-scale electrochemical energy storage demonstration projects have been successively started and completed in the world. The classification and working principle of electrochemical energy storage technologies are introduced, the main demonstration plants of large-scale energy storage system in China and abroad are summarized, as well as the installation site, scale and function in grid of electrochemical energy storage are pointed out. Then, the characteristics of main electrochemical energy storage, such as lead-acid battery, redox flow battery, sodium-sulfur battery, lithium-ion battery and so on, are comprehensively expounded. Finally, the existing problems, technical direction and future development trend of large-scale energy storage system are discussed and prospected.

 With the rapid progress in information technology, a novel concept—“Energy Internet”, that concentrates on the coordination and optimization of multi-type energy flows via advanced communication and internet technology, has received a lot of attention. The result of such an inevitable trend is that a fundamental technique—Big Data Analytics—must be developed to handle massive influx of data from multiple heterogeneous sources, as well as utilize the data to swiftly derive an economic value. The paper gives an overview on research works conducted at SGRI North America big data lab with highlights on hardware configuration and software deployment of the cluster environment. The paper reviews several ongoing research topics performed in the lab with an emphasis on customer segmentation and response targeting （collaboration with Stanford University）；and energy disaggregation. These works are built on an integrated power system data model that is supported by open source technology. Preliminary results show that our research will benefit both utility companies and customers.

±800 kV Jiuquan-Hunan UHVDC project sends large scale wind power to Hunan power system which is depending on the outside power source. Thus its reactive power compensation configurations not only need to consider the reactive power requirements of the DC system, but also should be optimized through equipped with reasonable dynamic reactive power compensation devices, according to weak reactive voltage supporting ability of AC grid in transmitter/receiver system. Because the AC grid connected to Jiuquan had large-scale wind power, the reactive power configuration scheme was proposed, in which static var compensator (SVC) was applied in the low-voltage side of substation-used transformer in converter station, and the filter capacity of converter station with SVC was determined. Aiming at low voltage risk of AC system connected to Hunan converter station, static synchronous compensator (STATCOM) was applied in the low-voltage side of substation-used transformer in Hunan converter station, the corresponding filter capacity was optimized and configured. Based on the calculation and analysis, it can be concluded that the dynamic reactive power compensation device applied in converter station can improve the voltage stability of the connecting AC system nearby converter station, reduce the voltage fluctuation of the converter bus caused by filter switching, and decrease the device investment.

Under the condition that the development and utilization of new energy are vigorously advocated in China, the construction of small hydropower has developed rapidly. However, due to the lack of standardized management, the operation of small hydropower often leads to overvoltage in regional power network. Therefore, combined with the characteristics of small hydropower, this paper constructed the equivalent analysis model of power grid with small hydropower. On this basis, the theoretical analysis was carried out on the serious overvoltage process occurred in three situations: the isolated operation of small hydropower, transferring power supply and going into the wet season. The generation mechanism of overvoltage was studied； and the restrain measures were proposed for the overvoltage from the technical and management level, according to different overvoltage conditions. Finally, based on simulation software DIgSILENT/PowerFactory, this paper constructed the model for actual power grid with small hydropower, and verified the correctness of theoretical analysis and the effect of restrain measures.

Integrated energy system （IES） can provide an effective solution to solve the low security, insufficient self-healing capability, and low utilization rate of energy equipment problems under the background of low-carbon economy, which has a significant potential to support the optimization and adjustment of China’s energy structure. Firstly, the basic concept of IES and its main features are given in detail. Then, considering the valuable IES construction experience around the world and the current status of China’s energy resources, some key issues about China’s IES from the prospective of national level, regional level, and terminal level are discussed. Also, the corresponding suggestions are proposed.

Traditional distribution networks undertake the function of distributing energy and providing electricity consumption, therefore the flowtransferringis unilateral. The increasing amount of distributed generation （DG） in todays highly complex restructured power networks change it to bidirectional flow. Due to the randomness and intermittence of DG, flow fluctuates wildly in a degree, which makes the distribution infrastructure cannot work in economical and efficient ways. For the better energy transferring ability of DG, provide high-quality power, Beijing Power Grid build the controllable and observable active distribution（ADN） in energy transferring and distribution operator system field, for the entire energy consumption of high-permeability DG, achieve the aim of efficient energy use and high-quality and high-reliability power supply.

首先比较了直流保护系统出口回路与传统交流保护出口回路的特点；然后结合实例分析了直流保护系统出口回路存在的问题，如投切压板操作易对保护出口继电器造成冲击，而且投入压板瞬间在保护出口继电器辅助接点副边侧可能感应出较高电压，从而导致误出口；最后提出了改进建议。

With the increasing integration of distributed energy resources（DER） and electric vehicles（EV）, the intelligent home and demand side response are being gradually popularized. As a result, the operation and planning complexity of distribution system are significantly enhanced. Moreover, the higher demands of power supply make the system optimization more difficult. As one development mode of the future distribution system, active distribution network begins to attract more and more attention. Its concept and management system are introduced, and the operation and planning strategy are reviewed including the present situation as well as the current concerns. Finally, the development trends are sorted out from three aspects： the source-network-demand interaction, the multi-period coordination, and the multi-layer distributed strategy.

There are rich renewable energy reserves in five provinces in Southern China and its offshore areas. The large-scale development of renewable energy, such as wind power and solar power, can help to alleviate the problems of energy shortage and environment pollution in Southern China. On the other hand, as an important component of Chinas western development strategy, west-east power transmission is an effective measure to optimize the allocation of electric power resources and promote the adjustment of economic structure for five provinces in Southern China. Based on the interaction mechanism of west-east power transmission characteristics in China Southern Power Grid and renewable energy generation characteristics, this paper uses the mid-long term production simulation method of China Southern Power Grid to analyze the impacts of west-east power transmission characteristics in China Southern Power Grid on the renewable energy acceptability, which could provide references for the reasonable determination of west-east power supply level and the reasonable arrangement of the exploiting priority scheduling of renewable energy in each province.

根据对已投运的高压直流输电二次系统反馈信息的分析研究,针对控制保护主机死机频繁、直流保护电路板卡故障、直流控制和保护系统不分导致保护误动等问题,在蔡家冲换流站二次系统的设计中,提出了设计改进措施,并得到了实际应用。同时还简要介绍了蔡家冲换流站二次系统国产化情况。

目前钢管结构已广泛应用于超高压、特高压变电构架中，而构架吊装中吊点及钢丝绳径的选择一般凭施工经验进行确定。以山东密州变电站500 kV 钢管构架吊装为例，通过理论计算阐述了构架吊装过程中钢梁和A字柱的吊点的最佳受力位置及钢丝绳径的选择，为构架吊装提供理论依据。

The active distribution network （ADN） provides an effective solution for large-scale integration and high-efficient utilization of renewable energy sources under the background of low-carbon economy, which is strategic significant to promote the optimization and adjustment of energy structure in China. The functional characteristics of ADN was analyzed, then the development objective, contents and effect of both domestic and oversea demonstration projects were introduced. After analysis the insufficient of traditional ADN planning, key technical issue of ADN planning was explored in this paper. Furthermore framework and critical factors of ADN planning method were proposed. It is pointed that engineering practice should develop from frame structure, distribution automation, intelligent communication network, information platform and intelligent power utilization, development direction and principle are put forward as well.

The reactive power balance and control strategies in three typical HVDC transmission system (UHVDC, EHVDC, BTBHVDC) were comprehensively analyzed and researched. First of all, the electric equipment and influence factors related to reactive power in HVDC transmission system were introduced. Furthermore, the existing reactive power control strategies of HVDC projects were summarized and the concept of reactive power control factor was proposed. Moreover, based on the relationships between voltage fluctuation and reactive power in AC system, the simplified scheme was presented, in which AC voltage was converted into reactive power, and the intersection of transformed reactive power and AC system reactive power was taken as control factor. Finally, the computation results of the proposed method for reactive power were compared with the operating results of actual projects. The experimental results verify the effectiveness of the reactive power model in the proposed scheme.

As a novel “Source-Net-Load” ternary structure of distribution system, active distribution network （ADN） is the main technical mean to solve the large-scale and high penetration of distributed energy in near future. This paper focused on the overall architecture and key features of ADN, elaborated the technique concepts of ADN and proposed scientific and complete evaluation index system for ADN, including the characteristic indexes of intermittent energy sources grid-connection, ADN control and operation. The quantitative analysis of “reason-process-result” of ADN was carried out with using these indexes, which had important guiding significance and reference value to the choice of the technical route and implementing scheme of ADN.

运用色谱分析技术判断变压器故障时 ,有特征气体组分法、成分超标分析法和比值判断法等 ,并可根据变压器油分子裂解产生的气体组分及比值来判断变压器故障类型及故障点温度。通过惠州 110kV马庄 2号主变压器大修时 ,由油气体的总烃值对该变压器的故障类型及故障点温度进行判断 ,证实了色谱分析预测、判断变压器故障的有效性。

In recent years, large-scale wind turbine tripping accidents occur frequently, causing a serious threat to the security and stability of power grid. Its necessary to study the mechanism of these accidents and propose strategy to prevent more accidents. This paper firstly analyzed the high voltage problem of wind machines with dynamic reactive power compensation devices during grid fault, and put forward simulation to study the impact of SVC （static var compensator） response time on the transient voltage characteristics of wind farms. The results point out that the adjustment lag of SVC transient reactive power is the main factor leading to wind turbine tripping accidents caused by high voltage under fault. Then the reactive power coordination control strategy was proposed for wind farms during grid fault, which through coordinating SVC and wind turbines reactive power output, could peremptorily lock SVC when the fault occurred and put crowbar into operation to protect circuit, and then make SVC back into operation with a certain time delay after the fault clearance, so as to improve the fault crossing ability of wind turbines. The simulation results show that the proposed control strategy can effectively suppress wind turbine high-voltage tripping accidents caused under fault.

To solve the influence of distributed generation （DG） on the fault location and voltage quality of distribution network, the influence of various DGs on the short-circuit current were analyzed. The adaptation range of traditional distribution automation system was obtained, in which the fault location was based on the fault current distribution. An improved fault process strategy was proposed to meet the requirement of much larger amount of DGs connection, based on the coordination of the reclosing procedure and DG escaping after faults. The influences of DGs on the voltage deviation and voltage fluctuation of distribution network were analyzed. The judging condition to meet the requirements of voltage quality without the control of DG was proposed. The DG that could not accord with the judging condition could be monitored by distribution automation system to meet the requirements of voltage quality. The examples show that the proposed method is feasible.

The large scale penetration of distributed generation will reshape electric distribution systems from a passive energy receiver to an active bi-directional energy network with flexible generation, transmission, storage and distribution. The evolution of a passive distribution system to an active distribution cannot be realized without advanced technologies. Therefore this paper provide a thorough review towards existing literatures from 6 aspects, i.e. protection, operation and control, system planning, integration of information communication systems and energy policy. Suggestions of future work are proposed based on the review, which can act as important reference to related scholars and engineers.

Because of oil assay error, the trip reason of a combined cycle unit caused by the acceleration protection action is complex. Although, reliability inspection and field anti-interference performance tests were carried out on feedback device and signal cable shielding grounding, as well as foreign experts were invited for on-site analysis, it still failed to find the fault reason. Then, the oil line was checked and the fault reason were found that a large number of soft skins existed in the valve control oil filter. The fault phenomenon was eliminated by replacing the valve's filter. Finally, the experience and lessons of the fault analysis process are summarized tosuggest preventive measures for trip fault, which will provide references for professionals.

This paper introduces equivalent no-wind scenarios and uses Monte Carlo method to evaluate the influence of wind power intermittent on system reliability, with considering the reliability of generators and transmission lines at the same time. Based on this scenario, the calculation method of wind power reserve requirement under reliability was proposed to quantize the influence of wind power intermittent characteristics on system reliability. Meanwhile, along with the gradual increase of wind power permeability in CSG, it is necessary to evaluate the capacity benefit of wind power in system planning and the contribution of system capacity adequacy, in order to reduce the deviation caused by power supply and demand forecasting and reduce excessive investment, which can also provide data reference and support for the capacity market development in future electric market reform. Based on the reliability evaluation model, this paper evaluates the credible capacity and capacity credit of wind power in CSG by using sequence operation. Finally, taking a practical case in CSG as example, the influence of wind power output characteristics, penetration factor and wind area relativity on capacity credit are studied.

输电线路工程货运架空索道是一种为满足复杂地形条件下运输施工而架设的临时性简易物料运输系统，其自身的临时性、简易性、快捷拆装性决定了货运架空索道在设计、架设等方面的特殊性。经过广泛调研，在总结我国输电线路工程货运架空索道设备研制、工程施工经验的基础上，研究和归纳了7种标准的输电线路工程索道施工方案。

If the power flow of transmission section exceeds the control limits, it will restrict the transmission capacity of power grid, using liaison channel to transfer power load between substations is a common way to solve this problem in actual power system. This paper introduced the relevance characteristics of loads between substations base on field operating experience, systematically discussed the basic principles that the load transfer method was used to improve grid transmission capacity, deduced the sensitivity coefficients calculation formula of load transfer between substations in a simplify form and proposed the control strategy of load transfer method with heuristic searching algorithms. The actual examples show that the proposed load transfer method has advantages of fast calculation, simple and practical operation, etc., and can effectively solve the over-limit problem during power flow control process, which can enhances the transmission capacity of power grid.

煤质多变和偏离设计工况，影响锅炉燃烧，造成锅炉结渣，严重影响锅炉的安全、稳定运行。针对某600 MW新建锅炉，分析其结渣原因，并提出了相应的预防措施和对策，对同类型锅炉基建调试和投产后防止锅炉结焦提供参考。

In the framework of the modern smart grid technologies,the optimal distribution of voltage sag monitoring device is an important research field in the study of power quality monitoring terminal.The installation location and monitoring scope of the monitoring device are described respectively based on the position vector and monitoring area matrix of monitoring device.The mathematical model of the optimal distribution of monitoring device is constructed by considering the specific requirements for distribution of monitoring device,and a 0-1 integer programming is proposed corresponding to the optimal model.Finally,the proposed method is applied to an IEEE-30 network to determine the optimal distribution of voltage sag monitoring device in the whole network,of which the correctness and validity is further analyzed.

Aiming at the increasingly significant problem of various natural disasters affecting power grid, a natural disaster risk assessment method for power grid is given in this paper. Combining the qualitative and quantitative analysis, improved analytic hierarchy process(AHP) is used to construct the hierarchical structure model of risk assessment, the weights of factors are calculated and then the degree of risk is determined. An example application shows the effectiveness of the assessment results. It will boost the power grid's capability to withstand natural disaster.

 Taking the conductor selection of ±800 kV UHV DC transmission line as research object, the 6-bundle conductor was determined according to the electrical performance comparison of conductors, and five types of conductors cross section were chosen from 720 mm2 to 1 520 mm2. Single factor and multi-factor sensitivity analysis were carried out on the selected conductor scheme from aspects of loss time, electric price, rated current and discounted present rate. The results show that the power loss cost increases with the increase of loss time, electric price, rated current and discounted present rate. Meanwhile, the economic of each conductor scheme was analyzed with using investment increment equilibrium analysis method, and the cross section scheme of the conductor used in typical engineering conditions was obtained. And then, 1 250 mm2 conductors of round wires and profile wires were compared. The results show that the comprehensive economic characteristic of profile wires is worse than that of round wires； the initial investment of aluminium conductor aluminium alloy reinforced is less and its comprehensive economic characteristic is better； the initial investment of medium strength aluminium alloy conductor is higher； and its comprehensive economic characteristic is better when loss time and electric price keep high level.

WMZF - 1型锅炉煤质在线分析仪是一种性能先进的煤质实时测量仪器 ,它利用微波双桥路法在线测量锅炉煤粉的灰分、水分、挥发分和低位发热量 ,并将所测得的数据在集控室微机屏上实时显示 ,还可并入DCS系统 ,为优化锅炉燃烧提供准确的煤质指标。当微波前进方向与煤粉的流动方向成 90°时 ,在某频率段 ,煤中混合碳含量与微波的相角呈一定的比例关系 ,可得出微波吸收和相角变化与煤质参数的关系式 ,使煤质在线分析仪能实时显示出该燃煤的低位发热量Qnet,ad、挥发分Vadf、灰分Aad和水分 4项煤质指标。