The passive start-up mode of a two-terminal MMC-HVDC with one terminal operating in islanded mode is introduced in this paper. The passive start-up mode includes the uncontrolled charging start-up stage and the controlled charging deblocking start-up stage. The equivalent circuit of the two-terminal MMC-HVDC in uncontrolled charging stage is established. The start-up process in uncontrolled charging stage is analyzed in detail, then the structure block diagram of MMC controller in controlled charging stage is given. Finally, based on RT-LAB real-time simulation technology, the mathematical simulation model of the two-terminal MMC-HVDC based on hardware in the loop is built, and appropriate MMC controller PI parameters are selected to simulate and analyze the passive start-up process of two-terminal MMC-HVDC. The effectiveness of the start-up mode is verified.

For the VSC-HVDC damper converter valve system, the voltage-balance characteristics of the charging are studied. The installation project of Zhoushan VSC-HVDC bridge arm damping recovery devices is taken as the background. Based on the design principle of the bridge arm damping converter valve, a sub-module mathematical model is constructed which can reflect the sub-module power supply and board power consumption. Through the theoretical analysis of the voltage-unbalance mechanism and the influencing factors of the sub-modules in the charging process of the damped converter valve, the corresponding solutions are put forward. The correctness of the theoretical analysis and the effectiveness of the solution are verified by simulation and test results, which provide technical support for the smooth implementation of the installation project of Zhoushan VSC-HVDC bridge arm damping recovery devices.

UHVDC converter valve generates up to mega-watt heat during operation, but the outlet water temperature of the converter valve is 50~60 ℃, which is a low-grade heat source, and is difficult to perform residual heat recovery and utilization effectively, resulting in a great waste of energy. To solve this problem, a new converter valve cooling system, comprehensive residual heat utilization system of converter valve, is proposed. The system uses heat pump technology to absorb the residual heat of the converter valve and improve its heat grade, so that the absorption system can be driven to carry out refrigeration or heating, and the cooling of the converter valve and the recovery and utilization of the waste heat can be realized. Experiments and simulation results show that the system proposed here can achieve the combined supply of cold and heat, satisfy the cooling and heating needs of valve hall. In addition, the system can improve the reliability of valve cooling system and has economic advantages.

Most of the power line faults are caused by insulation problems. In view of problems that the main treatment of insulation faults by electric power department are passive maintenance after faults, a power line insulation faults early warning system is developed based on traveling wave technology to eliminate the insulation fault in early stage. Firstly, the degradation process and flashover mechanism are analyzed. Secondly, a power line insulation faults early warning system is developed based on the principle of insulation fault early warning. Finally, the field test of the system is conducted. It shows that the insulator partial discharge can be early warned, the locating accuracy is high with the average error of 16.6 meters, which meets the requirements of field operation.

Experiments are carried out in a 5 m rod-plate gap under positive lightning impulses, and the discharge voltage, discharge current and video image are recorded synchronously. According to characteristics of the discharge current at different stages, three main discharge phases are identified, which are the first streamer discharge, the second one and the leader discharge. The influences of impulse amplitude and electrode shape on the characteristics of each discharge stage are studied. The results show that the space charge generated by the first streamer discharge is positively correlated with the voltage amplitude and the radius of curvature of the electrode, and its suppression makes the average value of the initial delay of the second streamer is approximately constant. The average velocity of the second streamer is 700~1 060 cm/μs, which increases with the voltage amplitude, and decreases with the radius of curvature. The average speed of the leader is 29~111 cm/μs, which increases linearly with the voltage amplitude, and decreases with the curvature radius of the electrode.

Reasonable price signal in electricity market can stimulate resource investment, ensure generation adequacy and it plays an important role in long-term efficient and secure operation of electricity market. The scarcity pricing mechanism based on reserve demand curves is introduced in energy and ancillary services market of the United States. The latest scarcity pricing mechanisms in NewYork, California, Pennsylvania-New Jersey-Maryland and Texas are analyzed and compared, including reserve demand curves, clearing and settlements mechanism. Finally, according to the electricity market reform in China, the corresponding policy suggestions for investment cost recovery mechanism in China are proposed.

The construction of distribution network will be the focus of China’s power grid investment in the future. However, it is difficult to match investment and benefit due to the network characteristics and the characteristics of multi-year continuous investment. Under the new trend of distribution network development, this paper constructs the investment performance evaluation index system from 6 aspects: structure of distribution network, power supply capacity, power supply quality, equipment level, automation level and green energy. Taking the characteristics of distribution network investment into consideration, this paper introduces the dynamic comprehensive evaluation method with speed characteristics to establish a comprehensive evaluation model of distribution network investment effectiveness. The model is verified through the analysis on the 6 city power supply bureaus from 2011 to 2015 about the distribution network investment. The results show that the proposed model considers the state and the trend of the change rate, so it can evaluate the benefit and dynamic development trend of distribution network with multiple different evaluated objects at specific stages.

Considering the trading rules, products and settlement mechanism of Guangdong power spot market, the credit risk management mechanisim is proposed in this paper, which includes credit warning mechanism, credit limit assessment and multi-market netting risk calculation. The “Occupying Coeffieient” is introduced as a signal in the credit warning mechanism. The credit limit assessment involves two components—the unsecured credit limit determined by credit rating based on the solvency, and the secured credit limit obtained by posting bank guarantee. Multi-market netting risk calculation includes “Meduim-And-Long-Term And Spot” bi-market netting risk calculation and “Meduim-And-Long-Term, Spot And Retailing” tri-market netting risk calculation. An example is introduced to demonstrate that, cooperating with the settlement mechanism, the netting risk calculation is more accurate in credit risk assessment, and reduces the collateral required from the retailers participating in the power market.

The accumulation and dissipation of surface charges play an important role in the insulation failure of the disc-type insulator in the gas insulated transmission line (GIL) and gas insulated switchgear(GIS). Introducing nanoparticles into epoxy resin to modulate dynamic behaviors of the surface charges and improve the flashover voltage is of great significance to ensure the safe operation of GIL and GIS. In this paper, epoxy resin/SiO₂ nanocomposites with mass fraction of 0%, 2%, 4%, 6% and 8% are prepared. With positive and negative DC voltages, the surface potential decaying process, trap distribution behaviors and flashover characteristics are obtained, a physical model of insulation failure is established based on modulating the trap distribution. The results show that the surface potential decaying rate is reduced with both positive and negative corona charging as the nano-SiO₂ is filled into epoxy resin, the minimum value is in the samples with the mass fraction of 4%. New hole and electron traps are introduced into epoxy resin by SiO₂ nanoparticles, which are with larger trap energy level and trap density, the maximum value is in the samples with the mass fraction of 4%. The flashover voltage of the specimen is enhanced by SiO₂ nanoparticles. Compared with pure epoxy resin, the flashover voltage of epoxy resin/SiO₂ nanocomposites with the mass fraction of 4% are respectively increased by 58.04% and 64.15% with positive and negative DC voltage.

Overhead conductor is the most important equipment material of transmission line, it works in the natural environment for a long time. Its performance and lifespan are subject to by the environment, and the influence of environmental corrosion on conductor is the most obvious. To understand the characteristics of the corrosion-proof steel core of high-anticorrosive conductors for coastal and high pollution areas, the accelerated corrosion comparative tests of four steel cores between aluminium clad steel wire, Zn-5% aluminium alloy coated steel wire, Zn-10% aluminium alloy coated steel wire and galvanized steel wire are carried out. The results show that, after 1 000 hours of neutral salt spray corrosion, the galvanized layer of galvanized steel wire almost disappeared, and obvious corrosion acceleration occurs, while the aluminum clad steel wire is only corroded on the outer layer of aluminium, Zn-5% aluminium alloy coated steel wire and Zn-10% aluminium alloy coated steel wire are only corroded on the surface layer, and the transition layer is not corroded. The other three wires have strong corrosion resistance, and the overall corrosion resistances are better than the galvanized layer of galvanized steel wire.

The dielectric properties of cross linked polyethylene (XLPE) and liquid silicone rubber (LSR) are affected by damp. In order to explore the effect of moisture on the dielectric properties of XLPE and LSR and its mechanism, in this paper, the XLPE and LSR samples are taken as the research object, and the dielectric spectrum, breakdown field strength, moisture content and infrared spectrum of the sample after different water immersion time at 65 ℃ are measured. It is found that after immersion in water, moisture has an effect on the dielectric properties of XLPE and LSR, and moisture has a greater influence on the dielectric properties of LSR. The loss factor at 0.1 Hz is more obvious in reflecting the moisture of XLPE and LSR. The relationship model between 0.1 Hz and 50 Hz tanδ is obtained by Pearson correlation analysis. After being immersed in water, XLPE samples are mainly affected by combined water, and LSR samples are mainly affected by free water.

The energy hub model is applied to couple the power network, natural gas network and traffic network simultaneously and the coupling system is decomposed into multiple terminal integrated energy units for energy balance analysis. Based on the characteristics of multi-energy complement, the distribution network layering planning model is proposed, which is taking into account the dual utility function of charging stations and the cost of system construction and operation. The outer layer of the model is used to determine variables including the upgrading and new construction of distribution lines, the supply of distributed generation and location of quick charging stations. The inner layer improves the operation efficiency of distribution network by optimizing the energy conversion behavior according to the decision variables of the outer layer. Finally, the model is solved by the method combined with the improved genetic algorithm, incremental piecewise linearization and second order cone programming, and a regional comprehensive energy system is taken as an example for simulation analysis to verify the effectiveness of the proposed method.