Abstract:In order to explore the interaction characteristics of double circuit on same tower, based on the closed-loop simulation system consisting of the actual control and protection system and real time digital system (RTDS), many kinds of operation conditions and faults of the Genan and Jinghu ±500 kV double circuit HVDC power system are analyzed. Compared with the conventional single transmission line, the influences of the double circuit HVDC system to their own transient characteristics are studied, and some possible faults are also analyzed. Simulation results and conclusions can provide effective and reliable basis for the functions design and parameter setting of double circuit HVDC power system.

Abstract:Based on the voltage hierarchical control and reactive source regional distribution characteristics and the scheduling needs of modern power grid energy management system (EMS), the principles of coordinated AVC for provincial power network are clarified and a joint optimization scheme for coordinated AVC for provincial power network is proposed. Besides, the control strategies of AVC in the provincial and the municipal control side are discussed and the realization of communication scheme between them is also given. The practical applications of actual power system show that the proposed technical scheme and control strategy are feasible and effective, which can solve the current coordination problems of AVC for provincial power network better.

Abstract:Due to the complexity of practical factors having effects on the formation of NOₓin coal-fired boilers as well as coal characteristics, operation conditions and so on, it's much difficult to analyze associated issues just using traditional experiments. In order to estimate different parameters influencing the emission of NOₓand specify the key factor, numerical model using software FLUENT has been developed in the paper just for the simulation of combustions under several operation parameters. The mechanism can then be analyzed qualitatively, and the experiments can also be simplified.

Abstract:The compressor is important auxiliary equipment in the phase modulation starting process of pumped storage power unit and also essential for the governor and ball valve system. So its safe and stable operation directly relates to the safety and stability of pumped storage power unit. In the paper, the failure analysis and solutions of incoming breaker in compressor are given. The △ and Y control relay auxiliary contacts are increased in the △ and Y control circuit of compressor breaker to ensure the operation reliability.

Abstract:The carrier channel is an important component of high frequency protection, and whether it is normal related to the protection action correct or not. In the paper, a case of fault in carrier channel was studied. The composition of the carrier channel and the fault phenomenon were analyzed to judge the fault spot in the carrier channel correctly. The paper can provide important basis for the rapid fault treatment and references for the high frequency channel fault treatment.

Abstract:Sulphur hexafluoride gas insulated switchgear (GIS) equipment is used widely in power system. However, due to the special set of current transformer (TA) and the imperceptibility of fault in GIS, it is more difficult in the GIS fault analysis. Thus, improving the failure analysis of GIS is very important for fast fault spot judging and the security of system operation. In the paper, through studying relay action caused a case of fault in 220 kV GIS equipment, the whole protection process was analyzed combined with the fault recording. And the secondary analysis method for GIS internal fault was put forward, which could be used for reference.

Abstract:Combined with the recent reconstruction project of 220 kV line production, by using the adjacent line of OPGW fiber spare core to form temporary circuitous channel, the paper proposed a rational reconfiguration for two 220 kV line protection without fiber channel. The optical fiber current differential protection and the carrier channel high frequency protection were applied as the configuration scheme. After technical improvement, two sets of optical fiber current differential protection were used, which may realize the best configuration of 220 kV double line protection.

Abstract:In order to reduce the overvoltage level and the trip rate in power system, the grounding method with arc suppression coil and low resistance in parallel is applied gradually in distribution network. In the paper, the distribution network model with neutral flexible grounding was established in PSCAD, including the arc grounding fault model and repeated calculated fault model. Voltage simulations were carried on from the aspects such as fault type, the time when small resistance into and the fault happen time. The results show that the fault type can be judged by the fault voltage waveform. In addition, the overvoltage is smallest when small resistance is into at the moment that the neutral voltage is 0 around.

Abstract:For the weak interconnected system, it can be solved by installing STATCOM additional damping control to inhibit low frequency oscillation. In the paper, the control effects of traditional STATCOM additional damping control at different operational mode with several common signals were compared and analyzed. In order to avoid the problems may occur due to using signal control signal, two appropriate signals were selected as the input signal to design the additional damping controller of STATCOM with parallel double channel. The results show that, compared with the traditional STATCOM additional damping controller, the additional damping controller of STATCOM with parallel double channel has better effect in restraining low frequency oscillation and has more strong robustness when system operation styles changes.

Abstract:At the background of Beijing-Shanghai express railway, for the autotransformer (AT) traction power supply, the calculation formula of current distribution in traction power grid in the signal line operation or double line up and down parallel operation were deduced and given in detail. And the current distribution with or without the line protection and mutual inductance were also compared. The simulation models of traction transformer and traction grid were established in MATLAB, and the simulation results proved the effectiveness of the calculation formula of current distribution. The results can provide references for analog of locomotive actual operation situation and analysis of influences of line faults in traction grid.

Abstract:The variable-speed constant-frequency (VSCF) wind generator is the main trend type of current wind generators. And as one part of the core components of VSCF wind generator control system, the pitch system can effectively ensure the safety, stability and efficient operation of the wind generator. In the paper, the principles and the two kinds of actuators of pitch control were briefly introduced, and the basic structures of electric drive pitch system were analyzed significantly. Besides, the applications of dc servo motor and ac servo motor in electric pitch system were also analyzed. Through comparing the respective advantages and disadvantages of dc servo and ac servo systems, it is concluded that the ac servo system has greater advantages than the dc servo system combined with the increasing single wind generator capacity.

Abstract:With the regional economic development, there are more large enterprises in Taizhou and the scale of the power grid is expanding. In the paper, the load characteristic of Taizhou power grid was analyzed and the discussion on how to do well in load forecasting was carried on. In addition, the main influence factors of load forecasting were analyzed in detail and the solutions for further improving the accuracy of load forecasting were presented.

Abstract:The web service (WebS) system is one of the important subsystems of EMS, and it has the functions such as information dissemination, information inquiry and service management. In the paper, the design methods of EMS web service (WebS) system were discussed. Based on the structures of Webs, the C/S mode and the B/S mode were analyzed and compared, the appropriate technology was searched for the design of EMS WebS in the asynchronous invocation B/S mode. Eventually, the server architecture of SVG&Ajax&HTTP was found, and the information refresh and response were realized through the web browser using HTML and JavaScript.

Abstract:Combined with the large-scale urban photovoltaic power applications and the convergence characteristics of the roof PV modules, the Z-source inverter is chosen to take the place of common inverter in grid-connected PV power system. In the paper, the working principles of Z-source inverter were analyzed in detail, and the mathematical derivation of main working states were also given. Compared with the common voltage source and current source topology, the Z-source inverter can realize any buck and boost. The design of the roof photovoltaic generation pilot project and the work effects using the Z-source inverter were introduced. Practices prove that roof grid-connected photovoltaic power generating system has better effects.

Abstract:It is difficult to judge the fault point of dead-zone fault, and it is also a difficult point for power dispatcher in fault treatment. If faults in the dead zone are not removed quickly, it will seriously threaten the security and stability of power system operation. In the paper, some common dead-zone fault phenomena were analyzed briefly. And the dead-zone fault treatments and preventive measures were proposed by examples.

Abstract:The reasons for the fluctuation of the statistical line loss and their impact characteristics were analyzed. And it is pointed out that the reasons could be divided into the objective factors and subjective factors. The fluctuations of the statistical line loss cannot be eliminated by the objective factors. However, the fluctuation range can be reduced by strengthening the line loss management to reduce the impacts of subjective factors.

Abstract:In order to build strong smart grid, it is necessary to monitor the operation state of the main power system components, and through the fault recorder the information can be recorded completely. In the paper, the current access methods of fault recorder to digital substation were discussed, and basic principle of each method was described. In addition, different solutions for fault recorder in digital substation were also discussed.

Abstract:Aiming to decrease the high exhaust flue gas temperature, associated factors are analyzed systematically, and experiments designed for the optimization have also been carried out. The results suggest that with the adoption of reasonable excess air coefficient, higher radio of secondary air, lower swirl intensity, lower primary air flow into coal mills and higher outlet air temperature, the exhaust gas temperature can be decreased effectively. The conclusion also indicates that the air distribution of the same layer combustors has little effect on the exhaust flue gas temperature, while the poor heat exchange efficiency of air preheaters may be the root cause.

Abstract:The characteristics as well as the practical operation conditions of field bus technique adopted by Xinhai Power Generation Company have been introduced in the paper. Due to the advantages of PROFIBUS field bus in reliability and installation methods, it's believed that this technique will be applied much widely in future.

Abstract:According to the actual characteristics of lignite, suggestions that flue gas heat recovery technology should be adopted especially for heat supply units in North China are proposed in the paper. In order to reduce the consumption of fuel as well as water, the exhaust gas is applied to heat the network steam and the condensation water, and significant economic benefits have already been achieved in the past two years.

Abstract:The practical conditions of ejector applied in the high parameter heat supply system of one thermal power plant, such as the problems occurred during the installation and adjustment process are introduced in the paper, and important announcements as well as factors having effects on economic operation are also presented in detail.

Abstract:Based on the detailed analysis on different conditions, the leak of main steam into HP exhaust steam mouth directly induced by the failure of sealing rings is believed to be the main reason for the high exhaust steam temperature, and the conclusion has already been validated by the adjustment measures applied during the maintance period.

Abstract:Based on the detailed introduction of flame characteristics as well as the basic principle of flame monitoring system for coal-fired thermal power plants, the associated problems are presented in the paper, and solutions aiming at higher stability of the monitoring system are then proposed to provide helpful guarantee for the safety of boilers.