The electrochemical migration（ECM） behavior and mechanism of immersion silver processing circuit board（PCB-ImAg）and hot air solder leveling circuit board（PCB-HASL） under the 0.1 mol/L Na2SO4 absorbed thin liquid...The electrochemical migration（ECM） behavior and mechanism of immersion silver processing circuit board（PCB-ImAg）and hot air solder leveling circuit board（PCB-HASL） under the 0.1 mol/L Na2SO4 absorbed thin liquid films with different thicknesses were investigated using stereo microscopy and scanning electron microscopy（SEM）.Meanwhile,the corrosion tendency and kinetics rule of metal plates after bias application were analyzed with the aid of electrochemical impedance spectroscopy（EIS）and scanning Kelvin probe（SKP）.Results showed that under different humidity conditions,the amount of migrating corrosion products of silver for PCB-ImAg was limited,while on PCB-HASL both copper dendrites and precipitates such as sulfate and metal oxides of copper/tin were found under a high humidity condition（exceeding 85%）.SKP results indicated that the cathode plate of two kinds of PCB materials had a higher corrosion tendency after bias application.An ECM model involving multi-metal reactions was proposed and the differences of ECM behaviors for two kinds of PCB materials were compared.展开更多
Short circuit and ground failures that are quite common in power transmission lines are investigated. These failures are designed considering a system that is supplied by this wind system, and analyses are interpreted...Short circuit and ground failures that are quite common in power transmission lines are investigated. These failures are designed considering a system that is supplied by this wind system, and analyses are interpreted. In the study, a system is set up and it is fed by the wind turbine. Furthermore, the mathematical model of wind turbine and generator is prepared and the results obtained from the simulation are evaluated. The short circuit and ground fault analyzes were performed separately for each of the three phases. ATP （alternative transient program）-EMTP （electromagnetic transients program） program is used in the analysis and the results obtained were found to be quite compatible.展开更多
Ventilation characteristic parameters are the base of ventilation network solution; however, they are apt to be affected by operating errors, reading errors, airflow stability, and other factors, and it is difficult t...Ventilation characteristic parameters are the base of ventilation network solution; however, they are apt to be affected by operating errors, reading errors, airflow stability, and other factors, and it is difficult to obtain accurate results. In order to check the ventilation characteristic parameters of mines more accurately, the integrated method of circuit and path is adopted to overcome the drawbacks caused by the traditional path method or circuit method in the digital debugging process of ventilation system, which can improve the large local error or the inconsistency between the airflow direction and the actual situation caused by inaccuracy of the ventilation characteristic parameters or checking in the ventilation network solution. The results show that this method can effectively reduce the local error and prevent the pseudo-airflow reversal phenomenon; in addition, the solution results are consistent with the actual situation of mines, and the effect is obvious.展开更多
Based on an analysis of the misunderstandings and problems concerning wind power development, this paper summarizes the experiences of the coordinated development of wind power and power grids in foreign countries, an...Based on an analysis of the misunderstandings and problems concerning wind power development, this paper summarizes the experiences of the coordinated development of wind power and power grids in foreign countries, and proposes principles and strategies for the coordinated development of wind power and power grids, and related measures and suggestions for large scale development of wind power in China.展开更多
This paper analyzes a DFIG （doubly fed induction generator） WT （wind turbine） fault current after a symmetrical network voltage dip. The goal is to identify the factors determining how fast the first zero crossing...This paper analyzes a DFIG （doubly fed induction generator） WT （wind turbine） fault current after a symmetrical network voltage dip. The goal is to identify the factors determining how fast the first zero crossings of the fault current occur. This is an important subject because the ftmdamental property of the CB （circuit breaker） is that it breaks the current when the current is very near zero. The study was conducted using a hardware-in-the-loop test environment constructed using two real time simulators （dSPACE and RTDS） and a commercial protection relay. It is found that the reactive current injection during a voltage dip demanded by the grid codes enhances the operation of the WT protection because the zero crossings of the currents through CB are attained earlier. In addition, the size of the crowbar resistance has a significant influence on the zero crossings.展开更多
基金Project(51271032)supported by the National Natural Science Foundation of China
文摘The electrochemical migration（ECM） behavior and mechanism of immersion silver processing circuit board（PCB-ImAg）and hot air solder leveling circuit board（PCB-HASL） under the 0.1 mol/L Na2SO4 absorbed thin liquid films with different thicknesses were investigated using stereo microscopy and scanning electron microscopy（SEM）.Meanwhile,the corrosion tendency and kinetics rule of metal plates after bias application were analyzed with the aid of electrochemical impedance spectroscopy（EIS）and scanning Kelvin probe（SKP）.Results showed that under different humidity conditions,the amount of migrating corrosion products of silver for PCB-ImAg was limited,while on PCB-HASL both copper dendrites and precipitates such as sulfate and metal oxides of copper/tin were found under a high humidity condition（exceeding 85%）.SKP results indicated that the cathode plate of two kinds of PCB materials had a higher corrosion tendency after bias application.An ECM model involving multi-metal reactions was proposed and the differences of ECM behaviors for two kinds of PCB materials were compared.
文摘Short circuit and ground failures that are quite common in power transmission lines are investigated. These failures are designed considering a system that is supplied by this wind system, and analyses are interpreted. In the study, a system is set up and it is fed by the wind turbine. Furthermore, the mathematical model of wind turbine and generator is prepared and the results obtained from the simulation are evaluated. The short circuit and ground fault analyzes were performed separately for each of the three phases. ATP （alternative transient program）-EMTP （electromagnetic transients program） program is used in the analysis and the results obtained were found to be quite compatible.
基金Supported by the National Natural Science Foundation of China （61772159）
文摘Ventilation characteristic parameters are the base of ventilation network solution; however, they are apt to be affected by operating errors, reading errors, airflow stability, and other factors, and it is difficult to obtain accurate results. In order to check the ventilation characteristic parameters of mines more accurately, the integrated method of circuit and path is adopted to overcome the drawbacks caused by the traditional path method or circuit method in the digital debugging process of ventilation system, which can improve the large local error or the inconsistency between the airflow direction and the actual situation caused by inaccuracy of the ventilation characteristic parameters or checking in the ventilation network solution. The results show that this method can effectively reduce the local error and prevent the pseudo-airflow reversal phenomenon; in addition, the solution results are consistent with the actual situation of mines, and the effect is obvious.
文摘Based on an analysis of the misunderstandings and problems concerning wind power development, this paper summarizes the experiences of the coordinated development of wind power and power grids in foreign countries, and proposes principles and strategies for the coordinated development of wind power and power grids, and related measures and suggestions for large scale development of wind power in China.
文摘This paper analyzes a DFIG （doubly fed induction generator） WT （wind turbine） fault current after a symmetrical network voltage dip. The goal is to identify the factors determining how fast the first zero crossings of the fault current occur. This is an important subject because the ftmdamental property of the CB （circuit breaker） is that it breaks the current when the current is very near zero. The study was conducted using a hardware-in-the-loop test environment constructed using two real time simulators （dSPACE and RTDS） and a commercial protection relay. It is found that the reactive current injection during a voltage dip demanded by the grid codes enhances the operation of the WT protection because the zero crossings of the currents through CB are attained earlier. In addition, the size of the crowbar resistance has a significant influence on the zero crossings.
