The increasing scale and complexity of power systems require high performance and high reliability of power system protection.Protective relaying based on directional comparison with power line carrier or microwave ch...The increasing scale and complexity of power systems require high performance and high reliability of power system protection.Protective relaying based on directional comparison with power line carrier or microwave channels is the most suitable protection scheme for long distance EHV transmission lines and is widely used in power systems.The key element of such protection is a directional relay used to discriminate the fault direction.In order to overcome the disadvantages of conventional directional relays,the authors of this paper put forward the directional comparison carrier protection based on the artificial neural network(ANN).The protection is extensively tested using electromagnetic transient program (EMTP) under various electric power system operating and fault conditions.It is proved that the directional comparison carrier protection based on ANN,which can recognize various fault patterns of the protected transmission line(such as fault direction,fault phases etc.)correctly in any kind of operating and fault conditions and the whole process,is satisfactory for EHV transmission line protection.展开更多
In order to study the dynamic response of high-voltage transmission lines under mechanical failure, a finite element model of a domestic 500-kV high-voltage transmission line system is established. The initial equilib...In order to study the dynamic response of high-voltage transmission lines under mechanical failure, a finite element model of a domestic 500-kV high-voltage transmission line system is established. The initial equilibrium condition of the coupling system model is verified by nonlinear static analysis. The transient dynamic analysis method is proposed to analyze the variation law of dynamic response under cable or insulator rupture, and the dynamic response of structural elements next to the broken span is calculated. The results show that upper crossarm cable rupture has no effect on cable tension at adjacent suspension points, but it has a significant influence on tension in the insulator and the tower component of the upper crossarm next to the broken span. The peak tension in the conductor of the upper crossarm at the suspension point exceeds the design value under insulator rupture. Insulator rupture has no effect on the tower component of the upper crossarm, but it has a significant influence on insulator tension of the upper crossarm. Insulator rupture should be taken into account in the design of overhead transmission lines. The research results can provide a theoretical basis for the design of transmission lines.展开更多
To simulate the process of electrode operation, a dynamic model describing the electrode system of three-phase electric arc furnace was developed. This new model can be divided into three submodels in terms of the pra...To simulate the process of electrode operation, a dynamic model describing the electrode system of three-phase electric arc furnace was developed. This new model can be divided into three submodels in terms of the practical situation. They are the power supply system model the electric arc model and the hydraulic actuator system model. According to the basic circuit theory, the power supply system model where the high voltage transmission circuit and mutual inductances were considered, was set up. The electric arc model, which was novel for the electrode control, served as the electrical load and was connected to the power supply system model. The hydraulic actuator system model consists of the proportional valve part that is modeled to capture the dead-zone nonlinear characteristics and the hydraulic cylinder part where the impact of the load force is taken into account. By comparing simulation data and actual data, the results show that the electrode system model is proved to be accurate.展开更多
Recently, smart grid solutions have started to extend the visibility of the electrical grid to the entire network; including high voltage transmission lines, medium voltage distribution networks, and the low voltage n...Recently, smart grid solutions have started to extend the visibility of the electrical grid to the entire network; including high voltage transmission lines, medium voltage distribution networks, and the low voltage networks to households. The typical data monitored includes: voltage, current, phase, and power measurements, together with network events and alarms. This paper analyses the key challenges facing smart grid solutions in providing effective access to large volumes of sensory data that is distributed over a large geographic area. A case study is described that outlines how the use of geospatial technology together with Web 2.0 technologies may be applied to improve user access and control to this data. The results show that a geospatial solution provides an effective mechanism for visualizing telemetry data monitored within the smart grid.展开更多
The DRM (dynamic contact resistance measurement) in high voltage circuit breakers is a manner of evaluating the internal ageing condition of the chamber. DRM is similar to static contact resistance measurement testi...The DRM (dynamic contact resistance measurement) in high voltage circuit breakers is a manner of evaluating the internal ageing condition of the chamber. DRM is similar to static contact resistance measurement testing, but instead of measuring a single value when the breaker contacts are closed (static value), the ohmic resistance is measured at various contact positions, from the beginning of the contact opening until a complete separation of the contacts. The relationship between the contact resistances of the new circuit breaker and the ageing circuit breaker in operation provides subsidy for the evaluation of both the main and arcing contact conditions. This research aims to analyze the correlation between the various levels of degradation of the contacts and the configuration of the DRM curve. This work considers curve samples from new acceleration tests. breaker chamber contacts and different levels of degradation by展开更多
This paper presents an ANN (artificial neural networks)-based technique for improving the performance of distance relays against open-circuit faults in transmission networks. The technique utilizes the small capacit...This paper presents an ANN (artificial neural networks)-based technique for improving the performance of distance relays against open-circuit faults in transmission networks. The technique utilizes the small capacitive current measured in the open-phase plus the currents in the two healthy phases in calculating the open-circuit fault distance. The results obtained show that a distance relay with the proposed scheme will not only be able to detect the open-conductor condition in HVTL (high voltage transmission line) but also to locate the place of this fault regardless the value of the pre-fault current loading. There is no need for especial communication schemes since the existing media could work properly for the needs of the proposed technique.展开更多
Helicopter inspection of ultra high voltage (UHV) transmission lines has unmatched advantages compared to manual work due to the inspection angle and high-tech equipment on board, especially in detailed inspections ...Helicopter inspection of ultra high voltage (UHV) transmission lines has unmatched advantages compared to manual work due to the inspection angle and high-tech equipment on board, especially in detailed inspections of tower heads and defect-detections in virtue of infrared/ultraviolet techniques. This paper deals with some key technical problems in the inspections of i 000 kV UHVAC lines with a helicopter, such as the safe distance of live-line working, electromagnetic field intensity and flight control. Based on the study results, a set of UHV line inspection methods was worked out and applied to the inspection of live UHV lines.展开更多
In this paper,a 3D upstream finite element method is developed to analyze the ionized electric field around the UHVDC transmission lines including the building near it.The ionized electric field around the building is...In this paper,a 3D upstream finite element method is developed to analyze the ionized electric field around the UHVDC transmission lines including the building near it.The ionized electric field around the building is reduced due to the shielding effect of the building and the shielding distance is about three times its height.The ionized electric field including the human body model on the building and away from the building is also taken into account.The ionized electric field distortion ratio of the human body model is discussed in this paper.The distortion ratios for the positions on the building are less than those on the ground.展开更多
This paper analyzes the fundamental frequency impedance presents a novel transmission line pilot protection scheme characteristic of a thyristor controlled series capacitor (TCSC) and based on fault component integr...This paper analyzes the fundamental frequency impedance presents a novel transmission line pilot protection scheme characteristic of a thyristor controlled series capacitor (TCSC) and based on fault component integrated impedance (FCII) calculated for a transmission line with TCSC and controllable shunt reactor (CSR). The FCII is defined as the ratio of the sum of the fault component voltage phasors of a transmission line with TCSC and CSR to the sum of the fault component current phasors where all the phasors are determined at both line's terminals. It can be used to distinguish internal faults occurring on the line from external ones. If the fault is an external one the FCII reflects the line's capacitive impedance and has large value. If the fault is an internal one on the line the FCII reflects the impedance of the equivalent system and the line and is relatively small. The new pilot protection scheme can be easily set and has the fault phase selection ability and also it is not affected by the capacitive current and the fault transition resistance. It is not sensitive to compensation level and dynamics of TCSC and CSR. The effectiveness of the new scheme is validated against data obtained in ATP simulations and Northwest China 750 kV Project.展开更多
A magneto-optical sensor, using a dual quadrature polarimetfic processing scheme, was evaluated for current metering and protection applications in high voltage lines. Sensor calibration and resolution were obtained i...A magneto-optical sensor, using a dual quadrature polarimetfic processing scheme, was evaluated for current metering and protection applications in high voltage lines. Sensor calibration and resolution were obtained in different operational conditions using illumination in the 1550-nm band. Results obtained indicated the feasibility of interrogating such sensor via the optical ground wire (OPGW) link installed in standard high power grids. The polarimetric bulk optical current sensor also was theoretically studied, and the effects of different sources of error considering practical deployment were evaluated. In particular, the interference from external magnetic fields in a tree-phase system was analyzed.展开更多
文摘The increasing scale and complexity of power systems require high performance and high reliability of power system protection.Protective relaying based on directional comparison with power line carrier or microwave channels is the most suitable protection scheme for long distance EHV transmission lines and is widely used in power systems.The key element of such protection is a directional relay used to discriminate the fault direction.In order to overcome the disadvantages of conventional directional relays,the authors of this paper put forward the directional comparison carrier protection based on the artificial neural network(ANN).The protection is extensively tested using electromagnetic transient program (EMTP) under various electric power system operating and fault conditions.It is proved that the directional comparison carrier protection based on ANN,which can recognize various fault patterns of the protected transmission line(such as fault direction,fault phases etc.)correctly in any kind of operating and fault conditions and the whole process,is satisfactory for EHV transmission line protection.
基金The National Natural Science Foundation of China (No.50578038)the Science and Technology Project of the State Grid Corporation of China(No.SGKJ[2007]116)
文摘In order to study the dynamic response of high-voltage transmission lines under mechanical failure, a finite element model of a domestic 500-kV high-voltage transmission line system is established. The initial equilibrium condition of the coupling system model is verified by nonlinear static analysis. The transient dynamic analysis method is proposed to analyze the variation law of dynamic response under cable or insulator rupture, and the dynamic response of structural elements next to the broken span is calculated. The results show that upper crossarm cable rupture has no effect on cable tension at adjacent suspension points, but it has a significant influence on tension in the insulator and the tower component of the upper crossarm next to the broken span. The peak tension in the conductor of the upper crossarm at the suspension point exceeds the design value under insulator rupture. Insulator rupture has no effect on the tower component of the upper crossarm, but it has a significant influence on insulator tension of the upper crossarm. Insulator rupture should be taken into account in the design of overhead transmission lines. The research results can provide a theoretical basis for the design of transmission lines.
基金Projects(2007AA04Z194, 2007AA041401) supported by the National High-Tech Research and Development Program of China
文摘To simulate the process of electrode operation, a dynamic model describing the electrode system of three-phase electric arc furnace was developed. This new model can be divided into three submodels in terms of the practical situation. They are the power supply system model the electric arc model and the hydraulic actuator system model. According to the basic circuit theory, the power supply system model where the high voltage transmission circuit and mutual inductances were considered, was set up. The electric arc model, which was novel for the electrode control, served as the electrical load and was connected to the power supply system model. The hydraulic actuator system model consists of the proportional valve part that is modeled to capture the dead-zone nonlinear characteristics and the hydraulic cylinder part where the impact of the load force is taken into account. By comparing simulation data and actual data, the results show that the electrode system model is proved to be accurate.
文摘Recently, smart grid solutions have started to extend the visibility of the electrical grid to the entire network; including high voltage transmission lines, medium voltage distribution networks, and the low voltage networks to households. The typical data monitored includes: voltage, current, phase, and power measurements, together with network events and alarms. This paper analyses the key challenges facing smart grid solutions in providing effective access to large volumes of sensory data that is distributed over a large geographic area. A case study is described that outlines how the use of geospatial technology together with Web 2.0 technologies may be applied to improve user access and control to this data. The results show that a geospatial solution provides an effective mechanism for visualizing telemetry data monitored within the smart grid.
文摘The DRM (dynamic contact resistance measurement) in high voltage circuit breakers is a manner of evaluating the internal ageing condition of the chamber. DRM is similar to static contact resistance measurement testing, but instead of measuring a single value when the breaker contacts are closed (static value), the ohmic resistance is measured at various contact positions, from the beginning of the contact opening until a complete separation of the contacts. The relationship between the contact resistances of the new circuit breaker and the ageing circuit breaker in operation provides subsidy for the evaluation of both the main and arcing contact conditions. This research aims to analyze the correlation between the various levels of degradation of the contacts and the configuration of the DRM curve. This work considers curve samples from new acceleration tests. breaker chamber contacts and different levels of degradation by
文摘This paper presents an ANN (artificial neural networks)-based technique for improving the performance of distance relays against open-circuit faults in transmission networks. The technique utilizes the small capacitive current measured in the open-phase plus the currents in the two healthy phases in calculating the open-circuit fault distance. The results obtained show that a distance relay with the proposed scheme will not only be able to detect the open-conductor condition in HVTL (high voltage transmission line) but also to locate the place of this fault regardless the value of the pre-fault current loading. There is no need for especial communication schemes since the existing media could work properly for the needs of the proposed technique.
文摘Helicopter inspection of ultra high voltage (UHV) transmission lines has unmatched advantages compared to manual work due to the inspection angle and high-tech equipment on board, especially in detailed inspections of tower heads and defect-detections in virtue of infrared/ultraviolet techniques. This paper deals with some key technical problems in the inspections of i 000 kV UHVAC lines with a helicopter, such as the safe distance of live-line working, electromagnetic field intensity and flight control. Based on the study results, a set of UHV line inspection methods was worked out and applied to the inspection of live UHV lines.
基金supported by the Key Project of the National Natural Science Foundation of China(Grant No.51037001)the National Basic Research Program of China("973"Program)(Grant No.2011CB209401)
文摘In this paper,a 3D upstream finite element method is developed to analyze the ionized electric field around the UHVDC transmission lines including the building near it.The ionized electric field around the building is reduced due to the shielding effect of the building and the shielding distance is about three times its height.The ionized electric field including the human body model on the building and away from the building is also taken into account.The ionized electric field distortion ratio of the human body model is discussed in this paper.The distortion ratios for the positions on the building are less than those on the ground.
基金supported by the National Natural Science Foundation of China (Grant Nos.50877061 and 51037005)
文摘This paper analyzes the fundamental frequency impedance presents a novel transmission line pilot protection scheme characteristic of a thyristor controlled series capacitor (TCSC) and based on fault component integrated impedance (FCII) calculated for a transmission line with TCSC and controllable shunt reactor (CSR). The FCII is defined as the ratio of the sum of the fault component voltage phasors of a transmission line with TCSC and CSR to the sum of the fault component current phasors where all the phasors are determined at both line's terminals. It can be used to distinguish internal faults occurring on the line from external ones. If the fault is an external one the FCII reflects the line's capacitive impedance and has large value. If the fault is an internal one on the line the FCII reflects the impedance of the equivalent system and the line and is relatively small. The new pilot protection scheme can be easily set and has the fault phase selection ability and also it is not affected by the capacitive current and the fault transition resistance. It is not sensitive to compensation level and dynamics of TCSC and CSR. The effectiveness of the new scheme is validated against data obtained in ATP simulations and Northwest China 750 kV Project.
文摘A magneto-optical sensor, using a dual quadrature polarimetfic processing scheme, was evaluated for current metering and protection applications in high voltage lines. Sensor calibration and resolution were obtained in different operational conditions using illumination in the 1550-nm band. Results obtained indicated the feasibility of interrogating such sensor via the optical ground wire (OPGW) link installed in standard high power grids. The polarimetric bulk optical current sensor also was theoretically studied, and the effects of different sources of error considering practical deployment were evaluated. In particular, the interference from external magnetic fields in a tree-phase system was analyzed.