This paper considers the influence of changes of the transmission lines of permissible load current depending on conductor and ambient temperatures, climate conditions. The theoretical background of the allowable cond...This paper considers the influence of changes of the transmission lines of permissible load current depending on conductor and ambient temperatures, climate conditions. The theoretical background of the allowable conductor temperature as well as load current determination principles are proposed. On one hand, the principles are based on mechanical limitations; on the other hand, they are based on thermal limitations. The simulation tasks were based on specific data information of three existing overhead lines of Latvian power system as well as the planned 330 kV overhead line. Moreover, the special thermovision device was used for precious determination of conductor temperature of the existing transmission lines. The simulation results of the obtained data are reviewed in the paper.展开更多
In the background of the design and construction of Smart Grid Operation Supporting System for District Power Networks, this paper established the weighted fault probability model of the overhead line which is based o...In the background of the design and construction of Smart Grid Operation Supporting System for District Power Networks, this paper established the weighted fault probability model of the overhead line which is based on equipment operating status, utility theory and fuzzy theory. In this model, the proper membership function is adopted to describe the influence of lightning, wind speed, line ice and temperature, and the outage rate of overhead line, derived from historical statistics, is amended. Based on this model, the power supply risk analysis software is developed to calculate the online risk indicators of district grid, and provide real-time decision support information based on risk theory for scheduling operations personnel.展开更多
Electrical power transmission is dominated by overhead line systems at present.This is mainly based on more than hundred years of experience of utilities in running overhead lines.Furthermore,overhead lines have prove...Electrical power transmission is dominated by overhead line systems at present.This is mainly based on more than hundred years of experience of utilities in running overhead lines.Furthermore,overhead lines have proven their operational reliability and functional assurance.In the past,cables were used in distribution networks in urban areas for the most part with the exception of direct current submarine cables.New developments of high voltage XLPE cables make it possible to use this technology for EHV level applications in transmission networks.Within this paper,mixed network configurations,consisting of overhead lines and high voltage cables,are investigated.An exemplary EHV transmission line with a total length of about 100 km,which is quite typical for Central Europe,has been studied.Several different line combinations are discussed with varied rates between overhead line sections and cable sections length in practice.The length of the cable sections are ranging from several kilometers up to lengths of 100 km.In this paper the work focuses on the transient behavior of combined 400 kV overhead and cable lines during switching processes and lightning impacts.A number of calculations were carried out to get an overview of the transient stress in numerous network nodes along the transmission system.Numerical programs like ATP/EMTP have been used for these simulations.Peak values and wave shapes of the transient voltage stress have been evaluated,based on different systems and within possible combinations.In respect of the insulation coordination and transient stress at network nodes,the voltage-time trends are also analyzed.The combination of high voltage overhead and cable transmission systems,especially such with lengths of more than about 50 km,are making tightened and extended demands to the network design,to the operational management and of course to the network protection also.As an output of this investigations,the results might influence the strategy in running this new type of combined transmission systems.展开更多
This paper presents an approach to accurately forecast the yearly occurrence of flashovers caused by lightning-induced voltage in overhead power lines in the presence of layered ground.The aim is to improve the accura...This paper presents an approach to accurately forecast the yearly occurrence of flashovers caused by lightning-induced voltage in overhead power lines in the presence of layered ground.The aim is to improve the accuracy of flashover rate estimation by using the insulator volt-time model.In particular,two-layer horizontal ground structures are considered.A 3D finite element method is used to calculate induced voltages and a Monte Carlo simulation is applied to determine the annual flashover rate.Volt-time insulator characteristics are used to identify the flashover condition.The results are compared with those obtained by using the standard 1.5 times the critical flashover(CFO)threshold criterion.The results indicate that the conventional 1.5 times the CFO criterion may underestimate the rate of flashovers,particularly in regions with horizon-tally stratified soil,as the volt-time method offers a more accurate presentation of the flashover process.Furthermore,the effect of upper soil depth,upper soil conductivity,pole spacing,and different flashover distance calculation techniques on flashover rates are analysed.This paper presents a new mathematical formula for estimating yearly flash-overs based on the results obtained by the volt-time method in the presence of stratified ground.The derived analytical formula provides an insightful tool for power system engineers to evaluate the lightning performance of overhead lines and implement efficient mitigation strategies.展开更多
The high-voltage direct current(HVDC)grid has been recognized as an effective solution for renewable energy integration.Currently,two main development trends for HVDC grids are being studied:a DC breaker based HVDC gr...The high-voltage direct current(HVDC)grid has been recognized as an effective solution for renewable energy integration.Currently,two main development trends for HVDC grids are being studied:a DC breaker based HVDC grid and fault-blocking converter based HVDC grid.Although the former has a perfect performance for fault clearance,its development is still highly constrained by the cost and maturity of DC breakers.The latter can extinguish DC faults by the fault-blocking converters.Without using DC breakers,there is no bottleneck in its technical feasibility.Nevertheless,in fault scenarios,such types of HVDC grids will be blocked at length for air-deionization,which is its main drawback.The aim of this paper is to minimize its power interruption time,by optimizing protection coordination strategies.To cover the most complex cases,the overhead line applications,in which the reclosure actions are required to be implemented,are considered.In this paper,the protection requirements of HVDC grids are first discussed,then the benefits of fault-blocking modular multilevel converters(MMCs)and their fault features are analyzed.Based on this,a control function is designed to reduce the air-deionization time.To minimize the influence of the DC faults,a separation methodology for restarting the system is proposed.The effectiveness of the proposed protection coordination schemes is validated by PSCAD/EMTDC simulations.展开更多
The UHVAC 1 000-kV transmission system is so far the one with the most advanced transmission technique applied and highest operation voltage.There are no guidelines or standards available for the design of 1 000-kV ov...The UHVAC 1 000-kV transmission system is so far the one with the most advanced transmission technique applied and highest operation voltage.There are no guidelines or standards available for the design of 1 000-kV overhead transmission line in China.Study on key technologies and design schemes shall be carried out to ascertain the technical principles and construction standards for project construction,which are presented in this paper based on the Southeast Shanxi-Nanyang-Jingmen test and demonstration transmission line.A comparison and analysis of technical data and economic indices between UHV line and other lines are also described.展开更多
Techniques of artificially-triggered lightning have provided a significantly useful means to directly measure various physical parameters of lightning discharge and to conduct research on protection methods of lightni...Techniques of artificially-triggered lightning have provided a significantly useful means to directly measure various physical parameters of lightning discharge and to conduct research on protection methods of lightning electromagnetic pulses.In this study,using capacitive and resistive dividers,current probes and optical fiber transmission devices,we measured and analyzed the induced overvoltage on the overhead transmission line and the overcurrent through Surge Protective Devices(SPD) when a lightning discharge was artificially triggered nearby on August 12,2008 at Conghua Field Lightning Experiment Site.The triggered lightning discharge contained an initial current stage and eight return strokes whose peak currents ranged from 6.6kA to 26.4kA.We found that overcurrents through SPD were induced on the power line both during the initial continuous current stage and the return stroke processes.During the return strokes,the residual voltage and the current through the SPD lasted up to the ms(millisecond) range,and the overcurrents exhibited a mean waveform up to 22/69μs with a peak value of less than 2kA.Based on the observed data,simple calculations show that the corresponding single discharge energy was much greater than the values of the high voltage pulse generators commonly used in the experiments regulated for SPD.The SPD discharge current peak was not synchronous to that of the residual voltage with the former obviously lagging behind the latter.The SPD discharge current peak was well correlated with the triggered lightning current peak and the wave-front current gradient.The long duration of the SPD current is one of the major reasons why the SPD was damaged even with a big nominal discharge current.展开更多
Overhead lines are the backbone of the electrical power transmission.Contrary to the distributions networks,the transmission system consists only in exceptional cases of longer cable lines.Typical exceptions are conne...Overhead lines are the backbone of the electrical power transmission.Contrary to the distributions networks,the transmission system consists only in exceptional cases of longer cable lines.Typical exceptions are connections of cavern power plants,approaches to airports or bird sanctuaries and lines in urban centres.In the majority of cases,an overhead line is the most economic and practicable solution for the energy transmission.In tourism regions,an overhead line will be seen as impairment of nature or landscape and so the approval chain and procedure is in most countries long-winded and circumstantial.At the other hand,the energy consumption in Europe is growing and the volatility of transmitted power is also increasing during the last decade caused by the opening of the electric energy market.This opening process leads to a stopping of the enlargement of the interoperation network and to a minimisation of the maintenance of existing lines.Today the network operates more often at the limit of the equipment and the small and large-areas disturbances and blackouts are increasing.The operators of transmission lines are forced to ensure the electrical power supply and so they have to improve the reliability of the network.One solution is to monitor the critical(heavy loaded)overhead lines.For example,with the knowledge of the thermal condition,the risk of unexpected outages can be reduced.Today several monitoring systems are available on the market.They differ in the principle and techniques of the condition evaluation.The three most interesting output variables are the line temperature,the capable transmission power and the actual sag of the investigated section.In this paper an overview of existing overhead line monitoring system and also an outline over the usage and benefit for the application will be given.Thermal monitoring is one technique to improve the reliability of the network and for increasing or optimising the capable transmission power.展开更多
Various technologies have recently been developed for high-speed railways, in order to boost commercial speeds from 300 km.h： to 400 km.h-1. Among these technologies, this paper introduces the 400 km-h-1 class curren...Various technologies have recently been developed for high-speed railways, in order to boost commercial speeds from 300 km.h： to 400 km.h-1. Among these technologies, this paper introduces the 400 km-h-1 class current collection performance evaluation methods that have been developed and demonstrated by Korea. Specifically, this paper reports details of the video-based monitoring techniques that have been adopted to inspect the stability of overhead contact line （OCL） components at 400 km.h-1 without direct contact with any components of the power supply system. Unlike conventional OCL monitoring systems, which detect contact wire positions using either laser sensors or line cameras, the developed system measures parameters in the active state by video data. According to experimental results that were obtained at a field-test site established at a commercial line, it is claimed that the proposed mea- surement system is capable of effectively measuring OCL parameters.展开更多
This work is carried out to predict the special distribution of electric field induced by multi-circuit intersecting overhead high-voltage (HV) transmission lines (TLs) within a large range without any expensive and t...This work is carried out to predict the special distribution of electric field induced by multi-circuit intersecting overhead high-voltage (HV) transmission lines (TLs) within a large range without any expensive and time-consuming computation. The two main parts of the presented methodology are 1) setting up a three-dimensional (3D) model to calculate the electric field based on combining ca- tenary equations with charge simulation method and 2) calculating the hybrid electric field excited by multi-circuit intersecting TLs using coordinate transformation and superposition technique. Examples of different TLs configurations, including a 220 kV single-circuit hori- zontally configured TLs, a 500 kV single-circuit triangularly configured TLs and a combination of the 220 kV TLs and the 550 kV TLs, are illustrated to verify the validity of this methodology. A more complicatal configurations, including a 500 kV double-circuit TLs and two 220 kV single-circuit horizontally configured TLs, are also calculated. Conclusions were drawn from the simulation: 1) The presented 3D model outperforms 2D models in describing the electric field distribution generated by practical HV TLs with sag and span. 2) Coordinate trans- formation and superposition technique considerably simplify the electric field computation for multi-circuit TLs configurations, which makes it possible to deal with complex engineering problems. 3) The electric field in the area covered by multiple intersecting overhead TLs is distorted and the hybrid electric field strength in some partial region increases so sharply that it might exceed the admissible value. 4) The configuration parameters of the TLs and the spatial configuration of multi-circuit TLs, for instance, the height of TLs, the length of span and the intersection angle of multiple circuits, influence the strength and the distribution of hybrid electric field. The influence regularities sum- marized in this paper can be referred by future TL designs to meet the electromagnetic environmental protection regulations.展开更多
At present, the on-line monitoring is widely applied to the power line monitoring. In this paper, a new mechanical calculation model is established according to the on-line monitoring. And this model is based on the p...At present, the on-line monitoring is widely applied to the power line monitoring. In this paper, a new mechanical calculation model is established according to the on-line monitoring. And this model is based on the parameters that tension sensors and angle sensors on suspended points detect, and combines with the parameters of the wire itself, and also considers the deflection angel of wires due to wind. In this model, mechanics parameters of wires are turned into the new coordinate plane after deflection angel of wires due to wind, or windage yaw plane. A statics tension balance equation is built in the vertical direction of the new windage yaw plane. According to the theoretical analysis and algorithm, we verify the accuracy of this newly developed mechanical calculation model.展开更多
In power systems, a large number of OPLs （overhead power lines） are more than 40 years old and some even exceed 50 years old. The key issue for power systems managers, public utilities companies and electrical engin...In power systems, a large number of OPLs （overhead power lines） are more than 40 years old and some even exceed 50 years old. The key issue for power systems managers, public utilities companies and electrical engineers today concerns the manner in which available financial resources should be invested in these OPLs to provide the greatest impact on the power system as a whole and to address the OPLs that require urgent revitalization. This paper presents the application of the software tool RevOPL, developed using Microsoft Access utilizing the ＂methodology for revitalization of high-voltage OPLs＂. The aim is to present both the methodology and software to objectively evaluate the condition of an OPL and determine its remaining service life. The application of this software tool provides a proposal for the scheduling and scope of planned revitalization activities, which are obtained through the optimization of the technical characteristics while remaining within the available budget.展开更多
There are two major protective methods against lightning outages on overhead distribution lines.One is a surge arrester,and the other is an overhead ground wire.The surge arresters have rather constant effect regardle...There are two major protective methods against lightning outages on overhead distribution lines.One is a surge arrester,and the other is an overhead ground wire.The surge arresters have rather constant effect regardless of the cause of the lightning outage.On the other hand,the effect of an overhead ground wire is quite different in two major causes,the direct lightning hit and the induced overvoltage.It is sufficient to provide surge arresters with an interval of 300 m for protection against the induced overvoltage caused by the nearby lightning stroke.Use of an overhead ground wire together with surge arresters is effective for lightning protection against the direct lightning hit to a distribution line.Puncture of surge arresters is the popular outage when the outage caused by the insulation break decreases sufficiently.Also,the existence of nearby trees leads to the line break due to the side flash from a tree.Advanced lightning protection equipment with ZnO arrester components is popular in Japan.Modeling of a pole transformer and application of an electromagnetic analysis method,such as FDTD method,to surge phenomena is considerably advanced.展开更多
Significant investments have been made regarding the construction of a great number of high-voltage overhead power lines of all voltage levels, and now the questions arise on where and how to direct the investments ne...Significant investments have been made regarding the construction of a great number of high-voltage overhead power lines of all voltage levels, and now the questions arise on where and how to direct the investments necessary for the maintenance of overhead power lines. To organise the process of maintenance of overhead power lines correctly, it is necessary to have the current information on the condition of particular components of a line. In this paper, special attention has been paid to the real condition of overhead power lines, with the aim of making the decision whether some of the following measures are necessary, and to what extent： the revitalisation for a certain number of years is perceived, the revitalisation up to five years and reconstruction of the overhead power line is performed, its restoration is performed or nothing is done. The approach to the perceiving of real condition of high-voltage overhead power lines is presented on a global block diagram. With the aim of setting out the list of priorities for revitalisation, the criteria have been defined with regards to the real condition of particular components of an overhead power line, as well as pursuant to the role and importance in an electric power system. The correctly defined criteria contribute to the solving of the problem of making a single list of priorities for the revitalisation of high-voltage overhead power lines. In that way, the recommendations are being given to the transmission companies, to achieve a higher reliability of an electric power system, with a minimum number of cancellations and a maximum extension of working life of all the components of overhead power lines. A correct maintenance of overhead power lines brings large financial savings to the owners of transmission companies, and that is the primary goal in a deregulated environment.展开更多
In order to increase the stability of the Mongolia power system, a single-phase automatic reclosing device (SPAR) was introduced on double-circuit power lines built with a size of 330 kV, operating on a voltage of 220...In order to increase the stability of the Mongolia power system, a single-phase automatic reclosing device (SPAR) was introduced on double-circuit power lines built with a size of 330 kV, operating on a voltage of 220 kV and a length of 250 km. These overhead power lines (L-213, L-214) connect the 220/110/35 kV “Songino” substation with the “Mandal” substation and form system networks. This paper presents the challenges encountered when implementing single-phase automatic reclosing (SPAR) devices and compares the changes in power system parameters before and after SPAR deployment for a long 220 kV line. Simulations and analyses were carried out using DIgSILENT PowerFactory software, focusing on rotor angle stability, and the overall impact on the power system during short-circuit faults. The evaluation also utilized measurement data from the Wide Area Monitoring System (WAMS) to compare system behavior pre- and post-implementation of SPAR. The findings reveal that SPAR significantly enhances system reliability and stability, effectively mitigating the risk of oscillations and stability loss triggered by short circuits. This improvement contributes to a more resilient power system, reducing the potential for disturbances caused by faults.展开更多
In order to ensure that the off-line arm of a two-arm-wheel combined inspection robot can reliably grasp the line in case of autonomous obstacle crossing,a control method is proposed for line grasping based on hand-ey...In order to ensure that the off-line arm of a two-arm-wheel combined inspection robot can reliably grasp the line in case of autonomous obstacle crossing,a control method is proposed for line grasping based on hand-eye visual servo.On the basis of the transmission line's geometrical characteristics and the camera's imaging principle,a line recognition and extraction method based on structure constraint is designed.The line's intercept and inclination are defined in an imaging space to represent the robot's change of pose and a law governing the pose decoupling servo control is developed.Under the integrated consideration of the influence of light intensity and background change,noise(from the camera itself and electromagnetic field)as well as the robot's kinetic inertia on the robot's imaging quality in the course of motion and the grasping control precision,a servo controller for grasping the line of the robot's off-line arm is designed with the method of fuzzy control.An experiment is conducted on a 1:1 simulation line using an inspection robot and the robot is put into on-line operation on a real overhead transmission line,where the robot can grasp the line within 18 s in the case of autonomous obstacle-crossing.The robot's autonomous line-grasping function is realized without manual intervention and the robot can grasp the line in a precise,reliable and efficient manner,thus the need of actual operation can be satisfied.展开更多
Forest fire accidents caused by distribution line faults occur frequently,resulting in heavy impacts on people’s safety and social and economic development.Currently,there are few risk assessments for forest fires in...Forest fire accidents caused by distribution line faults occur frequently,resulting in heavy impacts on people’s safety and social and economic development.Currently,there are few risk assessments for forest fires induced by over-head distribution lines,and existing assessment methods may have difficulties in data acquisition.On this basis,a novel as-sessment framework based on an analytic hierarchy process,a Bayesian network and a Fussel-Vesely importance metric is proposed in this paper.The framework combines field research and historical operation and maintenance data to assess the regional-scale risk of forest fires induced by overhead distribution lines to derive the probability of forest fires and to identify high-risk lines and key hazard events in the assessment region.Finally,taking the southern Anhui region as an ex-ample,the annual fire probability of forest fires induced by overhead distribution lines in the southern Anhui region is 5.88%,and rectification measures are proposed.This study provides management with a complete assessment framework that optimizes the difficulty of data collection and allows for additional targeted corrective measures to be proposed for the entire region and route on the basis of the assessment results.展开更多
In the background of the design and construction of Smart Grid Operation Supporting System for District Power Networks, this paper established the weighted fault probability model of the overhead line which is based o...In the background of the design and construction of Smart Grid Operation Supporting System for District Power Networks, this paper established the weighted fault probability model of the overhead line which is based on equipment operating status, utility theory and fuzzy theory. In this model, the proper membership function is adopted to describe the influence of lightning, wind speed, line ice and temperature, and the outage rate of overhead line, derived from historical statistics, is amended. Based on this model, the power supply risk analysis software is developed to calculate the online risk indicators of district grid, and provide real-time decision support information based on risk theory for scheduling operations personnel.展开更多
In the design of high voltage transmission lines inevitably needed to change the arrangement of wires, and the distance between the wires directly affected by changing the arrangement of the wires. The distance betwee...In the design of high voltage transmission lines inevitably needed to change the arrangement of wires, and the distance between the wires directly affected by changing the arrangement of the wires. The distance between the wires is difficult to judge by experiences. Therefore, it is urgently to develop a way to accurately calculating the minimum distance between the wires when changing the arrangement between the two wires, and determine the minimum distance can meet the requirements of standards and regulations or not. Through the thinking, based on the balance equation and the space curve wire calculus method, a more accurate method of calculating the two wires in a variety of conditions the minimum spacing was derivated, and the sensitivity of the minimum distance was analysized based on the method.展开更多
文摘This paper considers the influence of changes of the transmission lines of permissible load current depending on conductor and ambient temperatures, climate conditions. The theoretical background of the allowable conductor temperature as well as load current determination principles are proposed. On one hand, the principles are based on mechanical limitations; on the other hand, they are based on thermal limitations. The simulation tasks were based on specific data information of three existing overhead lines of Latvian power system as well as the planned 330 kV overhead line. Moreover, the special thermovision device was used for precious determination of conductor temperature of the existing transmission lines. The simulation results of the obtained data are reviewed in the paper.
文摘In the background of the design and construction of Smart Grid Operation Supporting System for District Power Networks, this paper established the weighted fault probability model of the overhead line which is based on equipment operating status, utility theory and fuzzy theory. In this model, the proper membership function is adopted to describe the influence of lightning, wind speed, line ice and temperature, and the outage rate of overhead line, derived from historical statistics, is amended. Based on this model, the power supply risk analysis software is developed to calculate the online risk indicators of district grid, and provide real-time decision support information based on risk theory for scheduling operations personnel.
文摘Electrical power transmission is dominated by overhead line systems at present.This is mainly based on more than hundred years of experience of utilities in running overhead lines.Furthermore,overhead lines have proven their operational reliability and functional assurance.In the past,cables were used in distribution networks in urban areas for the most part with the exception of direct current submarine cables.New developments of high voltage XLPE cables make it possible to use this technology for EHV level applications in transmission networks.Within this paper,mixed network configurations,consisting of overhead lines and high voltage cables,are investigated.An exemplary EHV transmission line with a total length of about 100 km,which is quite typical for Central Europe,has been studied.Several different line combinations are discussed with varied rates between overhead line sections and cable sections length in practice.The length of the cable sections are ranging from several kilometers up to lengths of 100 km.In this paper the work focuses on the transient behavior of combined 400 kV overhead and cable lines during switching processes and lightning impacts.A number of calculations were carried out to get an overview of the transient stress in numerous network nodes along the transmission system.Numerical programs like ATP/EMTP have been used for these simulations.Peak values and wave shapes of the transient voltage stress have been evaluated,based on different systems and within possible combinations.In respect of the insulation coordination and transient stress at network nodes,the voltage-time trends are also analyzed.The combination of high voltage overhead and cable transmission systems,especially such with lengths of more than about 50 km,are making tightened and extended demands to the network design,to the operational management and of course to the network protection also.As an output of this investigations,the results might influence the strategy in running this new type of combined transmission systems.
文摘This paper presents an approach to accurately forecast the yearly occurrence of flashovers caused by lightning-induced voltage in overhead power lines in the presence of layered ground.The aim is to improve the accuracy of flashover rate estimation by using the insulator volt-time model.In particular,two-layer horizontal ground structures are considered.A 3D finite element method is used to calculate induced voltages and a Monte Carlo simulation is applied to determine the annual flashover rate.Volt-time insulator characteristics are used to identify the flashover condition.The results are compared with those obtained by using the standard 1.5 times the critical flashover(CFO)threshold criterion.The results indicate that the conventional 1.5 times the CFO criterion may underestimate the rate of flashovers,particularly in regions with horizon-tally stratified soil,as the volt-time method offers a more accurate presentation of the flashover process.Furthermore,the effect of upper soil depth,upper soil conductivity,pole spacing,and different flashover distance calculation techniques on flashover rates are analysed.This paper presents a new mathematical formula for estimating yearly flash-overs based on the results obtained by the volt-time method in the presence of stratified ground.The derived analytical formula provides an insightful tool for power system engineers to evaluate the lightning performance of overhead lines and implement efficient mitigation strategies.
文摘The high-voltage direct current(HVDC)grid has been recognized as an effective solution for renewable energy integration.Currently,two main development trends for HVDC grids are being studied:a DC breaker based HVDC grid and fault-blocking converter based HVDC grid.Although the former has a perfect performance for fault clearance,its development is still highly constrained by the cost and maturity of DC breakers.The latter can extinguish DC faults by the fault-blocking converters.Without using DC breakers,there is no bottleneck in its technical feasibility.Nevertheless,in fault scenarios,such types of HVDC grids will be blocked at length for air-deionization,which is its main drawback.The aim of this paper is to minimize its power interruption time,by optimizing protection coordination strategies.To cover the most complex cases,the overhead line applications,in which the reclosure actions are required to be implemented,are considered.In this paper,the protection requirements of HVDC grids are first discussed,then the benefits of fault-blocking modular multilevel converters(MMCs)and their fault features are analyzed.Based on this,a control function is designed to reduce the air-deionization time.To minimize the influence of the DC faults,a separation methodology for restarting the system is proposed.The effectiveness of the proposed protection coordination schemes is validated by PSCAD/EMTDC simulations.
文摘The UHVAC 1 000-kV transmission system is so far the one with the most advanced transmission technique applied and highest operation voltage.There are no guidelines or standards available for the design of 1 000-kV overhead transmission line in China.Study on key technologies and design schemes shall be carried out to ascertain the technical principles and construction standards for project construction,which are presented in this paper based on the Southeast Shanxi-Nanyang-Jingmen test and demonstration transmission line.A comparison and analysis of technical data and economic indices between UHV line and other lines are also described.
基金A key project of China Meteorological Administration (CMATG2008Z07)Specialized Science Project for Public Welfare Industries (GYHY2007622)Key Science Project of the Guangzhou Regional Meteorological Center (GRMC2007B03)
文摘Techniques of artificially-triggered lightning have provided a significantly useful means to directly measure various physical parameters of lightning discharge and to conduct research on protection methods of lightning electromagnetic pulses.In this study,using capacitive and resistive dividers,current probes and optical fiber transmission devices,we measured and analyzed the induced overvoltage on the overhead transmission line and the overcurrent through Surge Protective Devices(SPD) when a lightning discharge was artificially triggered nearby on August 12,2008 at Conghua Field Lightning Experiment Site.The triggered lightning discharge contained an initial current stage and eight return strokes whose peak currents ranged from 6.6kA to 26.4kA.We found that overcurrents through SPD were induced on the power line both during the initial continuous current stage and the return stroke processes.During the return strokes,the residual voltage and the current through the SPD lasted up to the ms(millisecond) range,and the overcurrents exhibited a mean waveform up to 22/69μs with a peak value of less than 2kA.Based on the observed data,simple calculations show that the corresponding single discharge energy was much greater than the values of the high voltage pulse generators commonly used in the experiments regulated for SPD.The SPD discharge current peak was not synchronous to that of the residual voltage with the former obviously lagging behind the latter.The SPD discharge current peak was well correlated with the triggered lightning current peak and the wave-front current gradient.The long duration of the SPD current is one of the major reasons why the SPD was damaged even with a big nominal discharge current.
文摘Overhead lines are the backbone of the electrical power transmission.Contrary to the distributions networks,the transmission system consists only in exceptional cases of longer cable lines.Typical exceptions are connections of cavern power plants,approaches to airports or bird sanctuaries and lines in urban centres.In the majority of cases,an overhead line is the most economic and practicable solution for the energy transmission.In tourism regions,an overhead line will be seen as impairment of nature or landscape and so the approval chain and procedure is in most countries long-winded and circumstantial.At the other hand,the energy consumption in Europe is growing and the volatility of transmitted power is also increasing during the last decade caused by the opening of the electric energy market.This opening process leads to a stopping of the enlargement of the interoperation network and to a minimisation of the maintenance of existing lines.Today the network operates more often at the limit of the equipment and the small and large-areas disturbances and blackouts are increasing.The operators of transmission lines are forced to ensure the electrical power supply and so they have to improve the reliability of the network.One solution is to monitor the critical(heavy loaded)overhead lines.For example,with the knowledge of the thermal condition,the risk of unexpected outages can be reduced.Today several monitoring systems are available on the market.They differ in the principle and techniques of the condition evaluation.The three most interesting output variables are the line temperature,the capable transmission power and the actual sag of the investigated section.In this paper an overview of existing overhead line monitoring system and also an outline over the usage and benefit for the application will be given.Thermal monitoring is one technique to improve the reliability of the network and for increasing or optimising the capable transmission power.
文摘Various technologies have recently been developed for high-speed railways, in order to boost commercial speeds from 300 km.h： to 400 km.h-1. Among these technologies, this paper introduces the 400 km-h-1 class current collection performance evaluation methods that have been developed and demonstrated by Korea. Specifically, this paper reports details of the video-based monitoring techniques that have been adopted to inspect the stability of overhead contact line （OCL） components at 400 km.h-1 without direct contact with any components of the power supply system. Unlike conventional OCL monitoring systems, which detect contact wire positions using either laser sensors or line cameras, the developed system measures parameters in the active state by video data. According to experimental results that were obtained at a field-test site established at a commercial line, it is claimed that the proposed mea- surement system is capable of effectively measuring OCL parameters.
基金Project supported by Scientific Research Foundation of State Key Laboratory of Power Transmission Equipment ＆ System Security and New Technology （2007DA1051271 2204）, Natural Science Foundation of Chongqing Municipality （cstc201 ljjA20009）.
文摘This work is carried out to predict the special distribution of electric field induced by multi-circuit intersecting overhead high-voltage (HV) transmission lines (TLs) within a large range without any expensive and time-consuming computation. The two main parts of the presented methodology are 1) setting up a three-dimensional (3D) model to calculate the electric field based on combining ca- tenary equations with charge simulation method and 2) calculating the hybrid electric field excited by multi-circuit intersecting TLs using coordinate transformation and superposition technique. Examples of different TLs configurations, including a 220 kV single-circuit hori- zontally configured TLs, a 500 kV single-circuit triangularly configured TLs and a combination of the 220 kV TLs and the 550 kV TLs, are illustrated to verify the validity of this methodology. A more complicatal configurations, including a 500 kV double-circuit TLs and two 220 kV single-circuit horizontally configured TLs, are also calculated. Conclusions were drawn from the simulation: 1) The presented 3D model outperforms 2D models in describing the electric field distribution generated by practical HV TLs with sag and span. 2) Coordinate trans- formation and superposition technique considerably simplify the electric field computation for multi-circuit TLs configurations, which makes it possible to deal with complex engineering problems. 3) The electric field in the area covered by multiple intersecting overhead TLs is distorted and the hybrid electric field strength in some partial region increases so sharply that it might exceed the admissible value. 4) The configuration parameters of the TLs and the spatial configuration of multi-circuit TLs, for instance, the height of TLs, the length of span and the intersection angle of multiple circuits, influence the strength and the distribution of hybrid electric field. The influence regularities sum- marized in this paper can be referred by future TL designs to meet the electromagnetic environmental protection regulations.
文摘At present, the on-line monitoring is widely applied to the power line monitoring. In this paper, a new mechanical calculation model is established according to the on-line monitoring. And this model is based on the parameters that tension sensors and angle sensors on suspended points detect, and combines with the parameters of the wire itself, and also considers the deflection angel of wires due to wind. In this model, mechanics parameters of wires are turned into the new coordinate plane after deflection angel of wires due to wind, or windage yaw plane. A statics tension balance equation is built in the vertical direction of the new windage yaw plane. According to the theoretical analysis and algorithm, we verify the accuracy of this newly developed mechanical calculation model.
文摘In power systems, a large number of OPLs （overhead power lines） are more than 40 years old and some even exceed 50 years old. The key issue for power systems managers, public utilities companies and electrical engineers today concerns the manner in which available financial resources should be invested in these OPLs to provide the greatest impact on the power system as a whole and to address the OPLs that require urgent revitalization. This paper presents the application of the software tool RevOPL, developed using Microsoft Access utilizing the ＂methodology for revitalization of high-voltage OPLs＂. The aim is to present both the methodology and software to objectively evaluate the condition of an OPL and determine its remaining service life. The application of this software tool provides a proposal for the scheduling and scope of planned revitalization activities, which are obtained through the optimization of the technical characteristics while remaining within the available budget.
文摘There are two major protective methods against lightning outages on overhead distribution lines.One is a surge arrester,and the other is an overhead ground wire.The surge arresters have rather constant effect regardless of the cause of the lightning outage.On the other hand,the effect of an overhead ground wire is quite different in two major causes,the direct lightning hit and the induced overvoltage.It is sufficient to provide surge arresters with an interval of 300 m for protection against the induced overvoltage caused by the nearby lightning stroke.Use of an overhead ground wire together with surge arresters is effective for lightning protection against the direct lightning hit to a distribution line.Puncture of surge arresters is the popular outage when the outage caused by the insulation break decreases sufficiently.Also,the existence of nearby trees leads to the line break due to the side flash from a tree.Advanced lightning protection equipment with ZnO arrester components is popular in Japan.Modeling of a pole transformer and application of an electromagnetic analysis method,such as FDTD method,to surge phenomena is considerably advanced.
文摘Significant investments have been made regarding the construction of a great number of high-voltage overhead power lines of all voltage levels, and now the questions arise on where and how to direct the investments necessary for the maintenance of overhead power lines. To organise the process of maintenance of overhead power lines correctly, it is necessary to have the current information on the condition of particular components of a line. In this paper, special attention has been paid to the real condition of overhead power lines, with the aim of making the decision whether some of the following measures are necessary, and to what extent： the revitalisation for a certain number of years is perceived, the revitalisation up to five years and reconstruction of the overhead power line is performed, its restoration is performed or nothing is done. The approach to the perceiving of real condition of high-voltage overhead power lines is presented on a global block diagram. With the aim of setting out the list of priorities for revitalisation, the criteria have been defined with regards to the real condition of particular components of an overhead power line, as well as pursuant to the role and importance in an electric power system. The correctly defined criteria contribute to the solving of the problem of making a single list of priorities for the revitalisation of high-voltage overhead power lines. In that way, the recommendations are being given to the transmission companies, to achieve a higher reliability of an electric power system, with a minimum number of cancellations and a maximum extension of working life of all the components of overhead power lines. A correct maintenance of overhead power lines brings large financial savings to the owners of transmission companies, and that is the primary goal in a deregulated environment.
文摘In order to increase the stability of the Mongolia power system, a single-phase automatic reclosing device (SPAR) was introduced on double-circuit power lines built with a size of 330 kV, operating on a voltage of 220 kV and a length of 250 km. These overhead power lines (L-213, L-214) connect the 220/110/35 kV “Songino” substation with the “Mandal” substation and form system networks. This paper presents the challenges encountered when implementing single-phase automatic reclosing (SPAR) devices and compares the changes in power system parameters before and after SPAR deployment for a long 220 kV line. Simulations and analyses were carried out using DIgSILENT PowerFactory software, focusing on rotor angle stability, and the overall impact on the power system during short-circuit faults. The evaluation also utilized measurement data from the Wide Area Monitoring System (WAMS) to compare system behavior pre- and post-implementation of SPAR. The findings reveal that SPAR significantly enhances system reliability and stability, effectively mitigating the risk of oscillations and stability loss triggered by short circuits. This improvement contributes to a more resilient power system, reducing the potential for disturbances caused by faults.
基金Project(2006AA04Z202)supported by the National High Technology Research and Development Program of ChinaProject(51105281)supported by the National Natural Science Foundation of China
文摘In order to ensure that the off-line arm of a two-arm-wheel combined inspection robot can reliably grasp the line in case of autonomous obstacle crossing,a control method is proposed for line grasping based on hand-eye visual servo.On the basis of the transmission line's geometrical characteristics and the camera's imaging principle,a line recognition and extraction method based on structure constraint is designed.The line's intercept and inclination are defined in an imaging space to represent the robot's change of pose and a law governing the pose decoupling servo control is developed.Under the integrated consideration of the influence of light intensity and background change,noise(from the camera itself and electromagnetic field)as well as the robot's kinetic inertia on the robot's imaging quality in the course of motion and the grasping control precision,a servo controller for grasping the line of the robot's off-line arm is designed with the method of fuzzy control.An experiment is conducted on a 1:1 simulation line using an inspection robot and the robot is put into on-line operation on a real overhead transmission line,where the robot can grasp the line within 18 s in the case of autonomous obstacle-crossing.The robot's autonomous line-grasping function is realized without manual intervention and the robot can grasp the line in a precise,reliable and efficient manner,thus the need of actual operation can be satisfied.
基金This work was supported by the National Key Research and Development Program of China(2022YFC3003101)the Fundamental Research Funds for the Central Universities(WK2320000050)the Science and Technology Program of State Grid Anhui Electric Power Co.,Ltd.(521205220001).
文摘Forest fire accidents caused by distribution line faults occur frequently,resulting in heavy impacts on people’s safety and social and economic development.Currently,there are few risk assessments for forest fires induced by over-head distribution lines,and existing assessment methods may have difficulties in data acquisition.On this basis,a novel as-sessment framework based on an analytic hierarchy process,a Bayesian network and a Fussel-Vesely importance metric is proposed in this paper.The framework combines field research and historical operation and maintenance data to assess the regional-scale risk of forest fires induced by overhead distribution lines to derive the probability of forest fires and to identify high-risk lines and key hazard events in the assessment region.Finally,taking the southern Anhui region as an ex-ample,the annual fire probability of forest fires induced by overhead distribution lines in the southern Anhui region is 5.88%,and rectification measures are proposed.This study provides management with a complete assessment framework that optimizes the difficulty of data collection and allows for additional targeted corrective measures to be proposed for the entire region and route on the basis of the assessment results.
文摘In the background of the design and construction of Smart Grid Operation Supporting System for District Power Networks, this paper established the weighted fault probability model of the overhead line which is based on equipment operating status, utility theory and fuzzy theory. In this model, the proper membership function is adopted to describe the influence of lightning, wind speed, line ice and temperature, and the outage rate of overhead line, derived from historical statistics, is amended. Based on this model, the power supply risk analysis software is developed to calculate the online risk indicators of district grid, and provide real-time decision support information based on risk theory for scheduling operations personnel.
文摘In the design of high voltage transmission lines inevitably needed to change the arrangement of wires, and the distance between the wires directly affected by changing the arrangement of the wires. The distance between the wires is difficult to judge by experiences. Therefore, it is urgently to develop a way to accurately calculating the minimum distance between the wires when changing the arrangement between the two wires, and determine the minimum distance can meet the requirements of standards and regulations or not. Through the thinking, based on the balance equation and the space curve wire calculus method, a more accurate method of calculating the two wires in a variety of conditions the minimum spacing was derivated, and the sensitivity of the minimum distance was analysized based on the method.
