Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect ...Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect the safety and stability of transmission towers.In this study,the effects of bolt joint loosening on the dynamic characteristics of a 220-kV angle steel transmission tower are the main topic of concern.First,the mechanical properties of typical joints subjected to different degrees of bolt loosening are studied by finite solid-element simulation,based on which a finite hybrid-element modeling method is developed for a tower structure suffering varying loose degrees in the joints.Taking a 220-kV angle steel transmission tower as the object,the influence of the position and degree of loosening on the tower’s natural frequencies and mode shapes are simulated and discussed.The results demonstrate that the main-member splice joint and the main diagonal-horizontal member gusset plate joint account for the dominant impact on the dynamic characteristics of the tower.In addition,the dominant joint shifts from the main-member splice joint to the main diagonal-horizontal member gusset plate joint as the considered modal order increases.In the case of double joints loosening simultaneously,the loosening of nondomi-nant joints has nonnegligible effects on the tower as well.展开更多
To address the challenges of multi-scale differences,complex background interference,and unstable small target positioning in visual inspection of power towers,the existing methods still face issues such as insufficie...To address the challenges of multi-scale differences,complex background interference,and unstable small target positioning in visual inspection of power towers,the existing methods still face issues such as insufficient feature interaction and unstable confidence estimation,which lead to performance degradation in complex backgrounds and occlusion conditions.This paper proposes a precise inspection method for key power tower components using autonomous drone positioning.To this end,this paper makes three key improvements to the you only look once version 11(YOLOv11)framework.First,it constructs C3k2-adaptive multi-receptive field block(C3k2-AMRB),combining multiple dilated convolutions with a reparameterization mechanism to significantly expand the receptive field and enhance multi-scale feature extraction.Second,it designs a hierarchical wavelet interaction unit(HWIU),which leverages high-and low-frequency decomposition and reconstruction of wavelet transform(WT)to achieve cross-scale semantic alignment,enhancing feature discriminability in complex backgrounds.Third,it proposes a distribution-aware confidence refinement head(DACR-Head),which adaptively calibrates classification confidence based on the statistical characteristics of the predicted bounding-box corner distribution,improving the localization stability and accuracy of small targets.Experiments on the inspection of power line assets dataset(InsPLAD)dataset show that the integrated approach achieves a component detection accuracy at intersection over union(IoU)=0.5(CDA_(50))of 88.3%and a component detection robustness(CDR_(50:95))of 69.8%,respectively,improvements of 4.4%and 7.0%over the baseline.展开更多
Given the background of a transmission tower erected on a particular mining subsidence area,we used finite element modeling to analyze the anti-deformation performance of transmission towers under a number of differen...Given the background of a transmission tower erected on a particular mining subsidence area,we used finite element modeling to analyze the anti-deformation performance of transmission towers under a number of different load conditions,including horizontal foundation displacement,uneven vertical downward displacement,wind loads and icing conditions.The results show that the failure in stability of a single steel angle iron represents the limit of the tower given ground deformation.We calculated the corresponding limits of foundation displacements.The results indicate that compression displacement of the foundation is more dangerous than tension displacement.Under complex foundation displacement conditions,horizontal foundation displacement is a key factor leading to failure in the stability of towers.Under conditions of compression or tension displacement of the foundation,wind load becomes the key factor.Towers do not fail when foundation displacements are smaller than 1% (under tension) or 0.5% (under horizontal compression or single foundation subsidence) of the distance between two supports.展开更多
In this paper,an analytical framework to evaluate the along-wind-induced dynamic responses of a transmission tower is presented.Two analytical models and a new method are developed:(1)a higher mode generalized force s...In this paper,an analytical framework to evaluate the along-wind-induced dynamic responses of a transmission tower is presented.Two analytical models and a new method are developed:(1)a higher mode generalized force spectrum(GFS)model of the transmission tower is deduced;(2)an analytical model that includes the contributions of the higher modes is further derived as a rational algebraic formula to estimate the structural displacement response;and(3)a new approach,applying load with displacement(ALD)instead of force,to solve the internal force of transmission tower is given.Unlike conventional methods,the ALD method can avoid calculating equivalent static wind loads(ESWLs).Finally,a transmission tower structure is used as a numerical example to verify the feasibility and accuracy of the ALD method.展开更多
A large number of high-voltage power transmission towers have recently been constructed in mining areas prone to subsidence. In order to ensure the safety of the transmission towers and the safe operation of transmiss...A large number of high-voltage power transmission towers have recently been constructed in mining areas prone to subsidence. In order to ensure the safety of the transmission towers and the safe operation of transmission systems, it is imperative to carry out research on the anti-deformation performance of transmission towers. In our study, we performed experiments on the anti-deformation performance of a transmission tower in a subsidence area on a scale model with a geometric scale ratio of 1:5 and analyzed the failure mechanism of the tower members. The results show that, when the axial distance between two supports changes, destabilization failure most likely occurs in the members of the bottom transverse layer because some parts of the main diagonal member bars yield under the action of compression. The failure mechanism of the tower members basically coincides with the lever principle.展开更多
The earthquake resistance of transmission tower has been often discussed from the viewpoint of reinforcing the foundation of steel tower, but there are also few studies considering the damping characteristics of the t...The earthquake resistance of transmission tower has been often discussed from the viewpoint of reinforcing the foundation of steel tower, but there are also few studies considering the damping characteristics of the tower. This paper focuses on the viscous damper which has been adopted for seismic reinforcement of bridges in recent years. The purpose of this study is to improve the seismic performance of steel tower by giving the high damping to the tower. We construct a single tower model considering the influence of transmission line, and then simulate the vibration characteristics and seismic behavior of the tower by the eigenvalue analysis and the dynamic response analysis. The results show that the transmission tower with viscous damper can reduce its own response effectively and drastically. This research concludes that it is necessary to consider the extreme increase of steel tower＇s response depending on the seismic wave and the collapse of steel tower can be avoided by using the optimum damper in the design of the transmission tower.展开更多
We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1 000 kV transmission line project in P. R. China. The height of the cup t...We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1 000 kV transmission line project in P. R. China. The height of the cup tower is 181 m with a ground elevation of 47 m, which makes it a super flexible and wind-sensitive structure. Therefore, we should analyze the wind- resistant capacity of the system. We simulated applicable transverse fluctuating wind velocity field, developed a lead-rubber damper （LRD） for controlling wind-induced vibration of long-span transmission towers, deduced LRD calculation model parameter, and researched the best layout scheme and installation method of LRD. To calculate the wind-induced response of tower-line coupling system in seven layout schemes, we used the time history analysis method, and obtained the efficiencies of wind-induced vibration control. LRD deformation research proved that the damp of all LRDs was efficient under the designed wind velocity when they were laid along the edge of tower heads. We studied the controlling efficiency resulting fTom only applying stiffness to the tower polos where the dampers used to be laid under the designed wind velocity. The results show that the controlling efficiency was not ideal when the stiffness is increased on the poles only. Therefore, LRD should conlxibute to both the stiffness and damp of a structure to effectively reduce the dynamic response of a tower-line coupling system under strong winds. We also discussed the controlling efficiency of LRD under static winds. The results show that there was little difference between displacements derived by the finite clement time history method and those obtained by static wind method conducted by a design institute. This means the simulation on space relevant wind velocity field was accurate and reasonable.展开更多
To study the wind vibration response of power transmission tower, the lead viscoelastic dampers （LVDs） were applied to a cup tower. With time history analysis method, the displacement, velocity, acceleration and for...To study the wind vibration response of power transmission tower, the lead viscoelastic dampers （LVDs） were applied to a cup tower. With time history analysis method, the displacement, velocity, acceleration and force response of the tower was calculated and analyzed. The results show that the control effect of lead viscoelastic dampers is very good, and the damping ratio can reach 20% or more when they are applied to the tower head.展开更多
By combining the time-history response analysis and the eigenvalue buckling analysis, this paper developed a computational procedure to study the elastic dynamic stability of a transmission tower by APDL language in A...By combining the time-history response analysis and the eigenvalue buckling analysis, this paper developed a computational procedure to study the elastic dynamic stability of a transmission tower by APDL language in ANSYS. The influences of different input directions of seismic excitations and damping ratio on the elastic dynamic stability of tower were discussed. The following conclusions were obtained： （ 1 ） Longitudinal direction of the transmission lines is the worst input direction of seismic excitation for the transmission tower. （2） Dead load has no significant effect on the critical load and the occurrence time of buckling. （3） Vertical input of seismic excitations has no great effect on the dynamic stability of the transmission tower. （4） Damping effect has an influence on the dynamic stability of the transmission tower; however, the inherent characteristics of dynamic buckling is not changed.展开更多
Transmission towers play a crucial role in overhead transmission line systems and are the key target of transmission line inspections.With the help of remote sensing technology,transmission towers can be effectively d...Transmission towers play a crucial role in overhead transmission line systems and are the key target of transmission line inspections.With the help of remote sensing technology,transmission towers can be effectively detected in wide areas at reasonable costs and in a relatively short time period.However,it is difficult to identify the type of transmission towers in optical remote sensing images due to detail degradation caused by long-distance and high-altitude imaging.This paper proposes a transmission tower detection method in optical remote sensing images using an oriented object detector and object and shadow joint detection.To enrich the information,the transmission towers and their shadows are jointly detected through a CenterNet detector with an orientation prediction branch.To improve the detection accuracy of difficult objects,attention and deformable convolutional network modules are introduced to the backbone and orientation prediction branches,respectively.Considering the orientation and the aspect ratio of the objects and shadows,a focal loss function with an aspect ratio is employed to further improve the accuracy.Object and shadow joint detection are separately realized through the one-box and multi-box detection strategies.A transmission tower dataset RSITT labeled with horizontal and oriented boxes is established.Experiments conducted on the RSITT dataset have demonstrated that the detection accuracy and recall rate of the proposed joint detection algorithm reached 73.2%and 95.2%.展开更多
Rapid developments in EHV/UHV transmission systems require a deeper understanding of the mechanism of long air gap discharge.Leader propagation is one of the main processes in long gap breakdown.In this paper,the lead...Rapid developments in EHV/UHV transmission systems require a deeper understanding of the mechanism of long air gap discharge.Leader propagation is one of the main processes in long gap breakdown.In this paper,the leader propagation characteristics of real size±800 kV UHVDC transmission tower gaps under positive switching impulse voltages(185/2290μs)are investigated.An integrated observation platform consisting of an impulse voltage divider,a coaxial shunt,a high-speed video camera,and a set of integrated optical electric field sensors(IOES),is established.The waveforms of impulse voltage,discharge current,electric field variation at specific positions,and time-resolved photographs of discharge morphology are recorded.Axial leader velocity and the relationship between leader advancements and injected charge are obtained.The typical value of leader stable propagation velocity is 1.7–2.2 cm/μs,which varies slightly with the gap length and applied voltage amplitude.The leader velocity in the re-illumination process is much higher,and is seen as varying from 5 cm/μs to 30 cm/μs,with an average value around 10 cm/μs.The charge in leader channel per unit length is 20–40μC/m,which illustrates a near-direct proportion relationship between discharge current and leader velocity.The observed parameters are important for further simulation of the tower gap breakdown processes.展开更多
Big data technology is more and more widely used in modern power systems.Efficient collection of big data such as equipment status,maintenance and grid operation in power systems,and data mining are the important rese...Big data technology is more and more widely used in modern power systems.Efficient collection of big data such as equipment status,maintenance and grid operation in power systems,and data mining are the important research topics for big data application in smart grid.In this paper,the application of big data technology in fast image recognition of transmission towers which are obtained using fixed-wing unmanned aerial vehicle(UAV)by large range tilt photography are researched.A method that using fast region-based convolutional neural networks(Rcnn)convolutional architecture for fast feature embedding(Caffe)to get deep learning of the massive transmission tower image,extract the image characteristics of the tower,train the tower model,and quickly recognize transmission tower image to generate power lines is proposed.The case study shows that this method can be used in tree barrier modeling of transmission lines,which can replace artificial identification of transmission tower,to reduce the time required for tower identification and generating power line,and improve the efficiency of tree barrier modeling by around 14.2%.展开更多
The transmission line tower will be affected by bad weather and artificial subsidence caused by the foundation and other factors in the power transmission.The tower’s tilt and severe deformation will cause the buildi...The transmission line tower will be affected by bad weather and artificial subsidence caused by the foundation and other factors in the power transmission.The tower’s tilt and severe deformation will cause the building to collapse.Many small changes caused the tower’s collapse,but the early staff often could not intuitively notice the changes in the tower’s state.In the current tower online monitoring system,terminal equipment often needs to replace batteries frequently due to premature exhaustion of power.According to the need for real-time measurement of power line tower,this research designed a real-time monitoring device monitoring the transmission tower attitude tilting and foundation state based on the inertial sensor,the acceleration of 3 axis inertial sensor and angular velocity raw data to pole average filtering pre-processing,and then through the complementary filtering algorithm for comprehensive calculation of tilt angle,the system meets the demand for inclined online monitoring of power line poles and towers regarding measurement accuracy,with low cost and power consumption.The optimization multi-sensor cooperative detection and correction measured tilt angle result relative accuracy can reach 1.03%,which has specific promotion and application value since the system has the advantages of unattended and efficient calculation.展开更多
In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave th...In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave threat to the power grid security.The cause of the accident and the accident process were studied for the sake of further understanding of the impact of lightning on power grid.As an example,110 kV double circuit transmission line(Xilong-line) was analyzed.At first,the system topology was given.Through the analysis on relay protection actions and the fault recorder data,over voltage on the insulator strings was calculated.Based on the analysis and the calculation,accident cause and the process were presented respectively.Secondly,it comes to the conclusion that the lightning failure was caused by counterattack.The wave of the lightning over voltage would spread to the not grounded neutral point of the transformers,and make the neutral protective gap breakdown,then cause freewheeling with the frequency of 50 Hz.As results of the relay protection,the double circuit transmission line all tripped out.Finally,the causes of the accident were proposed that included terrain features,large corner towers,strong thunderstorm weather and poor grounded contact of the tower.展开更多
This paper describes the functions and the features of the integrated system of aerial survey and tower locations optimization for transmission lines, which includes all stages from data acquisition, data transmission...This paper describes the functions and the features of the integrated system of aerial survey and tower locations optimization for transmission lines, which includes all stages from data acquisition, data transmission and data processing to automatic optimization of the tower locations and drawing. The paper also briefly describes the economic benefit gained from this system, and finally proposes the directions of the future development for this system.展开更多
Transmission tower-line systems are designed using static loads specified in various codes. This paper compares the dynamic response of a test transmission line with the response due to static loads given by Eurocode....Transmission tower-line systems are designed using static loads specified in various codes. This paper compares the dynamic response of a test transmission line with the response due to static loads given by Eurocode. Finite element design software SAP2000 was used to model the towers and lines. Non-linear dynamic analysis including the large displacement effects was carried out. Macroscopic aspects of wind coherence along element length and integration time step were investigated. An approach is presented to compare the probabilistic dynamic response due to 7 different stochastically simulated wind fields with the response according to EN-50341. The developed model will be used to study the response recorded on a test line due to the actual wind speed time history recorded. It was found that static load from EN overestimated the strength of conductor cables. The response of coupled system considering towers and cables was found to be different from response of only cables with fixed supports.展开更多
There is a considerable number of works devoted to electrical characteristics of grounding. These characteristics are important in general. However, in application to grounding of transmission line towers they are not...There is a considerable number of works devoted to electrical characteristics of grounding. These characteristics are important in general. However, in application to grounding of transmission line towers they are not enough to determine what grounding construction is preferable in some particular case, because these characteristics are calculated or measured apart from the grounded object, and only limited number of current （or voltage） source waveforms is used. This paper indicates reasons in favor of the fact that to choose the optimum design of grounding, the calculation model should include the tower as it is. The probability of back flashover, which provides both qualitative and quantitative estimate of the grounding structure efficiency, can be taken as the criterion for the grounding design. The insulation flashover probability is calculated on the basis of engineering method, which evaluates breakdown strength of insulation for nonstandard waveshapes, and probability data on lightning currents. Different approaches are examined for identifying the back flashover probability, as not only amplitudes but also other parameters can be taken into account. Finite-difference time-domain method is used for calculations of transients. It is found that lightning current waveform can greatly influence calculated back flashover probability value.展开更多
基金The Youth Foundation Project of Jiangsu Province(No.BK20230337)the Natural Science Research of Jiangsu Higher Education Institutions of China(No.22KJB560004)the National Natu-ral Science Foundation of China(No.52278523)。
文摘Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect the safety and stability of transmission towers.In this study,the effects of bolt joint loosening on the dynamic characteristics of a 220-kV angle steel transmission tower are the main topic of concern.First,the mechanical properties of typical joints subjected to different degrees of bolt loosening are studied by finite solid-element simulation,based on which a finite hybrid-element modeling method is developed for a tower structure suffering varying loose degrees in the joints.Taking a 220-kV angle steel transmission tower as the object,the influence of the position and degree of loosening on the tower’s natural frequencies and mode shapes are simulated and discussed.The results demonstrate that the main-member splice joint and the main diagonal-horizontal member gusset plate joint account for the dominant impact on the dynamic characteristics of the tower.In addition,the dominant joint shifts from the main-member splice joint to the main diagonal-horizontal member gusset plate joint as the considered modal order increases.In the case of double joints loosening simultaneously,the loosening of nondomi-nant joints has nonnegligible effects on the tower as well.
基金supported by the National Natural Science Foundation of China(No.61702347)Hebei Academy of Sciences Basic Research Operating Fund Project(No.2025PF21)。
文摘To address the challenges of multi-scale differences,complex background interference,and unstable small target positioning in visual inspection of power towers,the existing methods still face issues such as insufficient feature interaction and unstable confidence estimation,which lead to performance degradation in complex backgrounds and occlusion conditions.This paper proposes a precise inspection method for key power tower components using autonomous drone positioning.To this end,this paper makes three key improvements to the you only look once version 11(YOLOv11)framework.First,it constructs C3k2-adaptive multi-receptive field block(C3k2-AMRB),combining multiple dilated convolutions with a reparameterization mechanism to significantly expand the receptive field and enhance multi-scale feature extraction.Second,it designs a hierarchical wavelet interaction unit(HWIU),which leverages high-and low-frequency decomposition and reconstruction of wavelet transform(WT)to achieve cross-scale semantic alignment,enhancing feature discriminability in complex backgrounds.Third,it proposes a distribution-aware confidence refinement head(DACR-Head),which adaptively calibrates classification confidence based on the statistical characteristics of the predicted bounding-box corner distribution,improving the localization stability and accuracy of small targets.Experiments on the inspection of power line assets dataset(InsPLAD)dataset show that the integrated approach achieves a component detection accuracy at intersection over union(IoU)=0.5(CDA_(50))of 88.3%and a component detection robustness(CDR_(50:95))of 69.8%,respectively,improvements of 4.4%and 7.0%over the baseline.
基金National Natural Science Foundation of China(No.50004008)Xuzhou Power Supply Company and the Fundamental Research Funds for the Central Universities(No.2011QNB18) for their financial and technical support for this work
文摘Given the background of a transmission tower erected on a particular mining subsidence area,we used finite element modeling to analyze the anti-deformation performance of transmission towers under a number of different load conditions,including horizontal foundation displacement,uneven vertical downward displacement,wind loads and icing conditions.The results show that the failure in stability of a single steel angle iron represents the limit of the tower given ground deformation.We calculated the corresponding limits of foundation displacements.The results indicate that compression displacement of the foundation is more dangerous than tension displacement.Under complex foundation displacement conditions,horizontal foundation displacement is a key factor leading to failure in the stability of towers.Under conditions of compression or tension displacement of the foundation,wind load becomes the key factor.Towers do not fail when foundation displacements are smaller than 1% (under tension) or 0.5% (under horizontal compression or single foundation subsidence) of the distance between two supports.
基金National Natural Science Foundation of China Under Grant No.50638010Foundation of Ministry of Education for Innovation Group Under Grant No.IRT0518
文摘In this paper,an analytical framework to evaluate the along-wind-induced dynamic responses of a transmission tower is presented.Two analytical models and a new method are developed:(1)a higher mode generalized force spectrum(GFS)model of the transmission tower is deduced;(2)an analytical model that includes the contributions of the higher modes is further derived as a rational algebraic formula to estimate the structural displacement response;and(3)a new approach,applying load with displacement(ALD)instead of force,to solve the internal force of transmission tower is given.Unlike conventional methods,the ALD method can avoid calculating equivalent static wind loads(ESWLs).Finally,a transmission tower structure is used as a numerical example to verify the feasibility and accuracy of the ALD method.
基金the National Natural Science Foundation of China (No. 50004008)the Science Fund of China University of Mining and Technology (No. OB061045)
文摘A large number of high-voltage power transmission towers have recently been constructed in mining areas prone to subsidence. In order to ensure the safety of the transmission towers and the safe operation of transmission systems, it is imperative to carry out research on the anti-deformation performance of transmission towers. In our study, we performed experiments on the anti-deformation performance of a transmission tower in a subsidence area on a scale model with a geometric scale ratio of 1:5 and analyzed the failure mechanism of the tower members. The results show that, when the axial distance between two supports changes, destabilization failure most likely occurs in the members of the bottom transverse layer because some parts of the main diagonal member bars yield under the action of compression. The failure mechanism of the tower members basically coincides with the lever principle.
文摘The earthquake resistance of transmission tower has been often discussed from the viewpoint of reinforcing the foundation of steel tower, but there are also few studies considering the damping characteristics of the tower. This paper focuses on the viscous damper which has been adopted for seismic reinforcement of bridges in recent years. The purpose of this study is to improve the seismic performance of steel tower by giving the high damping to the tower. We construct a single tower model considering the influence of transmission line, and then simulate the vibration characteristics and seismic behavior of the tower by the eigenvalue analysis and the dynamic response analysis. The results show that the transmission tower with viscous damper can reduce its own response effectively and drastically. This research concludes that it is necessary to consider the extreme increase of steel tower＇s response depending on the seismic wave and the collapse of steel tower can be avoided by using the optimum damper in the design of the transmission tower.
基金Funded by the Science and Technology Research Project of the State Grid Corporation (No. [2007]413)
文摘We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1 000 kV transmission line project in P. R. China. The height of the cup tower is 181 m with a ground elevation of 47 m, which makes it a super flexible and wind-sensitive structure. Therefore, we should analyze the wind- resistant capacity of the system. We simulated applicable transverse fluctuating wind velocity field, developed a lead-rubber damper （LRD） for controlling wind-induced vibration of long-span transmission towers, deduced LRD calculation model parameter, and researched the best layout scheme and installation method of LRD. To calculate the wind-induced response of tower-line coupling system in seven layout schemes, we used the time history analysis method, and obtained the efficiencies of wind-induced vibration control. LRD deformation research proved that the damp of all LRDs was efficient under the designed wind velocity when they were laid along the edge of tower heads. We studied the controlling efficiency resulting fTom only applying stiffness to the tower polos where the dampers used to be laid under the designed wind velocity. The results show that the controlling efficiency was not ideal when the stiffness is increased on the poles only. Therefore, LRD should conlxibute to both the stiffness and damp of a structure to effectively reduce the dynamic response of a tower-line coupling system under strong winds. We also discussed the controlling efficiency of LRD under static winds. The results show that there was little difference between displacements derived by the finite clement time history method and those obtained by static wind method conducted by a design institute. This means the simulation on space relevant wind velocity field was accurate and reasonable.
基金Research Fund of Chinese State Grid Company (No.SGKJ[2007]413)
文摘To study the wind vibration response of power transmission tower, the lead viscoelastic dampers （LVDs） were applied to a cup tower. With time history analysis method, the displacement, velocity, acceleration and force response of the tower was calculated and analyzed. The results show that the control effect of lead viscoelastic dampers is very good, and the damping ratio can reach 20% or more when they are applied to the tower head.
基金The National Natural Science Foundation of China (No.50878093)
文摘By combining the time-history response analysis and the eigenvalue buckling analysis, this paper developed a computational procedure to study the elastic dynamic stability of a transmission tower by APDL language in ANSYS. The influences of different input directions of seismic excitations and damping ratio on the elastic dynamic stability of tower were discussed. The following conclusions were obtained： （ 1 ） Longitudinal direction of the transmission lines is the worst input direction of seismic excitation for the transmission tower. （2） Dead load has no significant effect on the critical load and the occurrence time of buckling. （3） Vertical input of seismic excitations has no great effect on the dynamic stability of the transmission tower. （4） Damping effect has an influence on the dynamic stability of the transmission tower; however, the inherent characteristics of dynamic buckling is not changed.
基金supported by the National Key R&D Program of China(2020YFB0905900).
文摘Transmission towers play a crucial role in overhead transmission line systems and are the key target of transmission line inspections.With the help of remote sensing technology,transmission towers can be effectively detected in wide areas at reasonable costs and in a relatively short time period.However,it is difficult to identify the type of transmission towers in optical remote sensing images due to detail degradation caused by long-distance and high-altitude imaging.This paper proposes a transmission tower detection method in optical remote sensing images using an oriented object detector and object and shadow joint detection.To enrich the information,the transmission towers and their shadows are jointly detected through a CenterNet detector with an orientation prediction branch.To improve the detection accuracy of difficult objects,attention and deformable convolutional network modules are introduced to the backbone and orientation prediction branches,respectively.Considering the orientation and the aspect ratio of the objects and shadows,a focal loss function with an aspect ratio is employed to further improve the accuracy.Object and shadow joint detection are separately realized through the one-box and multi-box detection strategies.A transmission tower dataset RSITT labeled with horizontal and oriented boxes is established.Experiments conducted on the RSITT dataset have demonstrated that the detection accuracy and recall rate of the proposed joint detection algorithm reached 73.2%and 95.2%.
基金supported by the National Natural Science Foundation of China under Grant 51325703,51377094Fund of the National Priority Basic Research of China(2011CB209403)。
文摘Rapid developments in EHV/UHV transmission systems require a deeper understanding of the mechanism of long air gap discharge.Leader propagation is one of the main processes in long gap breakdown.In this paper,the leader propagation characteristics of real size±800 kV UHVDC transmission tower gaps under positive switching impulse voltages(185/2290μs)are investigated.An integrated observation platform consisting of an impulse voltage divider,a coaxial shunt,a high-speed video camera,and a set of integrated optical electric field sensors(IOES),is established.The waveforms of impulse voltage,discharge current,electric field variation at specific positions,and time-resolved photographs of discharge morphology are recorded.Axial leader velocity and the relationship between leader advancements and injected charge are obtained.The typical value of leader stable propagation velocity is 1.7–2.2 cm/μs,which varies slightly with the gap length and applied voltage amplitude.The leader velocity in the re-illumination process is much higher,and is seen as varying from 5 cm/μs to 30 cm/μs,with an average value around 10 cm/μs.The charge in leader channel per unit length is 20–40μC/m,which illustrates a near-direct proportion relationship between discharge current and leader velocity.The observed parameters are important for further simulation of the tower gap breakdown processes.
基金Technology project of Guangdong power grid(key technologies research on intelligent inspection of Multi-rotor UAVs in transmission lines)under Grant No.GDKJXM20162155(030600KK52160027).
文摘Big data technology is more and more widely used in modern power systems.Efficient collection of big data such as equipment status,maintenance and grid operation in power systems,and data mining are the important research topics for big data application in smart grid.In this paper,the application of big data technology in fast image recognition of transmission towers which are obtained using fixed-wing unmanned aerial vehicle(UAV)by large range tilt photography are researched.A method that using fast region-based convolutional neural networks(Rcnn)convolutional architecture for fast feature embedding(Caffe)to get deep learning of the massive transmission tower image,extract the image characteristics of the tower,train the tower model,and quickly recognize transmission tower image to generate power lines is proposed.The case study shows that this method can be used in tree barrier modeling of transmission lines,which can replace artificial identification of transmission tower,to reduce the time required for tower identification and generating power line,and improve the efficiency of tree barrier modeling by around 14.2%.
基金This work was supported by the National Natural Science Foundation of China(Nos.62172242,51901152)Industry University Cooperation Education Program of the Ministry of Education(No.2020021680113)Shanxi Scholarship Council of China.
文摘The transmission line tower will be affected by bad weather and artificial subsidence caused by the foundation and other factors in the power transmission.The tower’s tilt and severe deformation will cause the building to collapse.Many small changes caused the tower’s collapse,but the early staff often could not intuitively notice the changes in the tower’s state.In the current tower online monitoring system,terminal equipment often needs to replace batteries frequently due to premature exhaustion of power.According to the need for real-time measurement of power line tower,this research designed a real-time monitoring device monitoring the transmission tower attitude tilting and foundation state based on the inertial sensor,the acceleration of 3 axis inertial sensor and angular velocity raw data to pole average filtering pre-processing,and then through the complementary filtering algorithm for comprehensive calculation of tilt angle,the system meets the demand for inclined online monitoring of power line poles and towers regarding measurement accuracy,with low cost and power consumption.The optimization multi-sensor cooperative detection and correction measured tilt angle result relative accuracy can reach 1.03%,which has specific promotion and application value since the system has the advantages of unattended and efficient calculation.
文摘In recent years,several failures of double circuit transmission line on the same tower due to lightning were happened in Beijing power grid.Although it can be reclosed successful,the lightning strike caused a grave threat to the power grid security.The cause of the accident and the accident process were studied for the sake of further understanding of the impact of lightning on power grid.As an example,110 kV double circuit transmission line(Xilong-line) was analyzed.At first,the system topology was given.Through the analysis on relay protection actions and the fault recorder data,over voltage on the insulator strings was calculated.Based on the analysis and the calculation,accident cause and the process were presented respectively.Secondly,it comes to the conclusion that the lightning failure was caused by counterattack.The wave of the lightning over voltage would spread to the not grounded neutral point of the transformers,and make the neutral protective gap breakdown,then cause freewheeling with the frequency of 50 Hz.As results of the relay protection,the double circuit transmission line all tripped out.Finally,the causes of the accident were proposed that included terrain features,large corner towers,strong thunderstorm weather and poor grounded contact of the tower.
文摘This paper describes the functions and the features of the integrated system of aerial survey and tower locations optimization for transmission lines, which includes all stages from data acquisition, data transmission and data processing to automatic optimization of the tower locations and drawing. The paper also briefly describes the economic benefit gained from this system, and finally proposes the directions of the future development for this system.
文摘Transmission tower-line systems are designed using static loads specified in various codes. This paper compares the dynamic response of a test transmission line with the response due to static loads given by Eurocode. Finite element design software SAP2000 was used to model the towers and lines. Non-linear dynamic analysis including the large displacement effects was carried out. Macroscopic aspects of wind coherence along element length and integration time step were investigated. An approach is presented to compare the probabilistic dynamic response due to 7 different stochastically simulated wind fields with the response according to EN-50341. The developed model will be used to study the response recorded on a test line due to the actual wind speed time history recorded. It was found that static load from EN overestimated the strength of conductor cables. The response of coupled system considering towers and cables was found to be different from response of only cables with fixed supports.
文摘There is a considerable number of works devoted to electrical characteristics of grounding. These characteristics are important in general. However, in application to grounding of transmission line towers they are not enough to determine what grounding construction is preferable in some particular case, because these characteristics are calculated or measured apart from the grounded object, and only limited number of current （or voltage） source waveforms is used. This paper indicates reasons in favor of the fact that to choose the optimum design of grounding, the calculation model should include the tower as it is. The probability of back flashover, which provides both qualitative and quantitative estimate of the grounding structure efficiency, can be taken as the criterion for the grounding design. The insulation flashover probability is calculated on the basis of engineering method, which evaluates breakdown strength of insulation for nonstandard waveshapes, and probability data on lightning currents. Different approaches are examined for identifying the back flashover probability, as not only amplitudes but also other parameters can be taken into account. Finite-difference time-domain method is used for calculations of transients. It is found that lightning current waveform can greatly influence calculated back flashover probability value.
