UHV Transmission Research Articles

Susceptibility Analysis of Land Subsidence along the Transmission Line in the Salt Lake Area Based on Remote Sensing Interpretation

As the influence of extreme climate and human engineering activities intensifies, land subsidence frequently occurs in the Salt Lake area of Qinghai Province, China, which seriously threatens the stability of the UHV transmission line crossing the area. Current susceptibility analyses of land subsidence disasters have mostly focused on the classification of land subsidence susceptibility and have ignored the differentiation of susceptibility among different land subsidence intensities. Therefore, the land subsidence susceptibility map does not meet the operation and maintenance management needs of the UHV transmission line, let alone planning and designing of new lines in the Salt Lake area. Therefore, in this study, we proposed a susceptibility analysis of different land subsidence intensities along the transmission line in the Salt Lake area. The small baseline integrated aperture radar interferometry (SBAS-InSAR) method was used to obtain the land subsidence along the transmission line based on 67 Sentinel-1 remote sensing interpretation datasets from 2017 to 2021. Based on a combination of K-means clustering and the transmission line specifications, four annual land subsidence intensity grades were identified as 0~−2 mm/year, −2~−10 mm/year, −10~−20 mm/year, and <−20 mm/year. In addition, eight geological environmental factors were analyzed, and a multi-layer perceptron neural network (MLPNN) model was used to calculate the susceptibility of the different land subsidence intensities. The area under the curve (AUC) and practical examples were used to verify the reliability of the different land subsidence intensities susceptibility mapping. The AUC values of the four subsidence intensity grades showed that the results were accurate: the <−20 mm/year grade produced the largest AUC (0.951), with the −10~−20 mm/year, −2~−10 mm/year and 0~−2 mm/year grades producing AUCs of 0.926, 0.812, 0.879, respectively. At the same time, the susceptibility classification results of different land subsidence intensities were consistent with the interpretation and site tower deformation. The results of this study provided the distribution of land subsidence susceptibility along the transmission line, distinguished the susceptibility of different land subsidence intensities, and provided more detailed subsidence information for each transmission tower. The results provide important information for transmission line tower planning, design, protection, and operation management.

Research on the Influence of Various Attribute Factors on Passive Interference in UHV Transmission Lines Based on Orthogonal Test

Considering the problem of passive interference caused by electromagnetic scattering effects of transmission lines to neighboring radio stations and other communication equipment, this paper refines the passive interference calculation model for UHV transmission lines. The solution calculation is carried out by the Method of Moments, and the law of passive interference effect of the tower structure, auxiliary angles, and ground roughness under different frequency incident waves, is summarized. By designing an orthogonal test, the degree of influence of the above attributing factors on passive interference results in the established joint model of three towers with two stall distances was explored by using Analysis of Variance. The results demonstrate that both auxiliary angles and rough ground show a pattern of enhanced electromagnetic scattering effect with increasing plane wave frequency in single-factor analysis. When multiple factors are combined, the rough ground has a significant effect on the results. This method effectively evaluates the passive interference influence factor while reducing the modeling and simulation engineering and provides a reference for the passive interference prediction in subsequent practical projects.

Investigation on the Critical Wind Speed of Instability Failure of UHV Transmission Tower-line Coupling System under Typhoon

Wind is one of the most destructive external loads of transmission lines, and typhoon-caused severe damage or even destruction of electric power facilities occurred frequently. In order to research the critical wind speed of instability failure of UHV transmission tower-line coupling system under typhoon, the UHV transmission line in Zhejiang is chosen as the research subject and a finite element model of the UHV tower-line coupling system is established. By using the improved generalized force calculation method, the dynamic response of the transmission tower is converted to the static response. Then the LRC method is used to calculate the equivalent static wind load of the tower and obtains the wind response of the UHV transmission tower-line coupling system. The results show that under the typhoon wind field, the component at the junction of the tower head and the body first reaches the supercritical state. Specifically, when the wind speed at 10-meters height reaches 31m/s, the profile component of the tower head will be damaged. With the increase of wind speed, the damaged area of the tower head also expends. When the wind speed at 10-meters height reaches 37m/s, the main load-bearing component of the tower head-body junction will lose its stability, which will directly threaten the safety of the transmission tower.

Numerical Analysis on the Sub-Span Oscillation of Iced Eight-Bundle Conductors During Galloping

Under the excitement of wind loads, UHV transmission lines are subject to two types of vibration phenomena, namely, sub-span oscillation and galloping. This phenomenon can easily lead to conductor breakage, interphase flashover, fatigue damage to fittings, and even lead to tower collapse and disconnection accidents. The numerical analysis method is used to analyze the sub-span oscillation characteristics of the eight-bundle conductor during galloping. The results of the numerical simulation are compared to explore the influence of wind speed, span length, initial angle of wind attack, and turbulence intensity on the galloping line, looking for movement characteristics between each sub-conductor. The results provide a reference for research on the galloping principle of UHV transmission line and anti-oscillation to further improve the resistance of the power grid against disaster ability.

Improved Electrogeometric Model of UHV Transmission Line Based on Long Gap Discharge and Its Application

Based on long air gap discharge test data and lightning return stroke observation data, an improved electrogeometric model (EGM) considering terrain conditions is established and verified to analyze the lightning shielding performance of UHV transmission lines. The striking distance formula is modified as rs = 0.13 (I2 + 40I)0.814. In this paper, the lightning shielding failure rate of three-phase conductors of EHV and UHV transmission lines calculated by the improved EGM model is consistent with the lightning observation data of actual transmission lines in Japan and the scaled lightning discharge simulation experimental results of UHV transmission lines in plains and mountainous areas of China, which verifies the applicability of the improved EGM model to evaluate the lightning shielding performance of large-scale UHV transmission lines. The improved EGM model is applied to evaluate the influence of tower type and slope steepness on the shielding failure tripping rate of UHV transmission lines. The shielding failure tripping rate of the SZ322 tower is higher than that of the SZT1 tower, and the shielding failure tripping rate of UHV transmission lines is greatly affected by slope gradient and increases with the increase of slope gradient.

Numerical Simulation of Wind-induced Swing Angle of 1000kV Transmission Line Suspension Insulator Strings Considering Dynamic Response

The wind-induced swing angle of insulator strings directly affects the electrical insulation performance and the construction cost of the UHV transmission project. However, due to not considering the fluctuating wind pressure, the calculation results of wind-induced swing tend to be conservative when adopting the recommended guidelines of standard especially in the face of severe weather. This paper simulates the transient wind field of strong winds based on time-space correlation characteristics and constructs the fluctuating wind load distribution model exerting on the UHV transmission line. Then a refined finite element model of the multi-span transmission line including the entire tensile section is established. And the swing angle of the insulator strings calculation formula is fitted based on the calculation results of the wind-induced swing response. The calculation result shows the swing angle decreases with the increase of ice thickness, and the magnified coefficient of the wind-induced swing angle at the target tower under the basic wind speed of 15m/s is 1.03.

Simulation Research on Die Forging Process Optimization of the FDN Type Anti-vibration Hammer Head in UHV Transmission Lines

Traditional anti-vibration hammer heads are mainly manufactured by gravity casting technology, which has many internal defects and limited mechanical properties, which cannot meet the technical requirements for higher-strength anti-vibration hammers in the construction of UHV transmission lines. Die forging is an advanced material forming process for producing low defect and high strength anti-vibration hammer. However, the process parameters should be strictly controlled to realize the complete filling of forgings and reduce the damage of forgings and dies.In this paper, the die forging process of the FDN type anti-vibration hammer head was simulated by using Deform-3D software platform, and the optimal forging process parameters were proposed as follows: the diameter of the blank is 65mm, the length of the blank is 184mm, the pressing speed of the upper die is 200mm/s, and the preheating temperature range of the blank is 800?∼1000?. The mechanical properties of the anti-vibration hammer after process optimization met the requirements of the corresponding strength grade products.

Design and Mechanics Analysis of Tools for Live Replacement of UHV Whole String Insulators

The experimental results show that the method can effectively detect the contamination degree of the contact net insulator The replacement of whole string insulators is difficult tasks of live working for UHV transmission line and still remain blank. Based on the structure and layout of straight string and tensile string insulators of UHV transmission lines, this paper proposes design of tools for live replacement of the whole string insulators. Through three-dimensional simulation and analysis, the force characteristics of the various tools are determined, and developed the tools for live replacement of the whole string insulators of UHV, and the mechanical test of the tools are carried out. The test results confirm the feasibility of the tool design and the reliability of the mechanical simulation model proposed in this paper, which provides technical supports for the live replacement of UHV whole string insulators.

On-line Measurement Method and Technical Scheme of Transmission Line Crossing Point Based on Machine Vision

With the increasing demand for high voltage and UHV transmission, higher and higher requirements are put forward for transmission line monitoring and fault diagnosis. The traditional line measurement method has many shortcomings, which cannot ensure the measurement accuracy, measurement efficiency and high cost. Based on this, this paper first studies the principle of machine vision on-line measurement, then analyses the on-line measurement process of transmission line crossing point based on machine vision, and finally gives the error source and amelioration measures of transmission line crossing point on-line measurement.

Simulation analysis and calculation of electric field distribution characteristics of UHV wall bushing

Facing the unbalanced development of resource distribution and productivity, China needs long-distance power transmission and distribution. The long-distance power transmission will lead to a lot of power loss in the process of transmission. In order to achieve long-distance, large capacity, low loss power transmission, it is necessary to build UHV transmission and transformation lines in the power grid for cross regional power allocation. As the key equipment in UHV transmission and transformation, UHV bushing plays a very important role in UHV transmission and transformation line. However, due to working in UHV electric field for a long time, the reduction of UHV bushing failure rate is very important for the smooth operation of UHV transmission line. Therefore, it is necessary to study the electric field distribution characteristics of UHV bushing. In this paper, the electric field distribution characteristics of UHV through wall bushing are studied. The simulation analysis and calculation of electric field are carried out by using COMSOL Multiphysics finite element software. By analyzing the electric field distribution of the complex field areas such as the central conductor of the bushing, the end of the liner, the sheath and the capacitor core, the electric field distribution law and the edge electric field diagram of the bushing and its adjacent key areas under different voltage types are obtained. The radial axial electric field distribution of the capacitor core and the edge electric field distribution of the upper and lower steps are compared and analyzed Based on the analysis of the characteristics and local complex field, the variation law of the electric field distribution of the bushing with the structure design is obtained, which provides an optimization idea for the insulation structure design of UHV through wall bushing.

Design of electromagnetic induction calculation and auxiliary calculation software under UHV transmission line

With the development of 1000 kV UHV transmission technology and the shortage of line corridor resources, UHV will inevitably cross the building area. Although many scholars had studied the power frequency electromagnetic field under UHV AC transmission line, it is very difficult to accurately calculate the electric field strength and induced voltage, which cannot be applied in engineering. At present, there is no relevant literature to study the problem of induced electricity in buildings with a large number of steel frame structures under the line and the estimation method of induced electricity in buildings. By summarizing and analyzing the simulation data, the estimation method of induced voltage and induced current density of steel frame buildings under UHV lines was proposed. An auxiliary calculation system was developed. The calculated values of the software were compared with the measured values, which accuracy of voltage and current can reach 91.5% and 92.7%, and fully meet the engineering needs.

Control and application of ultra-high voltage insulator cleaning and detecting robot

With the development of global energy Internet and demand for UHV transmission, uHV transmission lines will increase rapidly and become more and more important for national economic development. The uHV transmission lines will increase year by year and become increasingly important to the economic development of the country. It is necessary to study the cleaning and detection technology of transmission line insulators that the insulators of UHVDC transmission lines such as large leakage rate, low detection efficiency and difficult cleaning of insulators. Therefore, the development of uhv transmission line insulator hot-line cleaning robot and detection integration has important engineering significance and practical value to improve the level of the operation of the uhv power transmission engineering maintenance, safe and reliable operation of the protection of uhv transmission lines. In this paper, the research on the integrated robot for live cleaning and detection of uHV transmission line insulators will greatly promote the live operation of UHV transmission lines in China. It can be directly applied to the live operation of UHV DC and can be promoted nationwide.

Simulation calculation and comparative analysis of three-dimensional temperature field of ultra high voltage through wall bushing under different current carrying capacity

As the key equipment of UHV transmission and transformation line, UHV bushing needs to carry the ultra-high voltage and large current of UHV power system at the same time. When the operating temperature of UHV bushing is too high, the operation failure rate will increase significantly, which will affect the stability and safety of UHV transmission line. Therefore, it is particularly important to analyze the temperature field characteristics of UHV bushing. This paper takes UHV bushing as the research object. The finite element software is used to calculate the electro thermal coupling. The three-dimensional thermal field distribution characteristics of UHV bushing are simulated and analyzed. This paper analyzes the influence of eddy current on the temperature distribution of UHV bushing under operation condition, and discusses the influence degree of eddy current on the temperature distribution of bushing, which provides an important basis for the temperature distribution, structure improvement and operation maintenance of bushing.

Differential design based on double pendulum anti-galloping device for important line

Based on the differential anti-galloping concept and Double Pendulum Anti-galloping Device, optimization analysis was carried out for the ordinary span and long span of 1000 kV Ultra-High-Voltage AC transmission project. Based on the full investigation of the design conditions of ordinary span and long span of the UHV AC line, and the stability mechanism, the influence of the theoretical pendulum length values of Double Pendulum Anti-galloping Device on the instability characteristics of iced conductor with different icing thickness and ambient wind speed were calculated and analyzed. The results showed that 900 mm should be taken as the theoretical pendulum length of the ordinary span, and 800 mm for the long span, which can obtain the best anti-galloping effect, which provides a reliable reference for the anti-galloping design of subsequent UHV transmission lines.

Simulation Research on Electric Field Distribution of Insulator String in ULTRA High Voltage Transmission Line

Insulators are one of the important components of overhead transmission lines. Because of their excellent characteristics, insulators have obvious advantages in the selection of external insulation in UHV AC transmission projects. The potential distribution of insulator string is not even due to the shape characteristics of insulator string, the structure of metal tool, the low conductivity of silicon rubber material and the stray capacitance between insulator string and wire, iron tower and metal tool. When the surface field intensity of insulators and fittings exceeds the initial field intensity, corona discharge will occur, which will affect the electromagnetic environment and the operation characteristics of insulating materials. Therefore, it is of great significance to determine the potential distribution of insulator strings of UHV transmission lines for detecting low and zero value insulators, implementing voltage equalization measures effectively, and ensuring the safe and stable operation of transmission lines. Based on Ansys software of 500kv transmission line insulator string, this paper establishes a three-dimensional model, the method of using finite element numerical simulation respectively with no equalizing ring and equalizing ring in both cases the umbrella skirt on simulation, the distribution of electric field along the roots, and further studies the equalizing ring the effect of different parameters on the electric field distribution. Finally, an optimal solution is established.

Electric Power Network Interconnection: A Review on Current Status, Future Prospects and Research Direction

An interconnection of electric power networks enables decarbonization of the electricity system by harnessing and sharing large amounts of renewable energy. The highest potential renewable energy areas are often far from load centers, integrated through long-distance transmission interconnections. The transmission interconnection mitigates the variability of renewable energy sources by importing and exporting electricity between neighbouring regions. This paper presents an overview of regional and global energy consumption trends by use of fuel. A large power grid interconnection, including renewable energy and its integration into the utility grid, and globally existing large power grid interconnections are also presented. The technologies used for power grid interconnections include HVAC, HVDC (including LCC, VSC comprising of MMC-VSC, HVDC light), VFT, and newly proposed FASAL are discussed with their potential projects. Future trends of grid interconnection, including clean energy initiatives and developments, UHV AC and DC transmission systems, and smart grid developments, are presented in detail. A review of regional and global initiatives in the context of a sustainable future by implementing electric energy interconnections is presented. It presents the associated challenges and benefits of globally interconnected power grids and intercontinental interconnectors. Finally, in this paper, research directions in clean and sustainable energy, smart grid, UHV transmission systems that facilitate the global future grid interconnection goal are addressed.

Research on Characteristics and Distribution of Audible Noise in UHV Converter Station Based on Artificial Intelligence

Because of its unique advantages in long-distance line loss, UHV transmission is widely used in large capacity transmission projects. As an important part of power transmission system, high voltage converter station is of great value to ensure transmission stability, applicability and practicability. However, UHV converter station will bring great noise pollution, so it is necessary to analyze and study its noise characteristics by certain means, so as to lay a foundation for noise suppression. Based on this, this paper first analyzes the test method of the noise source in UHV converter station, and then gives the specific suppression measures of audible noise in UHV converter station.

Study on safety management of guy wires in the construction of UHV (EHV) transmission lines

The guy wires play an important and key role in the erection of the tower. Temporary guy wires are also used extensively in the stringing engineer. This study summarizes the causes of many serious accidents caused by temporary guy wires that do not meet the requirements of use and operation. It focuses on the high-risk links in the guy wire operation, from the calculation and verification before the use of the guy wire, the construction technical plan, the control of key links, and the construction process. The implementation of management and control is analyzed and summarized, and the key monitoring links of safety management and control of guy wires are summarized. The study provides reference for the construction of other similar HUV (EHV) high voltage transmission lines.

Application of a robust faulted phase selector to high-resistance and weak-infeed fault conditions on a 1000-kV UHV transmission line

This work proposes the use of a novel faulted phase-selection phasor-based algorithm to solve the high-resistance and weak-infeed fault condition selection problem in existent long compensated transmission lines. The algorithm was originally developed for future half-wavelength lines (3000 km for 50 Hz system or 2500 km for 60 Hz), and was slightly modified and tested in a real 645 km 1000 kV Ultra High Voltage transmission system. The algorithm was implemented in a programmable protective relay and tested using a real-time simulator. A series of tests under extreme conditions (such as high impedance fault and very week infeed system together) were conducted to evaluate the performance and robustness of the proposed algorithm.

Model test on the effect of hillside on lightning shielding performance of ±1100 kV transmission lines

Lightning damage is one of the main causes of faults in transmission lines. To study the effect of terrain on the lightning shielding performance of UHV transmission lines, with negative 250/2500 μs switching impulse voltage, a large-sized model of the Z38102AL tower with the ratio of 1:12.5 for ±1100 kV UHV transmission lines is used to conduct the simulation tests in hillside in this paper. According to the pictures of discharge process, the discharge process of transmission line around the hillside area is analyzed. The results show that the ground potential rise in the hillside area changes the space electric field, and the attraction of the slope to the downward leader makes the transmission lines in the hillside area more vulnerable to lightning. The test results show that the equal probability curve of the shielding failure spatial region is inclined parabola curve, and the shielding effect of the slope is weak, the dispersion of discharge increases, which leads to the decrease of the difference in the attraction ability of the conductor voltage polarity to lightning. By comparing the test results with the plain model test, the results show that distribution of discharge is larger and the total shielding failure probability is higher in hillside area. Conclusively, under the influence of hillside slopes, the increase of exposure space and the change of space electric field caused by the rise of ground potential have a stronger effect on the shielding failure probability than the polarity effect of conductor voltage, which makes the difference of conductor polarity in hillside area smaller. It is found that the influence of voltage polarity of ±1100 kV conductor on the probability of shielding failure is stronger by comparing the results of ±1100 kV test and ±800 kV test.