Ultra High Voltage Transmission Lines Research Articles

Experimental Study on the Transient Electric Shock Characteristics Between Metal Sheds and the Human Body Near Ultrahigh Voltage Alternating Current Transmission Lines

With the development of ultrahigh voltage (UHV) transmission lines in China, line corridors are becoming increasingly limited, and the lines pass closer to inhabited areas and the occurrence probability of induced electric shocks are increased. The research on transient electric shock and human sensory is essential due to the displeasure and complaints of people on electric shock. In this article, a real-size metal shed was established near a 1000-kV UHV alternating current (ac) transmission line, and the induced voltage and transient current characteristics were studied when the human body was in contact with the shed. Then, the amplitude and pulsewidth of the transient electric shock current were investigated, and the associations between discharge energy and sensation were established. The research found that transient electric shock is the most serious when the grounded human body contacts the insulated shed, and the imparted electric shock energy reaches 25 mJ. When the body and the shed are grounded, there is no electric shock sensation. When the insulated human body is in contact with the insulated shed, the electric shock sensation is intermediate, and women's perceptions of pain are more intense. The results provide references to transient electric shock protection for power transmission lines.

Bird pecking damage risk assessment of UHV transmission line composite insulators based on deep learning

AbstractHere, a method for assessing the risk of bird pecking damage of composite insulators in ultra high voltage (UHV) lines is proposed using electric field (E‐field) simulation and deep learning. The distribution of E‐field on composite insulators is analysed via numerical simulation for different damage locations and damage sizes. Then, using the defective images of composite insulator strings captured in real inspection environments, the corresponding annotation image data set is constructed according to the finite element calculation results of E‐field under different damage conditions, and through the application of the YOLOX deep learning neural network, the risk assessment of the damage caused by bird pecking of insulators for UHV lines is conducted. Furthermore, to prevent overfitting of YOLOX with small‐scale images, transfer learning, as well as data enhancement, are applied to the YOLOX training process. According to the results, the mean average precision (mAP) of the model is 0.79, indicating that it is capable of high accuracy recognition, provides guidance for operation and maintenance personnel.

Research on Live overhaul Method and Equipment for V-hanging Insulator String of Medium Phase Bridge Shape Cross Bear in 500kV Transmission Line

Ultra-high voltage (UHV) transmission lines are important for electricity transmission. Medium phase bridge shape cross bear is a special structure; No tool can be used to replace the V-hanging insulator string with live power. In view of this problem, the live overhaul method of V-hanging insulator string of medium phase bridge shape cross bear in 500kV transmission line is invented, the security is analyzed, and the developed equipment is simulated and tested. The results of the research show that it can meet working conditions and accelerate working efficiency, which is important for the kind of maintenance.

Experimental Study on Vortex-Induced Vibration of Steel Tubes in Transmission Towers at Various Inflow Conditions

With the extensive construction of ultra-high voltage (UHV) transmission lines, the fatigue damage of steel tube members caused by vortex-induced vibration (VIV) in tubular towers has received growing attention. Although some progress has been made in the research of the VIV of steel tubes in uniform flow, there is still relatively scarce research on the VIV of steel tubes at various inflow conditions. In this paper, a series of wind tunnel tests are conducted to investigate the VIV of the steel tube subjected to uniform, turbulent, and oblique flows. Three turbulence intensities (Iu = 5.9%, 9.7%, and 12.6%), and four yaw angles (α = 10°, 20°, 30°, and 40°) are considered. The results show that the VIV response of the steel tube in the in-line (IL) direction is negligible compared to that in the cross-flow (CF) direction. The displacement amplitude gradually decreases as the turbulence intensity increases, accompanied by a more unstable response. For the inclined steel tube, the VIV maximum amplitude almost remains constant when α ≤ 20°, while it sharply decreased in the case of α = 30° and α = 40°. Furthermore, it was found that the so-called independent principle is applicable for α ≤ 10°.

Operational modal analysis of two typical UHV transmission towers: A comparative study by fast Bayesian FFT method

The ultra-high-voltage (UHV) transmission tower is currently the most advanced transmission tower in the world. The UHV transmission line is mainly composed of tangent towers and tension towers with different structural forms. This is interesting from a dynamic point of view, since the two typical structures may behave differently in terms of dynamic characteristics. In this study, a comparative study on operational modal analysis (OMA) of these two typical UHV transmission towers under ambient test is carried out by a fast Bayesian FFT method. Prior to the test, the selected frequency bands of modeling are determined by the sensitivity analysis. A structural health monitoring (SHM) system is installed on the towers during the maintenance period to monitor the acceleration response. The dynamic properties of the towers are obtained by the recently developed fast Bayesian FFT method and compared, the accuracy approximation of the Bayesian approach is verified by frequency domain information reconstruction. Furthermore, the damping ratio results as well as other voltage levels are compared with different nations codes. It is found that the stiffness of the tension tower is relatively higher than that of the tangent tower. The first-mode damping ratio results of tower in all directions exceeds 2.59% and the vertical cross-arm direction of tension tower reaches 4.54%. The research results can provide a reference for the wind resistance design for UHV transmission tower, and can be used in model updating in the future works.

Analysis of transient electromagnetic processes in the ultrahigh voltage transmission line during two-phase short circuits

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Direct current volt-ampere characteristics of long arc on ice surface

With the continuous construction of ultra-high voltage transmission lines, the problem of long insulator string ice flashover in the icing area is becoming more and more prominent. At present, only the volt-ampere characteristics of short arc on the ice-surface have been studied in the previous research. However, the volt-ampere characteristics of the long arc on ice-surface are significantly different from the short arc, so the flashover characteristics obtained from the short insulator string aren’t suitable for the long string under icing conditions. Therefore, in this paper, the volt-ampere characteristics of direct current long arc on the ice-surface are measured by using ice column in a multi-functional artificial climate chamber. The results show that the arc length has an effect on the volt-ampere characteristic constant A, exponent n and expression. In addition, the dynamic volt-ampere characteristics and the static volt-ampere characteristics are redefined and studied, which lays a foundation for the flashover voltage prediction of long iced insulator string. The research of this paper has important theoretical guiding significance for the external insulation design of ultra-high voltage direct current transmission lines in icing areas.

Study on Reradiation Interference Characteristics of Steel Towers in Transmission Lines

With the development of ultrahigh-voltage transmission lines in China, the reradiation interference caused by the steel tower used in ultrahigh-voltage transmission becomes increasingly aggravating for nearby radio stations. In this paper, using the multilevel fast multipole algorithm, the reradiation interference of an ultrahigh-voltage transmission steel tower is investigated. Additionally, the reradiation interference characteristics of a transmission steel tower were investigated with various frequencies and azimuth angles of incidence wave. The results show that the frequency and the azimuth angle of incident wave are the impact factors for the reradiation interference of steel towers. It is better to use a detailed angle steel model for the truss structure of steel towers at high frequency, while a simplified structural model can be used at low frequency. Additionally, the diffraction at the edge of the angle steel has a great influence on the reradiation interference, particularly at high frequencies.

The Optimization Study for Electromagnetic Radiation With Ultrahigh Voltage Transmission Lines

Several factors affect the electromagnetic environment changes generated underneath high-voltage transmission lines. This article carries out a study on the impact of the electromagnetic environment on high-voltage transmission lines based on different tower structures, voltage levels, conductor layouts, conductor parameters, and other full range of engineering factors. First, the model of wire three-phase phase sequence, ground height, horizontal phase spacing, wire splitting number, split spacing, and model values are built. By continuously adjusting and optimizing the parameters, the electromagnetic environment distribution curve at 1.8 m above the horizontal plane is obtained. Then, according to the characteristic analysis of the distribution law after optimization, the simulation results under some typical factors are compared with the standard limits. Simultaneously, the effect of this optimization is verified by comparison with relevant literature. Finally, some suggestions on the optimization of the pole tower structure, transmission line parameters, and the influence of electromagnetic radiation in transmission line corridors are proposed in high-voltage transmission line projects, which may potentially have constructive contributions and value.

PSO/DE combined with simulation current method for the magnetic field under transmission lines in 3D calculation model

Due to the construction of ultra-high voltage transmission lines, the lines will inevitably pass through residential areas. The power frequency magnetic field created by transmission lines will affect the location and design of transmission lines, as well as people’s health. In this paper, the intelligent optimization algorithm is used to optimize the Simulation Current Method (SCM) and study the magnetic field distribution under the transmission line. Firstly, the actual three-dimensional shape of the transmission line is considered in this optimized simulation current method (OSCM). Secondly, we combined the magnetic position error with the magnetic field error to construct the fitness function, and we used the algorithm to optimize position and number of simulated currents. Finally, the finite element method (FEM) is used to verify the calculation results. We calculate a 500 kV 3-D transmission line model and verify that the optimized SCM can reduce the calculation effort and ensure the accuracy of the calculation. In addition, the OSCM solves the problem that the number and location of the simulated current can only be determined empirically. On the one hand, the actual physical shape of the transmission line is considered, which makes the calculation precision higher; on the other hand, the calculation time is much lower than that of FEM. At the same time, it provides a theoretical basis for the magnetic field distribution of transmission lines and has a theoretical guiding significance for the construction of high-voltage transmission lines.

Time-Frequency Domain Conversion of UHVDC Transmission Line Corona Current Based on Fourier Transform

In the power system, Ultra-High-Voltage (UHV) transmission is an effective means to improve and solve the imbalance between power supply and demand. However, with the continuous improvement of the voltage level, the adverse effects caused by the electromagnetic environment of the transmission lines are also growing. Audible noise produced by corona discharge of transmission lines has seriously interfered with the daily life of residents near the transmission lines, which can not meet the requirements of protecting residents and environmental friendliness. In this article, the background noise in the time-domain waveform of corona current is removed by wavelet analysis. The time domain waveform of corona current is transformed into the frequency domain by a fast Fourier transform. Through the analysis of the spectrum of corona current, it is found that the corona current attenuates with the increase of frequency, and most of the energy is concentrated in the first 1.5 MHz frequency band. The relationship between each frequency band of corona current and audible noise is obtained by the multiple linear regression, and the regression model is proved to be well fitted by testing. The experimental analysis shows that the algorithm in this article is 8% better than the traditional finite element method, and is closest to the actual measurement value, which proves that the actual effect of the research contained in this article is more effective. These achievements are helpful for the further study of the electromagnetic environment of UHV transmission lines, which is conducive to promoting the vigorous development of the UHV DC transmission technology in China, allocating resources more reasonably and reducing environmental pollution, and meeting the strategic requirements of energy and environment in China.

Optimal planning energy storage for promoting renewable power consumption in the urgent situation of UHV systems

AC/DC hybrid ultra-high voltage (UHV) transmission network is an effective way to deliver large scale renewable energy. Unfortunately, the power transmission capacity is significantly restricted due to guaranteed transient stability. Energy storage systems (ESS) are regarded to be the most flexible means to enhance transient stability. However, optimal planning of ESS for UHV stability is challenge because it involves differential equations. For this, this paper firstly proposes the mathematic formulations for optimal planning of ESS with UHV transient stability. The proposed model considers the DC blocking fault that is simulated by component switching equivalent processing. Mathematically, the proposed model belongs to the nonlinear, mix-integer, discontinuous differential constrained programming. The existing simulation and numerical methods are challenging to solve the proposed model directly. For solving this problem, an effective method is proposed, combining with the methods of implicit trapezoidal integral method, sensitivity analysis method and interior point method. The simulation results show that ESS can enhance the transmission efficiency of UHV transmission lines. From the analysis of delivery capacity, voltage distribution, the generator rotor relative swing angle and angular velocity, the technical benefit can be maximized by optimal planning ESS with the proposed method.

A mathematical model of an ultrahigh voltage transmission line taking into account overhead ground wires

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Failure Analysis of Transmission Tower in Full-Scale Tests

With the rapid development of Ultra-High Voltage (UHV) transmission lines, it is necessary to study the performance of UHV transmission towers. First, we performed full-scale tests on a transmission tower under seven loading patterns. Then, the test results were compared with the calculation results of the Chinese tower design software Transmission Tower Analysis Program (TTA), and the failure location of the tower and the stress characteristics of the key parts were studied. Finally, we discuss the influence of bolt slippage and a new joint on the tower performance, and propose some design proposals for the current Chinese code, based on the test results. The results show that a bolt slip will significantly increase the displacement of the transmission tower, but the residual displacement can correct it. The new joint design has good mechanical performance. The bracing member at the bottom of the tower leg is located at the connection of the tower leg and the foundation, and there is a significant sudden change in stiffness, which we recommend designing according to 4% of the axial force of the main members.

Measurement of Electric and Magnetic Field Strengths under 765 kV UHVAC Single Circuit Transmission Line

Transmission line corridors of developing countries are increasingly dense and expensive with construction of new ultrahigh voltage (UHV) transmission lines. Right of way of transmission line in the corridor, construction cost of transmission lines including towers, is directly influenced by electric and magnetic field strength emission (EMF) of that line. In UHV range, emission of electric and magnetic field strength in the vicinity of lines is of great public concern, as are likely to have hazardous effects to human being when their exposure level exceeds specified limits. Higher the transmission voltage and stronger the electric field. Though the results on effect of EMF on human being is inconclusive, to create awareness to common public and working professional, it is mandatory to measure the emission level of EMF in lateral and longitudinal profile. This paper reports experiences of EMF emission measurement of 765 kV UHVAC quadruple ACSR bundled conductor single circuit transmission line in India. Measurement results of EMF with vegetation is reported.

Assessment of the Effect of Corona Discharge on Synchronous Generator Self-Excitation

The method of operative determination of active power losses (both loading and crown) in alternating current lines has been improved. The proposed technique allows monitoring of active power losses in lines. Based on the comparative analysis of different approximation methods, the most effective method of analytical representation of regression dependences of active power losses on the corona on voltage for different weather conditions is proposed. The validity and reliability of scientific statements, conclusions, and recommendations given in the dissertation are confirmed by the analysis of the results of comparative calculations performed for different models. The efficiency of the developed algorithms and programs was tested on control examples with reference source data, where the results of the calculations were compared with the results obtained by standard programs. The developed technique of operative determination of losses of active power (loading and on a crown) allows one to carry out current monitoring of losses and passive parameters of high-voltage power lines of alternating current. The phenomena of self-excitation of generators connected to unloaded power lines are considered at great length. A physical analysis of the ongoing processes is given, and calculation methods are proposed that have been experimentally tested on a dynamic model. The paper takes into account the effect of the wire corona on the conditions of self-excitation of generators with the necessary developments to prevent this negative phenomenon in the main electrical network. Models and methods have been developed for evaluating the effect of the wire corona on the conditions for the occurrence of self-excitation in ultra-high voltage transmission lines.

Loss Prediction of Ultrahigh Voltage Transmission Lines Based on EEMD–LSTM–SVR Algorithm

Line loss prediction of ultrahigh voltage transmission lines is the key for ensuring the safe, reliable, and economical operation of the power system. However, the strong volatility of line loss brings challenges to the prediction of transmission line loss. For more accurate prediction, this article uses ensemble empirical mode decomposition (EEMD) to decompose the line loss and proposes the EEMD–LSTM–SVR prediction model. First of all, this article performs feature engineering on power flow, electric energy, and meteorological data and extracts the exponentially weighted moving average (EWMA) feature from the line loss. After the integration of the time dimension, this article mines the curve characteristics from the time series and constructs a multidimensional input dataset. Then, through ensemble empirical mode decomposition, the line loss is decomposed into high-frequency, low-frequency, and random IMFs. These IMFs and the standardized multidimensional dataset together constitute the final input dataset. In this article, each IMF fusion dataset is sent to LSTM and support vector regression models for training. In the training process, the incremental cross-validation method is used for model evaluation, and the grid search method is used for hyperparameter optimization. After evaluation, the LSTM algorithm predicts high-frequency IMF1 and 2 and random IMF4 and 5; the SVR algorithm predicts low-frequency IMF6 and 7 and random IMF3. Finally, the output value of each model is superimposed to obtain the final line loss prediction value. Also, the comparative predictions were performed using EEMD–LSTM, EEMD–SVR, LSTM, and SVR. Compared with the independent prediction models EEMD–LSTM and EEMD–SVR, the combined EEMD–LSTM–SVR algorithm has a decrease in mean absolute performance error% by 2.2 and 25.37, respectively, which fully demonstrates that the combined model has better prediction effect than the individual models. Compared with that of SVR, the MAPE% of EEMD–SVR decreases by 11.16. Compared with that of LSTM, the MAPE% of EEMD–LSTM is reduced by 32.72. The results show that EEMD decomposition of line loss series can effectively improve the prediction accuracy and reduce the strong volatility of line loss. Compared with that of the other four algorithms, EEMD–LSTM–SVR has the highest R-square of 0.9878. Therefore, the algorithm proposed in this article has the best effectiveness, accuracy, and robustness.

Super‐resolution reconstruction method of infrared images of composite insulators with abnormal heating based on improved SRGAN

Abnormal heating of composite insulators on ultra-high voltage (UHV) transmission lines is widespread under high humidity and heat in southern China. The infrared imaging technology can be used of quickly and effectively detect insulators with abnormal heating and determine their defect types. However, it may cause misjudgement when the infrared images are not clear. A super-resolution reconstruction method of infrared images of composite insulators with abnormal heating based on improved super-resolution generative adversarial networks (SRGAN) is proposed in this paper, and the dense residual network in SRGAN is perfected by introducing the residual channel attention (ResCA). This method overcomes the problems that the resolution of images reconstructed by traditional methods is not significantly improved, and images are too smooth, and the edge details are easily lost. Compared with the traditional methods, the five reference-free image quality evaluation indexes of the image reconstructed by the improved SRGAN are increased by −0.73% to 63.84%. Further the effectiveness and superiority of the improved SRGAN are verified by comparing the changes in the distribution of grey values of infrared images before and after reconstruction. Finally, the improved SRGAN is used to perform super-resolution reconstruction of the low-resolution infrared image examples.

Induction mechanism and propagation characteristics of current in line conductors due to an electron avalanche

Transfer of bulk electric power required in the modern world can be realized only through Extra High Voltage and Ultra High Voltage transmission lines. The scenario is dominated by overhead lines in which electromagnetic noise generated by corona is an important concern. Corona-induced currents propagate along line conductors producing electromagnetic noise, which is essential to be quantified. Towards this end, the present work aims to investigate basic mechanism of current induction using an isolated avalanche developing under space charge modulated background field. Beginning with the complete electric field produced by an avalanche, the corresponding induced currents are quantified, and the structure of electric and magnetic fields is extracted. The well-known time-domain electric field integral equation is employed for the purpose. The basic issue with long transmission line modelling is amply demonstrated. Since single avalanche is the basic mechanism behind corona, general inferences drawn are applicable for corona on transmission lines.

Study on Improved CG Algorithm for Reradiation Interference Calculation of Transmission Steel Tower

With the development of extra-high voltage and ultra-high voltage transmission line in China, the reradiation interference generated by induced current on the surface of transmission steel tower becomes more serious to the radio station in the vicinity. In this paper, the calculation method for reradiation interference of transmission steel tower based on method of moment is analyzed. And in order to reduce the impedance matrix storage data in the memory space and the number of iterations in the calculation, the preprocessing of matrix sparse and diagonal norm precondition is presented to improve the performance of the conjugate gradient algorithm for the reradiation interference calculation. The reradiation interference of a standard 500 kV transmission steel tower is calculated using the improved conjugate gradient algorithm. And the results show that the algorithm enhances the convergence and stability after preprocessing and is suitable to calculate the reradiation interference of super-large metal truss structure target.