Ultrahigh-voltage Lines Research Articles

Experimental simulation of the generation of microwave radiation during the interaction of a lightning discharge with an aircraft

On a specialized testing installation — a high-voltage Marx generator, which allows the formation of a spark discharge up to 20 meters long, the process of the impact of lightning radio emission in the microwave range on an aircraft (AC) is simulated. A metal AC model made on a scale of 1:50 was placed in a 9 m long rod-plane spark gap. A positive voltage pulse was applied to the high-voltage electrode from the generator (front 100 μsec, duration 7500 μsec). The generated spark discharge passed through the AC model. It was found that when the spark channel passes through the body of the model, electromagnetic pulses of the microwave range with a duration of less than 500 psec and a rise time of less than 100 psec arise. The measurement of the resulting microwave pulses was carried out using special radio equipment in the subnanosecond range. High-speed photography of the discharge development, carried out synchronously with electromagnetic measurements, showed that microwave pulses (up to 10 GHz) arise at the stage of development of the spark discharge leader in the part of the “high-voltage electrode – insulated model” gap. Such pulses can be considered as a factor dangerous for various AC microwave radio systems, when the AC is struck by lightning, as well as for other objects, including power facilities, which contain equipment with microelectronics. Such microwave pulses can also occur during nearby lightning discharges (for example, in a lightning rod of a power substation), when a powerful streamer corona occurs on devices and wires of ultra-high voltage lines), and when a high-voltage spark discharge occurs when switching equipment (disconnectors, arresters) is triggered. In this case, disruptions are possible in the operation of control equipment (for example, relay protection devices) that contains microelectronics, as well as various communication means available at electric power facilities operating in the microwave range (above 1 GHz).

The characteristics of negative corona discharge and radio interference at different altitudes based on coaxial wire–cylinder gap

The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120‒4320 m, and data on the corona current pulse and radio interference level of 0.8-mm diameter fine copper wire under different negative voltages were collected. The experimental results show that the average amplitude, repetition frequency and average current of the corona current pulse increase with increasing altitude. The dispersion of pulse amplitude increases with increase in altitude, while the randomness of the pulse interval decreases continuously. Taking the average current as an intermediate variable, the relationship between radio interference level and altitude is obtained. The result of this research has some significance for understanding the corona discharge characteristics of ultra-high-voltage lines.

Simulation calculation of guano fault hazardous areas in overhead transmission lines in power systems

Guano flashover is the most typical type of bird damage fault, which can be divided into two types based on the formation mechanism: guano spatial flashover and guano pollution flashover. These two types of flashover are harmful to almost all levels of transmission lines. For 110 kV level transmission lines, guano flashover faults account for over 90% of all bird damage faults. Among them, guano space flashover has caused tripping faults in multiple foreign ultra-high voltage lines. From this, it can be seen that finding the mechanism of bird manure fault formation and formulating corresponding preventive measures are of great significance for the safe operation of 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.

Effect of flexible ultra-high-voltage power transmission on receiving power systems in China

Renewable energy sources are being increasingly adopted in power systems. However, these sources remain intermittent, and power flexibility is urgently required. Phasing out of coal power could potentially result in resource inadequacy and flexibility problems. Ultra-high-voltage (UHV) transmission systems have been used prominently in China for the power distribution of renewable energy. The flexible operation of UHV lines and its effect on production cost and carbon emissions have attracted considerable research attention. In this study, first, we modeled UHV transmission with stable and flexible operations. Next, we integrated the model into a unit commitment and economic dispatch model, which was incorporated into a framework for simulating the operations of a power system. Finally, we used the power system operation simulation tool to compare the two operation modes of UHV on a typical coal-fired power system in Shandong Province. The results of the simulation revealed that in the stable operation scenario, the utilization hours of import power were 332 h lower and the utilization hours of coal-fired units were 134 h higher than those in the flexible operation scenario, whereas carbon emissions were nearly 3% higher than those in flexible operation. The flexible operation mode of UHV can effectively enhance the electricity system’s operational economy and facilitate the decarbonization of future power systems.

Economics of planning electricity transmission considering environmental and health externalities

SummaryLong-distance electricity transmission can achieve environmental benefits through the transfer of air pollutants. However, current electricity transmission investment decisions do not take enough environmental factors into account. This study combines Greenhouse Gas–Air Pollution Interactions and Synergies model with power system planning to reveal how regional differences in environmental and health losses affect the allocation of electricity at the spatial level. Based on the analysis of inter-provincial electricity interconnection in China, we find that the regional differences in environmental and health external costs of power generation are significant. Considering external costs in investment decisions will largely improve the economy of long-distance inter-regional electricity transfer dominated by ultra-high voltage lines, thus replacing a portion of intra-regional electricity transfer dominated by high voltage lines. Meanwhile, the increases in local health losses in major electricity exporting provinces are not significant, which can alleviate the regional equity issues caused by pollutant transfer.

Study on the lightning shielding characteristics of the crossover area of UHV/HV transmission lines

Due to space limitations of transmission corridors, ultrahigh voltage (UHV) lines inevitably cross over other lines. UHV lines in a crossover section have a lightning shielding effect similar to that of a lightning conductor of lower lines. While, whether a 500-kV line below a crossover section meets the lightning protection requirements is unknown. Therefore, a calculation method for the shielding failure trip rate of transmission lines in a crossover section in a three-dimensional space is proposed. The calculation of the shielding failure trip rate of the 500-kV line without a ground wire below the UHV line was performed. The results revealed that the shielding failure rate of the lower line was positively correlated with the length of the lower line and was negatively correlated with the crossing angle and length of the upper line. The maximum traversal lengths for a 500-kV line without a ground wire below a UHV AC or DC line were 200 m and 150 m, respectively. These findings provide a scientific basis for lightning protection design of ultra-UHV line crossing areas.

Has the inter-regional transmission expansion promoted the low-carbon transition of China’s power sector?

China is facing unprecedented pressure to reduce carbon emissions than ever before. Significant differences do exist among regions in resource endowment, emission potential and environmental capacity. The introduction of inter-regional transmission lines is of great significance in alleviating environmental pressure and regulating the power mix. However, it is uncertain whether and to what extent the electricity sector has been locked into fossil fuel, as well as the regional differences in low-carbon transition. This study investigates whether the transmission grid expansion represented by more ultra-high voltage (UHV) lines construction will mitigate carbon emissions through a mixed complementarity problems equilibrium analysis. Through simulating the influence of various carbon emission caps on inter-regional transmission lines, it explores the regional differences in low-carbon transition in the power sector, and investigates the regions’ reliance on fossil-fuel from the perspective of carbon lock-in. We propose the following suggestions: (1) Mitigating the reliance on fossil fuel-fired power may relieve the low-carbon transition pressures of the central, eastern, and southern regions; (2) The inter-regional transmission lines help to regulate the distribution of carbon emissions by adjusting emission cost; and (3) The effect of the inter-regional transmission lines on mitigating the carbon lock-in of regional power sector will be weakened when facing a tight carbon emission cap.

THE DISTRIBUTIONAL EFFECT OF INTER-REGIONAL TRANSMISSION GRID EXPANSION ON CHINA’S POWER INDUSTRY

China suffers significant heterogeneities in resource endowments and geological conditions across the regions. Ultra-high voltage (UHV) line construction is a project put forward by the government to boost the inter-regional transmission grid expansion, benefiting economic development by reducing pollutant emissions and absorbing more clean energy. This study investigates the extent to which this giant infrastructure has distributional effects on China’s power industry. We estimate the distributional effect of UHV lines from the perspective of power deployment, carbon emissions, and producer surplus by simulating an equilibrium model of the national electricity market through the mixed complementarity problems (MCPs) method. Furthermore, the Lorenz curve is also employed to investigate the distributional effect of UHV introduction. The results indicate that: (1) the distributional effect of introducing UHV lines is regressive considering its limited contributions to the equalization of environmental and economic welfare; (2) the emission reduction effect of the UHV lines has been improved between 2015 and 2018; (3) power plants with a large installation capacity could seek more economic profits while emitting more pollution; (4) the deployment of clean power in the resource-abundant regions is far below its potential. Meanwhile, we propose improving the structure and technology of the power mix, which can accelerate China’s market-oriented reform of the power system by equally distributing the benefits.

Графический метод расчёта вторичных токов дуги в линиях сверхвысокого напряжения

The article discusses the issues of calculating secondary arc currents in the implementation of single-phase auto-reclosing for the elimination of unstable single-phase damages in ultra-high voltage lines of 500, 750 kV. The dependences of the extinguishing time of the feeding arc and the dead time of the single-phase auto-reclosing recommended in the literature on the amplitude of the forced component of the secondary arc current are given. A graphical method is proposed for calculating the secondary arc currents in ultra-high voltage lines in the dead time mode of the single-phase auto-reclosing. The adequacy of the simulation of the recharge arc is confirmed by comparing the calculated and experimental data as applied to the 750 kV line with a length of 525 km. Examples of using the graphical method for calculating the secondary currents of the recharge arc in 500 kV lines of various lengths are given. The features of the implementation of single-phase auto-reclosing in the line with a length of 300 and 1000 km and, in particular, the influence of zero-power reactors included in the neutral of shunt reactors are noted. An example of the implementation of single-phase auto-reclosing using automatic phase shunting in a 500 km line is also considered.

Modeling China’s interprovincial electricity transmission under low carbon transition

Interprovincial electricity transmission is expected to play an important role towards low carbon transition to facilitate new and renewable energy development in West China to meet the increasing electricity demand in East China. To analyze changes in interprovincial electricity transmission and transmission infrastructure construction under China’s Nationally Determined Contributions and the 2-degree target, this study develops an interprovincial electricity transmission model with multi-voltage levels and integrates it with an improved 30-province energy system model to simulate reference scenario (REF) and three low carbon scenarios from a whole energy system perspective, CP30 (emissions peak in 2030), CPE (emissions peak in advance) and C2D (2-degree target). In 2050, electricity transmission is expected to increase to 2526.5 TWh, 3299.3 TWh, 3714.2 TWh and 4002.0 TWh under the REF, CP30, CPE and C2D scenarios, respectively, and the ultrahigh-voltage transmission demand is expected to reach 595.5 GW, 843.3 GW 917.0 GW and 1198.0 GW respectively. The overall pattern of electricity transmission will become increasingly complex as long-distance and large-capacity transmission becomes more prominent. Inner Mongolia, Northwest China and Southwest China will be the major sources of electricity transmissions, and the Beijing-Tianjin-Hebei region, Guangdong, Central China and East China will be the major importers. Ultrahigh-voltage lines will form large-capacity and long-distance electricity transmission paths connecting the power generation bases and load centers. These findings suggest that there will be a significant increase in the demand for electricity transmission and infrastructure construction in the future and that the policies promoting ultrahigh-voltage lines development should be enhanced.

Optimal configuration of energy storage for remotely delivering wind power by ultra-high voltage lines

Abstract Power generated by large-scale wind farms in northwest China needs to be remotely delivered by ultra-high voltage lines (UHVs) before consumption. However, fluctuation and intermittency of wind power output results in high costs and low efficiency of transmission. This study proposes a novel optimal model and practical suggestions to design an energy storage involved system for remotely delivering of wind power. Based on a concept model of wind-thermal-storage-transmission (WTST) system, an optimization model is established to determine optimal configurations of the system. As validated by a case study, the model is capable of determining installed capacities of wind power plants, thermal power plants, pumped hydro storage stations, and maximum transmission capability of UHVs; and it can be fast solved by mixed integer programming. According to the results of case simulation, the best configuration can significantly reduce wind curtailment rate and improve operational efficiencies of UHVs by load shifting before and after power transmission. Specifically, improving energy storage capacity and remolding thermal power plants to be flexible ones are feasible ways to realize the objectives, which are vital to increase the penetration rate of wind power in China.

Controlled Shunt Reactor for UHVAC System Reactive Power Control

Background: In this paper, a novel technique for reactive power management of the Ultra High Voltage (UHV) lines having voltage level of 1200 kV line and above is suggested. The UHV power grid has to frequently face the problems associated with the power- frequency and switching over-voltages. Methods: The technique involves the use of three-phase UHV Transformers as a Controlled Shunt Reactor (CSR) in combination with the use of a fixed reactor. The performance of the UHV AC transmission line is studied using PSCAD software and working of CSR is evaluated. Results: Standard parameters of the proposed Wardha-Aurangabad 1200 kV transmission line in India are considered for simulation model. The use of CSR has been found to be effective in mitigating system problems. Conclusion: The system can be used for maintaining voltage profile, resulting in enhancement of the reliability of the UHV transmission system.

Analysis of Dynamic Properties for Double-swing Anti-galloping device Used in Long-span Section over Han River in 1000 kV UHV AC Jingmen-wuhan Transmission Line

The anti-galloping combination mode of “double-swing anti-galloping device + cable cleat rotary spacer” is the anti-galloping scheme which is frequently used at present. In order to enhance the anti-galloping capability of Long-span Section over Han River in 1000 kV UHV AC Jingmen-wuhan Transmission line, this text will research the influence of pendulum’s theoretical length on dynamic properties for the double-swing anti-galloping device, which is widely used in the ultra-high voltage line. Theoretical analysis shows that total mass rate of anti-galloping devices, including double-swing anti-galloping device as well as cable cleat rotary spacer, should reach 6.5%, and the pendulum’s theoretical length shoud be 650mm, then the theoretical anti-galloping capability of whole system became optimized.

Optimization Design on Anti-galloping Device of Long-span Section over Yellow River in 500kV Yangdong Transmission Lines II & III

To enhance the anti-galloping capability of the Long-span Section over Yellow River in 500kV Yangdong Transmission Lines II & III, this text will research the anti-galloping optimization design scheme of the double-swing anti-galloping device, which is widely used in the ultra-high voltage line at present. According to the existing anti-galloping standards and Technical Conditions, this Report will conduct optimization design targeting pendulum bob mass distribution and theoretical pendulum length of double-swing anti-galloping device, so as to provide reasonable and effective design scheme for the Long-span Section over Yellow River in Yangdong Transmission Lines II & III, and to provide reference for proposal and formulation of anti-galloping design scheme of other lines, thus providing scientific basis and effective guarantee to enhance anti-galloping and galloping suppression capabilities of smart grid.

Cost Effective Design of Extra High Voltage Transmission Lines for Minimizing Transmission Congestion Problems

In Country like India having dense population, laying down new transmission lines is a great challenge. Also country being on fast track development mode, there is unceasing demand of electricity due to ever increasing industrialization. With advent of Extra and Ultra High Voltage transmission lines, corridor width for transmission lines can be reduced significantly. This paper describes utilization of a novel objective function for optimizing the structural design of Extra High Voltage transmission lines. Right of way for transmission lines are decided based on the effects of electromagnetic fields and corona effects in vicinity of the transmission lines. Objective function developed here takes into account the combined effects of electromagnetic fields to optimize design of transmission line tower structure. With compaction of towers further Right of way reduces leading to cost benefits in land procurement. A real time case of a transmission line situated in Gujarat is considered for validating the results of Optimization algorithm developed by authors. MATLAB has been used as programming platform for mathematical modeling as well as a platform for developing GUI that facilitates plotting of fields in vicinity of transmission lines in 2D and 3D environment. Genetic Algorithm coding is used to solve the optimization problem. Significant cost benefits and compactness in transmission tower structure is achievable as is clear from the results shown in this paper. This optimization algorithm can be extended for Ultra High Voltage lines also.

An aerodynamic anti-galloping technique of iced 8-bundled conductors in ultra-high-voltage transmission lines

Galloping of iced conductors is a kind of self-excited aeroelastic vibration with low frequency and large amplitude causing various damages on transmission tower-line systems. A newly designed galloping simulation device is employed in the wind tunnel for developing an aerodynamic anti-galloping technique of iced 8-bundled conductors in ultra-high-voltage (UHV) transmission lines. The anti-galloping technique is based on the proposed rotary clamp spacers, which allow the connected sub-conductors to rotate around its axis. Iced 8-bundled conductor models of UHV lines with and without twistable sub-conductors have been tested in the wind tunnel under various wind attack angles and five different ratios of vertical vibration frequency over the torsional. Aerodynamic damping ratios were identified from measured response data, and were used as indicators of galloping for iced 8-bundled conductor models with and without twistable sub-conductors. Equations of motion for iced 8-bundled conductors with and without twistable sub-conductors are respectively established, and the aerodynamic instability of the system can then be predicted by solving the eigenvalue problem associated with equations of motion. In order to further validate the anti-galloping effects of the rotary clamp spacers, finite element simulation has been conducted for a real UHV transmission line with a span of 500 m located in the galloping-prone area.

Study on Protective Coal Pillar Size Design for Ultra High Voltage Line Tower Mining in Mountain Areas

High voltage line towers in mining areas are sensitive to surface deformation caused by mining. Protective coal pillar design for high voltage towers is one of the commonly-used technical measures. Aiming to solve the coal mining safety problem under the Ultra High Voltage transmission line in Sihe Coal Mine of Shanxi Province, the angle and size of protective coal pillars with the vertical line method were analyzed in this paper. The effect of additional displacement caused by landslide or slippage mining in mountain areas and repeated mining was considered. Based on the principle of the vertical line method, the protective coal pillar range and size were calculated. The amount of coal deposited in coal pillars for high voltage line towers was compared and analyzed between the vertical line method and the linear structure method. The results showed that the angle of critical deformation decreased by 2~10° caused by slippage due to mining in a mountainous area, and the angle in the uphill direction of building decreased more than that in the downhill direction; when multi-seams were mined repeatedly, the angle of critical deformation in the lower seam coal mining was reduced by 5~10° compared with that of the upper seam. The protective coal pillar design with the vertical line method can protect the high voltage line towers more effectively, and the amount of protective coal pillars with the vertical line method was 5.8 million tons less, which avoided the waste of coal resources.

System optimization of long-distance energy transportation in China using ultra-high-voltage power transmission

Energy transportation is an important issue for China's electricity system due to the unbalanced distribution of energy sources and electrical demands. The traditional method of energy transportation (e.g., coal transportation) is challenging due to both the long distance of transportation and the large amount of energy that it requires. In recent years, China has been developing ultra-high voltage (UHV) as an alternative way of transmitting energy over a long distance, and many UHV lines are being planned for construction during the 13th Five-Year Plan (FYP) period. This paper develops a system optimization model for exploring the optimal pathway for long-distance energy transportation in China during the 13th FYP period from the perspective of the minimum cost of an energy transportation system. The results show that (a) although UHV transmission will be increasingly adopted in the 13th FYP period, coal transportation will still play an important role; (b) eight UHV lines are suggested to be built and put into use as a priority in the 13th FYP period; (c) the high technology learning effect, electricity demand, and investment costs of power plants would promote the adoption of UHV. Based on these results, some policy suggestions are provided.

Circuit Breaker Rate-of-Rise Recovery Voltage in Ultra-High Voltage Lines with Hybrid Reactive Power Compensation

With the development of ultra-high voltage (UHV) technology, hybrid reactive power compensation (HRPC) will be widely applied in the future. To study the mechanism by which HRPC influences the characteristics of circuit breakers in UHV transmission lines, this paper establishes an improved electromagnetic coupling transmission line model for out-of-phase and short-line faults. Based on the HRPC equivalent model, a simulation analysis was performed on the characteristics of the circuit breaker when a fault occurs. Using an equivalent lumped parameter circuit, the rate-of-rise of recovery voltage (RRRV) computational formula was deduced and computed. The RRRV variation in the circuit breakers in the system, with and without HRPC, was obtained. Given the circuit breaker interruption characteristics, the research results provide an analysis foundation and a theoretical basis for optimizing the HRPC parameters and selecting the arrangements of circuit breakers in an UHV transmission line.