Transmission Lines In China Research Articles

Study on transient electric shock characteristics between human body and metal clothes hanger on residential platform near UHV AC transmission lines

AbstractWith the development of ultra‐high‐voltage (UHV) and extra‐high‐voltage transmission lines in China, the transmission lines are gradually approaching the residential areas. The phenomenon of induced electric shock caused by electrostatic induction effect can cause dissatisfaction and complaints from nearby residents. In this paper, a full‐size steel‐framed residential test platform was constructed near a 1000‐kV UHV alternating current (AC) transmission line, the transient shock characteristics of human bodies and metal hangers in different scenarios was investigated, then the relationship between transient shock energy and subjective perception of the human body was discussed. In addition, the shielding effect of shielding wires for transient electric shock situations is analyzed. It was found that the worst‐case scenario occurred when the grounded human body came into contact with the insulated metal clothes hanger, even eliciting a noticeable sensation of pain. In addition, increasing metal shielding wire number has a significant effect on weakening induced electric shocks.

Impact of Meteorological Factors on the Wire Icing Thickness and Growth Rate in Mountain Areas under Dry and Wet Growth Patterns

Wire icing events pose a significant threat to the southern power grid’s transmission lines in China. Fifteen such events were identified from 2018 to 2020 on the Guilin-Haiyang Mountain transmission line. Hourly measurements of ice thickness and concurrent meteorological data were analyzed using the Makkonen model’s freezing rate formula to categorize the events into distinct growth patterns: dry and wet. The relationship between wire icing and meteorological factors across different micro-topography (windward slope, leeward slope, and pass) was further explored. Several key conclusions can be drawn. First, the altitude is positively correlated to the icing thickness, but relatively independent of the icing rate; however, such independence between the icing rate and altitude cannot be interpreted by the negative correlation of altitude with temperature and the positive relationship between wind speed and liquid water content. Second, a pronounced connection of the icing rate with meteorological factors is not shown until the wet and dry patterns are separated. Notably, the correlations differ between these two patterns, with icing rate being negatively correlated with temperature for the wet growth process, but positively correlated with wind speed and liquid water content for the dry growth process. Third, both wet and dry growth processes exist across the icing events. A shift from wet to dry growth was evident with increasing altitude. At the mountain’s base, wet growth predominates, with the icing rate determined by the temperature close to the freezing point, whereas the higher temperature and lower liquid water flux account for the shorter wire icing duration, lower icing rate, and thus the thinner icing thickness at the leeward slope compared to the windward slope at a similar altitude. This study sheds light on the variations in icing rates under different micro-topographies and the underlying physical mechanisms governing icing growth patterns and provides a much-needed understanding of these distinct growth processes on the development of a more sophisticated predictive model for conductor icing.

Water consumption of electric power system in China: from electricity generation to consumption.

Understanding the water requirement of electricity generation is critical to the development of both electricity and water systems, while the water consumption of the whole electric power system remains unrevealed. Here, we examine the water consumption driven by electricity generation, transmission, and consumption in China, finding that 14 billion m3 of freshwater is consumed by electricity generation in 2019 and that 2.5 billion m3 of freshwater was virtually transferred via electricity transmission. Nationally, the freshwater consumption per unit of electricity generation was 1.9 m3/MWh. Based on the state-of-the-art electricity transmission data, we find that 59% of the transported electric power was from water-scarce provinces and 0.7 billion m3 of freshwater was lost due to the electricity loss in transmission lines in China. It is essential to link water resources with the whole electric power system (production, transmission, and consumption) rather than only part of the power system as in previous research.

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.

Passive Interference Characteristics of Transmission Lines on Rough Ground and Optimization of Protection Spacing

In order to more accurately calculate the passive interference level of the transmission line, combined with the topographic features of the transmission lines in China, four types of rough ground were selected. The influence of the presence or absence of rough ground on the passive interference of transmission lines is studied, the results show that the level of passive interference when the ground is rough ground is 49.1% lower than that when the ground is a pure conductor. Then, the influence of four different ground types on the passive interference of transmission lines is studied. The results show that under the excitation of short-wave radio stations, the sandy loam land has the strongest influence on the passive interference of transmission lines and surrounding environment. Finally, the traditional method of solving the shielding distance between the transmission line and the surrounding radio stations is optimized, and it is applied to the solution of the shielding distance between the medium and short-wave radio stations. The results show that there is a 6.7% error between the traditional algorithm and the optimized algorithm, and the protection distance value obtained by the optimized algorithm is more representative and accurate.

Review of Research Activities of Hybrid Superconducting Energy Pipeline in China

The transfer of high-power flows over long distances will be the one of the principal tasks for the energetics in this century. Increasing energy flows could be achieved by the use of hybrid energy lines, where energy is transferred by chemical and electrical carriers simultaneously in single channel. Superconducting power/cryogenic fuel integrated transmission technology is one of the potential solutions to achieve large-scale, long-distance energy transmission, which has developed rapidly in recent years. In this paper, the research activities of LH2 energy pipeline and LNG energy pipelines are reviewed, and their development trends are discussed. Results of recent developments of hybrid energy transmission lines in China are presented. Details about the construction of a superconducting energy pipeline in China are considered.

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.

Novel wavefront detection and fault location method based on Hilbert-Huang transform for long HVDC transmission lines

For the newly constructed ± 1 100 kV HVDC system with 3 324 km transmission lines in China, fast and accurate fault location is vitally important for its stable operation. This paper proposes a novel method based on Hilbert-Huang Transform (HHT) for detecting wavefronts and locating faults occurring on the HVDC transmission lines. False instantaneous frequency maximum points may reduce the accuracy and reliability of wavefront detection. The novel criterion, named the product of amplitude and frequency (PAF), has significant advantages and robustness in characterizing the singularity of the signal and precisely capturing the arrival time of wavefronts. A realistic model of the Changji-Guquan ± 1 100 kV transmission system is constructed using PSCAD/EMTDC to verify the effectiveness of the proposed method. The simulation results give the maximum location error of 0.843 km in given cases of different fault distance, fault impedance, sampling frequency, and other parameters. Noise conditions and the dynamic arc model are also considered in this paper. The comparison against other methods demonstrates the superior performance of the proposed method in terms of accuracy and robustness. The proposed method has broad application prospects and guiding significance for practical projects.

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.

Research on the material properties of corroded angle steel members of the in-service transmission tower

The number of old transmission lines in China is increasing, and corrosion is a common problem on old transmission towers, which reduces the load-bearing performance of the tower and leads to potential safety hazards. The paper conducts investigation and sampling of the actual engineering line towers, analyzes the reasons for the corrosion of the towers, and carries out the tensile test of the specimens, and obtains the relationship curve of the elongation loss ratio, the yield strength loss ratio, the tensile strength loss ratio and the elastic modulus loss ratio with the cross-sectional loss ratio, which provides a basis for the evaluation of the load-bearing performance of the old transmission tower.

Research on Wind and PV Power Consumption Strategy Considering Limited Flexible Regulation of Transmitted Bundling Power on Tie-Line

There are many “west-to-east” electricity transmission lines in China, some of which transmit bundling power among which including wind and photovoltaic (PV) power. On one hand, according to the interconnected power systems theory, the transmitted power on trans-regional tie-lines needs to keep relatively stable. Therefore, wind turbines and PV facilities have to be bundled with other controllable units, e.g., thermal units. On the other hand, the ratio of wind and PV electricity on tie-lines can be improved by making full use of flexible regulation strategy. With which, the transmitted power can be adjusted along with the day-ahead forecast results of wind energy and solar radiation intensity in some degree. Some work was done on the day-ahead limited flexible regulation. Firstly, the operation rules of the interconnected power systems were introduced, and the principle of how to improve the ratio of wind and PV electricity was explained. Then, considering the consumption and power supply economics of renewable electricity, an optimization model was established and the solving method was proposed. Finally, case studies were conducted. The variations of transmitted power curves under different focuses were analysed. The effectiveness of the proposed regulation strategy was confirmed.

Research on Controlling Limits for Electromagnetic Environment in China

With the remarkable growth of power demand, power transmission and transformation facilities are gradually developing towards the direction of large capacity and ultra high voltage. In China, 500kV EHV AC power grid is mainly used for long-distance power transmission. However, people have panic and psychological pressure for the electromagnetic environment problems caused by high-voltage transmission lines. This paper concentrates on electromagnetic environment control limits around 500kV EHV AC electric power transmission lines in China. The power frequency electric field and power frequency magnetic field of two buildings under the transmission lines are monitored. With the support of objective scientific data, reducing or even eliminating public excessive panic about the electromagnetic environment caused by 500kV EHV AC transmission system.

Puncture phenomena and mechanism analysis of RTV coated cap and pin insulators in steep-front impulse voltage test

In recent years, more than 6 million room temperature vulcanized (RTV) silicone rubber coated cap and pin insulators with high mechanical ratings were used in ultrahigh voltage transmission lines in China to improve pollution performance. However, the unexpected puncture phenomena of RTV coated insulators were exposed during steep-front impulse voltage tests; for instance, the steep-front impulse voltage test pass rate decreased to less than 50% for 550 kN glass insulators with RTV coatings. The steep-front impulse voltage test is the most effective method used to check the insulation quality of cap and pin insulators. This unexpected phenomenon once caused serious concerns to power utilities. In this paper, several possible factors that affect the puncture of insulators were analyzed. Then, the extent of the decline in the breakdown of the 550 kN glass cap and pin insulators with and without RTV coatings were studied. The initial puncture location was then found, and the developmental process of the arc on the insulator surface in steep-front impulse voltage tests was observed with an ultra-high-speed intensified charge coupled device camera. Lastly, a breakdown mechanism is proposed. The puncture phenomena of a RTV coated insulator in a steep-front impulse voltage test is essentially an electrical breakdown of the internal insulation. The RTV coating induces the close adherence of the arc to the surface of the insulator. Such closeness changes the arc development path on the insulator surface and facilitates easy breakdown in the shed weak part. All these factors result in a significant increase in the breakdown probability of RTV coated insulators in steep-front impulse voltage tests.

Study on the calculation of shielding failure for dc transmission lines

Lightning is the main cause of transmission line failure, and it is important to improve the lightning protection level of the transmission line for the stability of the power system. Traditional solutions for the shielding failure of transmission lines is to use the electrical geometric model method. However, with the improvement of the voltage level, the physical size increases, and the calculation of lightning protection for ultrahigh-voltage dc lines has a greater difference with operating experience. Based on the Ningxia-Shandong dc transmission lines in China, this study utilised the lead development model to describe the flashover of insulators and the breakdown of the gaps. A comprehensive calculation method of shielding failure trip-out rate considering terrain, earth resistance and weather was proposed. The accuracy was much higher when compared with the traditional calculation and the result can be a reference for other similar calculation for dc lines.

Electrical safety of suppressing wildfires near high-voltage transmission lines using water mist

Wildfires near transmission lines are important disasters that affect power transmission. Water mist is a highly efficient method for suppressing wildfires near electrical transmission lines, where it avoids line-tripping to ensure the safety of the grid. However, few studies have investigated the electrical safety during the water mist extinguishing process, including the risk of tripping transmission lines and the shock hazard for users. In this study, we systematically studied the influence of the gap distance and the electric conductivity of the water solution on the insulation characteristics of water mist with a Dv0.99 diameter of the droplets of ca. 500 µm, including the breakdown voltage and leakage current. Furthermore, we investigated the effect of water mist on the development of a long-gap discharge, and the insulation mechanism of water mist was also considered. Finally, water mist with multi-component additives was employed for suppressing wildfires near transmission lines in China, and we demonstrated the effectiveness of this method based on the reduction of line-tripping accidents caused by wildfires near transmission lines.

Development and Application of ±500 kV DC Transmission Line Arrester in China Power Grid

In order to solve the frequently occurring lightning flashover problems on ±500 kV dc transmission lines in China, the authors have conducted the research on the dc line arrester since 2011. In this paper, the structure and installation, technical parameters, and protection performances, as well as their deterministic processes of the arrester are presented and analyzed in detail. In 2013, the authors successfully developed the arrester products, and the type tests show that they have excellent performance parameters and can act effectively against the lightning impulse and cutoff the dc follow current. By now more than 500 dc line arresters have been installed and used on seven ±500 kV dc transmission lines in eight provinces of China. About four years of operating experience shows that the arresters work safely and reliably over a long period of time, and have been effectively reducing the lightning flashover rate of the ±500 kV dc lines.

Corrosion mechanism and process of hardware of disc suspension type Insulators on ±800 kV transmission lines

Hardware corrosion on porcelain and glass insulators has occurred on ±800 kV UHVDC transmission lines in China. Iron cap corroded insulators all located at the negative polarity and pin corroded insulators concentrated in positive polarity. The corrosion mechanism is analyzed from the aspect of electrochemistry and the corrosion process is researched by means of spray water simulation tests. Mechanical and electrical characteristics tests and simulation calculation have been done. Test and calculation results indicate that iron cap corrosion can aggravate the contamination accumulation on insulator�s surface and decrease the flashover voltage. Pin corrosion can decrease the mechanical strength of insulators. XP-4C type porcelain insulator and electrolytic cell are used to research the influence factors of corrosion rate of hardware. The test results show that the contamination degree on insulators' surface and its component have considerable influence on the corrosion rate. The more serious the degree of contamination is, the faster the corrosion rate is. The sequence of cation that lead to the corrosion rate from fast to slow is K+>Na+>Ca2+>Mg2+, the sequence for anion is Cl->SO42->NO3-.

Influence of pin corrosion on mechanical characteristic of UHVDC disc suspension insulators and solutions

Hardware corrosion has occurred upon lots of suspension-type porcelain and glass insulators of ±800 kV Chusui and Xiangshang UHVDC transmission lines in China since October 2011. The cause of pin corrosion and its influence on the mechanical property of insulators are researched in this paper. The mechanical load that insulator bears under the circumstance of conductor icing and galloping is calculated by means of ANSYS software. Also, the failure forms of insulators under large mechanical load condition are analyzed. On the basis of this, the method that installing organic material sleeve onto the zinc sleeve to vary its corrosion area is proposed. The problem of mechanical strength decreasing of the insulators caused by expansion of corroded by-products is solved. Insulator samples with organic material sleeves of three structures including zinc sleeve half package type, flush type, and whole package type are made, and pin electrolytic corrosion simulation tests are carried out upon the three kinds of samples respectively by means of the spray water method. It turns out that half package type organic material sleeve alters the corrosion part of zinc sleeve effectively and the pins of insulators with two other kinds of organic material sleeves were corroded seriously. The electric field intensity of insulators is calculated by means of ANSOFT software. Calculation results indicate that the semi-conductive rubber sleeve provides the insulator with better electric field intensity characteristic.

Statistical Analysis on Lightning Performance of Transmission Lines in Several Regions of China

Lightning is a substantial cause that leads to serious lightning failures, which has a significant influence on the normal operation of the entire power grid. This paper mainly focused on several regions of China with serious lightning activity, presenting the lightning performance of power grids by statistics obtained from long-term monitoring data, and intended to indicate some general characteristics. The lightning tripout rate, the shielding failure tripout ratio, the occurrence frequency corresponding tripout failures of different phases of single-circuit or double-circuit transmission lines, and the multicircuit simultaneous tripout failures of multicircuit transmission lines were analyzed. These statistical results presented a panorama of the lightning protection effect of transmission lines in China. The statistical data in this paper are informative to guide the future research or engineering practice of lightning protection of transmission lines, and will be helpful to evaluate the analysis methods of lightning performance of transmission lines.

Research and Establishment of UHV AC Transmission Model

There is different applicable transmission capacity and range between 1000kV and 500kV AC transmission. The traditional method is to use the continuous power flow algorithm by BPA simulation software. But this method is complicated and time-consuming. Calculation is particularly large when electricity has a variety of power demand analysis. This paper presents an algorithm based on the AC line transmission capacity, using MATLAB software programming to achieve the establishment of UHV AC transmission model and economical optimization strategy. The method can use thermal limit, voltage limit, landing stability constraints to get the AC line transmission capacity curve by considering the factor of power network strength. On the basis of this method, an UHV AC transmission model can be built combining with unit capacity annual cost algorithm, which can meet the power transmission of arbitrary transmission capacity and the optimal economic of any transmission distance, has an important reference significance and practical value for the planning and construction of electric transmission lines in China.