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Soft silicone has been widely used for anti-icing coating, but the ice adhesion strength is usually scaled with the iced area at a relatively large thickness. On the other hand, a thin rigid poly(vinyl chloride) (PVC) film could be independent of the iced area and was named a low-interfacial-toughness material. Thus, a soft and rigid integrated (SRI) coating was prepared by doping PVC particles into a silicone matrix here. The introduction of PVC particles not only served as phase II to accelerate the stress concentration but also favored the formation of a wrinkle structure. After further introducing plasticizers, this SRI coating not only has a very low ice adhesion strength at a low iced length but also tends to a limit value irrespective of the iced length, which further leads to excellent large-area deicing behavior. Furthermore, the SRI coating demonstrated outstanding chemical stability, mechanical robustness, and on-field repairability.

The effect of temperature on the service life of stranded carbon fiber composite core conductors was studied based on the kinetic theory of material pyrolysis. The thermal decomposition activation energy calculation for stranded carbon fiber composite cores was carried out by thermogravimetric analysis (TGA). The activation energy E of stranded carbon fiber composites was calculated according to the Flynn–Wall–Ozawa, Kissinger, and Coast–Redfern methods, which were 168.76 kJ/mol, 166.79 kJ/mol, and 160.35 kJ/mol, respectively. The results from these different treatments were within 10% or less, and thus the thermochemical reactions of stranded carbon fiber composite cores were considered to be effective. The life prediction model of the carbon fiber composite core was developed based on the kinetic equation of thermal decomposition. The service life is related to the reaction mechanism function G(α) and the reaction rate parameter k(t). The reaction mechanism function G(α) = ((1 − α)−3.3 − 1)/3.3 and the reaction rate parameter k(t) = 2.14 × 1012exp(E/RT) were obtained by fitting the thermal weight loss data of stranded carbon fiber composite cores. Based on the 5% mass loss criterion for the end of life of stranded carbon fiber composites, the service life of the carbon fiber composite core is given at various operating temperatures.

Retrofitting methods for transmission tower on-service conditions should avoid punching and welding. This paper presents a non-destructive retrofitting method, the T-shaped composite angles method, to meet the demand. The original angle was combined with retrofitting components by V-shaped clamps. Both numerical analysis and static loading test were carried out to verify the effectiveness of this retrofitting method. The test results show that compared with the lateral stiffness of the original transmission tower segment, the stiffness of the reinforced one increased. The load-bearing capacity of the reinforced transmission tower segment almost doubled that before the reinforcement. The proposed retrofitting method is non-destructive and effective.

To investigate the association between the failure pattern and the proportion of external load in the tower segment, the capacity experiment of the scaled segment model is designed in this paper, and the FE model of the experiment of the segment is build and compared with experiment results. The pattern of the tower segment failed is evaluated by the relationship of PH(horizontal load) and MP (bending moment). The critical points of P-MP curve were analyzed by selecting the capacity of diagonal and main elements. And the failure assessment theory for the tower segment was established. The results indicate that the FE model of the experiment segment can reflect the experiment loading process effectively. The capacity of the diagonal element has a significant impact on the tower’s PH, and the main element’s bearing capacity is an important factor affecting the flexural capacity. Using the proposed method, the weak positions and elements of the structure can be judged.

The power company has improved the safety of important crossover lines by installing backup clamps to the tensile wire clamps. However, it remains to be studied whether the backup clamp can withstand the impact of the wire tension when it breaks. In this paper, the finite element model of the tension clamp with backup clamp is established and verified the accuracy of the model with an actual line as the engineering background. The results show that the back-up clamp force instantaneously reaches 49501.1N at the moment of tension clamp breakage, and the effectiveness of the back-up clamp is indeed affected. Finally, the effect of the installation height on the impact coefficient is combined to give suggestions to improve the effectiveness of the backup clamp.

Ice accumulation on atmospheric structures will result not only in inconvenience to human activities, but also various catastrophic events. Many anti-icing coatings have been developed for anti-ice accretion on various atmospheric structures. However, such mitigating icing performances and developments in practical applications are restricted by various factors. Therefore, current mitigating icing coatings are far from practical implementation. Rough and smooth hydrophobic coatings have demonstrated their potential for mitigating ice formation. To advance the development of mitigating icing coatings, a perspective of hydrophobic coatings for mitigating icing is in need. Herein, this paper categorizes the mitigating icing coatings by their wettability firstly. Then, we recap the state-of-the-art hydrophobic coatings for mitigating icing. Afterwards, we point out the deficiency and limitations of current coatings for anti-icing. At last, we provide a perspective of future trends and development directions. This perspective review can guide the design of mitigating icing coatings towards practical implementation.

Conductor galloping is a common disaster of power transmission lines. However, at present, the research object of the galloping problem is mainly aluminium cable steel reinforced (ACSR), and there are few researches on the galloping of carbon fiber composite conductor (CFCC). Previous studies on the galloping of CFCC mainly used experimental methods. Due to the limitations of experimental sites, it is not possible to simulate the lines with any span and height difference. Therefore, it is necessary to use the simulation method to simulate the galloping of CFCC. In this study, a simulation model is established based on the actual circuit parameters to study the effect of ice thickness and the suppression effect of different anti-galloping measures on CFCC. Finally, the galloping responses of CFCC and ACSR are compared under the same conditions.

The DC current injected into the earth from the grounding electrodes of HVDC system could flow into the oil and gas pipelines through their grounding, lead to high pipe-to-soil potential. It is necessary to study the measures to solve the effect of DC current on metal pipelines. In this paper, the pipe-to-soil potential under field test is measured and calculated. Several measures on metal pipeline is discussed in a real case. It is found that the pipe segmental insulation and laying sacrificial anodes on pipe used jointly is effective to reduce the pipe-to-soil potential. Maintaining an effective safety distance of DC grounding electrode and metal pipeline is an important way to address the interaction.

As a new type of overhead wires, carbon fiber composite conductors have a wide potential application prospect in the capacity expansion project. When the conductors run at a relatively high temperature for a long time, the influence of temperature on carbon fiber composite mandrel which are wrapped inside the aluminum conductor cannot be neglected. Therefore, it is of great significance to study the thermal decomposition process of the composite cores. The pyrolysis process of the carbon fiber composite cores was analyzed by thermogravimetric analysis experiments at various heating rates, and the activation energy of the carbon fiber composite cores was calculated using two classic models based on thermal analysis kinetics. The results showed that the activation energy values calculated by the Flynn-Wall-Ozawa method and the Kissinger method were basically the same. It was found that the activation energy values at different conversion rates were stable in the early stage of the reaction and increased slightly in the later stage. To account for this phenomenon, the explanation was also given. The study of the activation energy of the composite core in this paper lay a certain foundation for revealing the aging mechanism and life evaluation of the carbon fiber composite cores.

In order to understand the effect of alkali factor on the material properties of carbon fiber composite conductor, the aging behaviors of the composite core are evaluated in alkali solution media. Accelerated aging test was carried out in alkali solutions. The resistance of the composite core was evaluated in terms of alteration in the mechanical (flexural), componential (by fourier transform infrared spectroscopy and thermogravimetic analysis), and microstructural (by scanning electron microscope observation) behaviors of the material. The results showed that alkaline immersion had great effect on the properties of the composite core. It was further proved that chemical aging of composite core occurred in alkaline solution. The performance of the composite core was directly related to the resin matrix and the compound interface due to the effect of resin matrix transferring load to carbon fiber.

Transmission lines are susceptible to the wind and it may cause conductor swing during their operation. UHV compact transmission lines are easily affected by conductor swing which could lead to interphase flashover due to their small inter-phase clearance. According to the current research, it is widely believed that the wind load on the transmission lines contains significant pulsating effects. Therefore, it is necessary to study the motion characteristics of the transmission lines under the action of pulsating wind. To analyze the dynamic behavior of the transmission lines, a three degrees of freedom (3DOF) nonlinear mechanical software was developed in this paper. The simulated results showed that compared with the steady wind, the minimum inter-phase clearance that can occur under pulsating wind was smaller, and the maximum unbalanced tension were greater. It was found that the minimum inter-phase clearance of the iced conductor decreased with the increase of the span length. In addition, it was also found that the reasonable installation of interphase spacers could play a positive role in suppressing the conductor swing of the iced conductor under the action of pulsating wind.

In developed area, there is not only dense electric power grid, but also dense gas pipelines. In this situation, the DC current injected into the earth through the grounding electrodes of a high-voltage DC system would aggravate the corrosion and even destroy the protection devices of the pipelines. In this study, a numerical approach is put forward to simulate the potential distribution in gas pipeline, which is regarded as long grounding system with insulating coating on the grounding conductor. The main cathodic protection methods for the pipeline are also modelled. The approach is validated by the experiment on a reduced-scale model. With this approach, the effectiveness of the measures to reduce the electrode potential distribution along the pipelines is analysed.

Transmission lines inevitably cross railroads, highways, and other facilities, and in order to ensure the safety and reliability of the cross-crossing section, the influence of various random factors on important cross-crossing transmission lines needs to be fully considered. In this paper, the transmission line crossing section is treated as a tandem system according to the force transmission route, and the reliability calculation method of the cross-crossing transmission line system based on the tandem system is proposed. The reliability calculation method of each component and the reliability calculation method of the tandem system are given. Finally, an example of the reliability calculation of a 220kV cross-crossing transmission line system is given, and the results show that the cross-crossing section has the highest reliability of tower FSJ404, with a reliability index of 8.61, the second highest reliability of insulators, with a reliability index of 7.22, and the lowest reliability of tower FSJ302, with a reliability index of 4.28. The failure probability of the cross-crossing section is 0.000009245, and the reliability index is 4.28.

With the development of camera hardware technology and computer vision algorithms, visual positioning technology has been paid more and more attention. Most of the research on visual positioning technology is based on single camera and single picture. that is, only the target tracking appears in the shooting range of a certain camera, the coverage and the obtained picture information are limited. The multi-camera-based visual positioning technology can not only provide a wider field of view but also overcome the problem of target occlusion by the cooperation among the cameras. The multi-camera visual positioning technology studied in this paper mainly applies several classical algorithms in this field. The KNN-based background segmentation algorithm is used to detect moving targets, and the KCF algorithm is used to achieve continuous and reliable tracking of targets. The SURF feature detection algorithm is adopted. Target matching is achieved by matching with FLANN, and finally the position and motion trajectory of the target in the bird’s eye view are obtained based on the planar homograph. The multi-camera visual positioning technology can be used to obtain the real-time position of the personnel in the substation, which can prevent the staff from entering the charging interval, and avoid the dangerous situation that the outside personnel enters the substation illegally.

It is anticipated that significant expansion of power systems will continue in next decade in China. Given constrains of limited transmission corridors, alternative augmented capacity wire is highly expected, with larger transmission capacity, excellent lower sag, lower losses, stronger corrosion and wind resistance. The paper developed an innovative overhead augmented capacity wire, aluminum conductor with multi-stranded composite core (ACMCC), based on stranded continuous carbon fiber. Its technical characteristics and cost benefit analysis were detailed, with comparison to other augmented capacity wires. ACMCC has been applied in several transmission lines in China Southern Power Grid. Field application showed that ACMCC may be one of the most promising wires because of its excellent properties, conductor structure reliability and fitting installation convenience.

The artificial short circuit test of transmission lines is one of the important steps for debugging of HVDC transmission projects. It plays an important role in assessing the ability of handle faults of DC systems, verifying the sequence of line fault recovery process, and checking fault location ability of the lines. This paper describes the basic method of short circuit test of the ±800kV UHVDC transmission line in China Southern Power Grid (CSG), and studies the selection of the copper wire for artificial grounding experiment of transmission lines, simulates the short-circuit currents under various operating conditions. The influence and distribution of the step voltage on the surface of the testing area is studied and the safety distance for testers is proposed. The study found that the calculated ground current and the actual measured value are not very different, and the calculation results can be used to guide the design of artificial short-circuit test. According to the simulated short-circuit current, the cross-sectional area of the copper wire is recommended to be 1.0mm2. The site tester’s personnel safety distance of at least 30m away from current injection location is suggested. And insulated boots and gloves are always recommended to put on. The research method in this paper can be used for the preparation and development of artificial grounding tests for UHVDC transmission projects.

Due to the corrosion problem, there emerge various fracture phenomena for composite insulators on several 500kV AC transmission lines in China, which has caused serious threat to the normal operation of power system. Therefore, it is urgent to analyze the fracture mechanism and propose feasible evaluation method for the failure of composite insulators. In this paper, appearance observation, water diffusion test and dissection test for the fractured 500kV AC composite insulators were carried out, and the results indicated that the main factor that led to the fracture was the bad adhesiveness between core rod and sheath. In view of this, one classification method was proposed to evaluate four operation composite insulators in order to investigate and evaluate the adhesiveness, and the results demonstrated that the adhesiveness was related to not only the bonding quality in production process but also the electric field intensity in operation process. The classification evaluation method was proved to be effective for the adhesiveness between core rod and sheath, which could provide valuable references for the production and maintenance of composite insulators.

This paper deals with the air gap insulation of ±800 kV DC transmission systems under composite DC and switching impulse voltage. The gaps studied were representative of ±800 kV DC transmission line, as rod-to-plane and conductor-to-tower gaps. The flashover voltages of the gaps at an altitude of 2100 m were determined for a pure switching impulse and composite voltages of DC and switching impulse. It is found that there are clear increase in the composite flashover voltage of both rod-to-plane and conductor-to-tower gaps, compared with those in the gap that only impulse voltage was applied. From the test results, the flashover voltage increases by 17-23%in the rod-to-plane gap and 5-10% in the conductor-to-tower gap, when the DC voltage of 800 kV is pre-stressed. The standard deviations have little obvious variation under the pre-stressed DC voltage and its average value is 4-4.5% in the tests. Additionally, a 1,000,000 fps high speed CCD camera is used to observe the breakdown process for investigation on the influence of pre-stressed DC voltage on the conductor. The leader inception and breakdown process properties were studied. These data and explanation are useful for ±800kV DC insulation design and testing.

The past and recent investigations show that front time of switching overvoltage waveforms in Ultra High Voltage (UHV) system of long distance transmission are mostly in long wave front time exceeding 1000μs. The long front time of switching impulse voltage has been deviated from the critical front time. This paper is involved with breakdown characteristics and external insulation design under long front switching impulse voltage in UHV system. All the Tests were performed on an outdoor UHV test site at altitude of 2100 m, China Southern Power Grid Co. Ltd. (CSG). Breakdown characteristics of rod-plane and actual size tower-conductor in /spl l.chemo/800 kV UHV DC transmission line are obtained under wide front time switching impulse voltages from 100 to 2350 μs. From the comprehensive studies of such tests, it is proposed that U50 of front time exceeding 1000 μs increases 20% compared with the results of standard switching impulse (250/2500 μs) tests and standard deviations of U50 is 6% in UHV transmission system. Finally, an air gap insulation design procedure in conductor-tower of UHV transmission line at altitude of 0-2000 m is presented. Long front time switching impulse strength of conductor-tower gap is proposed into selection by reference in UHV transmission line insulation design.

Lightning is the major cause of interruptions in power transmission lines. Ultra-high voltage (UHV) AC transmission line has been put into operation in China. Due to the large tower height up to 90 m and the high operation voltage up to 1000 kV, the shielding failure probability increase obviously. Nowadays the leader progression model is an advanced method to evaluate the shielding failure probability of transmission lines. The surface electric field is the key issue for lightning failure analyzing, because the upward leader inception mainly depends on the surface electric field. In this paper, the lightning leader model is introduced. A charge simulation method based piecewise linear function is adopted to analyze the surface electric field on phase conductors and ground wires. The influence factors, such as operation voltage, lightning peak current, lightning down leader position, protection angle, on surface electric field were analyzed.

The problem whether the upward leader can incept from the transmission lines in lightning shielding failure is still in question, since the upward leader emerging from transmission lines is difficult to be captured under natural circumstance. It is necessary to study the characteristics of upward leader. This paper presents some simulated experimental results of a 6-m long, combined plane-rod (PR) electrode to conductor (ground wire (GW)) air gap. A current measuring instrument with frequency response of DC-6.5 MHz was developed and used to measure the leader current. Besides, high speed CCD camera was used to observe the optical phenomenon of the whole process. In the experiment, upward leader emerging from bundle-conductors and GW was found. The velocity, surface electric field and charge of upward leader channel were obtained by analyzing the experimental data. Finally, the surface electric field of conductor for natural lightning circumstance was compared with the field in the experiment, in order to prove that the upward leader can emerge from transmission lines due to the downward leader of lightning.

Included angle selection for a V-shape insulator string applied in 750-kV compact transmission line is studied in this paper. The mechanical performance of V-shape insulator string is demonstrated from calculation and experiment. A new solution, which is based on the finite-element method and applied to calculate the deformation of V-string, is presented. This paper discusses the relation between deformation (displacements and force) and load on V-string. Loading experiment for V-string is conducted in order to verify the calculation results. Experimental data of displacements for V-shape composite and porcelain insulator string are obtained. Finally, combined with the calculation and experiment results, the selection of included angle for V-shape insulator string is discussed, and recommendations for the included angle value of V-shape insulator string in 750-kV compact transmission line are made.

Measuring the intensity of electric field is significant for many applications in power system, so DC electric field measurement has been a major subject over the past half century. While, because of some special properties, such as high field amplitude, space charged ions and the complicated electromagnetic environment, it's very difficult to design a sensitive and accurate DC electric field sensors (EFS). According to working principle, EFSs can be classified into two categories, the mechanical vibrating type and the electro-optical type. In recent years, the MEMS technology has been used to fabricate EFS, and gigantic achievement has been made. In this paper, the mechanisms of these three main kinds of the EFS were introduced, including the rotating electric field mill, MEMS electrostatic field meter and the integrated Optical E-field Sensor. The characteristics and perormances were thoroughly compared.

The problem whether the DC operation voltage can influence the characteristics of upward leader emerging from transmission lines is still in question since experiments and observation data is insufficient. It is necessary to study the relationship between the characteristics of the upward leaders and operation voltage. This paper presents some simulated experimental results of a combined plane-rod (PR) electrode to conductor air gap of 7 meter length. A current measuring instrument with frequency response of from DC to 6.5MHz was developed and used to measure the leader current. Besides, high speed CCD camera was used to observe the optical phenomenon of the whole process. The 200/2000µs impulse voltage up to 4MV and positive DC voltage up to 800kV was applied to the electrode and conductor respectively. The higher charge per unit in the leader channel and earlier inception time has been found along the higher DC voltage. These results have been compared with those in the gap that only impulse voltage was applied. Finally, the influence of positive DC voltage on the characteristics of upward leaders was discussed.

High altitudes and heavy pollution are special technical problems faced by UHV DC transmission line in China. Much research work of external insulation performance for ±800 kV DC Transmission Lines were carried out at National Engineering Laboratory for Ultra High Voltage (UHV) Engineering Technology (Kunming). For composite insulators, the shed design parameters have great influence on the flashover voltages. It was found that, with the same insulation distance, the flashover voltage had optimized values at a particular value of the radial extent of the shed and of the between-repeat distance. And the suspension patterns also play an important role in the flashover performance for composite insulators. The flashover voltage of the full scale post insulator decreased with the increasing of the SDD. The switching impulse strength of air gap clearance at a full scale conductor-to-tower model of Yunnan-Guangdong ± 800 kV UHVDC project is also studied.

Lightning is a major cause of power interruptions in power transmission lines. Nowadays the Leader Progression Model is an advanced method to evaluate the shielding failure probability of transmission lines. Calculating the surface electric field on phase conductors and ground wires precisely is important, because the surface electric field has great effect on the upward leader inception. In this paper, the influence of lightning current and some other factors on surface electric field were analyzed.

In order to guide the design and improvement of grading and shielding rings to meet the requirements of UHV projects in China, research on corona characteristics of these components is needed. One of the difficulties is that there is a lack of a proper definition of visible corona. It is common using visual observation, which is easily effected by subjectivity and the observation background. In this paper, a new definition of visible corona based on UV Corona Monitor was presented. According to the definition, measurements of the corona inception and extinction voltage on the rob tip in a rob-plate setting under both positive and negative DC voltage were carried out in laboratory. The same measurements on grading rings with different diameters under positive DV voltage were performed in Wuhan High Voltage Research Institute. The results show that the UV Corona Monitor can be used to find out visible corona and obtain the corona inception and extinction voltage.