Umbrella Skirt Research Articles

ICP registration with SHOT descriptor for arresters point clouds

Abstract Arresters are one of the critical components of the power system.
However, due to the arrester’s regular and uniform umbrella skirt, both traditional
manual detection methods and existing computer vision approaches exhibit limitations
in accuracy and efficiency. This paper proposes an automatic, robust, efficient arrester
point cloud registration method to address this problem. First, a robotic arm
maneuvers a depth camera to capture point cloud data from various perspectives.
Then, the fast global registration (FGR) point cloud coarse registration method
based on the signature of histograms of orientations (SHOT) descriptor to produce
preliminary registration results. This result is ultimately used as the initial value of
the improved iterative closest point (ICP) algorithm to refine the registration further.
Experimental results on various data sets collected from arrester and public data sets
show that the algorithm’s root mean square error(RMSE) is less than 0.1mm, meeting
the requirements of the engineering application of arrester detection.

Research on electric field characteristics under different length interface air gap defects in cable terminals of high-speed train

It is vital that accurately and effectively detecting the insulation status of cable terminal to ensure the safe and stable operation of high-speed trains. Accordingly, a novel monitoring system for the internal defect detection of cable terminal was proposed based on electric field strength. Firstly, partial discharge and electric field strength along the surface of the air gap defects cable terminal umbrella skirt were measured and analyzed. The development of internal defects in cable terminals can be divided into three stages: S1, S2, and S3. Then, the interquartile range, variance, average value and dispersion coefficient of electric field strength have been proposed to characterize the development state of air gap defects in cable terminal. The results shows that the internal defects of cable terminals develop from 20%l to 100%l, the slope of the interquartile range of the distribution of magnitudes of the electric field intensity increases from 0.126 to 0.671, and the absolute value of variance and offset increase by about 81.3% and 80.66%, respectively. Therefore, it is feasible and effective to detect the development state of air gap defects inside the cable terminal by measuring and analyzing the electric field strength characteristics along the surface of the cable terminal umbrella skirt.

Analysis of Aging Characteristics of Umbrella Skirts of Composite Insulators Operating under the Influence of a Wind and Sand Environment in South Xinjiang.

To study the influence of multi-factors, such as long sunshine, sand erosion, and so on, in southern Xinjiang, we selected two kinds of composite insulators for the transmission lines in southern Xinjiang to study the aging characteristics of the umbrella skirt surface. The results of scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) show that the surface roughness of the umbrella skirt is high and there are a large number of micron inorganic particles. The skirt has the characteristics of low C/O element ratio and high Al element content. The results of thermogravimetric analysis and micro infrared test show that the aging depth of the Myli Line skirt after 19 years of operation is 160~190 µm and that of Yuhe Line 1 after 14 years of operation is greater than 180 µm. The plasma discharge method was used to simulate the corona discharge in the actual operation to accelerate the aging of the surface of the umbrella skirt and the hydrophobic recovery of the umbrella skirt was investigated. The results show that the temperature has a great influence on the surface hydrophobic recovery performance after plasma treatment. These results may provide some theoretical guidance and technical support for the selection, operation, and maintenance of composite insulators in Xinjiang.

Reusable, Stable, Efficient and Multifunctional Superhydrophobic and Oleophilic Polyurethane Sponge for Oil-Water Separation Prepared Using Discarded Composite Insulator.

Oil spills and chemical leakages are a serious source of pollution in oceans and rivers, and have attracted worldwide attention. Many scientists are currently engaged in the development of oil-water separation technology. In this study, the umbrella skirt of a discarded silicone rubber insulator was utilized as feedstock, and polydimethylsiloxane (PDMS) was employed to immobilize the prepared powder (FXBW) onto a polyurethane (PU) sponge skeleton. Without any modifications using chemical reagents, a novel oil-water separation material, FXBW-PU, was developed, with a water contact angle of 155.3°. The FXBW-PU sponge exhibited an absorption capacity ranging from 11.79 to 26.59 g/g for various oils and organic solvents, while maintaining an excellent selective adsorption performance, even after undergoing ten compression cycles, due to its exceptional chemical and mechanical stability. With the assistance of a vacuum pump, the FXBW-PU sponge was utilized in a continuous separation apparatus, resulting in a separation efficiency exceeding 98.6% for various oils and organic solvents. The separation efficiency of n-hexane remains as high as 99.2% even after 10 consecutive separation cycles. Notably, the FXBW-PU sponge also separated the dichloromethane-in-water emulsions, which achieved the effect of purifying water. In summary, FXBW-PU sponge has great potential in the field of cleaning up oil/organic solvent contamination due to its low preparation cost, environmental friendliness and excellent performance.

The Detecting System and Method of Quasi-Distributed Fiber Bragg Grating for Overhead Transmission Line Conductor Ice and Composite Insulator Icing Load

Transmission lines icing is destructive to the operation of the power grid. There is a lack of methods to monitor overhead transmission line conductors and insulators for icing load simultaneously. In this paper, we implanted six optical fibers with three quasi-distributed FBGs each into the interface of a 110kV composite insulator and built an icing detection system, and proposed three ways for measuring overhead transmission lines icing load. A method for quasi-distributed FBG to differentiate between the measurement of running insulator umbrella and conductor icing load was proposed and validated. The effect of the number of implanted optical fibers on the measurement accuracy was studied. The results show that the relative error of simulated insulator umbrella skirt icing load measurement is -7.3%∼-2.7%. The 200m-span running conductor insulator umbrella skirt icing load measurement relative error is -11.5%∼-3.8%; the relative error of conductor ice measurement is -16.5%∼9.0% and absolute error is -0.83∼1.5mm. The composite insulator with an optical fiber embedded can accurately warn of serious icing on the conductor, with two can achieve the conductor icing measuring absolute error of about ±1mm. As for accurately measuring both the umbrella skirt and the conductor icing, it is necessary to implant six optical fibers.

Electric field distribution and performance optimization of high-speed train cable terminal with internal defects

High voltage cable terminal of high-speed electric multiple units (EMU) is an important part of on-board high voltage equipment. As the weak link of the cable assembly, the cable terminal is prone to penetrability discharge and resulting in insulation failure, which seriously affects the EMU’s safety and reliability. The electric field intensity distribution of high-voltage cable terminal with internal defects such as air gaps, moisture, semiconductors and carbons are simulated and studied. At the same time, in order to improve the distortion of the internal electric field intensity of the EMU cable terminal, nonlinear materials and high dielectric materials are used to replace the stress tube respectively, and the optimization effects of the two materials on the internal distortion electric field of the cable terminal are studied. The results show that the defects are closer to the multi-layer combination area among main insulation layer, stress tube layer and outer semiconducting layer of the cable terminal, the electric field distortion of multi-layer combination area become greater. With the increasing of defect size, the electric field intensity also gradually increases. However, the inner defect location and size have less effect on the electric field intensity along the cable terminal umbrella skirt. It is found that both nonlinear materials and high dielectric materials can effectively optimize the electric field intensity of cable terminal and improve the electric field distortion. This work can be helpful for operation and design of high-speed EMU’s cable terminal.

Formation Mechanism and Optimization Method of Streak-Shaped Pollution for the Roof Insulator of EMUs

Roof insulators are one of the key pieces of equipment to ensure the electrical safety of high-speed railways (HSRs). When the umbrella skirt of a roof insulator is seriously polluted in various environments, the risk of pollution-induced flashover rises. Field experience shows that the flashover possibility of roof insulators in coastal intercity railways is much higher than that in other regions. However, the pollution characteristics of roof insulators under those conditions are still unclear. In this work, we investigated the pollution characteristics of roof insulators used in the coastal intercity railway of electric multiple units (EMUs) of China. Aspects of the pollution spatial distribution, the statistical content, and the pollution constituent on the surface of the umbrella skirt of insulators are taken into account. The airflow field and electric field distribution around the pantograph support insulator (PSI) are also simulated based on finite element software. To reduce the formation of streak-shaped pollution, the umbrella skirt is optimized by the streamlined structure. The results indicate that a novel phenomenon of streak-shaped pollution distribution might form on the surface of the insulator, which would severely aggravate the distortion of electric field distribution. The calculated turbulence dissipation rates are found to spatially agree well with the streak-shaped pollution distribution. The streamlined structure effectively reduces the turbulence dissipation rate at the junction of the windward and leeward surfaces, to inhibit the formation of streak-shaped pollution.

Point cloud registration of arrester based on scale-invariant points feature histogram

Arrester is an important lightning protection device in the electrical field. The parameters of arrester such as creepage distance, umbrella distance and diameter are important for product quality, but they are difficult to measure because the shape of arrester is irregular. However, the three-dimensional (3D) reconstruction technique is efficient in measuring arrester parameters. The uniform distributed structure of umbrella skirt on the arrester surface restrict the registration of point cloud. In this paper, a scale-invariant points features histogram (SIPFH) descriptor is proposed; the descriptor combines the characteristics of Scale-invariant Feature Transform (SIFT) and fast point feature histogram (FPFH). Moreover, the improved Levenberg-Marquardt (LM) algorithm is presented, the maximum distance of corresponding points in the iterative process is adjusted to realize the local optimization. The point cloud registration method consists of two parts: primary registration method based on SIPFH, and secondary registration method based on improved LM algorithm. Point clouds of different arresters are collected to establish datasets, some of which have interference. Experimental results indicate that the root mean square error of the method is less than 0.02 m; the average running time is 2.7 s, which is 41.4% of the conventional method based on FPFH.

Analysis of Electric Field Distribution of Insulators YD-JZ 10 kV Oil-Immersed Transformers

The electric field distribution of the YD-JZ 10 kV oil-immersed transformer insulator is analyzed by COMSOL simulation, calculation, and actual measurement methods. The result shows that the first shed of the insulator accounts for 18% of the voltage drop. After that, the voltage of each umbrella skirt decreased gradually, and the proportion of voltage drop of the last two umbrella skirts increased again. The electric field of the insulator tip burr is 1.16 × 106 V/m; spherical burr is 2.84 × 105 V/m. The simulation result shows that the maximum electric field of spherical air gap defect in an insulator is 1.38 × 105 V/m; conical air gap defect is 1.61 × 105 V/m ; metal particle defect is 1.49 × 105 V/m. The simulated insulator umbrella skirt is covered with water. When the whole insulator umbrella skirt is short-circuited, there may be ground discharge. The measured results and simulation results show that the insulator can work normally if the umbrella skirt is not completely short-circuited.

Defect Identification of Composite Insulator Based on Infrared Image.

The deterioration of a composite insulator’s mandrel will cause a serious power-grid accident, so it is necessary to find the defect as soon as possible. Infrared imaging is an effective means to detect mandrel-deterioration defects, but sheath-aging defects will cause trouble to screen mandrel deterioration. Therefore, it is urgent to distinguish the two defects. In this paper, two composite insulators that are out of service with different heating characteristics are tested and analyzed, and the temperature-rise characteristics are analyzed by building a simulation model. The results show that the temperature rise of composite insulators with oxidative decomposition of epoxy resin is large, and the range usually extends from the hardware of the high-voltage side to several umbrella skirts. The temperature rise caused by the composite insulator with the fiber completely wrapped by epoxy resin is small, which mainly occurs from the hardware to the first umbrella skirt. The simulation model constructed in this paper is consistent with the experimental results, which verifies the accuracy of the model. The model can distinguish the mandrel-deterioration defect and sheath-aging defect, and has guiding significance and important reference value for the detection rate of the mandrel-deterioration composite insulator and ensuring the safe and stable operation of the power grid.

Analyzing influences of snowfall on electric field at the interface of composite cross-arm with finite element method

The composite cross-arm was used in large numbers in power systems due to its safety and economic advantages. The interfaces were the weak link in the property of composite cross-arm. However, the influence of severe weather such as ice and snow on the interface property was not clear, which would bring potential risks to operation safety for composite cross-arm. To this end, the finite element method was used to study the characteristics of the electric field at the FRP-silicone rubber and FRP-RPUF interfaces under snowfall conditions in this paper. Firstly, the snow and snowmelt models of the composite cross-arm were established by combining the natural snowfall conditions and the classical snowed model, then the influence of snowed degrees, snowmelt stages and dry-band on the interfaces electric field was analyzed. The results show that the snow without melting basically does not change the interface electric field. During the snowmelt stages, the average electric field intensity of the FRP-silicone rubber interface increases and the maximum electric field intensity of the two interfaces decreases. The distortion of the interface electric field caused by the dry-band in the middle snowmelt stage is the most serious, at this time, the electric fields at FRP-silicone rubber interfaces reach a maximum of 14.72 kV/cm and 8.53 kV/cm respectively. When the length of dry-band reaches or exceeds the distance between the high-voltage fitting and the eighth large umbrella skirt, it basically no longer causes the distortion of interface electric field. Compared to the FRP-RPUF interface, the FRP-silicone rubber interface is more severely affected by snowfall. The results can provide a reference for improving the interface property and ensuring the safety of the composite cross-arm in severe weather conditions.

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

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

Analysis and Optimization on Non-uniformity of Temperature Distribution in Hydrophobic Cycloaliphatic Epoxy Resin Insulators during the Curing Process

Hydrophobic cycloaliphatic epoxy resin (HCEP) insulators are a new generation of outdoor transmission line insulators with good application prospects. However, the HCEP has obvious curing internal stress due to the uneven internal temperature distribution. In this paper, the curing reaction of HCEP mixture is analyzed and a three-dimensional transient temperature field model of HCEP insulator is established. The internal temperature field of HCEP insulator during curing is analyzed for the first time. The results show that the curing reaction of HCEP mixture conforms to autocatalytic reaction. The structure of umbrella skirt causes the uneven temperature distribution inside HCEP insulator. Based on a surrogate model, it is found that thermal conductivity has a great influence on axial temperature distribution, while curing temperature plays a leading role in curing degree and temperature overshoot. The optimal curing temperature is found according to Pareto front. This paper is beneficial for the theoretical analysis and engineering guidance for manufacture of HCEP insulators.

Experimental Study on Surface Electric Field Distribution and Flash-over Voltage of Bushing Composite Insulator at High Altitude

At present, the high voltage bushing composite insulator is widely used in AC/DC system substation, and its structural parameters show the nonlinear growth trend with the increase of voltage level. Therefore, in 1000kV UHVAC and 800kV UHVDC system, bushing composite insulator has the typical characteristics of long insulation distance and large radial diameter. At present, with the proposal of high-voltage power equipment compact optimization design scheme, the radial diameter of the composite insulator for bushing can be effectively reduced by reasonable design of internal capacitor core or metal shield structure optimization design scheme, so as to realize its large aspect ratio compact design. On the other hand, the insulation distance of high voltage bushing composite insulator will be further increased when it is applied in high altitude area. The innovation of this paper is how to carry out flashover voltage test to fill the current test data gap. In view of this, this paper first establishes two typical structures of the high voltage bushing composite insulators, including the three-dimensional finite element models of the composite insulators for capacitive core converter transformer bushing and the double-layer metal shield through the wall bushing, obtains the distribution characteristics of typical voltage and electric field under the operating state, and analyzes the local high field strength and corona, the electric field distribution of composite insulators for bushing. Furthermore, the actual flashover tests between large fittings air metal grounding body and large fittings composite insulator metal grounding body are carried out in the laboratory environment, and the quantitative relationship curve between flashover voltage and space net distance is obtained. Based on the above theoretical analysis and test data, the size altitude correction and umbrella skirt contour topology optimization of composite insulator for the UHV AC/DC bushing are carried out. Finally, the DC withstand voltage test and one minute power frequency withstand voltage test are passed, which proves the rationality and effectiveness of the design of composite insulator for bushing at UHV level. In this paper, starting from the typical electric field distribution characteristics of all kinds of composite insulators for bushing, the flashover law is studied for the first time, and the flashover test is carried out in the laboratory to supplement the classical test data. The research results have good theoretical and practical significance for installation, design and operation maintenance of all kinds of composite insulators.

Design and test of a 10 kV HV brushing for triaxial HTS cable termination

The high voltage (HV) bushing design of insulation core, umbrella skirt, lead type, and production process were proposed according to the technical requirements of the 10 kV high temperature superconducting (HTS) cable system of Shenzhen Power Supply Bureau. The design took full consideration of the withstanding voltage, impulse voltage, partial discharge, thermal shock, and anti-condensation level. According to the proposed design, a verification prototype was built and tested. It subjected to five slow 77 K-300 K thermal shock cycles and five severe 77 K-300 K thermal shock cycles to verify its performance. The sensitive electrical quantities were tested after each cycle. After the 10 cycles, no degradation of performance and no breakdown or flashover occurred were found in the prototype. The results show that the design is qualified for the expected purpose.

Anti-icing capability of textured silicone rubber surfaces via laser processing

ABSTRACT It is an undisputable fact that surface texture has a profound influence on the functional behavior of products. A method is proposed for manufacturing an anti-icing surface on silicone rubber composite material. Using a multi-function laser engraving machine, cylindrical micro-textures with different size and depth parameters are processed on the umbrella skirt surface of composite insulator samples. The optimal dimensional parameter of the surface micro-texture was determined by the best superhydrophobic property. By analyzing the freezing time of droplets, the influence of texture depth parameters on the anti-icing performance of the silicone rubber surface was investigated, which clearly confirmed that the contact angle affected anti-icing performance. Studying on adhesion of the ice on the sample surface and changing of the water contact angle after ice coating demonstrated the influence of texture-depth parameter on the deicing performance of silicone rubber surface. Thus, the characteristics and optimality of the texture specimen were obtained.

Simulation of Electric Field Distribution along Insulator Surface in Polluted Environments

In recent years, more than 50% of the cities in the inland area of our country have suffered from moderate pollution. It can affect the distribution of electric field along the surface of insulator and the pollution characteristics of its surface area, even endanger the safe operation of transmission lines. This paper takes the XSP-160 porcelain three umbrella insulator under the action of 0–±30 kV DC voltage as the research object, and establishes the physical model of the insulator; uses COMSOL software to simulate the electric field of the insulator. The comparison with the results of the wind tunnel test of North China Electric Power University verifies the rationality of the simulation method. In view of the medium pollution environment which often occurs in the inland area, the force of the polluted particles deposited on the insulator under 110 kV DC voltage was analyzed. The distribution characteristics of the electric field along the surface in the clean and three kinds of pollution environment (light, medium and heavy) were simulated and compared. The results showed that: 1) In the moderate pollution environment, the influence of fluid drag force on the movement of polluted particles is greater at the initial stage (0.28–0.33 s); at the late stage (after 0.33 s), the influence of the electric field force begins to increase, and gradually plays a major role in the process of fouling. 2) In the three different polluted environments, the potential along the surface of each umbrella skirt of the insulator increases non-linearly with the increasing of the pollution concentration, and there are apparent potential inflection points near b and l. 3) The pollution particle concentration has the most obvious influence on the electric field along the low-voltage umbrella skirt, whose potential distortion rate can be up to 220 times in the heavy polluted environment.

Study on Improving Interface Performance of HVDC Composite Insulators by Plasma Etching

High-voltage direct-current composite insulators are faced with various challenges during operation, such as creeping discharge, umbrella skirt damage, abnormal heating and insulator breakage. Among them, the aging of the interface between the core rod and the sheath is one of the important causes of composite insulator failure. In order to improve the electrical resistance of the composite insulator interface, this study uses plasma etching to modify the surface of the glass-fiber-reinforced epoxy resin plastic to prepare the high-voltage direct-current composite insulator core rod–sheath samples. By analyzing the surface morphology of the epoxy resin, static contact angle and surface charge transfer characteristics, the control mechanism of the plasma etching treatment on the interface bonding performance and leakage current of composite insulator core rod–sheath samples were studied. The results show that proper etching time treatment can improve the trap energy level distribution and microstructure of epoxy resin and increase the discharge voltage along the surface; chemical bonding plasma etching can improve the interfacial bonding performance of core rod–sheath samples sheaths, reduce the leakage current of composite insulator core rod–sheath samples sheath specimens and improve their interfacial performance.

Study on the Electric Field Distribution Characteristics of the DC Arrester in the Case of Pollution

The DC electric field has a strong adsorption effect on the polluted particles of the substation, so the surface of the DC surge arrester is more prone to fouling. The DC pole bus arrester of the UHV converter station will change the electric field on the external insulation surface and the electric field between the resistance valve and the insulation jacket due to its internal resistance sheet structure characteristics, so it will have a certain impact on the operation status of the arrester. In this paper, by constructing a simulation model of the pollution electric field on the surface of the UHV DC pole bus arrester, the distribution characteristics of the surface pollution in the DC field are studied, and the radial electric field characteristics of the umbrella skirt surface when the surge arrester is wetted and the local drying zone occurs are calculated. It will enhance the surface field strength and the internal radial field strength of the insulating jacket, but the value is small, and it will not cause surface corona and flashover and other discharge phenomena; but when the local dry zone appears on the surface, it will be on the outer insulating surface and the resistance valve A penetrating discharge with the insulating jacket will have a serious impact on the safe and stable operation of the arrester.

Performance Investigation on Different Designs of Superhydrophobic Surface Texture for Composite Insulator.

To investigate the superhydrophobic properties of different surface textures, nine designs of textures with micro-nanostructures were produced successfully using the laser engraving technique on the surfaces of composite insulator umbrella skirt samples made of silicon rubber. The optimal parameters of the texture designs to give rise to the best hydrophobicity were determined. The surface morphology, abrasion resistance, corrosion resistance, self-cleaning and antifouling property of the different textured surfaces as well as water droplets rolling on the textured surfaces were studied experimentally using a contact angle meter, scanning electron microscope, three-dimensional topography meter and high-speed camera system. It was found that the diamond column design with optimal parameters has the best superhydrophobicity and overall performance. The most remarkable advantage of the optimal diamond column design is its robustness and long-term superhydrophobicity after repeated de-icing in harsh conditions. The reported work is an important step towards achieving superhydrophobic surface without coating for outdoor composite insulator in practical applications.