Degraded Composite Insulator Detection Method based on Spatial Electric Field Measurement

In order to detect the defects of composite insulator core rods, this article establishes a calculation method for the electric field around crack defect composite insulators by analyzing the relationship between the electric field distortion of the defective composite insulator core rods and the discharge of live end charges. By using this method, the corresponding crack parameters and positions can be calculated based on the abnormal electric field distribution around the composite insulator. In order to use the calculation method of the electric field around composite insulators with crack defects to detect composite insulator core rods, a detection method based on an ultraviolet imaging system was designed to detect electric field defects around the core rods. The accuracy and practicality of this detection method were experimentally verified using composite insulators in service. The experimental results show that this detection method can effectively detect the defects in composite insulators and restore the aging status of composite insulator core rods through defect features, thereby achieving live detection of the aging status of composite insulator core rods, improving the detection efficiency of composite insulators, and reducing the risk of accidents caused by core rod aging in composite insulators.

Composite insulators are widely used in modern power systems due to their excellent performance, which is very important for the detection of the operating state of insulators. At present, there is no efficient and feasible way to detect the internal defects of composite insulators. With the development of live working technology, the electric field method has a good prospect for detecting composite insulator defects. In this paper, the finite element analysis software ANSYS is used to simulate the electric field of the running composite insulator. The research shows that with the increase of the length of the defect, the field strength of the defect increases approximately linearly; when detecting the defect, the detection distance should be reduced as much as possible; when detecting the defect, the defect detection of 0 degree and 60 degree angle should be avoided as much as possible. Affect the accuracy of detecting defects. According to the simulation results, a detection method based on electric field distribution is proposed.

Insulators are the basis of the stable operation of transmission lines, and it is particularly important to regularly detect the insulation performance of insulators. After several years of research, contactless space electric field detection technology for degraded insulators, based on an unmanned aerial vehicles (UAV) platform, has developed rapidly. However, the existing technology is only limited to the typical vertical/horizontal state research category and cannot apply to complex operating conditions such as attitude disturbance and path tilt. This paper builds a simulation model of insulators at a voltage level of 220 kV by COMSOL finite element software and analyzes the space electric field distribution characteristics of degraded insulators and the influence of different surface conditions, attitude disturbance, path tilt, etc., on the space electric field distribution of insulators. To reduce the error of UAV detection under complex operating conditions of insulators, a method for detecting the electric field of degraded insulators based on sensitive insulators is proposed and verified by experiments. According to the research results, surface conditions of insulators have little influence on their space electric field, while the attitude disturbance and path tilt of UAVs have a great influence on the electric field of insulators. Sensitive insulators at a level of voltage below 220 kV are generally located at the low-voltage end. The principles of sensitive insulators are combined with the space electric field measurement method to measure the space electric field distribution, thus effectively judging whether there are degraded insulators in the string. The method specified in the paper greatly improves the accuracy and detection efficiency of the contactless electric field detection of insulators, which is of great significance for the promotion of the electric field detection method of insulators in practical applications.

Hydro-Quebec's experience with polymer insulators began in 1977. A sixteen km section of a 735 kV transmission line near Quebec City was then re-insulated with 282 composite insulators of three different makes in equal proportions. The objective was to study them under real service conditions in order to evaluate their performance and to assess the relative merits of each make. This experimentation was later extended to some other lines and/or voltage levels and has continued up to now. During all these years, various methods of testing composite insulators in-service have been experimented with and early in the 1990s, the first device developed at IREQ for the in-situ testing of porcelain insulators by the electric field method was modified and adapted for use on composite suspension insulators. This paper presents a few cases of insulators having a particularly dangerous type of failure mode and found on the lines by the use of the electric field method. Some background information on the detection of defects by this method is also given and some of the experiments done in the laboratory on composite insulators to define the limits of the method are described.

Electric and magnetic fields (EMF) are ubiquitous. The earth has static electric fields, which produce lightning during thunderstorms, and geomagnetic fields created by electric currents within its core. Electric and magnetic fields are also produced during electric power generation, transmission, and use.Electric power has generally been considered safe during the more than 100 years of its use, although shocks and burns from direct contact with electrical conductors are a recognized health hazard. Of the approximately 1100 deaths from electric shock that occur each year in the United States, about three‐fourths result from unsafe operation of household appliances; accidents in the workplace account for the rest. The possible health consequences of electric and magnetic field exposure are a much more recent concern.Power‐frequency EMF exposure—unavoidable since the use of electricity has spread throughout the world—has been under investigation since the early 1970s. Investigations have included epidemiologic as well asin vitroandin vivolaboratory studies encompassing a wide range of diseases. The literature on EMF and health is vast, comprising over 1000 published studies, and has been reviewed in depth by several authoritative committees. Of note are reviews by the National Research Council of the National Academy of Sciences (NAS), the National Institute of Environmental Health Sciences (NIEHS) and the U.K. National Radiological Protection Board (NRPB).Electric power systems in the United States, Canada, and Mexico generate and transmit electricity as alternating current (ac), which oscillates at a frequency of 60 cycles per second, or 60 hertz (Hz). Most of the rest of the world generates power at 50Hz. Power‐frequency 50‐ and 60‐Hz fields occupy the extremely low‐frequency (ELF), nonionizing range of the electromagnetic spectrum. The ELF range includes frequencies from 3 to 3000Hz. Above 3000Hz are, in order of increasing frequency or decreasing wavelength, radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, x‐rays, and gamma rays. Microwaves have enough photon energy to heat tissue; ionizing radiation like x‐rays and gamma rays can damage biological systems by breaking chemical bonds. Extremely low‐frequency electric and magnetic fields can neither break bonds nor heat tissue, and the electric currents they induce in the body are very weak.Power‐frequency fields have very long wavelengths of about 5000km. Exposure distances are much shorter than this wavelength; under these circumstances, electric and magnetic fields are independent.Electric field strength increases with increasing voltage, or electric potential; magnetic field strength increases with increasing current. Both electric and magnetic fields decline rapidly with distance from their source, with a faster decline of fields from point sources such as machinery and a slower decline of fields from power lines. Electric fields are further reduced when shielded by conducting objects like buildings and have little penetrative ability; magnetic fields, on the other hand, are capable of penetrating tissue and are not easily shielded.Occupational exposure to electric and magnetic fields occurs from proximity to large motors as well as from wiring in buildings and the use of computers, office machines, and heating and air conditioning systems. Power transmission and distribution facilities are other sources.Accurate assessment of EMF exposure has presented many difficulties in epidemiologic studies and continues to be a considerable challenge. EMF have several unique characteristics that make them more difficult to measure than most other types of exposures. EMF are not readily detectable, are variable in time and space, and are to some extent present in all environments. Additionally, electric fields are both perturbed and intensified by conducting objects like the human body, so that fields measured at various points on the body's surface have different values. Because of the complexity of exposure circumstances, exposure reports from workers are not reliable.

We use the sensitive response to electric fields of Rydberg atoms to characterize all three vector components of the local electric field close to an atom-chip surface. We measured Stark-Zeeman maps of $S$ and $D$ Rydberg states using an elongated cloud of ultracold Rubidium atoms ($T\sim2.5$ $\mu$K) trapped magnetically $100$ $\mu$m from the chip surface. The spectroscopy of $S$ states yields a calibration for the generated local electric field at the position of the atoms. The values for different components of the field are extracted from the more complex response of $D$ states to the combined electric and magnetic fields. From the analysis we find residual fields in the two uncompensated directions of $0.0\pm0.2$ V/cm and $1.98\pm0.09$ V/cm respectively. This method also allows us to extract a value for the relevant field gradient along the long axis of the cloud. The manipulation of electric fields and the magnetic trapping are both done using on-chip wires, making this setup a promising candidate to observe Rydberg-mediated interactions on a chip.

The high polarizability of Rydberg atoms enables the multi-parameters measurement of electromagnetic fields. In this paper, we report on an atomic antenna based on Rydberg atoms in a room temperature vapor cell. The EIT is a destructive interference spectroscopy with a narrow linewidth and can be used to detect small electric fields through Autler-Townes splitting or Stark shifts. In our experiments, we employ cascade-type two-photon excitation electromagnetically induced transparency (EIT) spectroscopy to measure the shift of the Rydberg energy level. We introduce a low-frequency electric field (~kHz frequency) using a built-in electrode technique in the cesium cell. The interaction between the Rydberg atom and electric field induces the Stark shifts, where the amplitude of the electric field is converted into corresponding two-photon detuning by the EIT effect. Furthermore, the amplitude of the low-frequency electric field is converted into an intensity signal of EIT probe beam. Under weak field conditions, it is an approximate linear relationship between EIT transmission signal and input electric field amplitude, enabling measurement of waveform, amplitude, and frequency. We have demonstrated optical measurements of low-frequency electric field using Rydberg atoms. By increasing the power of probe beam and coupling beam, the EIT can increase the response bandwidth from ~MHz to hundreds of MHz. This provides a scalable approach for measuring high-frequency electric fields.

Typical composite insulators are widely used in the electric power system, including the composite insulators for the transmission lines, the composite pillar insulators for substations and the hollow composite insulators of transformer bushing. The composite insulators have different operating environment and surface E-field distribution characteristics, so it is urgent to make reasonable evaluation of the operation status. Firstly, the typical composite insulators are observed by the ultraviolet and infrared imaging technology to form the database of electrical-thermal image. The original images are denoised by the wavelet imaging technology, and the image region of the composite insulators is segmented based on the clustering algorithm. The adaptive recognition of composite insulators and the matching of external contours are realized by visual depth learning. At the same time, three-dimensional modeling technology is applied to simulate the electric field distribution law of typical composite insulators, to visualize the E-field in the high field strength area of composite insulators. Finally, the post-processing results of image and the characteristics of electric field distribution are combined to form evaluation strategy of composite insulators operation status . This study has guiding significance for operation and maintenance of composite insulators used in power system.

Localized overstress due to electric field concentration is a threat to the long-term performance of the high-voltage insulators, as electric field stresses that exceed the threshold values and they are applied for long periods of time which lead to degradation and deterioration of the housing materials and therefore to failure of the composite insulators in service. So, knowledge of the distribution of the electric field in and around high-voltage composite insulators is a crucial aspect of their design and operation. This paper is intended to improve the electric field and potential distributions by minimizing the corona discharges on AC 400 kV transmission line composite insulator. For this goal, a Functional Graded Material (FGM) is designed for the composite insulators housing materials to obtain uniform field stress along the surface of the composite insulator in order to overcome the above problem. An FGM insulator is graded with different permittivity for three cases grading to High, Grading to low and U-Shape.

The low-frequency electric field generated by various electromagnetic effects in the ocean overwrites the useful signal in amplitude and frequency, as a background distraction field for electric field detection. Effective electric field characteristic analysis and prediction methods are helpful to improve the environmental adaptability of the equipment and the ability of target detection. The deep learning method is used to mine the characteristics of underwater electric field in the marine environment to improve the prediction accuracy. In order to explore the relationship between seawater environmental parameters and electric field characteristics, parameters including measure time, seawater conductivity, water depth and wave height are used as independent variables, and the amplitude of the underwater electric field in the marine environment is used as the dependent variable. The relationship model between independent variables and dependent variables are established by deep neural network training to realize the prediction of underwater electric field characteristics in the marine environment. The results of 103 training samples and 2 test samples show that the method can effectively identify the test samples, and can be used for the mining and prediction of underwater electric field characteristics, as well as the detection and identification of weak electric field signals submerged in the marine environment.

In this paper, a dynamic model that simulated and tested the flashover of polluted insulators with HV voltage is presented. Generally, developing the performance of the transmission line depends on the improvement of the insulators due to the pollutants deposited on its surface. This study focused on the classification of insulators and the factors that affect the insulators to cause flashover as well as the analysis of the insulator’s electric properties. The electric field and voltage distribution along with composite insulators used in transmission systems under different conditions were also presented. The problem of nonlinearity of the electric field and voltage distribution, especially along insulators used for HV transmission systems, was investigated and a solution for improving the electric field and voltage distribution along the insulators was suggested. Findings showed that the presence of water droplets and pollution layer distributed on weather sheds enhanced the local electric field but it did not really affect the electric field distribution inside the fibre reinforced plastic core. Moreover, for the pollution case, the effect of pollution layer conductivity was significant to the electric field. For thicker pollution layers, the maximum electric field point moved from the triple junction point. Finally, the study also found that the corona ring might be necessary for the HV insulator for both ends (HV and ground) and its behaviour was affected under polluted and wet conditions.

Rapidly increasing growth and automation of power are given the opportunity to power engineers to incorporate new ideas in the field of online monitoring of power apparatus for reliable operation of electrical system. As a part of new innovation in power system, photonics play an important role for driving innovation toward the sensor development, optical data communication to imaging, lighting and displays. In any power apparatus, degradation of insulation occurs due to the accumulation of mechanical, thermal and electrical effects for a long period. As the insulation of high voltage (HV) power apparatus are deteriorated by partial discharges (PDs), detection and measurement of PDs are of utmost important for the quality assessment of HV power equipment. In this chapter, an attempt has been made to detect the PDs with the help of photonic technology which eliminates the electrical interference; a challenge is being faced by power engineers in recent decades. It is understood from the several studies, PDs of HV power apparatus can be detected by electrical, chemical and acoustic methods. Electrical detection focuses on capturing the electrical impulses created by the current streamer in the void and impurities. Electrical detection method has some limitations. The primary limitation is its susceptibility to noise. The high voltage transformer (HVT) environment contains high levels of electrical noise, both narrowband and broadband. Chemical detection has also some drawbacks. Firstly, this detection method does not give any information about the location of the PD and the insulation condition. Secondly, the main problem is that chemical tests cannot be performed continuously when the HV equipment are in working operation. To explore the detection of PDs through acoustic method, acoustic phenomenon of PDs has been studied, and it is found that it leads to the propagation of acoustic waves having frequencies typically between 30 and 1000 kHz inside the transformer. The propagation of acoustic wave modulates the refractive index of the medium, which modulates the intensity of the laser beam in sympathy with the acoustic waves. Acoustic methods have many advantages over other methods in that they are immune to electromagnetic interference (EMI), which can greatly reduce the sensitivity of electrical methods and they can be applied to find failure spot and location of discharges. Optical technique is also capable to couple PDs with the optical signal. To capture the acoustic waves, an optical method is demonstrated in this chapter for detection and localization of PD sources by using photo detector inside the HV power apparatus. In this work, a new concept such as direct optical partial discharge detection technique has been introduced, where the energy exchange mechanism of electrical to acoustic is used for online monitoring of PDs. The acoustic signals are collected directly through the photonic technology, which is free from electrical interference, and finally they are converted to electrical signals for detection of amplitude as well as location of PDs occurring inside the HV power apparatus. This is a cost-effective tool for online monitoring of PDs and can be used as a predictive maintenance tool for utilities.

A silicon (Si) protrusion, grown on a narrow path of a Si(001) wafer by surface melting via resistive heating, was sharpened by applying a local high electric field under a magnetic field during the growth. The electric field caused local stress to the surface-melted Si, which was pulled upward along the field. Consequently, the melted Si formed a sharper protrusion on solidification, with an apex surrounded by {001}, {113}, and {111} facets. The field emission from the protrusions was measured. The onset voltage of the emission from protrusions was lower when they were grown under the electric field. We used Fowler–Nordheim plots to characterize the emission current and voltage conversion factor, β. The results indicated that the application of electric field is beneficial to sharpening Si protrusions grown from Si melt. Such protrusions surrounded by facets are suitable for field emission electron sources with a high local electric field.

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Composite insulator has advantages in antifouling property, light weight, easy installation and transportation. It has been widely used in 1000kV UHV transmission lines. As the increase of operating voltage, the nonuniformity of potential and electric field distribution on the high voltage end of composite insulator is more serious due to its geometry configure, and the aging problem is easier to occur. Porcelain insulator has higher permittivity and better electrical erosion resistance when compared with composite insulator. Therefore, in order to improve the voltage-sharing and anti-aging performance, this paper proposed a novel configuration scheme of composite insulator with series connection of several porcelain disc insulators for 1000kV AC transmission line. One type of 1000kV suspension composite insulator string was taken as an example. Porcelain disc insulators of different number were installed to the high voltage end respectively, while the length of composite insulator string was decreased in order to guarantee the same total insulation length. The three-dimensional (3D) finite-element method (FEM) models of combined insulator strings were built with software ANSYS. The potential and electric field distributions on the whole insulator string were calculated, and the influence of the number of porcelain disc insulators was analyzed. The grading ring configuration for the whole insulator string was also put forward in order to decrease the surface electric field strength on sheds and fittings of insulators. The analysis result shows that the composite insulator with series connection of several porcelain disc insulators could improve the uniformity of potential and electric field distribution effectively. This research could provide valuable references for application of combined insulator string in the 1000kV UHV AC transmission line.