UV Imager Research Articles

Corona Onset Characteristics of Contact Box in Switchgear With Condensation Under High Humidity and Pollution Conditions

Corona discharge occasionally occurs to the contact box of switchgear due to condensation under high humidity and pollution conditions, which may result in a switchgear insulation fault. In this article, we develop an experimental platform for the condensation of contact boxes in switchgear. A metallographic microscope is used to measure the size and distribution characteristics of dewdrops on the surface of the contact box under various temperature, humidity, and pollution conditions. A simulation model for the distribution of dewdrops is established using fractal theory, and the simulation results match the measured results well. The corona onset voltage is predicted and verified by the UV imager’s measurements by substituting the electric field distribution around the contact box with different dewdrops into the streamer inception criterion. The research results indicate that higher humidity and temperature differences result in a larger dewdrop and a shorter condensation formation time, resulting in a lower corona onset voltage. The effect law is similar under high pollution conditions, but the dewdrop is larger, the condensation formation time is longer, and the corona onset voltage is significantly lower than under clean conditions. As a result, high humidity and pollution conditions must be avoided during the operation of switchgear.

Achieving UV and X-ray Dual Photochromism in a Metal-Organic Hybrid via Structural Modulation.

Rational design and synthesis of new photochromic sensors have been active research areas of inquiry, particularly on how to predict and tailor their properties and functionalities. Herein, two thulium 2,2':6',2''-terpyridine-4'-carboxylate (TPC)-functionalized metal-organic hybrids, Tm(TPC)2(HCOO)(H2O) (TmTPC-1) and Tm(TPC)(HCOO)2 (TmTPC-2) with different photochromic response behaviors, have been successfully prepared, allowing for straightforward investigations of the structure-property correlation. Single-crystal X-ray diffraction and electron paramagnetic resonance analyses revealed that the incorporation of a unique dangling decorating TPC unit in TmTPC-1 offers a shorter and more accessible π-π interaction pathway between the adjacent TPC moieties than that in TmTPC-2. Such a structural feature leads to the production of radical species via a photoinduced intermolecular electron-transfer (IeMCT) process upon UV or X-ray irradiation, which ultimately endows TmTPC-1 with a rather unusual UV and X-ray dual photochromism. A linear relationship between the change of UV-vis absorbance intensity and X-ray dose was established, making TmTPC-1 a promising dosimeter for X-ray radiation with an extremely high energy threshold (30 kGy). To advance the development for real-world application, we have fabricated polyvinylidene fluoride (PVDF) membranes incorporating TmTPC-1 for functioning either as a UV imager or as an X-ray radiation indicator. Lastly, TmTPC-1 exhibits high thermal stability (up to 400 °C) and radioresistance (at least 900 kGy), and also excellent reversibility of photochromic transformation (at least 5 cycles).

Influencing of water droplets on corona inception characteristics of composite insulator recorded by UV imager

Water droplets on the surface of insulators can distort the electric field and cause the generation of surface partial discharge or flashover. In this study, the inception and the development of surface partial discharges on a 110 kV composite insulator were evaluated by using a solar-blind ultraviolet imager. Several experiments were conducted by using water droplets differing in volume, conductivity, and position on an insulator housing. The results showed that the corona inception voltage decreases with the increasing volume of the water droplets. The relative permittivity of the water droplet decreases with the increase of the conductivity and then reduces the electric field intensity and increases the corona inception voltage. Installing the grading ring can increase the value of the corona inception voltage by 38% at most. To investigate the influence of the water droplets on the corona inception characteristics of the insulator, the sheath and shed models were proposed according to the feature of the electric field distribution. By changing the parameters of the water droplets, the corona inception voltage, discharge position, and electric field were analysed. Furthermore, the flashover voltage of the water droplets is influenced by its conductivity, while the corona inception voltage by its relative permittivity.

Study on the Interaction between Channels of Image Intensifier

The experiment of mutual interference between channels of the UV imager was carried out. The plateform consists of jamming light with large area and target light with small area was established. The curve of the gray value of target light in image intensifier with the intensity of interference light was measured. Experimental results show that there is mutual interference between channels when the UV imager is irradiated by continuous laser and the mutual effects will benefit to suppress the target signal by reducing the gain of the adjacent channels. Theoretical mechanism of this phenomenon was studied. The electrical coupling model between channels was established, and the influence of transverse resistance between adjacent channels on the gain characteristics of adjacent channels was studied by nodal analysis. Numerical simulation results show that the transverse resistance between channels is the main cause of mutual interference between channels, which greatly influence the gain of the adjacent channels.

Corona Discharge Detection System Based on Ultraviolet Sensor and Optical Lens

Ultraviolet radiation produced by corona discharge can be used for discharge diagnosis, but the ultraviolet imager is expensive and the ultraviolet signal is susceptible to external interference during the day, so it can not accurately identify the occurrence of corona discharge. In this paper, an optical lens is designed to collect ultraviolet signal. In this paper, a corona detection method based on ultraviolet sensor and optical lens was proposed. The design of optical lens to concentrate the ultraviolet signal so as to suppress external interference was presented. By carrying out insulator corona discharge experiments, the feasibility of the proposed method was studied. Finally, a comparison and verification was made with the combination of corona discharge images collected by UV imager. Research results by this paper indicate that, when the detection distance is smaller than 5 m, and the power supply is about 700 V, the proposed corona detection method can effectively collect the ultraviolet rays generated by corona discharge, thus realizing the feasible recognition of corona discharge. Moreover, this method can feasibly reflect the changing of UV intensity with applied voltage and detection distance. The research results can provide important reference for the development and calibration of ultraviolet detection equipment.

Design and construction of a new insulator detection robot for application in 500 kV strings: Electric field analysis and field testing

Extra high voltage/ultra-high voltage (EHV/UHV) transmission lines have long insulator strings, and a number of porcelain insulators. Hence, it is convenient and efficient to use an insulator detection robot. The existing insulator detection robots are mainly of a climbing style, with large sizes and complex structures. It is inconvenient to carry them up the tower, and it is inefficient to move them on the insulator strings. Therefore, a lightweight insulator detection robot with a simple structure is designed in this study. To prevent corona discharge on the robot, a 3-D model of the robot along the insulator string is established, to calculate and analyse the electric field distribution. The structure of the robot is optimized according to the simulation results. The field test of the robot is carried out on 500 kV insulator strings, and a UV imager is used for observation. The test results show that no corona discharge occurs on the optimized robot, and it can operate safely and steadily along insulator strings.

The Optimum Method for Determining the Corona Onset Voltage Gradient of Bundle Conductors on UHV AC Power Line

The COG (Corona Onset Voltage Gradient) of bundle conductors, as an important parameter in the design of transmission lines, is related to the electromagnetic environment around the transmission lines. Therefore, it is important to accurately determine the COG. At present, there are several methods to determine the COG, the values of COG obtained by different methods are quite different, and the reasonableness of these methods is still not clear. In this paper, combined with the UHV corona cage set in Ping’an County, Xining city (elevation 2200 m), the corona characteristic measurement system and UV imager, the platform for measuring corona discharge characteristics of bundle conductors was built. For the 8 × LGJ-630 bundle conductors commonly used on UHV transmission lines, the change of corona discharge intensity was observed by UV imager. Then, the E (field intensity)–I (resistance current), the E–√P (square root of corona loss), E–PH (UV photon number), E–RI (radio interference), E–AN (audible noise) curves were measured. By using the tangent method, the experimental values of COG were obtained. Finally, the COG obtained by the five methods are analyzed and discussed, the COG values obtained by the E–I curve and E–√P curve are basically the same, with a deviation of about 1.5%, it has clear physical significance. While the deviation of the COG obtained by the E–PH, E–RI, and E–AN curves are about 10.4%, 29.9%, and 5.7%, respectively. And the optimal method proposed for determining the COG is E–I curve or E–√P curve.

Impacts of Intense Geomagnetic Storms on NavIC / IRNSS System

The Total Electron Content (TEC) of Navigation with the Indian Constellation (NavIC)/ Indian Regional Navigation Satellite System (IRNSS) was examined under the influence of an intense geomagnetic storm occurred on 8 September, 2017, in the low latitudes of the Indian re- gion. One week (3 September, 2017 to 9 September, 2017) data from five stations located in the equatorial region and in the Equatorial Ionization Anomaly (EIA) area in India are collected from Accord NavIC/IRNSS dual-frequency (L5 and S-band) receivers for the investi- gation. The diurnal TEC comparison between IRI-2007 empirical model and NavIC/IRNSS dual frequency model is done. Through a com- parative study, of TEC at the five locations, we clearly observed geomagnetic storms using dual-frequency NavIC/IRNSS receivers, while the diurnal TEC behavior of the IRI-2017 model was the same on all observation days. On the intense stormy day, we observed an increase of about 19 TECU for the area near the equator and decrease of about 20 TECU in the EIA region compared to other observed quiet days. As a result, positive correlation between TEC and storm occurrence were found in the equatorial region, while a negative one in EIA re- gion. In order to support dramatic change in TEC during intense geomagnetic storm, geomagnetic indices and solar wind/IMF parameters maps are added. The results have been further validated using TEC map from IGS data and thermosphere O/N2 ratio map from Global UV Imager (GUVI).

Extraction of Ultraviolet Spectrum Discharge Parameters of Power Equipment Based on OpenCV

Ultraviolet imaging technology is an effective method to detect the discharge of high-voltage electrical equipment. At present, the photon number is the main method to characterize the discharge severity of UV imaging. However, there is a complex nonlinear relationship between the parameter size and the gain and observation distance of the UV imager. The discharge was quantified. In order to quantify the analysis of discharge, based on the OpenCV image processing technology, the UV image was segmented by a combined threshold method, and the effective discharge region was extracted by the multi-region contour algorithm; Using the statistical information of foreground information pixel points, parameters such as area of discharge spot, perimeter, major axis minor axis, and spot profile are obtained. The method can quickly and efficiently judge the severity of UV fault images, save manpower and material resources, and have higher practical value.

UV‐flashover evaluation of porcelain insulators based on deep learning

Based on the analysis of the principle and structure of the convolutional neural network (CNN) model in a deep learning theory system, an intelligent method for judging the flashover of a porcelain insulator with ultraviolet discharge is proposed. In this method, the porcelain insulator chip was subjected to power frequency flashover testing, and the ultraviolet spectra of different discharge states without discharge, weak coronal discharge, and strong spark discharge were captured by FILIN UV imager. The Alexnet deep convolution neural network model was used to predict the discharge state of the UV spectrum for classification training and identification assessment. The new method doesn't use UV imaging to detect flashover warnings. It is necessary to extract the characteristics of the UV spectra and leakage current parameters manually. The multi-layer combination of UV imaging method with end-to-end autonomous learning with deep learning training and the adopted test method provided classification identification, through a large number of UV images in the deep CNN training. This allowed flashover evaluation of abstract feature parameters of the independent extraction. The results show that this method has the advantages of high accuracy, and provides a new idea for the intelligent detection of UV flashover.

Effects of view angle and measurement distance on electrical equipment UV corona discharge detection

A UV radiation detecting platform is set up to evaluate the influence of view angle and measurement distance in UV detection technology, then a coordinate conversion equation is proposed to compensate the influencing factors. Since the photon number of dischargeable power equipment changes with the varied external factors including distance, angle, humidity, and wind force, the research studies the effects of both view angle and distance while others are invariant. Results show that the variation of view angle and distance has an impact on UV detection. Given that different observation points have different view angle and observation distance, photon numbers at different points could be calibrated to the optimal position in accordance with the proposed equation. In addition, the 3-D simulation and conversion curves also verify the validity of proposed theory. Accordingly, the results of this study can provide a reference to improve the effectiveness and application of UV imager in fault diagnosis.

Scattering Properties of the Venusian Clouds Observed by the UV Imager on board Akatsuki

Abstract We analyze the albedo of Venus obtained from the UV Imager on board Akatsuki. A relative global mean albedo over phase angle is used in this study, and we confirm the glory feature at 283 and 365 nm in the data acquired in 2016 May. We successfully simulate the observation using a radiative transfer model. Our results show that cloud aerosols of μm and (mode 2) can explain the glory, consistent with a property of aerosols previously suggested by using the Venus Monitoring Camera on board Venus Express. We find that SO2 and the unknown UV absorber are necessary factors to explain the decreasing trend of the observed relative albedo at phase angles larger than 10°. We suggest a range of possible SO2 abundance from 80 to 400 ppbv at the cloud top level, depending on atmospheric conditions assumed.

Comparison of different characteristic parameters acquired by UV imager in detecting corona discharge

UV imager has promising application prospect in the detection of corona discharge because of its advantages, such as high sensitivity, intuitive and non-contact discharge detection. In order to make better use of ultraviolet imager to detect corona of the high voltage electrical equipment, experiments are carried out to observe insulator corona discharge using the DayCor® Superb UV imager in this paper. During the experiments, voltages are applied on a FXBW-35/70 insulator, and corona discharge was detected through the ultraviolet imager. The relationship between the detected photon number, the instrument gain and the distance are studied. Then through extracting the discharge facular area from UV image using Matlab package, the differences of photon number and facular area in quantifying the corona discharge intensity are compared and analyzed. Research shows that the photon number increases first and then decrease with the rise of UV gain. Differently, the facular area increases monotonically with the rise of gain. There will be no multi-valued problem when the facular area is used to quantify the discharge. Both the photon number and facular area decrease with the increase of detecting distance, but the fluctuation of the facular area-distance curve is smaller than the photon number — distance curve. Using the facular area to quantify the corona discharge can be more accurate. The study results of this paper provide references for better assessing the electric equipment corona discharge intensity by ultraviolet imager.

World Space Observatory-Ultraviolet: ISSIS, the imaging instrument

The Imaging and Slitless Spectroscopy Instrument (ISSIS) will be flown as part of the science instrumentation in the World Space Observatory-Ultraviolet (WSO-UV). ISSIS will be the first UV imager to operate in a high Earth orbit from a 2m class space telescope. In this contribution, the science driving the ISSIS design and the main characteristics of this instrument are presented.

Retrieval of polar mesospheric cloud properties from CIPS: Algorithm description, error analysis and cloud detection sensitivity

The Cloud Imaging and Particle Size (CIPS) instrument has been in operation on the NASA Aeronomy of Ice in the Mesosphere (AIM) satellite since May 2007. CIPS is a multi-camera UV imager that makes unprecedented hemispheric-scale measurements of polar mesospheric clouds (PMC). The primary CIPS data products are cloud frequency, albedo, mean particle radius, ice water content and vertical column particle density. These quantities are retrieved at 25km2 resolution at latitudes between ~55° and 84° over a range of local times in the summer hemisphere. CIPS has obtained data for six Northern Hemisphere and five Southern Hemisphere PMC seasons to date and is still in operation and performing flawlessly. The CIPS data are made available to the scientific community in a variety of formats and spatial and temporal resolution, including full-resolution single-orbit level 2 data files and images, daily (hemispheric) albedo maps and images, and full-season latitude-binned summary files. In this paper we describe the CIPS measurement strategy and sampling characteristics, calibration and the Version 4.20 processing algorithms and retrievals. We also provide a quantitative evaluation of the CIPS cloud detection sensitivity and estimated random and systematic errors of the V4.20 cloud data products.

OVATION‐SM: A model of auroral precipitation based on SuperMAG generalized auroral electrojet and substorm onset times

OVATION‐SM, an empirical model for different types of auroral energy flux, has been developed. OVATION‐SM is a linear combination of the SME index (or square root of SME index for monoenergetic auroras), time since the last substorm onset, and time until the next substorm onset. Because OVATION‐SM is based on ground magnetometer data and products of that data, it is possible to calculate continuous auroral power at a 1 min cadence for 30+ years. OVATION‐SM captures the gross auroral morphology, including onsets and other brightening and dimming events. The detailed spatial auroral morphology is beyond the scope of the current version of OVATION‐SM. OVATION‐SM explains more than 70% of the variance in Polar UV Imager nightside auroral power, which makes it a better predictor of nightside auroral power than any other model currently available.

A New Approach to Dissolution Testing by UV Imaging and Finite Element Simulations

Most dissolution testing systems rely on analyzing samples taken remotely from the dissolving sample surface at different time points with poor time resolution and therefore provide relatively unresolved temporally and spatially information on the dissolution process. In this study, a flexible numerical model was combined with a novel UV imaging system, allowing monitoring of the dissolution process with sub second time resolution. The dissolution process was monitored by both effluent collection and UV imaging of compacts of paracetamol. A finite element model (FEM) was used to characterize the UV imaging system. A finite element model of the UV imaging system was successfully built. The dissolution of paracetamol was studied by UV imaging and by analysis of the effluent. The dissolution rates obtained from the collected effluent were in good agreement with the numerical model. The numerical model allowed an assessment of the ability of the UV imager to measure dissolution-time profiles. The simulation was able to extend the experimental results to conditions not easily obtained experimentally. Combining FEM,experimental dissolution data and UV imaging provided experimental validation of the FEM model as well as a detailed description of the dissolution process.

Effect of Rain Drops on Corona Discharge in Alternating Current Transmission Lines with a Corona Cage

The dielectric distributed around the surface of electrodes has a significant effect on the corona discharge. Corona discharge in power transmission lines in fine weather is different from that in rainy days as the surface condition is greatly changed. The surface of conductors is filled with the drops of rainwater; hence, the electric field around the conductors will be distorted. The use of a corona cage is an effective and economical means for duplicating corona progress in power transmission lines with lower voltage on the conductor in the cage. The practical conductor was utilized in this experiment under both fine and rainy conditions. The process of corona discharge was recorded and investigated. It was found that the corona discharge turned to be much more intense when rain drops were enlarged and more compressed around the conductor. The corona inception voltage, which is an important parameter of corona discharge, was also gained using an ultraviolet imager (UV imager). The corona inception voltage under the rainy condition was about 25% lower than that under the fine condition. The results of the comparison of audible noise and radio interference were analyzed.

Reconnection electric field estimates and dynamics of high-latitude boundaries during a substorm

Abstract. The dynamics of the polar cap and the auroral oval are examined in the evening sector during a substorm period on 25 November 2000 by using measurements of the EISCAT incoherent scatter radars, the north-south chain of the MIRACLE magnetometer network, and the Polar UV Imager. The location of the polar cap boundary (PCB) is estimated from electron temperature measurements by the mainland low-elevation EISCAT VHF radar and the 42 m antenna of the EISCAT Svalbard radar. A comparison to the poleward auroral emission (PAE) boundary by the Polar UV Imager shows that in this event the PAE boundary is typically located 0.7° of magnetic latitude poleward of the PCB by EISCAT. The convection reversal boundary (CRB) is determined from the 2-D plasma drift velocity extracted from the dual-beam VHF data. The CRB is located 0.5–1° equatorward of the PCB indicating the existence of viscous-driven antisunward convection on closed field lines. East-west equivalent electrojets are calculated from the MIRACLE magnetometer data by the 1-D upward continuation method. In the substorm growth phase, electrojets together with the polar cap boundary move gradually equatorwards. During the substorm expansion phase, the Harang discontinuity (HD) region expands to the MLT sector of EISCAT. In the recovery phase the PCB follows the poleward edge of the westward electrojet. The local ionospheric reconnection electric field is calculated by using the measured plasma velocities in the vicinity of the polar cap boundary. During the substorm growth phase, values between 0 and 10 mV/m are found. During the late expansion and recovery phase, the reconnection electric field has temporal variations with periods of 7–27 min and values from 0 to 40 mV/m. It is shown quantitatively, for the first time to our knowledge, that intensifications in the local reconnection electric field correlate with appearance of auroral poleward boundary intensifications (PBIs) in the same MLT sector. The results suggest that PBIs (typically 1.5 h MLT wide) are a consequence of temporarily enhanced longitudinally localized magnetic flux closure in the magnetotail.

Rise dynamics and relative ash distribution in vulcanian eruption plumes at Santiaguito Volcano, Guatemala, revealed using an ultraviolet imaging camera

Santiaguito Volcano, Guatemala, regularly produces small vulcanian eruption plumes which rise to heights of up to 2 km. A combined study using a novel UV camera coupled with classical analysis of the fluid dynamics of finite‐volume buoyant releases (thermals) has been used to develop a detection algorithm for ground‐based volcanic ash monitoring. Analysis of plume rise dynamics shows that vulcanian eruption plumes at Santiaguito behave as axisymmetric buoyant thermals, and this behaviour is consistent with eruption of volcanic gas and particle mixtures whose initial momentum is dissipated by flow through a porous capping layer. The UV imager has been adapted to detect relative ash burdens through the use of a single filter, centred on 307 nm, an edge detection and background fitting procedure and normalising to a simple theoretical model. The method provides the capability to observe and measure the internal structure of the plume, and processes occurring during plume rise, including concentration of ash over time into the thermal ‘head’, increased ash at the plume edges during early formation of the thermal and dilution at the top of the plume head as entrainment occurs.