Lightning Impulse Voltage Correction of Power Transmission and Transformation Project Typical Gap

2014 ◽  
Vol 986-987 ◽  
pp. 345-348
Author(s):  
Ying Jie Peng ◽  
Yu Jian Ding ◽  
Fang Cheng Lü
Keyword(s):  
Power Transmission ◽  
Theoretical Aspect ◽  
Correction Factors ◽  
Atmospheric Conditions ◽  
Atmospheric Parameters ◽  
External Insulation ◽  
Lightning Impulse ◽  
Improvement Method ◽  
Main Factors ◽  
Power Project

External insulation design of UHV power project is important. The lightning impulse (LI) voltage is one of the main factors that determine the air gap distance. Based on existing LI voltage results of power project typical gap, impact of gap structure and distance on LI discharge correction is analyzed. And from a theoretical aspect, existing LI discharge correction methods are summarized. Furthermore, by the use of common correction methods, LI voltage correction factors of rod - plane were calculated and analyzed. Results show no significant impact of gap type or gap distance on LI voltage correction is found out. Average atmospheric conditions are effective when atmospheric parameters method is used for LI voltage correction. DL/T 620, IEC 60060-1 and IEC 60071-2 can be used for LI voltage correction at areas with altitudes of 1000-5000m. While GB311.3-improvement method can be used for LI voltage correction at areas with altitudes blow 4000m.

Experimental Researches on Micro-Droplet Freezing on a Solid Surface Under Atmospheric Conditions: Part I

2008 ◽  
Author(s):  
Heyun Liu ◽  
Xiaohui Ma
Keyword(s):  
Transmission Lines ◽  
Power Transmission ◽  
Electrostatic Force ◽  
Droplet Diameter ◽  
Ccd Camera ◽  
Freezing Process ◽  
Ice Accretion ◽  
Power Transmission Lines ◽  
Atmospheric Conditions ◽  
Air Stream

Atmospheric ice accretion on structures is a problem of fundamental importance to a number of industries. Examples of engineering problems caused by ice accretion involving aircraft, power transmission lines, telecommunication towers, electrical railway contact-wires, and other structures. Under atmospheric icing conditions two basic types of ice may form; rime or glaze. The supercooled micro-droplets in clouds are an important factor in icing. The objective of this study was to develop a new experimental method to investigate a single supercooled micro-droplet freezing process, in order to better understand the mechanism of rime or glaze ice accretion. The experimental device and principles are described in this paper. The experimental set has two small cold rooms, which is separated by a board with a central hole. A droplet with diameter of 15∼40 μm, temperature of 0∼−5°C was levitated in the cold air stream by electrostatic force. A CCD camera tracked its trace. The air temperature is from 0∼−10°C, the micro-droplet diameter is from 15∼40μm, and its temperature is from 0∼−5°C in the experimental study. This article focused on the experimental set and the experimental principles, and the next article will focus on the experimental data analysis.

Meteorological Parameters Affecting Supersonic Transport Operations

1967 ◽  
Vol 20 (1) ◽  
pp. 53-63 ◽  
Author(s):  
Richard Scherhag ◽  
Gunter Warnecke ◽  
Werner Wehry
Keyword(s):  
Working Group ◽  
Meteorological Parameters ◽  
Sonic Boom ◽  
Atmospheric Ozone ◽  
Atmospheric Conditions ◽  
Atmospheric Parameters ◽  
Free Atmosphere ◽  
Supersonic Transport ◽  
Supersonic Aircraft ◽  
Initial Task

In 1965, following the Eastbourne Conference, the British, French and German Institutes of Navigation formed a Working Group to make a study of the environment in which the supersonic transport will operate and of its implications for the navigation of such aircraft. The Group's initial task has been one of education, largely through discussion of a series of papers submitted to it. Some of the papers considered have already been published in the Journal (Vol. 19) and a further selection is published below. Table I was contributed by Mr. G. E. Beck. The illustrations to these papers have not all been reproduced.1. Atmospheric Conditions. It will be useful to distinguish between different kinds of atmospheric influences on supersonic aircraft operations. They may be classed as follows:(a) Sporadic effects near the ground(b) Sporadic effects in the free atmosphere(c) Effects on sonic boom(d) Effects of atmospheric ozone(e) Permanently effective atmospheric parameters, such as temperature, density and wind.

Factors Contributing to Haze and the Influence on External Insulation of Power Equipments

2014 ◽  
Vol 700 ◽  
pp. 631-636 ◽  
Author(s):  
Song Gao ◽  
Zhi Cheng Zhou ◽  
Lin Jun Yang ◽  
Yong Liu ◽  
Feng Bo Tao ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Power Transmission ◽  
Rapid Development ◽  
Temporal And Spatial Distribution ◽  
External Insulation ◽  
Weather Phenomenon ◽  
Haze Pollution ◽  
Power Load ◽  
Pollution Flashover ◽  
Temporal And Spatial

Haze-fog has been a severe pollution weather phenomenon in China due to a large number of emissions of pollutants with the rapid development of economy. The areas burst haze are usually coincidence with high density of electricity transmission line corridor or power load areas, and so the pollution flashover accidents happen frequently. In this paper the haze pollution situations and factors contributing to haze are introduced, and the mechanisms of haze inducing and aggravating the pollution flashover accidents are explained by analyzing the temporal and spatial distribution of PM2.5 and size characteristics of dust deposited transmission. Moreover, the influences of haze on power transmission and transformation equipment external insulation are discussed with combining the simulation pollution flashover experiments of high conductivity fog.

Frost Halo Dynamics on Superhydrophobic Surfaces

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Wei Su ◽  
Longnan Li ◽  
Xiao Yan ◽  
Nenad Miljkovic
Keyword(s):  
High Speed ◽  
Power Transmission ◽  
Superhydrophobic Surfaces ◽  
Droplet Radius ◽  
Atmospheric Conditions ◽  
Halo Formation ◽  
Vapor Diffusion ◽  
Industrial Sectors ◽  
Field Disturbance

Abstract Understanding the frosting mechanisms on solid surfaces is crucial to a broad range of industrial sectors such as aerospace, power transmission, and refrigeration. During the last few decades, extensive studies have been conducted on fundamental frosting phenomena, including ice nucleation, growth, bridging, and frost propagation, with few studies focusing on frost halo formation which has been shown to affect frosting dynamics on hydrophilic substrates. The role of frost halo dynamics formation on superhydrophobic surface remains unclear due to limited characterization in the past. Here, in order to study frost propagation dynamics, particularly freezing-induced vapor diffusion and frost halo formation, condensation frosting on highly-reflective nanostructured superhydrophobic surfaces (θ ≈170º) was visualized using high-speed top-view optical microscopy. Condensation frosting was initiated by cooling the surface to -20 ± 0.5°C in atmospheric conditions (relative humidity ≈50% and air temperature ≈25°C). We show that the wave front reaches neighboring supercooled droplets along the path of frost propagation, resulting in supercooled droplet freezing within ~100 ms and numerous microscale (~1 µm) condensing droplets forming around the primary freezing droplet. The microscale droplets form a condensate halo stretching two times the freezing droplet radius. The condensate halo was formed by the rapid evaporation of the supercooled recalescent freezing droplet due to the fast (~100 ms) release of latent heat, resulting in the heating of the freezing droplet and thus outwards diffusion of vapor. Further diffusion of vapor led to the subsequent evaporation of the halo condensate droplets within ~4 s. Interestingly, accompanied by the freezing of the primary droplet and condensate halo formation, the neighboring satellite droplets in the halo zone were observed to oscillate directionally and dramatically, indicative of the presence of a strong flow field disturbance due to rapid vapor diffusion. The visualizations presented here not only help to quantify the physics of condensate halo formation during frost wave propagation on superhydrophobic surfaces, but also provide insights into the role of freezing-induced vapor diffusion during frost dynamics.

scholarly journals Filtering techniques to enhance optical turbulence forecast performances at short time-scales

2019 ◽  
Vol 492 (1) ◽  
pp. 140-152 ◽  
Author(s):  
E Masciadri ◽  
G Martelloni ◽  
A Turchi
Keyword(s):  
Adaptive Optics ◽  
Time Scales ◽  
Coherence Time ◽  
Atmospheric Conditions ◽  
Atmospheric Parameters ◽  
Optical Turbulence ◽  
Efficient Management ◽  
Science Operations ◽  
Short Time ◽  
Filtering Techniques

ABSTRACT The efficiency of the management of top-class ground-based astronomical facilities supported by adaptive optics (AO) relies on our ability to forecast the optical turbulence (OT) and a set of relevant atmospheric parameters. Indeed, in spite of the fact that the AO is able to achieve, at present, excellent levels of wavefront corrections (a Strehl ratio up to 90 per cent in H band), its performances strongly depend on the atmospheric conditions. Knowing in advance the atmospheric turbulence conditions allows an optimization of the AO use. It has already been proven that it is possible to provide reliable forecasts of the OT (${C_N^2 }$ profiles and integrated astroclimatic parameters such as seeing, isoplanatic angle, wavefront coherence time, etc.) for the next night. In this paper, we prove that it is possible to improve the forecast performances on shorter time-scales (order of 1 or 2 h) with consistent gains (order of 2–8) employing filtering techniques that make use of real-time measurements. This has permitted us to achieve forecasts accuracies never obtained before and reach a fundamental milestone for the astronomical applications. The time-scale of 1 or 2 h is the most critical one for an efficient management of the ground-based telescopes supported by AO. We implemented this method in the operational forecast system of the Large Binocular Telescope (LBT), named Advanced LBT Turbulence and Atmosphere (ALTA) Center that is, at our knowledge, the first operational system providing forecasts of turbulence and atmospheric parameters at short time-scales to support science operations.

scholarly journals Ground-based direct-sun DOAS and airborne MAX-DOAS measurements of the collision-induced oxygen complex, O<sub>2</sub>O<sub>2</sub>, absorption with significant pressure and temperature differences

2015 ◽  
Vol 8 (2) ◽  
pp. 793-809 ◽  
Author(s):  
E. Spinei ◽  
A. Cede ◽  
J. Herman ◽  
G. H. Mount ◽  
E. Eloranta ◽  
...  
Keyword(s):  
Cross Sections ◽  
Spectral Band ◽  
Specific Humidity ◽  
Optical Absorption Spectroscopy ◽  
Correction Factors ◽  
Absorption Cross ◽  
Atmospheric Conditions ◽  
Absorption Bands ◽  
Wide Range ◽  
Simultaneous Fitting

Abstract. The collision-induced O2 complex, O2O2, is a very important trace gas for understanding remote sensing measurements of aerosols, cloud properties and atmospheric trace gases. Many ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of the O2O2 optical depth require correction factors of 0.75 ± 0.1 to reproduce radiative transfer modeling (RTM) results for a nearly pure Rayleigh atmosphere. One of the potential causes of this discrepancy is uncertainty in laboratory-measured O2O2 absorption cross section temperature and pressure dependencies due to difficulties in replicating atmospheric conditions in the laboratory environment. This paper presents ground-based direct-sun (DS) and airborne multi-axis (AMAX) DOAS measurements of O2O2 absorption optical depths under actual atmospheric conditions in two wavelength regions (335–390 and 435–490 nm). DS irradiance measurements were made by the Washington State University research-grade Multi-Function Differential Spectroscopy Instrument instrument from 2007 to 2014 at seven sites with significant pressure (778 to 1013 hPa) and O2O2 profile-weighted temperature (247 to 275 K) differences. Aircraft MAX-DOAS measurements were conducted by the University of Colorado (CU) AMAX-DOAS instrument on 29 January 2012 over the Southern Hemispheric subtropical Pacific Ocean. Scattered solar radiance spectra were collected at altitudes between 9 and 13.2 km, with O2O2 profile-weighted temperatures of 231 to 244 K and nearly pure Rayleigh scattering conditions. Due to the well-defined DS air-mass factors during ground-based measurements and extensively characterized atmospheric conditions during the aircraft AMAX-DOAS measurements, O2O2 "pseudo" absorption cross sections, σ, are derived from the observed optical depths and estimated O2O2 column densities. Vertical O2O2 columns are calculated from the atmospheric sounding temperature, pressure and specific humidity profiles. Based on the ground-based atmospheric DS observations, there is no pressure dependence of the O2O2 σ within the measurement errors (3%). Two data sets are combined to derive the peak σ temperature dependence of the 360 and 477 nm dimer absorption bands from 231 to 275 K. DS and AMAX-derived peak σ ( O2O2) as a function of T can be described by a quadratic function at 360 nm and linear function at 477 nm with about 9% ± 2.5% per 44 K rate. Recent laboratory-measured O2O2 cross sections by Thalman and Volkamer (2013) agree with these "DOAS apparent" peak σ( O2O2) at 233, 253 and 273 K within 3%. Changes in the O2O2 spectral band shape at colder temperatures are observed for the first time in field data. Temperature effects on spectral band shapes can introduce errors in the retrieved O2O2 column abundances if a single room temperature σ( O2O2) is used in the DOAS analysis. Simultaneous fitting of σ( O2O2) at temperatures that bracket the ambient temperature range can reduce such errors. Our results show that laboratory-measured σ( O2O2) (Hermans, 2011, at 296 K and Thalman and Volkamer, 2013) are applicable for observations over a wide range of atmospheric conditions. Column densities derived using Hermans (2011) σ at 296 K require very small correction factors (0.94 ± 0.02 at 231 K and 0.99 ± 0.02 at 275 K) to reproduce theoretically calculated slant column densities for DS and AMAX-DOAS measurements. Simultaneous fitting of σ( O2O2) at 203 and 293 K further improved the results at UV and visible wavelengths for AMAX-DOAS.

Identifying and linking flash flood prone atmospheric conditions to flooding occurrences in central Western Europe

2021 ◽  
Author(s):  
Judith Meyer ◽  
Audrey Douinot ◽  
Malte Neuper ◽  
Luca Mathias ◽  
Carol Tamez-Meléndez ◽  
...  
Keyword(s):  
River Basin ◽  
Western Europe ◽  
Flash Flood ◽  
Flash Floods ◽  
Precipitation Data ◽  
Atmospheric Conditions ◽  
Flood Events ◽  
Atmospheric Parameters ◽  
Circulation Patterns ◽  
Daily Precipitation Data

&lt;p&gt;In recent years, flash floods occurred repeatedly in temperate regions of central Western Europe (e.g., Orlacher Bach (GER), Hupselsebeek (NL), White Ernz (LUX)). This type of extreme flood events is unusual for these regions, as opposed to Mediterranean catchments that are more prone to flash floods. In the second half of the 20&lt;sup&gt;th&lt;/sup&gt; century, and more specifically in the 1990&amp;#8217;s, westerly atmospheric fluxes were the dominating triggering factor of large scale (winter) floods in central Western Europe.&lt;/p&gt;&lt;p&gt;With a view to gain a better understanding of the mechanisms controlling the recent flash flood events at higher latitudes, we explore various avenues related to the non-stationarity of environmental systems. We hypothesize that an increase in the occurrence of flash flood prone atmospheric conditions has recently led to higher precipitation totals and a subsequent increase in flash flood events in central Western Europe.&lt;/p&gt;&lt;p&gt;Therefore, we first analysed relevant atmospheric parameters from the ERA 5 reanalysis dataset. Second, we linked the atmospheric parameters to the concept of general circulation patterns as per Hess and Brezowsky (1977). Third, we analysed precipitation data from a set of stations located in the Moselle river basin (35.000 km&lt;sup&gt;2&lt;/sup&gt;). These three pillars build the base for identifying flash flood prone atmospheric conditions over space and time that are then compared to actual occurrences of extreme discharge events in streams within the Moselle river basin.&lt;/p&gt;&lt;p&gt;To validate our hypothesis, spatial and temporal patterns in the occurrence of extreme precipitation and discharge events need to match atmospheric patterns. Preliminary results suggest that daily precipitation data and meridional circulation patterns do not show a clear trend towards an increased occurrence of precipitation events or higher precipitation amounts. Due to the limitations inherent to the available long-term dataset of daily data, the hypothesis can only be partly evaluated, and more detailed analyses are added. For that reason, discharge data with a 15-minute resolution, along with precipitation radar data of 5-minute time steps will be employed at a limited spatial extent in future analyses. In case of rejection of our working hypothesis this may pinpoint to other flash flood triggering mechanisms, such as changes in land use, soil moisture conditions or cultivation methods.&lt;/p&gt;

scholarly journals Direct sun and airborne MAX-DOAS measurements of the collision induced oxygen complex, O<sub>2</sub>O<sub>2</sub> absorption with significant pressure and temperature differences

2014 ◽  
Vol 7 (9) ◽  
pp. 10015-10057 ◽  
Author(s):  
E. Spinei ◽  
A. Cede ◽  
J. Herman ◽  
G. H. Mount ◽  
E. Eloranta ◽  
...  
Keyword(s):  
Cross Sections ◽  
Pressure Dependence ◽  
Spectral Band ◽  
Specific Humidity ◽  
Correction Factors ◽  
Absorption Cross ◽  
Atmospheric Conditions ◽  
Absorption Bands ◽  
Wide Range ◽  
Simultaneous Fitting

Abstract. The collision induced O2 complex, O2O2, is a very important trace gas in remote sensing measurements of aerosol and cloud properties. Some ground based MAX-DOAS measurements of O2O2 slant column density require correction factors of 0.75 ± 0.1 to reproduce radiative transfer modeling (RTM) results for a near pure Rayleigh atmosphere. One of the potential causes of this discrepancy is believed to be uncertainty in laboratory measured O2O2 absorption cross section temperature and pressure dependence, due to difficulties in replicating atmospheric conditions in the laboratory environment. This paper presents direct-sun (DS) and airborne multi-axis (AMAX) DOAS measurements of O2O2 absorption optical depths under actual Earth atmospheric conditions in two wavelength regions (335–390 nm and 435–490 nm). DS irradiance measurements were made by the research grade MFDOAS instrument from 2007–2014 at seven sites with significant pressure (778–1013 hPa) and O2O2 profile weighted temperature (247–275 K) differences. Aircraft MAX-DOAS measurements were conducted by the University of Colorado AMAX-DOAS instrument on 29 January 2012 over the Southern Hemisphere subtropical Pacific Ocean. Scattered solar radiance spectra were collected at altitudes between 9 and 13.2 km, with O2O2 profile weighted temperatures of 231–244 K, and near pure Rayleigh scattering conditions. Due to the well defined DS air mass factors and extensively characterized atmospheric conditions during the AMAX-DOAS measurements, O2O2"pseudo" absorption cross sections, σ, are derived from the observed optical depths and estimated O2O2column densities. Vertical O2O2 columns are calculated from the atmospheric sounding temperature, pressure and specific humidity profiles. Based on the atmospheric DS observations, there is no pressure dependence of the O2O2 σ, within the measurement errors (3%). The two data sets are combined to derive peak σ temperature dependence of 360 and 477 nm absorption bands from 231–275 K. DS and AMAX derived peak σ(O2O2) as a function of T can be described by a quadratic function at 360 nm and linear at 477 nm with about 9 ± 2.5% per 44 K rate. Recent laboratory measured O2O2 cross sections by Thalman and Volkamer (2013) agree with these "DOAS apparent" peak σ(O2O2) at 233 K, 253 K and 273 K within 3%. Changes in the O2O2 spectral band-shape at colder temperatures are for the first time also observed in field data. Temperature effects on spectral band shapes can introduce errors in the retrieved O2O2 column abundances if a single room temperature σ(O2O2) is used in the DOAS analysis. Simultaneous fitting of σ(O2O2) at temperatures that bracket the ambient temperature range can reduce such errors. Our results suggest that laboratory measured σ(O2O2) (Hermans et al. (2011) at 296 K and Thalman and Volkamer (2013)) are applicable for observations over a wide range of atmospheric conditions. Column densities derived using Hermans et al. (2011) σ at 296 K require very small correction factors (0.94 ± 0.02 at 231 K and 0.99 ± 0.02 at 275 K) to reproduce theoretically calculated SCDs for DS and AMAX-DOAS measurements. Simultaneous fitting of σ(O2O2) at 203 and 293 K further improved results at UV and visible wavelengths for AMAX-DOAS.

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