Features characterizing the surface state of HV insulator glass model under desert pollution

This paper deals with the monitoring of the surface state of HV insulator model under discontinuous layer of pollution. Natural desert sand is used to simulate the pollution influence in Algerian Sahara regions. Experimental tests are carried out on a glass plane model of 1512L cap-pin insulator largely used in the said regions. Leakage current LC signal is recorded for different positions and widths of the polluted-band. First, the obtained results are discussed to describe the behavior of the insulator model. For each configuration, time-frequency decomposition is established using Discrete Wavelet Transform (DWT) for information extraction corresponding to the flashover process. Decomposition results indicate that the detail D3 is highly correlated with the measured LC signal. Recurrence Plot (RP) technique and Recurrence Quantification Analysis (RQA) are applied to quantify the temporal patterning in LC signal, giving information on the position and width of the polluted-band on the insulating surface. It was found that RQA indicators increase with the polluted-band width according to the position of this polluted-band. Based on the plan model, the findings demonstrate the capability of RQA indicators for the glass insulator monitoring, providing information on the width and position of the polluted-band on its surface

Extreme Solar Events: Setting up a Paradigm

The Sun is magnetically active and often produces eruptive events on different energetic and temporal scales. Until recently, the upper limit of such events was unknown and believed to be roughly represented by direct instrumental observations. However, two types of extreme events were discovered recently: extreme solar energetic particle events on the multi-millennial time scale and super-flares on sun-like stars. Both discoveries imply that the Sun might rarely produce events, called extreme solar events (ESE), whose energy could be orders of magnitude greater than anything we have observed during recent decades. During the years following these discoveries, great progress has been achieved in collecting observational evidence, uncovering new events, making statistical analyses, and developing theoretical modelling. The ESE paradigm lives and is being developed. On the other hand, many outstanding questions still remain open and new ones emerge. Here we present an overview of the current state of the art and the forming paradigm of ESE from different points of view: solar physics, stellar–solar projections, cosmogenic-isotope data, modelling, historical data, as well as terrestrial, technological and societal effects of ESEs. Special focus is paid to open questions and further developments. This review is based on the joint work of the International Space Science Institute (ISSI) team #510 (2020–2022)

Tree-Rings Reveal Two Strong Solar Proton Events in 7176 and 5259 BCE

The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as 14C, 10Be and 36Cl have been found. Analyzing annual 14C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric 14C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric 14C recorded for both events exceed all previously known 14C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure. © 2022, The Author(s).The Laboratory of Ion Beam Physics is partially funded by its consortium partners PSI, EAWAG, and EMPA. N.B. is funded by the Swiss National Science Foundation (SNSF grant #SNF 197137). The establishment of the BRAMS Facility was jointly funded by the NERC, BBSRC and the University of Bristol and the measurements in this work were partly funded by an ERC Proof of Concept grant awarded to R.P.E. and financing E.C. postdoctoral contract (LipDat H2020 ERC-2018-PoC/812917). We thank Bisserka Gaydarska for sub-sampling the inter-laboratory replicates from M49, M234, Q2729 and Q2750, Cathy Tyers for reviewing the dating of the Irish and German samples, and Alexander Land for assistance in dating sample M49. P.F. received funding from the SNF Sinergia project CALDERA (no. 183571). R.H. is funded by Russian Science Foundation (grant № 21-14-00330). I.U. acknowledges the support from the Academy of Finland (grant 321882 ESPERA). C.L.P.’s and M.W.S.’s work on bristlecone pine was funded by the M.H. Wiener Foundation (ICCP Project). K.N. acknowledges the support provided by the Austrian Science Fund FWF (grant I-1183-N19)

ELECTRIC FIELD MEASUREMENT IN ROD-DISCONTINUED PLANE AIR GAPS USING DISTRIBUTED CAPACITY PROBE

<p>The present experimental carried out investigations<em> </em>aimed at elucidating the effect of earth discontinuity on the breakdown voltage of short rod-plane air gap (80 to160 mm) under negative lightning impulses (-1.2/50ms).We also carried out investigations on electric field measurement on the surface of a discontinuous plane of a rod-plane air gap arrangement. For this purpose, we used a probe with distributed capacity, under negative lightning applied impulse voltage. The probe is incorporated on the same level of plane surface.The interface locally reinforces the electric field. The electric field increases at the interface may lead to a discharge between the high voltage rode and the interface. In the vicinity of the interface, we observe a kind of discontinuity in the evolution of the electric field intensity. This one becomes greater than the value obtained in the case of gaps with homogeneous plane earth.</p

Multiscale Analysis of Naturally Weathered High-Voltage XLPE Cable Insulation in Two Extreme Environments

Crosslinked polyethylene (XLPE) insulation is widely used in power cables because of its excellent properties. Due to the remoteness of end users, the energy is generally transported over long distances. These cables cross various areas being sometimes exposed to different environmental stresses that affect their performance and increase their degradation. While most published literatures are limited to laboratory scales, this article uniquely deals with a multiscale analysis of a 30 months naturally weathered XLPE samples in two harsh environments. The first site is a marine environment with high humidity level, sea salt content in the air, seasonal variation of temperature, and concomitant radiation doses. The second one is a desert environment characterized by extremely high temperatures, which reached 50 °C during summer, coupled with thermal cycling and large solar radiation doses with UV rays of high energy wavelengths. Modifications in the XLPE insulation characteristics due to weathering were studied using different experimental techniques. The testing matrices included dielectric and mechanical characterization, scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and differential scanning calorimetry (DSC) measurements on fresh and weathered XLPE insulation samples. It is found that the degradation rate was faster in the arid desert climate compared with the coastal one. Furthermore, correlation mechanisms between the obtained results are discussed in order to better understand the weathering degradations

A New Model for Polluted insulators Flashover under HVDC

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