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Using a first-principles theory, the structural and electronic behaviors of noble metal atom (Rh, Pd, and Pt)-decorated N3-CNTs were investigated. Meanwhile, the adsorption behavior of CO and CH4 molecules onto Rh-, Pd-, and Pt-decorated N3-CNTs was studied as well to exploit their potential applications. Results indicate that noble metal atoms are likely to be adsorbed on the N3 center of pyridine-like N3-CNTs under electrophilic attack. Moreover, the noble metal-embedded N3 group would provide CNTs with enhanced performance for gas adsorption compared with noble metal-embedded surfaces because of the improvement of chemical activity and electron mobility in our proposed configurations. The findings in this report would be beneficial for exploiting a possible adsorbent for CO scavenging with excellent adsorbing ability and a possible sensor for CH4 detection with good sensitivity and recovery behavior.

The application of weak-base anion-exchange resin for removal the SO42− from the citrate solution to guarantee its good performance for adsorption of SO2 is proposed in this work. The weak-base anion-exchange resin that has prior adsorption towards SO42− compared with citrate, allows the effective removal of such impure anion. We initially chose four kinds of resins, namely D301R, D301G, D370 and D315, to investigate their behavior upon SO42− adsorption and then determined D301R and D315 to give a comprehensive understanding towards their adsorption performance in various condition. Results indicate that D315 possessing better adsorption ability than D301R could be a potential candidate for SO42− removal from the citrate acid solution during the desulphurization process using citric method. The pretreatment of protonation for resins could effectively facilitate their adsorption behavior towards SO42− under the same pH condition. Moreover, we assume that the protonated D315 would meet the practical requirement well given its good performance.

High voltage endurance is a fundamental characteristic of dielectrics. Ideally, the structure of dielectric, electrode design and type of employed electric field has no effect on internal breakdown endurance. On the other hand, experimentally estimated breakdown strengths are quite different under high voltage for the material given. This paper demonstrates space charge dynamics utilizing PEA (pulse electro-acoustic) system under high dc electric voltages to investigate the dependence of varying XLPE thickness on dielectric breakdown. As XLPE is employed for insulation of HVDC cables so it is mandatory to examine the space charge effects under high dc fields for varying insulation thickness. Generally, the influence of space charge leading to breakdown at high stresses is not considered for various bulk insulation thicknesses. However, we demonstrate the long time space charge profiles under high dc electric stresses for various thicknesses ranging from 0.07mm to 0.2mm. We examined that the time dependent internal field and space charge exhibit decreasing pattern with increasing thickness up to 0.1mm and then increasing pattern up to 0.2mm. Space charge measurements under high dc applied electric fields also depict a correspondence with short time dc breakdown test results. This observed phenomenon could find its importance in designing XLPE (material) insulation for HVDC transmission systems.

Insulating liquids have been applied to electrical insulation of transformers, circuit breakers and switch gears and have been investigated in different ways to enhance their performance. Dielectric liquids have been used for the transformer insulation and cooling applications since more than a century. Dielectric breakdown tests and the events and processes that affect the breakdown of the transformer insulation have been studied since last 40-50 years. Transformer oil can give a thorough picture of the internal transformer conditions. The fault diagnosis can also be done by investigating the transformer oil. For this reason, oil samples from a transformer that is out of service due to the internal faults are taken and tested to realize the reason behind the faults. Gas Chromatography Mass Spectrometry (GCMS) was employed to investigate the oil condition of the power transformer. GC-MS results show that high molecular weight substances in faulty oil are more than fresh oil. The results are compared with that of the fresh mineral oil supplied by the same manufacturer and presented in detail.

Vegetable insulating oils are gaining importance worldwide to be used in power transformers as an alternative to petroleum based mineral oils because of their biodegradable nature and higher fire points than conventional mineral oils. However, these oils (whether natural or synthetic esters) easily absorb moisture and hence tend to affect the dielectric and physiochemical properties of insulation oils. This paper presents the effect of moisture absorbed by commonly used rapeseed oil on its AC breakdown voltage. A mathematical relationship was developed between breakdown voltage and percentage moisture absorbed to access the values of BDV at any moisture level and this relationship holds good for any moisture content in the oil. Moreover, effect of suspended water molecules on breakdown voltage was simulated using COMSOL Multiphysics. Empirical relationship developed was tested and verified and can be used to find out the BDV of these oils as the percentage moisture increases.

Acrylonitrile Butadiene Styrene (ABS) is a thermo plastic material which is widely used for making bodies of countless electrical and medical appliances. It is low cost amorphous thermoplastic which belongs to poly styrene class of thermoplastics. It has very high tensile strength and almost unbreakable. It is a beneficial encapsulating and insulating material which is usually employed for indoor insulation and encapsulation purposes. A very little literature is reported on its performance when used in outdoor environment. In present work, ABS was molded into 11kV distribution class insulator and aged under several mechanical and electrical stresses in severe environmental conditions simulating outdoor environment according to IEC 1109 5000h aging standards. The aim of this study is to investigate the scope of using ABS for making outdoor insulators since it is a low cost material. Results show that this study is particularly useful for the researchers worldwide.

Nanoparticles enhance the positive and negative lightning breakdown voltages of vegetable insulating oils due to a reduced streamer velocity. Pre-breakdown streamers in vegetable oil based h-BN and Fe3O4 nanofluids were observed using the shadowgraph method under a lightning impulse voltage. The propagation of streamers until their stopping length is analyzed using shadowgraph images for the different nanofluids. The results suggest that these nanofluids present a higher breakdown voltage per unit length compared with pure oil. Secondary reverse streamers are observed to appear at the dissipation stage of the streamer. In particular, the secondary reverse streamer of the nanofluids appeared earlier and seemed to be shorter than that of pure oil under positive impulse voltages. The underlying mechanism was analyzed using space charge theory.

Surface discharge may cause irreversible damage to turn-to-ground insulation in valve windings of converter transformer, where withstand with AC-DC combined voltage. This paper analyzes the phenomenon and characteristics of surface discharge on oil-impregnated pressboard (OIP) under AC-DC combined voltage, and develops a discharge state recognition method. The cylinder-plate discharge model was used to simulate surface discharge. The results showed that discharge development and OIP failure were significantly accelerated by white marks on OIP which were essentially gaseous channels. The discharge characteristics before and after white mark occurrence were both dominated by AC component because of its bigger contribution to electrical field distribution (EFD), and the DC component had obvious effect on accelerating OIP failure. A set of features representing discharge state after white mark occurrence was selected out by the entropy weight method (EWM), based on which the discharge process was classified into three states (stable, fast development and pre-breakdown state) by fuzzy C means clustering method (FCM). A support vector machine (SVM) classifier to recognize discharge state was trained and showed a good performance, whose average assessment accuracy was up to 91.98%. Moreover, the ratio between negative and positive discharge numbers could be used as an auxiliary indicator of pre-breakdown state.

Natural esters, as the renewable resources, offer excellent physiochemical and dielectric properties such as the fire-resistance, high biodegradability and satisfactory dielectric breakdown performance. Thus, natural esters are selected as the insulation and heat dissipation medium for electrical equipment. However, the electrical performance of natural esters with different structures under the long gap and higher electrical stress needs further evaluations. In this paper, streamer propagation of various natural esters under the long gap and higher electrical stress were observed optically. The influence of voltage polarity, liquid types and gap distances on streamer characteristics of natural esters were analyzed. Results show that the maximum propagation velocity of streamer in natural esters is greater than that in the hydrocarbon liquids. Breakdown voltage of natural esters under negative polarity is much higher than that under positive polarity for the same gap distance. Among all the natural esters concerned, the camellia liquid demonstrates slower streamer velocity and slight greater lightning breakdown voltages for the positive and negative polarity. The lower content of unsaturation triacylglycerol molecules in camellia liquid contributes to the inhibition of ionization and streamers propagation. Results would be valuable reference for the design, manufacture and operation of the electrical equipment filled with natural ester.