Polarity Reversal Test Research Articles

Removal of Organic Pollutants Via Electrochemical Oxidation Near Anodes During Electrokinetic Remediation: Proof of Concept

This study designed a practical approach of separating electrodes chambers to prove the influence of electrochemical oxidation on pyrene removal during electrokinetic (EK) remediation. The anode and cathode electrodes were arranged in two independent soil chambers, and the soil chambers were connected by salt bridges. Salt bridges electrokinetic (SBEK) remediation avoided acid–base neutralization and facilitated the intensity of the current. The results showed that 99.5% of pyrene was removed within 7 days in anodic chamber. The removal rate of pyrene was ∼99.6–99.9% at SBEK1 anode and 29.5–36.2% at SBEK1 cathode after 42 days. The changes in current, pH, and redox potential values indicated that an efficient “oxidizer” was formed in the anode chamber. Compared with conventional EK remediation, SBEK can take place under a suitable oxidizing condition because of increasing current intensity and decreasing soil pH in the anode chamber. Furthermore, SBEK with electrode polarity reversal test had better decontamination efficiency of pyrene than fixed electrodes. Removal rate of pyrene increased to 62.9% after 14 days with polarity reversal; correspondingly, the energy consumption of SBEK test was ∼13 times higher than that of the conventional EK test. The novel application of separated electrodes chambers appears to be a viable strategy for removing organic pollutants.

Advanced insulating materials contributing to “carbon neutrality”: Opportunities, issues and challenges

Advanced insulating materials contributing to “carbon neutrality”: Opportunities, issues and challenges

Characterization of Ion Transport Properties in Synthetic Ester Oil by Polarization Current and Dielectric Spectroscopy

The accurate estimation of the charge carrier mobility in synthetic ester oil-based insulation systems is required for the reliable prediction of the electric field induced by dc voltages. Some discordance is observed in the literature, therefore, this quantity is investigated by two alternative methods. First, the mobility is estimated in a material sample by measuring the polarization current and the ion time-of- ight during a voltage polarity reversal test. Next, the mobility is derived from the frequency-dependent loss tangent measured by dielectric spectroscopy. The values obtained by the two methods are consistent, in the range of ≈ 2-4·10^-10 [m2/Vs] at 303 K.

Designing HVDC GIS/GIL spacer to suppress charge accumulation

To suppress the charge accumulation on the spacer surface in direct current (DC) gas insulated transmission line (GIL) is an important and emergent issue for the development of a clean, safe and economic smart grid. A design method of the DC spacer is proposed, and a spacer prototype is prepared and evaluated both by simulation and type test. The DC withstand voltage test and polarity reversal test are performed using the new DC spacer compared with a commercialised 220 kV AC spacer. The simulation results indicate that the surface electric field and surface charge of the DC spacer are lower than those of the alternating current (AC) spacer under DC voltage. The test results verify that the surface flashover voltage of this DC spacer is higher than that of the AC spacer. The potential feasibility of the spacer design for HVDC is discussed. It is hoped that the content of this paper can bring new ideas in the development of HVDC gas insulated equipment.

Understanding the impact of gamma irradiation of epoxy titania nanocomposites on surface and bulk charge characteristics

Epoxy titania nanocomposites were prepared under optimum process conditions through shear mixing of titania nanoparticles in to epoxy resin, for its potential application as insulant in nuclear power plants and space applications. The complex intrinsic nature of properties, its characteristic variation due to ageing of nanocomposite insulating material upon its continuous exposure to gamma irradiation, and their charge trap and space charge characteristics are explored. Surface potential variation studies were carried out under DC voltage. In the present study, the charge trap performance was assessed under switching impulse voltage. It is observed that surface potential decay and shallow trap formation are high with gamma irradiated specimen. In addition, the potential decay is high under switching impulse voltage compared to DC voltage. Also, the trap depth formed is less under switching impulse voltage compared to DC voltage and it is high under negative DC voltage. The space charge analysis through Pulsed electro acoustic (PEA) studies has shown increase in accumulation of space charge and enhancement of electric field with increase in dosage of gamma-irradiation. Polarity reversal tests have revealed that the electric field enhancement is high before reversal of polarity, irrespective of level of gamma irradiation dosage. The direct correlation between characteristic variation in trap depth values with the gamma irradiated specimen and its contact angle was observed.

Investigation on space charge and charge trap characteristics of Al–epoxy nanocomposites

Optimised quantity of nano-aluminium (Al) filler mixed with epoxy resin using percolation threshold criteria was adapted to fabricate nanocomposite with desired space-charge and charge-trap properties. Surface potential variation due to charge deposition on to the insulating material under transient voltages was investigated, and it showed the improved decay rate with reduced trap depth for the nanocomposites with nanofillers addition in the range between 0.5 and 5 wt%. Threshold electric field calculated based on space-charge density variation by pulsed electroacoustic measurement was found to be between 7–9 kV/mm and maximum electric field calculated through polarity reversal test is about 9 kV/mm, for 5 wt% (for the optimised value of nanofiller) epoxy nano-Al composites.

Influence of material volume conductivity on electric field and surface charge of RIP valve-side bushing core under DC electro-thermal coupling stress

Modifying the volume conductivity of resin impregnated paper (RIP) material is a promising way to eliminate the electric field and the surface charge along the RIP valve-side bushing core surface. In this paper, an electro-thermal coupling model is established based on the geometry of a ±200 kV RIP valve-side bushing and the conductivity of RIP material taken from cuts of an actual bushing core. The influence of volume conductivity of RIP material on the surface charge, the duration of capacitive-resistive field transition, and the tangential electric field along the core surface are studied. Results indicate that decreasing the volume conductivity of RIP material can help reduce the positive surface charge and the tangential electric field along the core surface. On the contrary, it increases the duration of capacitive-resistive field transition. To meet the requirements of polarity reversal test, the volume conductivity of RIP material should be decreased by two orders of existing material's volume conductivity to reduce surface charge and tangential electric field. The results are valuable for the design of RIP converter valve-side bushings.

A symmetric aqueous redox flow battery based on viologen derivative

Due to the diversity and feasibility of structural modification for organic molecules, organic-based redox flow batteries (ORFBs) have been widely investigated, especially in aqueous solution under neutral circumstance. In this work, a symmetric aqueous redox flow battery (SARFB) was rationally designed by employing a bipolar redox active molecule (N,N'-dimethyl-4,4-bipyridinium diiodide, MVI2) as both cathode and anode materials and combining with an anion exchange membrane. For one MVI2 flow battery, MV2+/ MV·+ and I−/I3− serve as the redox couples of anode and cathode, respectively. The MVI2 battery with a working voltage of 1.02 V exhibited a high voltage efficiency of 90.30% and energy efficiency of 89.44% after 450 cycles, and crossover problem was prohibited. The comparable conductivity of MVI2 water solution enabled to construct a battery even without using supporting electrolyte. Besides, the bipolar character of MVI2 battery with/without supporting electrolyte was investigated in the voltage range between −1.2 V and 1.2 V, showing excellent stable cycling stability during the polarity-reversal test.

The influence of polarity reversal time on interface charges in oil-impregnated pressboard insulation under non-uniform electric field

The polarity reversal test is one of the routine tests for the evaluation of electric insulation in converter transformers. The polarity reversal time (PRT) has significant effect on the accumulation of interface charges in oil-impregnated pressboard insulation. IEC standard recommends that polarity reversal should be performed within 2 min so as to match with the dispersion rate of interface charges in uniform filed, but not necessarily in the non-uniform field. In order to investigate the influence of PRT on the dissipation rate of interface charges in non-uniform electric field, the density of interface charges was measured by an electrostatic capacitance probe in the needle-plate non-uniform field at the PRT of 2 ms, 4 ms and 2 min respectively. The results showed that the polarity of interface charges did not change with the applied voltage jump at the PRT of 2 ms and 4 ms, while the polarity of interface charges almost synchronously changed with the polarity reversal of applied voltage at the PRT of 2 min. For the PRT of 2 ms and 4 ms, the electric field nearby the needle electrode would be enhanced with applied electric field of the same direction, whilst the total electric field of insulation system would be weakened at the PRT of 2 min. It was inferred that polarity of interface charge might have not enough time to change in polarity reversal test within the PRT of 4 ms under non-uniform electric field, which was more close to the severe condition of covert transformer. The paper suggest that the value of PRT be reconsidered when the polarity reversal test is performed in non-uniform electric field.

Novel HVDC spacers by adaptively controlling surface charges – part ii: experiment

Charge accumulation on the surface of high voltage direct current (HVDC) spacers decreases their surface flashover voltage and affects the reliability of the insulation systems. In part I of this study, a novel HVDC spacer in which the surface charges can be adaptively controlled is proposed, and the aim of this paper is to experimentally verify the design. The experimental results of three kinds of model spacers, including a regular spacer, a spacer with a novel shape, and a spacer with charge adaptively controlled are provided. AC and DC surface flashover experiments and a polarity reversal test were performed. The effect of surface charges on triggering the surface flashover phenomenon are discussed. The results show that the surface flashover voltage increases both for the novel shaped spacer and the charge-adaptivelycontrolled spacer under application of AC bias, owing to a modification of the spacer shape that increases the creep distance. However, the surface breakdown voltage is the lowest for the novel shaped spacer under DC application and polarity reversal test. The charge adaptive control spacer displayed more advantages than the other samples under application of DC bias and in polarity reversal tests owing to its superior surface charge dissipation properties. It is hoped that this work could offer a new perspective for the design of a suitable spacer to avoid surface flashover when implementing HVDC energy transmission systems.

The single-active-part structure of the UHVDC converter transformer with the UHVAC power grid

The studied sending-terminal's UHVDC converter transformer with the UHVAC grid is currently one of the largest-capacity converter transformers, which is characterized by strong support for the large-scale grid power delivering out, strengthening grid's fault tolerance and backup capability, improving grid operation's flexibility and security, lowering the short-circuit currents. The proposed single-active-part converter transformer structure is well-designed, including the single-phase five-leg iron core, the special winding arrangement, the special structure of the spacers and angle rings, and so on, which is a smaller footprint, easier to install and test on site, but is more challenging in the structural design due to the critical railway transportation limitations on aspects of both size and weight. The feasibility of the proposed structure schema is verified by a series of tests, concerning the wave process, the short circuit force, the temperature field, the main insulation, and so on. Among them, the main insulation's electric fields at the import positions are verified to be reasonable, including the AC impressed voltage test, the DC impressed voltage test, and the polarity reversal test. It shows that the proposed single-active-part design scheme is practicable and conductive to manufacture and application for the UHV large-capacity converter transformers.

Transient Electric Field Analysis in Consideration of the Electric Field Dependence of Resistivity in the Converter Transformer

SUMMARYIn this paper, values of the electric field in the pressboard and oil during the polarity reversal test of the converter transformer were calculated with transient analysis. First, we confirmed the accuracy of the nonlinear analysis in the model test. Next, we carried out nonlinear transient electric field analysis for polarity reversal test of the converter transformer. In the results, when the applied time of dc voltage before the polarity reversal is 360 min, the values of the electric field of oil area are the same as when it is 90 min. Although, the electric field in the pressboard becomes higher in response to the applied time dc voltage, it does not cause a problem on the insulation. Because withstand voltage of pressboard is very high. In the results, the correlation between the applied time of dc voltage before the polarity reversal and the withstand voltage of transformer is considered low. This result can be applied to the design of the converter transformer.

Interface charge behavior of multi-layer oil–paper insulation under DC and polarity reversal voltages

Transformer oil, insulating paper, high voltage direct current (HVDC) bushings and on-load tap changer (OLTC) are essential parts of converter transformers. When the power flow of the HVDC system is reversed or a sudden outrage occurs, the charge field will deform the dielectric internal electric field, thus easily leading to the occurrence of discharge or insulation damage. In this case, it is necessary to carry out the characterization of the oil–paper interface to avoid these consequences. This paper analyses the interface charge accumulation and dissipation characteristics of an oil–paper insulation system under DC and polarity reversal voltages. In this paper, induced electrification was used to charge the composite oil–paper insulation. The amplitude of DC and polarity reversal voltages applied in this paper was 4 kV, and paper with thicknesses of 0.08 and 0.13 mm was used. This research offers a theoretical exploration to optimize the transformer oil– paper insulation structure and prevent damage to its insulation systems. From the research on different layers and thicknesses of paper, it can be concluded that the decay is fast in the initial period and then becomes slower with the lapse of time until finally the decay curve tends to become flat. With an increase in the number of the paper layers, the interface charge density decreases. So in real life multilayer paper is used to avoid failures owing to its structural weakness. Regarding the DC polarity reversal effect, increasing the thickness of the paper is equivalent to adding paper layers. The dissipation rate of the positive interface charge is quicker than that of the negative one. In the polarity reversal test, the dissipation rate becomes smaller as the reversal time gets longer.

Late Triassic paleomagnetic result from the Baoshan Terrane, West Yunnan of China: Implication for orientation of the East Paleotethys suture zone and timing of the Sibumasu-Indochina collision

In order to better understand the paleogeographic position of the Baoshan Terrane in the northernmost part of the Sibumasu Block during formation of the Pangea supercontinent, a paleomagnetic study has been conducted on Late Triassic basaltic lavas from the southern part of the Baoshan Terrane in the West Yunnan region of Southwest China. Following detailed rock magnetic investigations and progressive thermal demagnetization, stable characteristic remanent magnetizations (ChRMs) were successfully isolated from Late Triassic Niuhetang lava flows. The ChRMs are of dual polarity and pass fold and reversal tests with magnetic carriers dominated by magnetite and subordinate oxidation-induced hematite; we thus interpret them as a primary remanence. This new paleomagnetic result indicates that the Baoshan Terrane was located at low paleolatitudes of ∼15°N in the Northern Hemisphere during Late Triassic times. Together with available paleomagnetic data from the Baoshan Terrane and surrounding areas, a wider paleomagnetic comparison supports the view that the East Paleotethys Ocean separated the Sibumasu and Indochina blocks and closed no later than Late Triassic times. We argue that the currently approximately north-to-south directed Changning-Menglian suture zone is very likely to have been oriented nearly east-to-west at the time of the Sibumasu-Indochina collision.

Practical Application of ±250‐kV DC‐XLPE Cable for Hokkaido–Honshu HVDC Link

SUMMARYThe long‐term dc properties of DC‐XLPE insulation materials, which have been developed for dc use, were investigated. It was found that the lifetime of DC‐XLPE under dc voltage application is extended by the addition of nano‐sized filler. The time dependence of the space charge distribution at 50 kV/mm was observed for 7 days. Almost no accumulation of space charge in DC‐XLPE was found. The 250‐kV DC‐XLPE cables and accessories were manufactured and subjected to a type test and PQ test for use in the Hokkaido–Honshu dc link facility owned by the Electric Power Development Co., Ltd. These tests were performed under conditions that included a polarity reversal test for line commutated converter (LCC) systems as recommended in CIGRE TB 219. The test temperature was 90 °C. The type test and PQ test were successfully completed. The DC‐XLPE cable and accessories were installed in summer 2012 for the Hokkaido–Honshu dc link. After the installation of the dc extruded cable system, a dc high‐voltage test at 362.5 kV (=1.45 PU) for 15 min was successfully completed in accordance with CIGRE TB 219. This dc extruded cable system was put into operation in December 2012 as the world's highest‐voltage extruded dc cable in service and the world's first dc extruded cable for a LCC system including polarity reversal operation.

Practical Application of +/-250kV DC-XLPE Cable for Hokkaido-Honshu HVDC Link

Long term DC properties of DC-XLPE insulation material, which have been developed for DC use, were investigated. It was found that the life time of DC-XLPE under DC voltage application becomes longer by addition of nano-sized filler. The time dependence of space charge distribution at 50kV/mm was observed for 7 days. As a result, there is almost no accumulation of space charge in DC-XLPE. The 250kV DC-XLPE cables and accessories were manufactured and subjected to a type test and PQ test for the use in the Hokkaido-Honshu DC link facility owned by the Electric Power Development Co., Ltd. These tests were done under the conditions that include a polarity reversal test for line commutated converter (LCC) systems as recommended in CIGRE TB 219. The test temperature was set at 90°C. The type test and PQ test were successfully completed. The DC-XLPE cable and accessories were installed in summer 2012 for the Hokkaido-Honshu DC link. After the installation of the DC extruded cable system, a DC high voltage test at 362.5kV (=1.45PU) for 15 minutes was successfully completed in accordance with CIGRE TB 219. This DC extruded cable system was put into operation in December 2012 as the world's highest voltage extruded DC cable in service and the world's first DC extruded cable for a LCC system including polarity reversal operation.

Research on Key Technologies of Detecting 1553B Avionics Data Bus Network

Abstract 1553B avionics data bus network may fail due to vibration, temperature, humidity or human error. Therefore, the research on detection technology of 1553B avionics data bus network is an important subject. The key technologies are studied by analyzing the possible faults of the network, including four-wire DC resistance measurement method for conductors-to-shield short test and stub continuity test, equivalent impedance measurement of coupling transformer for main bus continuity test, polarity reversal test base on duty ratio measurement, attenuation measurement base on coupler model, and data path integrity test base on bit error rate calculation. Finally, the implementation methods of key technologies are researched, a portable integrated automatic test system of 1553B data bus network is constructed based on PC104 computer, and the hardware configuration and test process are especially designed.

Paleomagnetism of early Paleogene marine sediments in southern Tibet, China: Implications to onset of the India–Asia collision and size of Greater India

We report a paleomagnetic study of Paleocene marine sediments in the Gamba area of the Tethyan Himalayan terrane, southern Tibet, which aims to accurately locate the position of the northern margin of Greater India and further constrain timing of initial contact between India and Asia. Following detailed rock magnetic and paleomagnetic experiments on a total of 675 drill-core samples collected from the Zongpu and Upper Jidula formations, characteristic remanent magnetizations (ChRMs) were successfully isolated from most samples following alternating field (AF) or integrated thermal and AF demagnetization. The ChRMs are of dual polarity and pass fold and reversal tests indicating a pre-folding origin. Together with detailed biostratigraphic investigation of the sampling section, a magnetic polarity sequence is constructed from data at 167 sampled horizons and satisfactorily correlates with polarity chrons C24r to C27r dating the Zongpu Formation between ~ 56.2 and 61.8 Ma on the geomagnetic polarity time scale. The ChRM directions from the Zongpu Formation are grouped stratigraphically into 33 sites and yield two paleopoles of 71.6°N, 277.8°E (A 95 = 2.5°) and 67.3°N, 266.3°E (A 95 = 3.5°) for the time intervals comprising 56 to 59 Ma and 59 to 62 Ma, respectively. These new paleopoles imply that the Tethyan Himalayan terrane was sited at low latitudes in the Northern Hemisphere during the interval ~ 62–56 Ma, suggesting that initial contact between the Tethyan Himalaya and Lhasa terranes was established before 60.5 ± 1.5 Ma, and very likely occurred near the Cretaceous–Tertiary boundary, at least in the central part of the suture zone. The results also indicate that at least 1500 ± 480 km of post-collisional crustal shortening occurred within the Himalayas. From the analysis of available paleomagnetic data obtained on both sides of the suture zone, we propose a conceptional collision model for the India–Asia collision.

Paleomagnetic results of the Cretaceous marine sediments in Tongyouluke, southwest Tarim

Paleomagnetic and rock magnetic studies on samples of 18 sites from the Cretaceous marine sedimentary rocks in the Tongyouluke section, Akto County, southwest Tarim, China show that the magnetic carriers of the Lower Cretaceous are dominated by hematite with some magnetite, while the magnetic carriers of the Upper Cretaceous are characterized by a combination of magnetite and titanomagnetite as well as hematite and goethite. Stepwise thermal demagnetization is performed and vector analysis is used to isolate magnetic components, which illustrates a single magnetic component or double magnetic components. The high temperature stable components are dual polarities and pass polarity test, reversal test and consistency test. The overall mean direction of the Lower Cretaceous is D = 27.0°, I = 42.0°, a95=6.5° with pole position at f = 190.3°, ?=63.1°, dp=4.9°, dm=8.0°. The overall mean direction of the Upper Cretaceous is D = 29.1°, I = 39.4°, a95=11.2° with pole position at f =190.9°, ?=60.3°, dp= 8.0°, dm=13.4°. Compared with the inclination of the Early Cretaceous from red beds of north Tarim, the contemporary inclination of southwest Tarim is 10.0° ± 7.8° sharper, but it is still 8.1°±8.9°, shallower than that of Early Cretaceous basalts in southwest Tarim. Although these pa-leomagnetic data show slightly larger confidence limit, the paleolatitude of the marine Cretaceous tends to lie between that of terrestrial red beds and volcanic rocks.

Long-term reliability testing of 500 kV DC PPLP-insulated oil-filled cable and accessories

This paper describes the results of a long-term reliability test of a newly developed 500 kV DC oil-filled cable and accessories that transmit up to 2800 MW. This is the largest capacity ever used for submarine cables. The test line was 500 m and consist of submarine cables, land cables and several kinds of accessories. An optical fiber sensor was first installed in the oil duct of the cable to measure the conductor temperature directly under application of DC voltage. From 1994 to 1996, the authors carried out an accelerated electrical and thermal aging test equivalent to 40 years, a load cycle test, a polarity reversal test and a transient overloading current test. Satisfactory breakdown strength was confirmed in the residual test which followed the long-term test. These results have been instrumental to the decision to construct 500 kV DC commercial submarine cable lines.