scholarly journals Time Development of Voltage Frequency Dependence of Partial Discharge Activity in Voids

2019 ◽  
pp. 139-144 ◽  
Author(s):  
Torstein Grav Aakre ◽  
Erling Ildstad ◽  
Sverre Hvidsten
Keyword(s):  
Partial Discharge ◽  
Discharge Activity ◽  
Glass Fiber Reinforced ◽  
Conditioning Period ◽  
Voltage Application ◽  
Voltage Frequency ◽  
Frequency Sweeps ◽  
The One ◽  
By Products ◽  
Test Objects

Condition assessment of high voltage equipment based on partial discharge measurements is often performed after a voltage pre-conditioning period. The aim of this paper is to present results from experimental examinations of time variance of partial discharge activity and to propose physical explanations of the phenomena observed. Experiments were performed on laboratory made 3 mm thick discs of generator bar insulation, consisting of mica and glass fiber reinforced epoxy with a 0.5 mm thick cylindrical void surfaces of 10 mm in diameter. The effect of conducting and insulating void surfaces was examined using copper tape as upper and lower electrodes of the voids. All objects were tested by 12 one-minute long AC voltage frequency sweeps at frequencies from 50 Hz to 0.1 Hz distributed in time from start of the experiment, after initial one-hour constant 50 Hz voltage application and during object short-circuiting for 20 h. The main result shows that in case of insulating voids the apparent charges vanished after the one-hour constant 50 Hz voltage application. After a grounding period of 5 minutes, the charge magnitudes slowly increased with time until reaching steady state after about 4-8 hours. Test objects with conductive void surfaces showed such reduction in case of PD testing at 0.1 Hz only. At voltage frequencies above 10 Hz the measured PD magnitudes were found to be nearly constant, close to the expected high theoretical value. This indicate that PD by-products strongly affected the void resistivity and thereby affect the PD activity of insulating voids. These by-products are temporary and disappear with time.

Bright-Field Images (Ctem) of Phase Objects at High Resolution

1976 ◽  
Vol 34 ◽  
pp. 490-491 ◽  
Author(s):  
Sumio Iijima
Keyword(s):  
High Resolution ◽  
Electron Beam Irradiation ◽  
Fine Particles ◽  
High Resolution Electron Microscopy ◽  
Good Test ◽  
Resolution Electron ◽  
Single Crystal Films ◽  
Crystal Films ◽  
By Products ◽  
Test Objects

We have developed a technique to prepare thin single crystal films of graphite for use as supporting films for high resolution electron microscopy. As we showed elsewhere (1), these films are completely noiseless and therefore can be used in the observation of phase objects by CTEM, such as single atoms or molecules as a means for overcoming the difficulties because of the background noise which appears with amorphous carbon supporting films, even though they are prepared so as to be less than 20Å thick. Since the graphite films are thinned by reaction with WO3 crystals under electron beam irradiation in the microscope, some small crystallites of WC or WC2 are inevitably left on the films as by-products. These particles are usually found to be over 10-20Å diameter but very fine particles are also formed on the film and these can serve as good test objects for studying the image formation of phase objects.

Partial Discharge Activity of Inter-turn Insulation under Different Parameters of Square Wave Voltage

2009 ◽  
Vol 129 (12) ◽  
pp. 922-930 ◽  
Author(s):  
Kai Zhou ◽  
Guangning Wu ◽  
Xiaoxia Guo ◽  
Liren Zhou ◽  
Tao Zhang
Keyword(s):  
Partial Discharge ◽  
Square Wave ◽  
Discharge Activity ◽  
Turn Insulation

scholarly journals Recovery of Anthocyanins and Monosaccharides from Grape Marc Extract by Nanofiltration Membranes

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2003
Author(s):  
Paul Muñoz ◽  
Karla Pérez ◽  
Alfredo Cassano ◽  
René Ruby-Figueroa
Keyword(s):  
Functional Foods ◽  
General Trend ◽  
Value Added ◽  
Operating Conditions ◽  
Permeate Flux ◽  
Ultrasound Assisted Extraction ◽  
Grape Marc ◽  
Assisted Extraction ◽  
The One ◽  
By Products

Wastewaters and by-products generated in the winemaking process are important and inexpensive sources of value-added compounds that can be potentially reused for the development of new products of commercial interest (i.e., functional foods). This research was undertaken in order to evaluate the potential of nanofiltration (NF) membranes in the recovery of anthocyanins and monosaccharides from a clarified Carménère grape marc obtained through a combination of ultrasound-assisted extraction and microfiltration. Three different flat-sheet nanofiltration (NF) membranes, covering the range of molecular weight cut-off (MWCO) from 150 to 800 Da, were evaluated for their productivity as well as for their rejection towards anthocyanins (malvidin-3-O-glucoside, malvidin 3-(acetyl)-glucoside, and malvidin 3-(coumaroyl)-glucoside) and sugars (glucose and fructose) in selected operating conditions. The selected membranes showed differences in their performance in terms of permeate flux and rejection of target compounds. The NFX membrane, with the lowest MWCO (150–300 Da), showed a lower flux decay in comparison to the other investigated membranes. All the membranes showed rejection higher than 99.42% for the quantified anthocyanins. Regarding sugars rejection, the NFX membrane showed the highest rejection for glucose and fructose (100 and 92.60%, respectively), whereas the NFW membrane (MWCO 300–500 Da) was the one with the lowest rejection for these compounds (80.57 and 71.62%, respectively). As a general trend, the tested membranes did not show a preferential rejection of anthocyanins over sugars. Therefore, all tested membranes were suitable for concentration purposes.

NON-DISCRIMINATORY TRADE RESTRICTIONS AFTER KECK

2002 ◽  
Vol 61 (1) ◽  
pp. 1-52
Author(s):  
Alan Dashwood
Keyword(s):  
Case Law ◽  
Sales Promotion ◽  
Trade Restrictions ◽  
Member States ◽  
The Public ◽  
Court Of Justice ◽  
Equivalent Effect ◽  
The One ◽  
Domestic Products ◽  
By Products

IN its Keck judgment—famous or notorious according to taste—the Court of Justice drew a distinction, for the purposes of the application of the prohibition in Article 28 EC against measures having equivalent effect to quantitative restrictions (“MEEQRs”), between two categories of national measures. On the one hand were “product requirements”: measures specifying requirements to be met, in order to obtain access to the market of a Member State, by products coming from other Member States where they are lawfully manufactured and marketed, like the minimum alcohol requirement for fruit liqueurs in Cassis de Dijon (Case 120/78 [1997] E.C.R. 649). Such product requirements are liable to constitute MEEQRs, and therefore require specific justification, in order to escape prohibition, on one of the public interest grounds recognised by Community law. On the other hand was the category of measures described in the judgment as “provisions restricting or prohibiting certain selling arrangements”. An example was the legislation at issue in the main proceedings in Keck, which prohibited the resale of products below their purchase price, thereby depriving retailers of a form of sales promotion. Other examples, attested by the case law post-Keck, are measures regulating advertising methods, the kind of shop in which goods of a certain description can be sold, shops’ opening hours and Sunday trading. National provisions in this latter category are not normally such as to hinder trade between Member States under the test formulated by the Court in Dassonville (Case 8/74 [1974] E.C.R. 837, at para. 5), and so do not call for justification; not, that is, “so long as those provisions apply to all relevant traders operating within the national territory and so long as they affect in the same manner, in law and in fact, the marketing of domestic products and those from other Member States”: see Joined Cases C-267 and 268/9 [1993] E.C.R. I-6097, at paras. 15–17.

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