scholarly journals Electrical Detection of Degradation in Specimens of HVDC Cable Insulation

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3963
Author(s):  
Douglas Jutsell Nilsson ◽  
Stanislaw M. Gubanski ◽  
Yuriy V. Serdyuk
Keyword(s):  
Published Data ◽  
Cable Insulation ◽  
Isolation System ◽  
Service Environment ◽  
Injection Process ◽  
Electrical Tree ◽  
Metal Seal ◽  
Environmental Isolation ◽  
Inception Voltage ◽  
By Products

One of the challenges in laboratory investigation of degradation and ageing of HVDC cable insulation is related to securing, or in other words, imitating the real service environment of the material specimens. So far, the published data refer to experiments conducted in thermo-oxidative conditions, which is not the case during normal cable operation. In service, the cable insulation is protected by a metallic barrier that blocks the transfer of any substances in and out of the construction. By-products from the cross-linking reactions cannot diffuse out and any foreign substances are blocked from entering the insulation. Thus, in order to generate results that are valid, these conditions must be replicated in laboratory experiments. This contribution presents a methodology elaborated for performing ageing experiments in a hermetically sealed environment. Degradation of the material is evaluated through changes in the electrical tree inception voltage and test object capacitance over time. Securing the environmental isolation is accomplished with an isolation system consisting of a glass enclosure with attached metallic electrodes. Indium is used to create a glass-to-metal seal between the glass and the electrodes. The electrode geometry is of needle–plane type and the needle injection process is semi-automated to ensure specimen repeatability.

scholarly journals Electrical detection of degradation in specimens of HVDC cable insulation

2019 ◽  
pp. 43-46
Author(s):  
Douglas Jutsell Nilsson ◽  
Stanislaw Gubanski
Keyword(s):  
Large Degree ◽  
Published Data ◽  
Specimen Preparation ◽  
Cable Insulation ◽  
Isolation System ◽  
Injection Process ◽  
Electrical Tree ◽  
Metal Seal ◽  
Environmental Isolation ◽  
Inception Voltage

One of the challenges in laboratory investigation of degradation and ageing of HVDC cable insulation is related to securing, or in other words, imitating the real service environment of the material specimens. So far, the published data refer to experiments conducted in thermo-oxidative conditions, which is not the case during normal cable operation. In reality the cable insulation is protected by a metallic barrier that blocks the transfer of any substances in and out of the construction. By-products from the cross-linking reactions cannot diffuse out and any foreign substances, such as oxygen and water, are blocked from entering into the insulation. Thus, in order to generate results that are valid, these conditions must be replicated in laboratory experiments.This contribution presents a methodology elaborated for performing ageing experiments in a hermetically sealed environment. Degradation of the material is evaluated through measurements of changes in the electrical tree inception voltage and test object capacitance over time. Securing the environmental isolation is primarily accomplished with an isolation system consisting of a glass enclosure with attached metallic electrodes. Indium is used to create a glass-to-metal seal between the glass and the electrodes. The electrode geometry is of needle-plane type and the needle injection process is semi-automated to secure a large degree of repeatability in specimen preparation.

Polymer Insulation for Superconductive Application

2017 ◽  
pp. 350-386
Keyword(s):  
Low Temperature ◽  
Epoxy Resin ◽  
Pulse Frequency ◽  
Void Defect ◽  
Electrical Tree ◽  
Important Quality ◽  
Solid Dielectrics ◽  
Number Of Discharges ◽  
Inception Voltage

With the research and development of high temperature superconducting technology, superconducting insulating materials under liquid helium and nitrogen temperature have been gradually taken seriously. Considering the unique operating environment, epoxy resin and PI face the challenge of low temperature. Electrical tree is one of the aging failure phenomena occurring in solid dielectrics. These imperfections could cause the field concentration with the application of high voltage, which results in partial discharges (PD). PD testing is an important quality check for the insulation of HTS cable. This chapter presents a study aimed at clarifying the influence of low temperature, pulse frequency and pulse duration on the electrical tree characteristics in epoxy resin, as well as PD characterization of PI film in LN2. The results show that the number of discharges and the discharge quantity in PI films increase with the increasing of the applied voltage and the defect size. The PD inception voltage decreases when the void defect diameter in PI enlarged and it is higher in LN2 than that at room temperature.

scholarly journals Electrical Treeing in Power Cable Insulation under Harmonics Superimposed on Unfiltered HVDC Voltages

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3113 ◽  
Author(s):  
Mehrtash Azizian Fard ◽  
Mohamed Emad Farrag ◽  
Alistair Reid ◽  
Faris Al-Naemi
Keyword(s):  
Electric Fields ◽  
Direct Current ◽  
Asset Management ◽  
Diagnostic Techniques ◽  
Power Cable ◽  
Operational Parameters ◽  
Cable Insulation ◽  
Electrical Tree ◽  
Double Electrode ◽  
Electrical Trees

Insulation degradation is an irreversible phenomenon that can potentially lead to failure of power cable systems. This paper describes the results of an experimental investigation into the influence of direct current (DC) superimposed with harmonic voltages on both partial discharge (PD) activity and electrical tree (ET) phenomena within polymeric insulations. The test samples were prepared from a high voltage direct current (HVDC) cross linked polyethylene (XLPE) power cable. A double electrode arrangement was employed to produce divergent electric fields within the test samples that could possibly result in formation of electrical trees. The developed ETs were observed via an optical method and, at the same time, the emanating PD pulses were measured using conventional techniques. The results show a tenable relation between ETs, PD activities, and the level of harmonic voltages. An increase in harmonic levels has a marked effect on development of electrical trees as the firing angle increases, which also leads to higher activity of partial discharges. This study of the influencing operational parameters of HVDC converters on power cable insulation is predicted to contribute to enhancements in cable design and progressive advancement in condition monitoring and insulation diagnostic techniques that can lead to more effective asset management in HVDC systems.

scholarly journals Tokopherols in Okara (Soy Pulp): Highly Efficient Liquid Chromatography

2020 ◽  
Vol 50 (2) ◽  
pp. 194-203
Author(s):  
Svetlana Petrova ◽  
Irina Maksimova
Keyword(s):  
Liquid Chromatography ◽  
Chromatographic Separation ◽  
High Performance ◽  
Lipid Fraction ◽  
Scientific Data ◽  
Published Data ◽  
Structural Formulas ◽  
Fat Soluble Vitamins ◽  
Positive Effect ◽  
By Products

Introduction. Soy pulp, or okara, is a soy milk by-product. It contains a complex of valuable macro- and micronutrients, including fat-soluble vitamins. Recently, there has been a growing interest in replacing synthetic antioxidants with a mix of natural tocopherols. Soy beans and their by-products contain vitamin E and therefore can be used in food production, cosmetic, etc. Study objects and methods. The present research featured soy pulp. The content of tocopherols in the soy product was determined by high performance liquid chromatography using Sigma Aldrich standards and corresponding calibration dependencies. The research also involved spectrophotometry for determining tocopherols in standard solutions followed by chromatographic separation using fluorimetric detection. Results and discussion. To determine tocopherols in the okara, the test samples were treated with hexane. The filtered solution was exposed to low temperatures, after which the phases formed by centrifugation were separated. The samples were tested for all forms of tocopherols with the exception of β- and γ-forms. The chromatographic separation of the peaks of these forms was difficult due to the fact that their structural formulas were similar and differed only in the arrangement of methyl groups, i.e. the ortho- and paraposition. As a result, it was decided to determine the sum of the β- and γ-forms, which did not affect the objectivity of the analysis, since, according to published data, the content of β-tocopherol in soy products stays within 5%. Conclusion. The proposed method for sample preparation made it possible to improve the separation of the lipid fraction, which had a positive effect on the results of the analysis. The method also determined not only the quantitative, but also the qualitative content of tocopherols in the product. This reduced the risk of malfunctioning chromatographic equipment: the method proved more economical in terms of labor and reagent use. The obtained results corresponded to the existing scientific data on the content of tocopherols in soy products. The content of tocopherols in soy okara was 109 mg%.

Sign in / Sign up

Export Citation Format

Share Document