scholarly journals Dynamics model for electrical tree propagation in cross-linked polyethylene cable insulation under high frequency voltage

2008 ◽  
Vol 57 (6) ◽  
pp. 3828
Author(s):  
Xie An-Sheng ◽  
Li Sheng-Tao ◽  
Zheng Xiao-Quan
Keyword(s):  
High Frequency ◽  
Dynamics Model ◽  
Cable Insulation ◽  
Electrical Tree

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 Effect of Air Gap on Electrical Tree in Epoxy Resin Under High Frequency Bipolar Square-Wave Voltage

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5722
Author(s):  
Shihang Wang ◽  
Chuang Zhang ◽  
Hang Fu ◽  
Jiao Xiang ◽  
Jianying Li ◽  
...  
Keyword(s):  
Epoxy Resin ◽  
High Frequency ◽  
Air Gap ◽  
Heat Accumulation ◽  
Air Gaps ◽  
Square Wave ◽  
Electrical Tree ◽  
Electrical Trees ◽  
Voltage Frequency ◽  
Tree Characteristics

Insulation fails quickly under high-frequency AC high voltage, especially bipolar square-wave voltage with a high dV/dt. It is of great significance to study the failure mechanism of epoxy casting insulation under such kind of voltage. In this paper, pin-plane epoxy casting insulation samples with air gaps were prepared, and the relation between the electrical trees under the high frequency bipolar square-wave voltage and the air gap conditions and voltage frequencies (1~20 kHz) were studied. Results indicated that, with the presence of air gaps, the electrical trees were bush-type and had a relatively slow growth rate, which was different from the fast-growing branch-type trees in the samples without air gap. The electrical tree characteristics related with the size of air gap and voltage frequency were also studied. The electrical tree grew faster under higher voltage frequency or with a smaller air gap. Results proved that discharge introduced a lot of defects for the surface layer of the epoxy resin samples and hence induced the possibility of multi-directional expansion of electrical trees. In addition, the resulting heat accumulation and unique charge transport synergistically affected the electrical tree characteristics under the high frequency bipolar square-wave voltage.

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 Adaptive Disturbance Rejection Control for Automatic Carrier Landing System

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Xin Wang ◽  
Xin Chen ◽  
Liyan Wen
Keyword(s):  
High Frequency ◽  
Disturbance Rejection ◽  
Closed Loop ◽  
Simulation Studies ◽  
Dynamics Model ◽  
Rejection Algorithm ◽  
Output Tracking ◽  
Disturbance Rejection Control ◽  
Control Scheme ◽  
Final Approach

An adaptive disturbance rejection algorithm is proposed for carrier landing system in the final-approach. The carrier-based aircraft dynamics and the linearized longitudinal model under turbulence conditions in the final-approach are analyzed. A stable adaptive control scheme is developed based on LDU decomposition of the high-frequency gain matrix, which ensures closed-loop stability and asymptotic output tracking. Finally, simulation studies of a linearized longitudinal-directional dynamics model are conducted to demonstrate the performance of the adaptive scheme.

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