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 Electrical Treeing in Cable Insulation under Different HVDC Operational Conditions

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2406 ◽  
Author(s):  
Mehrtash Fard ◽  
Mohamed Farrag ◽  
Scott McMeekin ◽  
Alistair Reid
Keyword(s):  
Electric Fields ◽  
Asset Management ◽  
Partial Discharge ◽  
Polymeric Materials ◽  
Operational Parameters ◽  
Cable Insulation ◽  
Operational Conditions ◽  
Diagnostic Strategies ◽  
Electrical Trees ◽  
Electrical Treeing

Electrical treeing (ET) can irreversibly deteriorate the insulation of polymeric power cables leading to a complete failure. This paper presents the results of an experimental investigation into the effects of unipolar and polarity reversing DC voltages on electrical tree (ET) and partial discharge (PD) behavior within high voltage direct current (HVDC) cross linked polyethylene (XLPE) cable insulation. A double needle configuration was adopted to produce non-uniform electric fields within the insulation samples, potentially leading to electrical trees. The development of trees was monitored through an optical method and the associated partial discharge signals were measured through an electrical detection technique, simultaneously. The analysis of the results shows reasonable relation between the formation of ETs and the type of the applied voltages. The polarity reversing attribute of the test voltages has a pronounced effect on formation and growth of electrical trees. This implicates an interaction between the space charges that accumulate within polymeric materials and the operational polarity reversing electric fields, which causes insulation degradation. Therefore, study of influencing HVDC operational parameters on insulation degradations can contribute to improvements in cable design and advancement in insulation diagnostic strategies applicable in HVDC systems leading to more effective asset management.

scholarly journals Application of the Gaussian Mixture Model to Classify Stages of Electrical Tree Growth in Epoxy Resin

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2562
Author(s):  
Abdullahi Abubakar Mas’ud ◽  
Arunachalam Sundaram ◽  
Jorge Alfredo Ardila-Rey ◽  
Roger Schurch ◽  
Firdaus Muhammad-Sukki ◽  
...  
Keyword(s):  
Epoxy Resin ◽  
Gaussian Mixture Model ◽  
Mixture Model ◽  
Tree Growth ◽  
Asset Management ◽  
Gaussian Mixture ◽  
Growth Stages ◽  
Insulation Material ◽  
Electrical Tree ◽  
Electrical Trees

In high-voltage (HV) insulation, electrical trees are an important degradation phenomenon strongly linked to partial discharge (PD) activity. Their initiation and development have attracted the attention of the research community and better understanding and characterization of the phenomenon are needed. They are very damaging and develop through the insulation material forming a discharge conduction path. Therefore, it is important to adequately measure and characterize tree growth before it can lead to complete failure of the system. In this paper, the Gaussian mixture model (GMM) has been applied to cluster and classify the different growth stages of electrical trees in epoxy resin insulation. First, tree growth experiments were conducted, and PD data captured from the initial to breakdown stage of the tree growth in epoxy resin insulation. Second, the GMM was applied to categorize the different electrical tree stages into clusters. The results show that PD dynamics vary with different stress voltages and tree growth stages. The electrical tree patterns with shorter breakdown times had identical clusters throughout the degradation stages. The breakdown time can be a key factor in determining the degradation levels of PD patterns emanating from trees in epoxy resin. This is important in order to determine the severity of electrical treeing degradation, and, therefore, to perform efficient asset management. The novelty of the work presented in this paper is that for the first time the GMM has been applied for electrical tree growth classification and the optimal values for the hyperparameters, i.e., the number of clusters and the appropriate covariance structure, have been determined for the different electrical tree clusters.

scholarly journals Ameliorated Electrical-Tree Resistant Characteristics of UV-Initiated Cross-Linked Polyethylene Nanocomposites with Surface-Functionalized Nanosilica

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 313 ◽  
Author(s):  
Yong-Qi Zhang ◽  
Ping-Lan Yu ◽  
Wei-Feng Sun ◽  
Xuan Wang
Keyword(s):  
Fractal Dimension ◽  
Electric Fields ◽  
Tree Growth ◽  
Electrical Resistance ◽  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Sio2 Nanoparticles ◽  
Polyethylene Matrix ◽  
Electrical Tree ◽  
Electrical Trees

Given the high interest in promoting crosslinking efficiency of ultraviolet-initiated crosslinking technique and ameliorating electrical resistance of crosslinked polyethylene (XLPE) materials, we have developed the funcionalized-SiO2/XLPE nanocomposites by chemically grafting auxiliary crosslinkers onto nanosilica surfaces. Trimethylolpropane triacrylate (TMPTA) as an effective auxiliary crosslinker for polyethylene is grafted successfully on nanosilica surfaces through thiolene-click chemical reactions with coupling agents of sulfur silanes and 3-mercaptopropyl trimethoxy silane (MPTMS), as characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. The functionalized SiO2 nanoparticles could be dispersively filled into polyethylene matrix even at a high filling content that would generally produce agglomerations of neat SiO2 nanofillers. Ultraviolet-initiated polyethylene crosslinking reactions are efficiently stimulated by TMPTA grafted onto surfaces of SiO2 nanofillers, averting thermal migrations out of polyethylene matrix. Electrical-tree pathways and growth mechanism are specifically investigated by elucidating the microscopic tree-morphology with fractal dimension and simulating electric field distributions with finite-element method. Near nano-interfaces where the shielded-out electric fluxlines concentrate, the highly enhanced electric fields will stimulate partial discharging and thus lead to the electrical-trees being able to propagate along the routes between nanofillers. Surface-modified SiO2 nanofillers evidently elongate the circuitous routes of electrical-tree growth to be restricted from directly developing toward ground electrode, which accounts for the larger fractal dimension and shorter length of electrical-trees in the functionlized-SiO2/XLPE nanocomposite compared with XLPE and neat-SiO2/XLPE nanocomposite. Polar-groups on the modified nanosilica surfaces inhibit electrical-tree growth and simultaneously introduce deep traps impeding charge injections, accounting for the significant improvements of electrical-tree resistance and dielectric breakdown strength. Combining surface functionalization and nanodielectric technology, we propose a strategy to develop XLPE materials with high electrical resistance.

Study on the Methodology of Detection for Power Cable Insulation Defects Based on Oscillatory Wave

2013 ◽  
Vol 805-806 ◽  
pp. 880-883
Author(s):  
Yu Sheng Quan ◽  
Dai Juan Wang ◽  
Guang Chen ◽  
Zong Cheng Zhang
Keyword(s):  
Failure Rate ◽  
Partial Discharge ◽  
Reference Database ◽  
Power Cable ◽  
Signal Source ◽  
Cable Insulation ◽  
Water Tree ◽  
Detection Technology ◽  
Electrical Tree

Water tree, electrical tree and electrochemical tree formed by premature defects of the cable can induce fault. The failure rate of the cable connecter which is higher than cable itself can emerge water tree, electrical tree and electrochemical tree. Meanwhile, the flashover, partial discharge and overheated of the cable joint are also the important reasons for fault. The oscillatory wave of detecting the power cable insulation defects based on is put forward in this paper in terms of the problems existed in the cable detection technology. With the application of oscillatory wave and signal source on the spot, this method dynamically generates reference database of detecting the cable insulation defects, to discriminate the fault patterns correspond to the maximum of function and detect the type, location and severity of cable insulation's defects. Water tree fault of premature cable itself and cable joint can also be detected in this method.

scholarly journals Highly insulating thermoplastic blends comprising a styrenic copolymer for direct‐current power cable insulation

High Voltage ◽  
2021 ◽  
Author(s):  
Yingwei Ouyang ◽  
Amir Masoud Pourrahimi ◽  
Ida Östergren ◽  
Marcus Mellqvist ◽  
Jakob Ånevall ◽  
...  
Keyword(s):  
Direct Current ◽  
Power Cable ◽  
Cable Insulation ◽  
Thermoplastic Blends

Analysis of electrical tree propagation in XLPE power cable insulation

2011 ◽  
Vol 406 (8) ◽  
pp. 1556-1560 ◽  
Author(s):  
Minghui Bao ◽  
Xiaogen Yin ◽  
Junjia He
Keyword(s):  
Power Cable ◽  
Cable Insulation ◽  
Electrical Tree ◽  
Xlpe Power Cable

scholarly journals Study on the Relationship between Electrical Tree Development and Partial Discharge of XLPE Cables

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Chaofei Gao ◽  
Yanlong Yu ◽  
Zan Wang ◽  
Wei Wang ◽  
Liwei Zheng ◽  
...  
Keyword(s):  
Statistical Characteristics ◽  
Time Frequency ◽  
Experimental Platform ◽  
Equivalent Time ◽  
Electrical Tree ◽  
Electrical Trees ◽  
Insulation Breakdown ◽  
The Relationship ◽  
Frequency Diagram ◽  
Tree Development

Based on the slice materials of 35 kV and 110 kV XLPE cables, an experimental platform is built to study the relationship between electrical tree and PDs in XLPE with different voltage levels. There are three significant statistical characteristics of the PDs during the growth of electrical trees. The analysis of the results shows that each growth stage has certain characteristics. Different features existed between the growth of the electrical trees and the PD in the insulation of the 35 and 110 kV cables. Evident characteristics such as large spans of time and frequency were present as the electrical trees grew violently in the equivalent time-frequency diagram at every stage. These results could provide criteria for the identification of the deterioration using PD to monitor cables in service at rated voltages. The results are important for the identification of defects in cable insulation in order to provide an early warning of insulation breakdown in the cables.

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