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The impact of layout and concentration of defects on the electromechanical constraints in the MV cables insulation

Medoukali Hemza, Zegnini Boubakeur

Diagnostyka

2023

Vol. 24, No. 2

art. no. 2023206

The problem of the dense presence of voids in the solid insulation of cables remains a concern for researchers in terms of diagnosis and maintenance. The focus of this paper is to investigate the influence of both the layout and density of microcavities on the electrical and electromechanical constraints in the XLPE insulation of MV cables using numerical simulation. The simulation is based on the resolution of Laplace’s equation by the finite element method (FEM) using MATLAB. The electrostatic pressure and the elongation of the microcavities are estimated. This elongation leads to the formation of microchannels and then develops due to partial discharges to arborescence and in the end, the cable becomes out of service. This process takes a long time, so we use simulations to deepen the understanding of this phenomenon in a very short time. The electromechanical constraints are determined for different layouts and densities of microcavities.

The effect of protrusions on the initiation of partial discharges in XLPE high voltage cables

AlShaikh Saleh Mohammad, Refaat Shady S., Olesz Marek, Abu-Rub Haitham, Guziński Jarosław

Bulletin of the Polish Academy of Sciences. Technical Sciences

2021

Vol. 69, nr 1

art. no. e136037

This paper is focusing on 3D Finite Elements Analysis (FEA) based modelling of protrusions as defects or imperfections in the XLPE high voltage cable. This study is aiming to examine the impact protrusions have on the initiation of partial discharges. Spherical and ellipsoidal protrusions with different sizes at the conductor screen of the high voltage cable is an essential content of this paper. In addition, a spherical gas-filled void is placed inside and outside the protrusions, and a water tree produced from protrusions is under consideration. The partial discharge influence taking place at the protrusions and the stress enhancement factor is determined for all the variations mentioned to quantify the rise in the inception of partial discharges due to the protrusions.

Measurements on treeing resistance with a new electrode design.

Huuva R., Englund V., Gubański S., Hjertberg T.

Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

2007

Vol. 46, nr 19

75-81

Electrical treeing in high voltage cable insulation has been studied for several years and today the mostly used laboratory test set-up is the needle-plane electrode configuration. In this paper another electrode configuration is suggested. The new electrode configuration makes use of a thin tungsten wire as the electrode that delivers the high and divergent electric stress needed to initiates electrical tree growth in insulation material. Multiple electrical trees are formed during the testing, which allows determining the treeing initiation field as well as the rate of tree growth. A comparison between tree initiation conditions in samples prepared of pure LDPE and XLPE materials is shown and the data are fit by 3-parameter Weibull distributions. Electrical trees start to develop in LDPE material at lower field strength than in XLPE one and two different mechanisms of tree initiation are identified in LDPE. Improvement imposed on the treeing initiation field by adding voltage stabilizing additives to XLPE is also illustrated.