TELKOMNIKA, Vol. 13, No. 4, December 2015, pp. 1194~1203 ISSN: 1693-6930,
accredited A by DIKTI, Decree No: 58DIKTIKep2013 DOI: 10.12928TELKOMNIKA.v13i4.2362
1194
Received July 27, 2015; Revised October 13, 2015; Accepted October 27, 2015
Modelling on Tracking Test Condition of Polymer Nanocomposite using Finite Element Simulation
Fatin Liyana Muhamedin, MAM Piah and Nordiana Azlin Othman
Institute of High Voltage and High Current, Faculty of Electrical Engineering, UniversitiTeknologi Malaysia, 81310, UTM Johor Bahru, Johor, Malaysia
e-mail: fendifke.utm.my
Abstract
Electrical tracking is a formation process of a permanent conducting path across the insulating material due to surface erosion under high voltage stress. The existing of leakage current LC on the wet
contaminated material surface causes the generation of surface discharges that resulted in the material degradation. The effects of electric field distribution and current density on LLDPE-Natural Rubber blends
material were investigated using finite element method FEM analysis. In this paper, a variety of physical parameters particularly contaminant flow rate, various applied voltages, material properties of permittivity
and conductivity were studied when nanofiller is added to LLDPE-Natural rubber blend. The simulation works using FEM software of Quickfield was applied to the tracking test condition of IEC 60587 standard.
The results show that the electric field distributions are critical on the edges of contaminant solution path at higher voltage level. The current density and electric field distribution is increase with higher applied
voltage. The polymer nanocomposite with 1-5 of nanofiller exhibits a good resistance to tracking and erosion test.
Keywords: Finite Element Method, electric field, current density, surface discharges and, IEC 60587 Copyright © 2015 Universitas Ahmad Dahlan. All rights reserved.
1. Introduction
The wide usage of polymer as insulation materials in high voltage HV equipment has led to further investigation in their performances, mainly in term of electrical aspect. The aging
of polymer due to environmental stresses can cause degradation of insulator polymer through surface tracking phenomena.Insulating surface are exposed to environmental stresses such as
contaminant, UV ray stress, pollution and low severity fogconditions [1, 2]. Leakage current LC exists on the insulator surface when a certain voltage gradient is sufficient to cause the LC to
flow under a wet contaminant condition.The continuous flow of LC will heat the insulator surfaceand the accumulated heat dissipation in narrow path on the insulator surface eventually
formed a dry band arcing at the surface of the insulator. Dry band arcing occurs at the lowest surface resistance when non-uniform water layer is formed due to hydrophobicity loss. The
hydrophobicity feature in the materials can reduce the onset of LC by increasing the failure time.Hydrophobicity loss could increase the development of LC and reduce the insulator
resistance hence contribute in degradation [3]. Meanwhile, surface discharges occur when the air gap reached the critical flashover voltage across the dry band. Carbonized track and erosion
will be formed when an arc burns the insulator material due to surface discharges. The carbonized track that developed pathway between two electrodes eventually will cause
insulation failure to the system.
To study the electrical performances of polymeric insulating materials, LC measurement are used as the tools to indicate the deterioration of the materials [4, 5].The online monitoring of
LC has been developed by previous researchers and this LC are acquired throughout the duration of six-hour [6-8]; Indeed, the obtained LC are proportional to degradation of polymer
materials [9, 10]. The influence of contaminant conductivity was studied using three conditions which are coastal with conductivity of 4746 µScm, industrial 818µScm and NH
4
Cl 550 µScm and the result shows that industrial contaminant gives a smallest LCvalue of 327.6 mA
with the lesser degradation [11]. The study of hydrophobicity loss in term of LC waveform was conducted ini [12] since the hydrophobicity loss of the materials affect the material’s resistance
towards surface tracking and erosion. Hydrophobicity will be destroyed by the presence of local
ISSN: 1693-6930
TELKOMNIKA Vol. 13, No. 4, December 2015 : 1194 – 1203
1195 high electric field and when hydrophobicity ability of the material loss, the tendency of the
surface insulator to degrade rise [13]. In the simulation analysis of electrical stresses on the surface of insulator,the investigation of electric field distribution around water droplet or water
films are conducted by several researchers [14, 15]. Their result showsthat the contact angle of water droplet in the shed model which applied voltage is perpendicular to the insulator surface is
neglected as the maximum strength of electric field are found to be appeared on top of the droplets [16]. However, the contact angle of water droplets affect the electric field distribution in
the sheath model where voltage is appliedalong the insulator surface [17]. The maximum electric field is lowest when the distance between two water droplets reduce and increasing of a
water droplet on the insulator surface [18]. When the contact angle of water droplet is low, it forms water layer on the insulator surface. In tracking and erosion resistance experiment, the
contaminant solution layer are intended to be flown at certain flow rate on the insulator surface. This can initiate the dry band arcing when the contaminant layer is dry near the ground
electrode when the voltage is supplied. Corona disharges emmision occured at the tips of the droplets whereas the dry band arcing occured during wet conditions and water droplets
deformation affected the LC waveform obtained from the current density in the simulation [13].
The previous research in the field simulation is conducted mainly on the partial discharge, phenemona with a focus of the void and water droplet as the parameters [19, 20].
There is little attempt to investigate the field simulation in the inclined plane tracking test in related to surface tracking studies. Therefore, there is a possiblityto conduct this field work to
encounter the correlation between the field simulation and actual experiment. If the approach of the field simulation in IPT test could forecast the result of the experiment of IPT test, then the
field simulation work can be used as another option in investigating the surface tracking resistance. In this paper, the electric field, voltage and current density distribution are studied
using Finite Element software on LLDPE-Natural Rubber materials with and without nanofiller. The analysis was conducted at various applied voltages under wet contaminant conditions. The
simulation works were applied on the test configuration of IEC 60587 standard tracking and erosion test. The parameters used to investigate the electric field and current density distribution
of insulator surface are applied voltage, electric conductivity and permittivities of insulating sample and contaminant solution.
2. Research Method 2.1. FEM Simulations
