1 M. A. Salam a,* , Q. M. Rahman b , S. P. Ang a , F. S. Wen a , H. A. Hadi a , M. Fadil a , S. Hassan b , W. Voon c a Institut Teknologi Brunei, Brunei Darussalam b University of Western Ontario, London, ON, N6A 5B9, Canada c Berakas Power Management Company, Brunei Darussalam * Corresponding author at: M. A. Salam, Institut Teknologi Brunei, Brunei Darussalam,. Tel: 00673-2461020 Ext 1315 E-mail address: [email protected](M. A. Salam) Abstract: For an extended period of time, long-rod porcelain and silicone rubber insulators are being used in transmission lines by two power utility companies, the Department of Electric Services (DES) and the Berakas Power Management Company (BPMC), in Brunei Darussalam. Over time, these insulators have got polluted by sand, sodium chloride (salt), coastal dust and seawater. The pollution levels in terms of the equivalent salt deposit density (ESDD) of those insulators were measured and the results reported in this paper. It is found that the pollution levels fall in the range of 0.273-0.301 mg/cm2 at the bottom surface and 0.227-0.261 mg/cm2 at the top surface of the porcelain insulators. Whereas the pollution level for long-rod silicone insulators is found to be 0.363-0.372 mg/cm2 at the bottom and 0.319-0.329 mg/cm2 at the top of the silicone rubber insulators. In addition, simulations of electric potential and field distributions of these insulators were carried out under clean, uniform and non-uniform pollution, and broken surface conditions using the COMSOL Multiphysics software platform. Article Information: Keywords: Pollution layers Long-rod porcelain Long-rod silicone rubber insulator Electric potential distribution Electric field distribution Submitted: 15 Aug 2015 Revised form: 24 Oct 2015 Accepted: 27 Oct 2015 Available Online: 27 Oct 2015 1. Introduction DES and BPMC are the two power utility companies in Brunei Darussalam. These two companies transfer power from substations to Tutong and Kuala Belait districts through double circuited transmission lines, respectively. These transmission lines pass near the South China Sea and forest. Insulators exposed to environments in these areas are polluted by sand, sodium chloride (salt), coastal dust and seawater. These pollutants are accumulated on the surface of the insulators by natural wind, and a dry pollution layer is finally formed. This dry pollution layer does not affect the insulator performance in sunny days. However, the pollution produces a conducting layer in the presence of light rain or dews [1]. Under this condition, the small arcs appear on the surface which may cause insulator flashover and hence disturbance on transmission networks [2]. The resulting electric field distributions due to the above mentioned condition were analyzed for an 11 kV composite insulator using the COMSOL Multiphysics software platform in [3]. Based on this platform, C. Volta [4] applied volume and surface approaches to determine the voltage distribution of a 28 kV dead-end thermoplastic elastomeric (TPE) insulator. The potential and electric field distributions were calculated inside and around I, II and V cap-and-pin insulators in 400 kV transmission lines with the COMSOL Multiphysics 3.5 software platform [5]. It was also mentioned that these distributions were affected by the tower, voltage magnitude, corona, contamination and environmental conditions. A comparative study between 2D axisymmetric and 3D modeling of an extra high voltage (EHV) post insulator equipped with a standard corona ring was presented in [6], and it was demonstrated by the results that the creation of a complete electrical link between the grading ring and the high voltage (HV) electrode could result in a reduction of the electric field strength in the vicinity of a HV electrode. T. Doshi et al [7] calculated the electric field distribution for composite insulators up to 1200 kV using a 3D software package based on the Boundary Element Method, and the impacts of corona and grading rings, single and bundled conductors, insulator orientation (dead-end and suspension), single and double units, and surface conditions (dry and wet) on the electric field distribution were analyzed. Suat Ilhan et al [8] studied the AC and transient electric field distributions along a 380 kV V-string insulator using the COMSOL Multiphysics software by considering a 2-mm thick uniform pollution layer. However, the pollution layer is seldom uniform in practice. H. Akkal et al [9] presented some solutions, using grading rings, for improving the performance of an EHV post station insulator under severe icing conditions. In addition, the COMSOL Multiphysics software was used for simulating electric fields and voltage distributions. The voltage distribution of the insulator was examined for situations polluted with the combination of NaCl, CuSo4 and distilled water in [10]. The performance of an insulator in terms of withstanding voltage and electric field distributions, is different for different types of coating under pollution conditions [11]. Imre Sebestyenbthe [12] determined the electric stresses acting around and inside the insulator considering the interactions with the three-dimensional environment using a domain decomposition approach for the finite element method. Given the above mentioned background, measurements of pollution levels of aged long rod porcelain and silicon rubber insulators are reported in this work. Also, the voltage and electric field distributions are investigated under clean, polluted and broken surface conditions. 2. Measurement of Pollution Levels Two heavily polluted, and approximately 30 years old insulators were brought in from DES, for the pollution measurement experiment. Some parts of these insulators were found to be cracked. However, extreme cautions were taken during the collection process of the pollutants. The insulators were brought to the laboratory, and the pollutants were collected by brushing them off; later on, pollutants were mixed with distilled water Characteristics of Aged Long-rod Porcelain and Silicone Rubber Insulators under Pollution Conditions An Open Access Journal www.measpublishing.co.uk/BJRE British Journal of Renewable Energy British Journal of Renewable Energy 01(01) 01-08 (2015)
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1
M. A. Salam a,*
, Q. M. Rahman b, S. P. Ang
a, F. S. Wen
a, H. A. Hadi
a, M. Fadil
a, S. Hassan
b, W. Voon
c
a Institut Teknologi Brunei, Brunei Darussalam b University of Western Ontario, London, ON, N6A 5B9, Canada c
Berakas Power Management Company, Brunei Darussalam
* Corresponding author at: M. A. Salam, Institut Teknologi Brunei, Brunei Darussalam,. Tel: 00673-2461020 Ext 1315