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Performance Assessment of High Temperature Vulcanized Silicone Rubber Insulators Using Ansys 3D Analysis
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This paper describes in detail a step-by-step methodology for obtaining specimens from the housing material (high temperature vulcanized (HTV) silicone rubber with aluminum trihydrate (ATH) filler) of composite insulators (finished products), for five well known and commonly used tests. The aim of the paper is to render practical clarifications and additions to the instructions for five tests on composite insulators provided by international standards. Additionally, the ranges of the results of these tests are presented. More specifically, shore A hardness measurement, tensile strength and elongation at break test, tear strength test, density measurement and inclined plane test were conducted on the housing material of ten, new, unaged medium voltage composite insulators made by six different manufacturers. The results of these tests are presented as a contribution to the existing knowledge and a comparative study of corresponding results of previous investigations is performed. The presented procedures for specimens’ preparation, as well as the results (arithmetical ranges), could be used as guidelines for future testing on the housing material (HTV silicone rubber with ATH filler) of composite insulators, either by researchers and manufacturers, during laboratory testing and material development processes, or by customers (distribution and transmission networks owners), during batch acceptance tests.
In recent years, room temperature vulcanizing (RTV) coated insulators have been increasingly applied in transmission lines. A large number of RTV coating damages on insulators are currently found. In this paper, three typical damage modes of the RTV coating were simulated, and then, the pollution flashover characteristics were studied. Results indicated that there is a big difference between the ac flashover performances of RTV coated insulators under different damage modes. The flashover voltage, as well as the critical leakage current, is largely influenced by salt deposit density (SDD), damage modes, and damage area. The relationship between SDD and U
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still meets negative power function when RTV coating was damaged. Insulators with fan-shaped damage have lowest flashover voltage and greatest critical leakage current. Both 2D and 3D FEM models of the RTV coating damaged insulator pollution layer were developed to calculate leakage current density on the damaged surface; it is discovered that the starting position of the arc usually occurs where the current density is maximum. Different damage modes lead to the change of the surface pollution layer conductivity and the uneven distribution of the current density, which is the main reason that pollution flashover characteristics are directly related to the damage modes.
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.
The study describes the use of nano aluminum nitride in developing thermally conductive and electrically insulating materials. An experimental approach is followed, starting with the hydrophobic surface treatment of nanofillers using HMDS. TEM and XRD analysis are used to confirm the nanofiller presence and gain insight regarding the filler shape, dimensions, and phase. EDX, FTIR and XRD analysis revealed the co-existence of aluminum oxide in traces along with aluminum nitride. XRD patterns revealed no change after surface modification and confirmed the presence of an amorphous functionalized layer. The protocol for composite compounding is described in detail. SEM analysis of composites revealed a moderate degree of dispersion with localized pockets of agglomeration. Further, the TEM analysis performed gave insight into the dispersion of nanofillers. Finally, DSC analysis is performed to understand the effects of nano aluminum nitride on glass transition, melting point, and crystallization temperatures. An interesting pattern of increase in glass transition temperatures with nanofiller loading levels is discussed, drawing attention to the aggregated filler effect and the disentangling of silicone chains with increasing interfacial interaction. TGA analysis revealed an early onset of degradation with increase in nano aluminum nitride loading levels. Thermal conductivity increased with nanofiller loading levels, peaking at 3 phr by weight. Dielectric studies of breakdown strength and frequency domain spectroscopy from 1 mHz to 1 KHz is studied under different thermal points. The results are presented and discussed here.
This study investigates the role of filler interface on suppressing the erosion of room temperature vulcanized silicone rubber composites filled with fumed silica, nano alumina trihydrate and sub-micron hexagonal boron nitride fillers during DC dry-band arcing. Simultaneous thermogravimetric-differential thermal analyses indicate a superior effect for fumed silica in suppressing the depolymerization of silicone rubber and promoting radical based crosslinking. This can be attributed to favorable interactions at the fumed silica-silicone interface tethering the siloxane chains. At low filler loading of alumina trlhydrate, water of hydration has insignificant effects on suppressing depolymerization compared to that influenced by fumed silica's interface at equal filler loading. Similarly, incorporating thermally conductive boron nitride filler in silicone rubber does not show improvement in the depolymerization rate compared to that influenced by fumed silica. These findings correlate with the +DC inclined plane tracking and erosion test outcomes indicating superior erosion performance for the fumed silica filled composite. This accordingly supports the influential role of the filler interface over the water of hydration and thermal conductivity enhancement in suppressing the DC erosion of silicone rubber composites under the test conditions of this study. A statistical boxplot analysis technique is introduced to elucidate the inception of the stable dry-band arc in terms of the change in leakage current randomness during the +DC inclined plane tracking and erosion test. The boxplots reveal a slow inception of the stable dry-band arc with the fumed silica filled composite delaying the erosion of silicone rubber during the test. This finding confirms the influence of the filler interface over composite thermal conductivity in suppressing erosion of silicone rubber under DC dry-band arcing.
Under conditions of high temperature, high humidity, and strong ultraviolet radiation, RTV coating on the insulators may get aged, powdered and even peeled off. The physical damage of the RTV coating on the insulator surface can result in a reduction in the pollution flashover performance. Therefore, this study investigated the influence of location, lateral length, and longitudinal length of the damage on the pollution flashover voltage of RTV-coated insulators. From the experimental results, it was found that the longitudinal length of the damage along the creepage distance direction was the most influential factor on the pollution flashover voltage. According to the flashover voltage function obtained by fitting, the concept of “effective path” distance was proposed. This concept can be used to analyse the influence of multiple damages on the pollution flashover voltage. To validate the analysis, verification experiments were performed using typical industrial insulator. The results showed that the pollution flashover voltage of the insulator was also in a linear relationship with the proposed “effective path” distance, which confirmed the mechanism analysis.
This paper presents the comprehensive analysis of Leakage Current (LC) of a silicone rubber insulator under uniform and longitudinal non-uniform pollution conditions based on a large amount of test data. The experimental tests are carried out under different humidity levels for un-aged and aged samples. The results obtained indicate that the LC harmonics magnitudes increase with increasing the salt deposit density, aging time, and humidity, while they decrease with increasing the pollution non-uniformity degree. The analysis of phase angle difference between LC and applied voltage (θI-V°) demonstrates that the θI-V° is in the range of 54.3°–60.4°, 20.1°–32.5°, and 7.5°–11.8° under clean condition, light pollution and moderate pollution conditions, respectively. In addition, the θI-V° is less than 2.3° under heavy pollution condition. The non-uniformity of pollution distribution and insulator aging time have very little effect on the θI-V°, while the increase of humidity leads to a slight decrease in the θI-V°.
The paper reviews previous work on the DC inclined plane test and suggests equivalent DC voltage levels in parallel to AC voltage in the ASTM inclined plane tracking and erosion test. The aim of this work is to provide a basis for standardizing the inclined plane test for DC voltage. Round robin tests done in five laboratories on five specimens of a silicone rubber material were done with the purpose of establishing appropriate ratios by which the equivalent DC voltages can be determined with respect to the corresponding AC voltages. These levels were determined as 67% and 87%, for +DC and -DC respectively, of the AC initial tracking voltage, and for practical purposes, these levels are rounded to 70 and 90%.
The paper presents the results of inclined plane tests on ATH and silica composites of Silicone rubber (SiR) and EPDM to evaluate the effect of filler type and loading on the tracking and erosion resistance of the composites formed. The effect of test voltage on the outcome of the incline plane was also examined. A laser ablation test was also used to evaluate the various composites. A critical test voltage of 4.5 kV was shown to cause failures in samples which emphasizes the importance of testing composites at voltages above this critical level. In comparing the two test methods, both the inclined plane and laser ablation test methods showed the same order for EPDM composites of ATH and silica while the laser method showed silica SiR composites to perform somewhat better than in the inclined plane test which showed similar results.
The use of organic materials in making polymeric insulators has many advantages. However, it also has a draw back that organic compounds degrade in outdoor environment by many factors. The major issue is that how long they will perform satisfactorily before the end of their useful life. This paper present the result of multistress lab aging on HTV SiR insulators. The environment used was of Islamabad, Pakistan. The day/night & summer/winter cycles were made. An HTV-SiR insulator was installed in multistress aging chamber and energized. UV radiation, rain, and fog were applied. The insulator was aged for nine years. Leakage current, hydrophobicity was monitored at regular intervals. The samples of rubber from energized and un energized ends were cut at the end of each year. These samples were analyzed using FTIR. The results from all techniques were incorporated together to estimate the life of these insulators in environment of Islamabad.
Composite polymeric insulators are increasingly being accepted by
the traditionally cautious electric utilities worldwide. They currently
represent about 70% of installed new high voltage insulators in North
America. The tremendous growth in the applications of non-ceramic
insulators is due to their advantages over the traditional ceramic and
glass insulators. However, because polymeric insulators are relatively
new the expected lifetime is not known and is of critical interest to
the users. In this paper a review is presented of the recent performance
experience of high voltage composite polymeric insulators in outdoor
service, testing methods, the ranking of the materials, the `role' of
the fillers, the role of the low molecular weight components present in
the most widely used insulator types, the mechanisms responsible for the
loss and recovery of one of the most important properties of polymers
(the hydrophobicity), various methods to optimize the electrical
performance and a relatively new method for evaluating polymeric systems
in the field
Aging Exploration of Long Term Multistressed HTV-Silicone Rubber/Silica/Alumina Composites for High Voltage Insulation
- Arooj Rashid
Arooj Rashid et al., "Aging Exploration of Long Term Multistressed HTV-Silicone Rubber/Silica/Alumina Composites for High Voltage
Insulation," Materials Research Express, vol. 5, no. 9, 2018. [CrossRef] [Google Scholar] [Publisher Link]
Electrical Insulating Materials Used under Severe Ambient Conditions -Test Methods for Evaluating Resistance to Tracking and Erosion
IS 9947 : 2011, IEC 60587 : 2007, Electrical Insulating Materials Used under Severe Ambient Conditions -Test Methods for Evaluating
Resistance
to Tracking and
Erosion,
Bureau of
Indian Standards,
Delhi,
2011.
[Online].
Available:
https://law.resource.org/pub/in/bis/S05/is.9947.2011.pdf
Effect of ATH Content on Electrical and Aging Properties of EVA and Silicone Rubber Blends for High Voltage Insulator Compound
- M A Pradeep
M.A. Pradeep et al., "Effect of ATH Content on Electrical and Aging Properties of EVA and Silicone Rubber Blends for High Voltage
Insulator Compound," Journal of Applied Polymer Science, vol. 104, no. 6, pp. 3505-3516, 2007. [CrossRef] [Google Scholar] [Publisher
Link]