Yanuar Z. Arief

Partial discharge characteristics of XLPE cable joint and interfacial phenomena with artificial defects

This paper deals with partial discharge (PD) causing degradation of XLPE cable joint and interfacial phenomena of XLPE/EPR interface due to artificial defects such as metal particles, needle-like void and fiber soaked with water. We measured aging time dependence of phase-resolved PD (phi-q-n) patterns and PD statistic parameters when such kinds of defects were placed at XLPE/EPR interface. As a result, phi-q-n patterns were found to depend upon the defect type varying with aging time. In order to grasp the degradation mechanisms, we compared a practical XLPE cable joint with a model sample to simulate the real one. Moreover, electron spectroscopy for chemical analysis (ESCA) was also carried out to interpret the degradation mechanism.

Enhanced bowtie UHF antenna for detecting partial discharge in gas insulated substation

UHF method to detect partial discharge (PD) phenomenon has been proven to be an effective way. Many types of UHF antenna have been developed in order to achieve a better sensitivity and accuracy in certain bandwidth (300 MHz-3.0 GHz) for detecting the ultra-high frequencies generated by partial discharge. Bowtie antenna is proven to be sensitive, accurate and easily designed and fabricated. This paper focuses on the enhancement of bowtie antenna to achieve better performance in detecting partial discharge using UHF method. Characteristics of antenna both on the simulation result prior to the fabrication and measurement using a network analyzer show the good agreement. Experiment was carried out in a gas insulated switchgear (GIS) model with a protrusion on the conductor as PD source and antenna located at different positions with applied voltage range from 20-25 kV. EM wave intensity and frequency captured by antenna were observed. The relation between the distances of PD source to antenna, either from one spacer aperture to others, or distance from one spacer aperture were investigated. Antenna mounted 55 cm from the closest spacer aperture to the PD source can still detect EM wave intensity very well. The lowest EM wave peak envelope intensity measured at 30.03 mV from the same spacer aperture compared to 1.952 mV peak-peak EM wave intensity from internal GIS UHF sensor demonstrates a sufficient sensitivity performance.

Partial Discharge Characteristics of Polymer Nanocomposite Materials in Electrical Insulation: A Review of Sample Preparation Techniques, Analysis Methods, Potential Applications, and Future Trends

Polymer nanocomposites have recently been attracting attention among researchers in electrical insulating applications from energy storage to power delivery. However, partial discharge has always been a predecessor to major faults and problems in this field. In addition, there is a lot more to explore, as neither the partial discharge characteristic in nanocomposites nor their electrical properties are clearly understood. By adding a small amount of weight percentage (wt%) of nanofillers, the physical, mechanical, and electrical properties of polymers can be greatly enhanced. For instance, nanofillers in nanocomposites such as silica (SiO2), alumina (Al2O3) and titania (TiO2) play a big role in providing a good approach to increasing the dielectric breakdown strength and partial discharge resistance of nanocomposites. Such polymer nanocomposites will be reviewed thoroughly in this paper, with the different experimental and analytical techniques used in previous studies. This paper also provides an academic review about partial discharge in polymer nanocomposites used as electrical insulating material from previous research, covering aspects of preparation, characteristics of the nanocomposite based on experimental works, application in power systems, methods and techniques of experiment and analysis, and future trends.

Temperature effect on electrical treeing and partial discharge characteristics of silicone rubber-based nanocomposites

This study investigated electrical treeing and its associated phase-resolved partial discharge (PD) activities in room-temperature, vulcanized silicone rubber/organomontmorillonite nanocomposite sample materials over a range of temperatures in order to assess the effect of temperature on different filler concentrations under AC voltage. The samples were prepared with three levels of nanofiller content: 0% by weight (wt), 1% by wt, and 3% by wt. The electrical treeing and PD activities of these samples were investigated at temperatures of 20°C, 40°C, and 60°C. The results show that the characteristics of the electrical tree changed with increasing temperature. The tree inception times decreased at 20°C due to space charge dynamics, and the tree growth time increased at 40°C due to the increase in the number of cross-link network structures caused by the vulcanization process. At 60°C, more enhanced and reinforced properties of the silicone rubber-based nanocomposite samples occurred. This led to an increase in electrical tree inception time and electrical tree growth time. However, the PD characteristics, particularly the mean phase angle of occurrence of the positive and negative discharge distributions, were insensitive to variations in temperature. This reflects an enhanced stability in the nanocomposite electrical properties compared with the base polymer.

Organo-montmorillonite as an electrical treeing retardant for polymeric insulating materials

This paper presents investigation on the propagation of electrical treeing in silicone rubber samples filled with Montmorillonite (MMT) and Organo-montmorillonite (OMMT) nanoclays as fillers for electrical tree inihibition. Treeing experiments were conducted by applying ac voltage with increasing rate of 0.5 kV per second at power frequency on pure silicone rubber, silicone rubber filled with 1% MMT and silicone rubber filled with 1% OMMT samples respectively and treeing propagation length and inception voltage within 30 minutes aging period were observed. Result from this study showed that the silicone rubber/OMMT sample exhibited the shortest tree length as well as highest tree inception voltage followed by the silicone/MMT sample with the pure silicone rubber having the least electrical performance. This finding suggests the OMMT can be used a filler in polymeric insulating materials for electrical tree inhibition.

Insulating performance of LLDPE/natural rubber blends by studying partial discharge characteristics and tensile properties

A series of linear low-density polyethylene (LLDPE)/natural rubber (NR) blends of composition 80/10, 70/20, 60/30, 50/40 and 40/50 containing nano-sized fillers montmorillonite (MMT) and Titanium(IV) Oxide (TiO2) were produced by a twin-screw extruder with maleic anhydride grafted linear low-density polyethylene (LLDPE-g-MAH) of 10 wt% as a compatibilizer. An electrical performance test through partial discharge (PD) characteristics using CIGRE Method II test was conducted to study the electrical performance of the samples. Applied voltage was set on 7kVrms for 1 hour. The discharge characteristics were observed using picoscope™ and LabView™ programming. Then tensile test carried out to investigate the mechanical performance of the composites. The combine results of PD characteristics and tensile properties described the insulating performance of the composites. The results revealed that total PD numbers decreasing as increasing of weight percentages of natural rubber in the composition of the composite without any filler. In addition, it is found that total PD numbers significantly decreases on sample with MMT filler compared to TiO2 one.

Partial discharge characteristics of natural rubber blends with inorganic nanofiller as electrical insulating material

In electrical engineering, electrical discharge can occur in gaseous, liquid or solid insulating medium. Localized dielectric breakdown that occur at a small portion of a solid or fluid electrical insulation under high voltage stress is called partial discharge (PD). This phenomenon can cause the material to breakdown if there is no proper action taken. Usually it begins within voids, cracks, or inclusions within a solid dielectric, at conductor-dielectric interfaces within solid and in bubbles within liquid dielectrics. In order to modify electrical properties of the original structure then nanocomposite need to be introduced. Nanocomposite is the original structure that has been inserted by nano component (nanofiller) such as silicone dioxide and titanium dioxide. Nanocomposites are also found in nature, for example in the structure of the abalone shell and bone. By adding nano component inside the original component, it can change the mechanical and electric properties. In this study, PD characteristics of polymer-natural rubber blends nanocomposite have been investigated. The samples of nanocomposites were developed by using extrusion method. The high voltage is applied at the electrode arrangement of the test sample. The signals of partial discharges are detected by CIGRE Method II and RC detector and the signals are transferred to the personal computer using LabViewTM software. The result from the software is analyzed to find out the PD characteristics. The results revealed that the highest PD numbers are compositions with no filler while the lowest PD numbers come from sample that use 4% SiO2 as its nanofiller. The physical morphology observation is also conducted to investigate the degradation of the samples.

Influence of nano-titanium dioxide (TiO 2 ) on electrical tree characteristics in silicone rubber based nanocomposite

Electrical tree is recognized as one of the pre-breakdown phenomena that occurs in high voltage insulation material. In addition, under high divergent field, the electrical tree grows rapidly and severely which may cause the breakdown of insulation to occur. In view of foregoing, nano-filler was added into the base insulating materials to enhance their properties against the growth of electrical tree. Thus in this study, nano-titanium dioxide was chosen as filler in order to improve the characteristics of silicone rubber which in turn inhibits the growth of electrical tree. The test samples were prepared in the form of leaf-like specimen. Nano-titanium dioxide was chosen as filler in order to improve the characteristics of silicone rubber. The number of partial discharge occurrence, partial discharge magnitude and breakdown time of the nanocomposites were investigated under different percentage of nano-titanium dioxide. The applied voltage and frequency were fixed at 10 kVrms AC and 50 Hz respectively. Treeing growth was recorded and partial discharge was observed at the constant applied voltage. The findings in this research showed that under high concentration of nano titanium dioxide, the treeing propagation were reduced and partial discharge number increased. The function of nano titanium dioxide as obstacle for the tree path in the silicone rubber samples was successfully tested. The results have shown that physical bonding between nano-titanium dioxide and silicone rubber matrix was improved, the tree propagation speed decreased, and this resulted in the increment of partial discharge magnitude. However, further experimentation is required to give more clarifications regarding to this finding.

Electrical treeing initiation and propagation in silicone rubber nanocomposites

Electrical tree initiation voltage and tree propagation length for unfilled silicone rubber, silicone rubber nanocomposites filled with 1% and 3% of OMMT and SiO2 was presented in this paper. This study investigates the capabilities of OMMT and SiO2 in silicone rubber in order to inhibit the growth of electrical treeing. From the result of this study has indicated that in the filled nanocomposite sample, the OMMT acts as barrier to unfilled silicone rubber and silicone rubber filled with SiO2 because the capabilities to decreased the tree propagation length of electrical tree. This result revealed that OMMT could be used as filler in silicone rubber insulating material for the purpose of retarding electrical tree growth.

Statistical study on tree inception voltage of silicone rubber and epoxy resin

Weibull distribution has been used widely by many researches around the world especially in the analysis of high voltage experimental data. Unfortunately, most of the experimental data analysis was not following the accurate statistical technique. Thus in this paper, a statistical study on the tree inception voltage of silicone rubber and epoxy resin is presented. The tree inception voltage of silicone rubber and epoxy resin was measured via camera-equipped online monitoring system. The leaf-like specimen was used as test sample. The experiment was performed based on IEC 1072:1991 “Methods of Test for Evaluating the Resistance of Insulating Materials against the Initiation of Electrical Trees”. The obtained results were analysed statistically by using fitting method. Anderson-Darling goodness-of-fit test was performed in order to obtain the best fitting distribution. Comparison exercise was made between the fitted distribution and Weibull distribution. Based on Anderson-Darling tests, the tree inception voltage of silicone rubber and epoxy resin was best fitted with Johnson SB distribution. Based on this fitted distribution, the value of tree inception voltage for silicone rubber and epoxy resin was calculated and equalled to 3.1529 kV and 4.6528 kV respectively. Thus, it was found that, the fitting method by means of Anderson-Darling goodness-of-fit test was successful to recognize the best fitted distribution for the value of tree inception voltage for silicone rubber and epoxy resin.