Dry Band Arcing Research Articles

계면활성제가 첨가된 염수용액에 따른 폴리머 애자의 트래킹 성능 평가

Recently, polymer insulators that are used for high voltage applications have some advantages such as light weight, small size, vandalism resistance, hydrophobicity and easy making process. During outdoor service of polymer insulators, the surface of the insulating material is frequently subjected to moisture and contamination that lead to dry band arcing. Their tracking resistance, erosion resistance, end sealing and shed design are very important because dry band arcing causes degradation of polymer surface. Aging test to estimate life property of polymer insulator is executed through several international standard such as IEC 61109 and CEA tracking wheel test, but is not getting clear conclusion yet. There are two methods in the diagnosis method of polymer insulator such as off-line and on-line. The diagnosis methods in off-line are external condition analysis by the eye, contaminant analysis on surface, surface analysis, pollution withstand voltage test, power frequency flashover voltage test, lightning impulse flashover test, tensile fracture load test and flexural load test. Polymer material is also investigated it`s tracking resistance by adding surface active agent in IEC 587. In this paper, the tracking performance of polymer insulator with salt solution which is added surface active agent. The diagnosis of insulator sample has been analyzed by leakage current and visual examination, STRI guide and thermal image camera.

Development of the Dry-Band Arc on All-Dielectric Self-Supporting Cables During Laboratory Tests

Utilities frequently install All-Dielectric Self-Supporting (ADSS) fiber-optic cables on transmission lines. The cable jackets suffer damage due to dry-band arcing caused by high electric fields and pollution on the cable. A test method to determine cable resistance to dry-band arcing is being considered for standardization by the IEEE. A new nozzle arrangement for the test is proposed in this paper. Using this nozzle the repeatability of the test is significantly improved over previous arrangements. Each test cycle consists of three stages: wetting, drying, and arcing. The three stages are examined in detail. Development of the dry-band arc on the cable jacket during the arcing period is presented. It is shown that the length of the arc increases exponentially with time and reaches a stable length. The stable length is shown to be a function of the applied voltage.

Experimental Studies of the Characteristics of Dry Band Arcing on ADSS Fiber Optic Cables

A series of simulated arcing experiments are conducted in a laboratory setting to investigate the characteristics of dry band arcs on ADSS fiber optic cables. The measurement of resistance, power, and energy of dry band arcs is described. The impact of voltage and current on arc resistance is presented. The power and energy of dry band arcing is measured under different short-circuit current and open-circuit voltage. An equation which relates arc power to open-circuit voltage and short-circuit current is proposed. Experiments show that arc power has a threshold to cause the damage of cable jackets. The study of arc power and energy can be used to predict a potential damage of ADSS cables.

A Study on Erosion Resistant Characteristics of ATH-filled Silicone Rubber Exposed to Dry Band Arc Discharge

A Study on Erosion Resistant Characteristics of ATH-filled Silicone Rubber Exposed to Dry Band Arc Discharge

Thermal conductivity of filled silicone rubber and its relationship to erosion resistance in the inclined plane test

Silicone rubber samples having various concentrations and mean particle sizes of either alumina tri-hydrate or silica filters, prepared by room temperature and heat cured under pressure (hot pressed), are tested for erosion resistance in the ASTM D2303 inclined plane tracking and erosion test. Their corresponding thermal conductivities are determined using a transient temperature technique in which an infrared laser is employed as the heat source and a thermal imaging camera as a temperature detection device. Scanning electron microscope observations show greater filler bonding to the silicone matrix in the hot pressed samples than in the room temperature vulcanized samples leading higher thermal conductivity and increased resistance to erosion, for both ATH and silica filled samples. The correlation study shows a strong relationship between the erosion resistance and the thermal conductivity of the tested samples, highlighting the importance of an outdoor insulating material to have high thermal conductivity in order to withstand dry band arcing. The results can be used to provide guidance on filler selection for silicone rubber compounding for outdoor insulation applications.

The role of inorganic fillers in silicone rubber for outdoor insulation alumina tri-hydrate or silica

A systematic study to understand how alumina tri-hydrate (ATH) and silica fillers improve the erosion resistance of silicone rubber during dry band arcing showed that the thermal conductivity of the resulting composite material is the main criterion governing material erosion. The thermal conductivity of the composite material is dependent on the thermal conductivity, concentration, particle size, and bonding of the filler particles to the silicone matrix. In this context, either filler can be shown to perform better than the other, depending on the formulation, in the ASTM inclined plane tracking and erosion test. Therefore, the industry perception that ATH filler imports better erosion resistance than silica in silicone rubber can be misleading. The release of water of hydration from ATH appears to have a secondary effect that may be more relevant in silicone compositions having a low concentration of a filler.

Correlation of damage, dry band arcing energy, and temperature in inclined plane testing of silicone rubber for outdoor insulation

Silicone rubber samples, filled with 30% alumina trihydrate, subjected to the ASTM inclined plane test, show good correlation between the measured harmonic power components of dry band arcing and the surface temperature recorded with a thermovision camera. The simultaneous study of the low frequency fast Fourier transform and variations in temperature shows that when the temperature rises above 100/spl deg/C there is a well defined increase in the low frequency harmonic components of the measured power; however, this trend is not verified by the fundamental component. The eroded mass of the samples is measured independently by a laser approach and a model to rank the tested samples using the inclined plane test is developed. The model is validated by applying it to both the recorded harmonic power components and temperature, resulting in the correct ranking of damage on the samples tested in the inclined plane test.

Evaluation of insulation performance of polymeric surface using a novel separation technique of leakage current

This paper describes a novel method to separate the leakage current, obtained in polymeric materials during a salt fog aging test, into three components of conductive current, corona discharge current and dry band arc discharge current. First, we investigated that the relationship between optical emissions due to discharges and a leakage current. Based on experimentally defined discharge types, the separation of the leakage current was carried out. Finally, the polymer surface was analyzed using an electron spectroscopy for chemical analysis (ESCA), and the change in the polymeric constituents was evaluated. The results showed that the cumulative charges due to the dry band arc discharge and the corona discharge to the total charge were about 20 and 10%, respectively. It was also found that a high temperature vulcanized (HTV) silicone rubber could retain its insulation performance better than a room temperature vulcanized (RTV).

Portable ADSS surface contamination meter calibrated in high voltage environment

All dielectric self-supporting (ADSS) fiber optic cable is known to have a limited service lifetime in some environments when installed near high voltage transmission lines. Dry band arcing can cause deterioration of the cable jacket and thus has been identified as a contributing factor to this short lifetime for some cables. It has been shown that wet contamination on the jacket of the ADSS cable increases the likelihood of dry band arcing, and hence, is a predictor of short service life. In this work, a portable transducer for measuring wet contamination levels (e.g., electrical resistance per meter) on the jacket of an ADSS cable has been designed, constructed, and calibrated in a high voltage environment. It is simple to operate and can be used while the transmission line is energized. More specifically, it has been shown effective when used on an ADSS cable in electric fields comparable to those near 500 kV transmission lines.

Study of Temperature Distribution Along an Artificially Polluted Insulator String

Insulator becomes wet partially or completely, and the pollution layer on it becomes conductive, when collecting pollutants for an extended period during dew, light rain, mist, fog or snow melting. Heavy rain is a complicated factor that it may wash away the pollution layer without initiating other stages of breakdown or it may bridge the gaps between sheds to promote flashover. The insulator with a conducting pollution layer being energized, can cause a surface leakage current to flow (also temperature-rise). As the surface conductivity is non-uniform, the conducting pollution layer becomes broken by dry bands (at spots of high current density), interrupting the flow of leakage current. Voltage across insulator gets concentrated across dry bands, and causes high electric stress and breakdown (dry band arcing). If the resistance of the insulator surface is sufficiently low, the dry band arcs can be propagated to bridge the terminals causing flashover. The present paper concerns the evaluation of the temperature distribution along the surface of an energized artificially polluted insulator string.

Fundamental and low frequency harmonic components of leakage current as a diagnostic tool to study aging of RTV and HTV silicone rubber in salt-fog

The paper presents the results of using the fundamental and the low frequency harmonic components of leakage current to study aging of silicone rubber in salt-fog. Experiments have been conducted on RTV and HTV coated rods at different fields (0.25-0.6 kV/cm) and conductivities (1000 to 2500 /spl mu/S/cm). The onset of dry-band arcing on samples could be determined by measuring the low frequency harmonic components. A correlation has been found between the fundamental and low harmonic components of leakage current and different forms of aging. Where erosion could be associated with an increase in the level of both the fundamental and low frequency harmonic components of leakage current. For example, surface damage for HTV rods occurred when the fundamental component of leakage current was greater than 2 mA. On the other hand, when the samples approached failure, the fundamental component of leakage current reached relatively high values ( > 6 mA for HTV rods and > 2 mA for RTV rods) and the low frequency harmonic components of the leakage current tended to decrease. The results suggest that both the fundamental and low frequency harmonics of leakage current can be used as a tool to determine both the beginning of aging and end of life of silicone rubber in salt-fog.

A method for detecting the transition from corona from water droplets to dry-band arcing on silicone rubber insulators

The paper presents an investigation on the use of partial discharge (PD) as a means to study the development of leakage current (LC) on silicone rubber insulators in a salt-fog chamber. Simultaneous measurements of LC and PD on dead-end type silicone rubber insulators exposed to different combinations of electrical stress and salt-fog salinity are performed. The results show that for an electrical stress of 33 V/mm applied to the insulator, the average LC experiences gradual changes and reaches a critical level (around 1 mA) where dry-band arcing is observed after 20 minutes at 2300 /spl mu/S/cm, and after 25 minutes at 1800 /spl mu/S/cm. The corresponding PD levels reach hundreds of pC after 15 minutes at 2300 /spl mu/S/cm, and after 20 minutes at 1800 /spl mu/S/cm. For a salinity corresponding to 1800 /spl mu/S/cm and stress of 26 V/mm, the LC changes much more gradually and reaches the critical level only after approximately 60 minutes. The corresponding PD reaches hundreds of pC after 30 minutes and more than 1500 pC after 60 minutes. Pattern recognition techniques have been applied to investigate the transition from corona to dry-band arcing. The features extracted from the maximum and mean apparent charge trends are found to be useful to cluster and classify the two phenomena. Simultaneous visual observations of the discharges on the insulator surface support the results. The investigation, therefore, shows that PD is a sensitive method for detecting the transition from corona from water droplets to dry-band arcing and an alternative method for studying the early aging stage of silicone rubber insulators.

波形歪みに基づく高分子絶縁材料の表面漏れ電流分離計測アルゴリズムの提案

We propose an algorithm of analytical measurement which can separate conductive and dry-band arc components of leakage current flowing on the surface of polymer insulating materials according to the waveform distortion considered. The waveform distortion gives useful information to distinguish discharge types and evaluate the degree of degradation of the polymer surface. We have also developed a measurement system capable of separating the leakage current into the two components. We confirmed effectiveness of the measurement system by applying it to an artificial aging test based on Rotating Wheel Dip Test method.

塩霧試験における漏れ電流の自動分離·解析法の提案

This paper presents a new method to separate leakage currents into three components which are: conductive current that flows in the water film, partial discharge current as corona discharge and dryband arc discharge current; and analyze each cumulative charges automatically by using FFT and differential techniques.

Algorithm to predict dry-band arcing in fiber-optic cables

Utilities frequently use ADSS (all dielectric self-supporting) fiber-optic cables installed on transmission lines 3-6 m below the high voltage conductors. Dry-band arcing occurs on the fiber-optic cables when the cables are polluted and wet. This has been assumed to cause cable failures. An equivalent circuit has been developed to represent the polluted fiber-optic cable in the high voltage environment. The objective of this paper is to present a novel numerical method that can be used to predict dry-band arcing in fiber-optic cables. KCL (Kirchoff's current law) is used to derive node point equations for the equivalent circuit. Forward elimination and backward substitution of node voltage is used to solve the equations. The effect of pollution, tower arrangement, and conductor sag is analyzed. The numerical method has speed advantages over circuit simulation methods. This method includes conductor sag, nonuniform pollution, and variable capacitance. This algorithm can be used to predict dry band arcing in fiber-optic cables.

Leakage current monitoring and outdoor degradation of silicone rubber

The degradation process of silicone rubber was investigated by leakage current monitoring in the inclined-plane method. A data acquisition system (DAS) with 12-bit, 8-channel analog/ digital (AD) converter was prepared. The maximum erosion depth was measured for use as the degradation indicator. The result suggests that the discharge duration and current waveform are well corresponding with the degradation process. And fast Fourier transform (FFT) analysis from the stored waveform shows that the harmonic ratio I3/I1 corresponds with the initial surface transition from hydrophobic to hydrophilic, and with further progressive degradation. In addition, it may be possible to use cumulative charge and peak pulses as quantitative indicators of failure. Furthermore, the contact angle was adopted for assessing surface degradation. These results indicate that the surfaces are divided into top and bottom areas depending on the degree of exposure to dry band arcing. It seems that the bottom area subjected to most of the dry band arcing contains very short chains of silicone rubber as well as alumina trihydrate fillers, while the top area shows the loss of filler particles.

Electrical and environmental stress and the hydrophobic stability of SIR, EVA and their blends

This paper treats the effects of electrical and environmental stresses on the hydrophobicity of polymers intended for use in nonceramic insulators. We investigated the effect of UV radiation, corona discharges, dry-band arcing, acid rain and water absorption on hydrophobic transfers in, and the aging of, room temperature vulcanized (RTV)-silicone rubber (SIR), high temperature vulcanized (HTV)-silicone rubber (SIR), ethylene vinyl acetate (EVA) rubber and the blends made from HTV-SIR and EVA. Acid rain had little influence on hydrophobicity in any of the samples. EVA and the blends with low silicone ratios to EVA allowed much larger reduction in hydrophobicity after or while subjected to the above stresses (except for acid rain) than did the silicone rubbers and a blend with a high silicone ratio to EVA. Salt-fog tests were conducted to correlate the hydrophobic stabilities of materials with leakage current levels thereon. The hydrophobic stability of the silicone rubbers was attributed to low-molecular-weight silicone components that were able to migrate and finally cover the aged surface layers. Because EVA possessed less fluid components and less chemical stability under electrical and environmental stresses, its hydrophobicity was readily reduced and hardly recovered, which led to higher current leakage and early material aging. For each material, the critical hydrophobic level permitting leakage current to develop was determined by adding a non-ionic wetting agent to saline water.

Electrical design parameters of all-dielectric-self-supporting fiber optic cable

A lumped circuit model for calculating voltages and currents on all-dielectric self-supporting (ADSS) fiber optic cable near high voltage transmission lines has been developed. The model has been used to show that contamination levels, tower attachment points, relative ADSS and conductor sag and electrical phasing of the conductors are important parameters and must be considered in calculations, especially when determining the possibility of dry band arcs which could lead to cable damage.

Performance of nonceramic insulators under tropical field conditions

This paper presents the results of investigations on the performance of nonceramic insulators in tropical field conditions. Six different types of 33 kV insulators (silicone rubber, EPDM composite, porcelain, and RTV coated porcelain) were installed at six different test sites exposed to marine, industrial and clean environments in Sri Lanka and Tanzania. The visual scrutiny, hydrophobicity class (HC) and surface conductivity were used for the evaluation of the field performance. The silicone rubber and RTV coated insulators preserved the hydrophobic properties although some biological growth was found on them. The EPDM insulators showed distinct surface changes. At the same time, damage due to dry-band arcing appeared on the porcelain insulators exposed to marine pollution.

Electrical and environmental aging of silicone rubber used in outdoor insulation

This is a laboratory study on the aging of SIR and hydrophobicity recovery. UV radiation, corona discharges, acid rain, dry-band arcing are employed as sources of the aging. Chemical and morphological analysis is used to detect the surface chemical and structural changes derived from these stresses. The nature of highly mobile low molecular weight (LMW) chains achieving a quick recovery of the hydrophobicity is carefully examined. Their generation and extinction caused by these stresses are investigated. From this study, it is shown that oxidation that induces crosslinking, branching, interchanging and a formation of silanol groups are the most dominant chemical reactions during the aging of SIR. Furthermore, silanol groups that are byprodncts of oxidation restrict the diffusion of mobile LMw chains, which decreases the recovery speed of hydrophobicity and accelerates the aging. A typical aging scenario of SIR from the installation to the end of their life is drawn.