Electrical Aging Research Articles

Influence of Different XLPE Cable Defects on the Initiation of Electric Trees

Defects in the insulation layer of cross-linked polyethylene (XLPE) cable are the leading cause of electrical tree. The mechanism that how the different insulation defects influence on the starting of electrical tree should be explored, and it will be utilized to improve cable insulation in the production and installation. In the paper, firstly the spike-air gap defect as the main defect characteristics of cable fault has been determined by analyzing the actual cable defect type and influence. Then, the needle-electrode short cable test system was built and the representative defect model was constructed, in order to simulate the influence of the spike-air gap defect of different sizes in the outer semiconductor layer on the initial voltage of electrical tree. Thirdly, the Physical model was created to analyze the influence of each defect parameters. The research showed that the electrical tree of XLPE cable was mainly caused by defects in the semiconductor layer. The maximum electric field distribution can be formulized by the maximum field strength Mason model. According to the formulation and the test results, the main parameters, including the spur curvature, the micro-pore pressure and the initial energy of generating electric tree, have a positive promotion on the initial voltage of the electrical tree and can hinder the tree developing. Therefore, utilizing the interface treatment method between the insulation layer and the semiconductor layer, the insulation heat treatment process and the filling of the inert gas are to improve the parameters and further resist electrical tree aging in the production and installation.

Electric Tree Characteristics of Glass Fiber Reinforced Epoxy Insulation Composites with Different Contents

Electric tree aging due to the action of long-term partial discharge stress of epoxy resin casting insulation is a major problem in electrical engineering. On the discharge experimental platform, initiation and culture experiments of the electric trees were carried out at a power frequency voltage of 20 kV. The mass fractions of the spherical glass fibers were 0, 0.5, 1, 2 and 3 %. The results showed that the electrical dendritic process of epoxy resin experienced initiation, growth, lag and burst periods, the phase maps of the corresponding partial discharges in the four periods were all “mountain-like”. The electric tree of pure epoxy resin showed a typical dendritic structure, after the glass fiber was properly added, the electric tree became lighter in color with a more complicated shape, the damage also became more serious, however, the growth of the electric branch was suppressed. The electric tree aging channel of the epoxy resin appeared black and under microscopy the micro-branched channel wall appeared white. When the amount of glass fiber was 2 %, the initiation time of the electric trees was prolonged, the growth rate of the electric trees decreased and suppressing development of the electric tree branches was optimal.

Temporal and frequency‐domain assessment of thermal and electrical ageing of mineral and vegetable oils

This study focuses on the effect of accelerated thermal and electrical ageing on the dielectric properties of two vegetable oils (olive and soya oils) and a mineral oil which are thermally aged in sealed bottles at 110°C for durations up to 720 h and electrically submitted up to 2500 low-energy discharges under DC voltage. The investigated properties are the real part of the complex relative permittivity, dissipation factor and conductivity in a large frequency range (20 Hz–10 MHz) using frequency domain spectroscopy. This study also discusses the discharge currents generated in these oils and their corresponding fast Fourier transforms followed by power spectral density analysis. The electrical discharges are applied to the oil samples in a plane–plane configuration electrodes and 2.5 mm gap under DC voltage. The frequency-domain investigated descriptors are: maximum peak, mean value, rms value, peak factor, variance and standard deviation of magnitude spectrum, in addition to the resonance and bandwidth frequency of discharge currents. Furthermore, the spectrograms of these discharge currents are presented, illustrating how the frequency composition and the intensity of each frequency change with time.

Influence of ambient conditions on electrical partial discharge resistance of epoxy anhydride based polymers using IEC 60343 method

Epoxy resins are the most used polymeric systems when it comes to high voltage insulations. Their excellent electrical and mechanical properties in combination with the ability to withstand high thermal stress are what makes them so appreciated. During usage, partial discharges (PD) can occur in high voltage machines, e.g., generators or electric motors. They may deteriorate the insulation system. To prevent machine failures of high voltage machines and to guarantee longer operating times, it is important to know the influencing factors of PD. This study deals with the evaluation of the influencing factors of partial discharge and makes an effort to assess the partial discharge resistance (PDR) of bisphenol-A epoxy resin. Neat epoxy samples and samples loaded with SiO 2 -nanoparticles are prepared and submitted to partial discharge under different atmospheres using a method similar to the IEC 60343. After electrical aging, the specific eroded volume of the polymers is measured via a non contact surface metrology system. The determining factors of the partial discharge resistance were identified. Using SiO 2 — nanoparticles, an improvement of the chemical resistance, which has decisive influence on the partial discharge resistance, was found.

Self-Powered 380 V DC SiC Solid-State Circuit Breaker and Fault Current Limiter

This paper presents a new ultrafast dc solid-state circuit breaker (SSCB) that uses a silicon carbide cascode as the main switching and limiting semiconductor and an isolated photovoltaic driver to control it. The proposed topology is self-powered and fully implemented with discrete parts. The SSCB's cascode can work in three different states—fully on during nominal operation, linear mode for current limitation, and fully off to disconnect the load. The time the SSCB operates in linear mode and the maximum current limit is easily set by discrete components. Control inputs have also been included to reset the SSCB after a fault has been removed or to remotely switch it on or off . This device can be used in dc distribution avoiding deterioration due to the problems associated with electric arcs and mechanical aging of moving parts, limiting inrush currents and also minimizing conduction losses respect other kind of circuit breakers. Functional, thermal, and efficiency tests have been carried out with three different 380 V prototypes. Experimental results show the excellent behavior of the SSCB, it is able to block a 380 V short circuit failure in 570 ns; the authors have not found any faster results in the literature.

Dielectric Aging and Dielectric Degradation (Breakdown) of Polymer Films in AC Electric Fields

An explanation is proposed for the difference of the electric-strength properties of polymers in dc and ac electric fields. The energy release upon the recombination of electrons and holes injected into a polymer dielectric is considered as a factor accelerating the processes of electric aging of these dielectrics in an ac electric field. It is shown that the nonradiative relaxation of electron excited states, which causes the bond scission in macromolecules and the formation of free radicals, leads to the formation of deep electron traps in the polymer dielectric; as a result, the macromolecule ionization in an electric field is accelerated due to the transition of electrons into these traps. In the solid-state plasma, screening effect, which decreases the molecule ionization potential, appears. As a result, the macromolecule ionization rate, i.e., the rate of charge carrier formation, increases, which leads to a decrease in the lifetime of a polymer dielectric in an ac electric field as compared to the polymer lifetime in a dc electric field.

Summary of Research on Causes and Aging Mechanisms of Insulation Defects of Power Capacitors

As an important operation equipment in the power system, power capacitors mainly play the role of reactive power com-pensation, AC/DC filtering and so on. This paper describes the structure and insulation materials of power capacitors and analyses its typical defects. The research status of insulation aging mechanism of power capacitors, including electrical aging, thermal aging, space charge aging, etc., is summarized. Then, recommendations of the research direction of insula-tion aging mechanism are provided, and some suggestions on the production process of power capacitors are given.

A comparative study of electrical aging of multiwalled carbon nanotubes and carbon black filled cross-linked polyethylene

In this work, XLPE/MWCNT and XLPE/CB nanocomposites have been prepared in order to investigate AC electric field and water effects on electrical aging of XLPE. The mechanical, AC breakdown strength and AC conductivity were tested and the morphologies after 30 days electrical aging were observed using an optical microscope. The results showed that all samples exhibit excellent insulation properties and mechanical properties. Compared with CB addition, the MWCNT composites exhibit better resistance to electrical aging, with the length of electrical aging-induced microcracks in the MWCNT blends decreasing from 104 to 22 µm, and the width decreasing from 87 to 17 µm, which means a reduction of ∼80% compared of values for neat XLPE in both length and width. However, the XLPE/CB composites have a tendency to promote electrical aging. The mechanism is revealed by comparing the results of the fibrous MWCNTs with the spherical CBs.

Deterioration of Porcelain Insulators Utilized in Overhead Transmission Lines: A Review

Reliability of a power system is generally designated as a measure of the ability of the system to provide customers with adequate and constant supply. Power system failure have adverse effects and become a great concern for important large scale industries in South Korea such as semiconductors, steel and chemicals which require a high quality, stable power supply. In South Korea, nearly 80% of transmission system failures are caused by either natural eventualities such as lightning strikes or failure of insulators. Ageing assets pose significant challenges for utilities. Moisture with high temperature, fluctuation in temperature, contamination and electric stress accelerates aging in suspension insulators. The primary goal for the utility is to utilize the full life of an asset, but ageing increases the probability of deterioration and failure of equipment. The average age of vital assets, is estimated to be more than 35 years. In South Korea near about 1,223,538 porcelain insulators are reported to be in functional state. Among them only 65.19% of insulators are reported to be in operative state over 35 years. Insulators demand only 5–8% of installation costs. However, it demands more than 50% of maintenance costs. Thus, deterioration of insulator enhances capital expenditure and decrease returns on the asset base. Therefore, insulators should possess excellent electrical aging resistance to prevent deterioration of insulators. Korea Electric Power Corporation (KEPCO), largest power generation and distribution utility in South Korea utilize porcelain for almost all suspension insulators employed in transmission lines. Porcelain insulators are usually employed in transmission system as they are cost-effective and possess near about 30 to 60 years of lifespan. Lifetime evaluation of porcelain insulators in overhead transmission line is absolutely challenging, owing to aging process. This work highlights investigation of various failures of suspension type porcelain insulators, influencing factors responsible for degradation in lifetime and deterioration of suspension type insulators, various laboratory test methods available for evaluation of insulators employed in overhead transmission lines.

Therapy for the ‘age of anxiety’: Probing connections between R. D. Laing and Marshall McLuhan

This article links Marshall McLuhan and R. D. Laing based upon their common emphasis on relationships as environments. In contrast to the classic psychiatric understanding of diagnosis, Laing proposes a much more environmentally – or relationally – focused definition, which echoes McLuhan’s discussion of the changes from print to electric culture. I argue that both Laing and McLuhan would agree that psychoanalysis’ emphasis upon the individual fails and must be replaced – precisely because it attempts to retain the culture, logics and values of print culture, even while reflecting the symptoms of an electric age. However, I conclude, Laing fails to recognize ways in which his own way of seeing is blind to the power imbalance in his recasting of the therapeutic situation. Therefore, there is a need to account for the unequal relations implicit in Laing’s approach, better connecting it, again, to the electric ‘global village’ that McLuhan described so well.

Degradation In Insulating Oil Gases Due To Stresses

This paper represent the experimental investigation on power transformer insulation based on accelerated electrical & thermal stresses. In this paper, effect of accelerated thermal and electrical stresses on dissolved gas analysis has been experimentally investigated. A new terminology accelerated electrical aging factor (AEAF) & accelerated thermal aging factor (ATAF) is introduced which is mathematically correlated with dissolved gas analysis (DGA). DGA were determined experimentally for fresh and stressed oil samples.

Effects of praseodymium doping on the electrical properties and aging effect of InZnO thin-film transistor

Amorphous indium gallium zinc oxide is a popular semiconductor candidate for amorphous oxide semiconductor thin-film transistors in the field of flat-panel display. However, the existence of gallium component restricts the enhancement of mobility dramatically. In this study, we report a new praseodymium (Pr) dopant as a stabilizer in amorphous indium zinc oxide semiconductor (IZO) with high mobility and stability. Meanwhile, the PrIZO TFTs were fabricated to investigate the effects of Pr on electrical properties, stability and aging effect. The optimal PrIZO TFT exhibited a desired performance with a saturation mobility (μsat) of 25.8/32.6 cm2 V−1 s−1, an Ion/Ioff ratio of 3.5 × 107/5.4 × 107, a subthreshold swing value of 0.14/0.13 V dec−1 and a threshold voltage (Vth) of 2.9/2.1 V, respectively, before and after an air environment storage period of 90 days without passivation layer, which exhibits lower sensitivity of the channel region to oxygen/moisture from the atmosphere than IZO TFT. XRD analysis revealed that the Pr dopant had no effect on the amorphous state of IZO thin film with annealing up to 400 °C. XPS analyses suggested that the fraction of oxygen vacancy subpeak decreased significantly with Pr incorporated into IZO. The μ-PCD decay analyzation and the subgap density of states indicate that acceptor-like trap states induced by Pr ions lead to the suppression of ambient-induced excess carrier in conduction band. This work is anticipated to provide a kind of reliable stabilizer for amorphous oxide semiconductor without deteriorating mobility significantly.

A Genetic Algorithm Basrd Problem Detection for Unit Commitment (UC) Problems

This recommendation watches out for the Unit Commitment (UC) issue, which be a notable combinatorial improvement issue climbing being made masterminding of intensity structures. In the UC issue, one wishes to structure a division of a particular system of age units with notwithstanding pick their age yield during regulate toward satisfy immensity needs by any rate cost larger than a specified instance prospect. Also, the framework should assure a great deal of mechanical along with stipulate imprisonments. The monstrous scale course of action of practical resources has starting late brought centrality up in advantageous techniques for submitting locational holds to affirm the structure against potential outcomes and the shocking and exceedingly factor shortcoming of reachable power source supply, while tending to power stream goals obliged through the broadcast make. during This paper we keep in mind frameworks designed for filing locational holds: stochastic unit determination moreover a mutt reinforce of situation manual protection-obliged willpower. This paper turns giving a recognizable assessment of the trendy method utilized in improving UC problems for each stochastic and deterministic hundreds, which has been gotten from special amigo examined dispersed papers. It has been limits into diverse factors which be a part of severa desires problem to preferred function, security, flood and time. This paper, proposes a go breed genetic algorithm is proposed to cope with the Unit Commitment (UC) problem. It need to be reminded that in the UC problem, one needs to layout a subset of a given get-cosllectively of electrical power age devices and other than

Incipient Faults Monitoring in Underground Medium Voltage Cables of Distribution Systems Based on a Two-Step Strategy

Incipient faults in underground cables are often resulted from electric stress and cable aging. If such faults occur as current spikes in short periods, permanent faults may appear. Moreover, incipient faults may disturb electricity transmissions because of detection delays and thus, precise well-timed protection decisions cannot be made. Therefore, one of the most important considerations of utilities in the monitoring process is to recognize this type of faults from other conditions as soon as possible. In this paper, a precise approach based on CUmulative SUM and ADAptive LInear NEuron has been proposed. In addition to its high-speed detection ability, the practical on-line implementation of the proposed approach is simple as well. The simulation results in EMTPWorks environment demonstrate that the proposed approach has a strong capability in distinguishing the cable incipient faults from other similar conditions in distribution systems.

Analysis of Temperature Conditions Influence on Cables Insulation Operation Life

Electrical equipment fault current interruptions reduce is one of the most important problems of electrical power engineering and diagnostics. Power cables operation life is one of the parameters mostly affecting fault current interruptions on cables. The paper describes the research on thermal degradation of low voltage cables insulating materials and its influence on insulation operation life. The known mathematical models of the insulation aging depending on its temperature are considered. Low voltage cables have an insignificant electrical aging influence, so it is assumed that such cables aging mostly caused by their thermal operating conditions. Experimental research of cables insulation temperature monitoring is performed. Seven weeks of the experiment showed a temperature change between 17˚C and 27˚C. The mean temperature was 21.9˚C. Assuming that cable has normal operation life with an average temperature of 20˚C and accounting thermal conditions cable insulation operation life is reduced for about 20%. Such operation life reduce is significant and shows a considerable influence of insulating material thermal deterioration.

Planing Structure and Preparation of Cost Effective Sun Oriented Vitality Based Electrical Power Framework System at Alakh Prakash Goyal Shimla University Himachal Pradesh

The vital reason behind this paper is to plan, structure and set up a perfect electric power age using feasible power source at Alakh Prakash Goyal Shimla University, Shimla. A daylight based crucial rate has been suggested that will cover the sun based power age cost, then again called the cost recovery program. Likewise one of the significant parts of this investigation is to diminish vitality utilization in Alakh Prakash Goyal Shimla University, Shimla; this paper endeavors to propose electrical power age with the utilization of sun powered vitality. The point was to show that sustainable power source can be a suitable elective hotspot for providing the required electrical power vitality. The photovoltaic power plant has a normal sun based radiation of 6.54 KWh/m2 for most recent multi year. All out burden on college is around 200 KW and the college expends units between 40000 - 75000 units, bringing about a normal charging of INR.₹ 2.0 – 3.5 Lakhs bill. After establishment of Solar PV modules power bill has been lessen by INR.₹ 0.5-1.20 Lakhs.

Research on the Multi-factor Aging Resistance for the materials of Composite Poles

A multi-factor faster aging test with 5000h was carried to evaluate the aging resistance of running composite tower materials outdoor, which accelerates aging test includes different factors such as solar aging, mechanical aging, electrical aging, heat aging and environmental aging of materials. The flexural modulus retention rates of resin-based and resin-system composite samples decrease with aging time, except for the sample made of isophthalic unsaturated polyester, the flexural modulus retention rates of other composite samples are above 90%. Meanwhile, the modulus of the unsaturated polyester resin and E44 epoxy resin decreased significantly, the modulus retention of unsaturated polyester rate was 88% after aging test, and the damage flextural strength for E44 epoxy based glass fiber composite sample was 92%, while the bending strengh retention ratioes of other composite materials were higher than 96%. The multi-factor accelerated aging test results show that the modified polyurethane resin and vinyl resin have good aging resistance, and meet the application for composite materials’ poles and crossarms outdoor.

High sensitive Polyimide-based single-walled carbon nanotube thermal film sensor for fluid shear stress measurements

A flexible polyimide-based single-walled carbon nanotube (SWCNT) thermal film sensor has been developed for wall shear stress measurements in both air and water. To ensure high sensitivity, vacuum thermal annealing and electrical aging are conducted to enhance the electric properties of the sensor with low-resistance and the high temperature coefficient of resistivity (TCR). The TCR of sensors can reach to 8040 ppm/°C to the author’s knowledge, which is the highest reported value of thermal sensors used for shear stress measurements. In calibration, the output voltage of the sensor is proportional to the one third power of wall shear stress with the sensitivity on the order of mV Pa−1 in the constant current operation mode. The repeatability error is no more than 1% in both air and water, which confirms the capability of the flexible SWCNT thermal film sensor for fluid wall shear stress measurements with high sensitivity.

Castling of phases in BaZrO3 doped (Na0.52K0.48)(Nb0.95Sb0.05)O3: Synergistic effect on electrical fatigue, ageing and thermal stability

BaZrO3 doped (Na0.52K0.48)(Nb0.95Sb0.05)O3 ceramics were prepared using solid state route. The optimization of processing parameters like calcination temperature (800 °C), sintering temperature (1140 °C) and poling parameters (3 kV/mm at 120 °C/60 min) was carried out on base composition. Optimized parameters yielded a piezoelectric charge coefficient of 171 pC/N in composition having 4 mol% BaZrO3. Low temperature dielectric measurements and high temperature X-ray diffraction studies, along with structural refinement using Rietveld method were performed to ascertain the new found phenomenon. A castling-like phenomenon was observed in (1-x)(Na0.52K0.48)(Nb0.95Sb0.05)O3 – xBaZO3 (0.00 ≤ x ≤ 0.08) ceramics, where two phases interchanged their position. Also, BaZrO3 led to negative ageing behavior in these ceramics. Doping of BaZrO3 improved the electrical fatigue behavior and degraded the ferroelectric and thermal stability of ceramics.

Molecular Dynamics Simulation of Improving the Physical Properties of Polytetrafluoroethylene Cable Insulation Materials by Boron Nitride Nanoparticle under Moisture-Temperature-Electric Fields Conditions.

The physical properties in amorphous regions are important for the insulation aging assessment of polytetrafluoroethylene (PTFE) cable insulation materials. In order to study the effect of boron nitride (BN) nanoparticles on the physical properties of PTFE materials under moisture, temperature, and electric fields conditions at the molecular level, the amorphous region models of PTFE, BN/PTFE, water/PTFE, and water/BN/PTFE were respectively constructed by molecular dynamics (MD) simulation. The mechanical properties including Young’s modulus, Poisson’s ratio, bulk modulus, and shear modulus, along with glass transition temperature, thermal conductivity, relative dielectric constant, and breakdown strength of the four models have been simulated and calculated. The results show that the mechanical properties and the glass transition temperature of PTFE are reduced by the injection of water molecules, whereas the same, along with the thermal conductivity, are improved by incorporating BN nanoparticles. Moreover, thermal conductivity is further improved by the surface grafting of BN nanoparticles. With the increase of temperature, the mechanical properties and the breakdown strength of PTFE decrease gradually, whereas the thermal conductivity increases linearly. The injection of water molecules increases the water content in the PTFE materials, which causes a gradual increase in its relative dielectric constant. This work has shown that this effect is significantly reduced by incorporation of BN nanoparticles. The variation of physical properties for PTFE and its composites under the action of moisture, temperature, and electric fields is of great significance to the study of wet, thermal, and electrical aging tests as well as the life prediction of PTFE cable insulation materials.