Showing papers on "Partial discharge published in 2013"
TL;DR: A method for modeling the life span of insulation materials in a partial discharge regime that reduces the number of time-consuming experiments, increases the accuracy of the results, and allows life span modeling under various stress conditions, including coupling effects between the factors.
Abstract: The aim of this paper is to present a method for modeling the life span of insulation materials in a partial discharge regime. Based on the design of experiments, it has many advantages: It reduces the number of time-consuming experiments, increases the accuracy of the results, and allows life span modeling under various stress conditions, including coupling effects between the factors. Accelerated aging tests are carried out to determine the life span of these materials. The resulting model presents an original relationship between the logarithm of the insulation life span and that of electrically applied stress and an exponential form of the temperature. Results show that the most influential factors can be identified according to their effects on the insulation life span. Moreover, the life span model validity is tested either with additional points which have not been used for modeling or through statistical tests. Finally, it is shown that fractional plans are not suitable to reduce the number of experiments. This application of the experimental design is best used during the initial phase, before the final drive has been built and any online diagnosis.
106 citations
TL;DR: In this paper, a lumped parameter model of RC is presented and an experiment-based methodology is developed to determine its parameters for detection and measurement of high-frequency (pulsed) signals such as partial discharge (PD) current pulses.
Abstract: Rogowski coil (RC) is a low-cost, air-cored, and flexible induction sensor for nonintrusive condition monitoring and thus can be used in a variety of applications. In this paper, a lumped parameter model of RC is presented and an experiment-based methodology is developed to determine its parameters. The performance of the RC is analyzed for detection and measurement of high-frequency (pulsed) signals such as partial discharge (PD) current pulses. A simple and efficient technique of numerical integration is adopted to avoid the conventional type of expensive and complex design analogue integrators. RC is modeled and simulated in the alternative transient program-electromagnetic transient program environment. The designed coil is tested to measure PDs in the laboratory. Simulated and experimental performance of RC is compared with a high-frequency current transformer. This comparison shows a good match and, hence, validates the design of RC for PD applications.
80 citations
TL;DR: Partial discharges (PD) are very familiar in the electrical insulation world and are a phenomenon able to reveal or cause incipient failure, as well as need of maintenance, of an electrical apparatus as discussed by the authors.
Abstract: Partial discharges (PD) are very familiar in the electrical insulation world. A phenomenon able to reveal or cause incipient failure, as well as need of maintenance, of an electrical apparatus must play a fundamental role in the development of electrical asset diagnosis and design.
77 citations
TL;DR: In this paper, four antennas are thoroughly studied by means of their theoretical and experimental behavior when measuring electromagnetic pulses radiated by PD activity and the results are analyzed in detail.
Abstract: Partial discharge (PD) detection is a widely extended technique for electrical insulation diagnosis. Ultrahigh-frequency detection techniques appear as a feasible alternative to traditional methods owing to their inherent advantages such as the capability to detect PDs online and to locate the piece of equipment with insulation problems in substations and cables. In this paper, four antennas are thoroughly studied by means of their theoretical and experimental behavior when measuring electromagnetic pulses radiated by PD activity. The theoretic study of the band of frequencies in which the pulse emits and the measurement of the parameters $S_{11}$ are complemented with the frequency response and wavelet transform of a set of 500 time signals acquired by the antennas, and the results are analyzed in detail.
76 citations
TL;DR: In this paper, spectral power analyses of PD pulses and the spectral power ratios at different frequencies were calculated to classify PD sources and noise by means of a graphical representation in a plane, which is a flexible tool for noise identification and will be useful for pulse characterization.
Abstract: Partial Discharges (PDs) are one of the most important classes of ageing processes that occur within electrical insulation. The measurement of PDs is useful in the diagnosis of electrical equipment because PDs activity is related to different ageing mechanisms. Classical Phase-Resolved Partial Discharge (PRPD) patterns are able to identify PD sources when they are related to a clear degradation process and when the noise level is low compared to the amplitudes of the PDs. However, real insulation systems usually exhibit several PD sources and the noise level is high, especially if measurements are performed on-line. High-frequency (HF) sensors and advanced signal processing techniques have been successfully applied to identify these phenomena in real insulation systems. In this paper, spectral power analyses of PD pulses and the spectral power ratios at different frequencies were calculated to classify PD sources and noise by means of a graphical representation in a plane. This technique is a flexible tool for noise identification and will be useful for pulse characterization.
75 citations
TL;DR: In this article, a method for autonomous recognition of PD patterns recorded under conditions in which a phase-reference voltage waveform from the HV conductors is not available, as is often the case in on-line PD based insulation condition monitoring.
Abstract: On-line Partial Discharge (PD) monitoring is being increasingly adopted in an effort to improve asset management of the vast network of MV and HV power cables. This paper presents a novel method for autonomous recognition of PD patterns recorded under conditions in which a phase-reference voltage waveform from the HV conductors is not available, as is often the case in on-line PD based insulation condition monitoring. The paper begins with an analysis of two significant challenges for automatic PD pattern recognition. A methodology is then proposed for applying the K-Means method to the task of recognizing PD patterns without phase reference information. Results are presented to show that the proposed methodology is capable of recognising patterns of PD activity in on-line monitoring applications for both single-phase and three-phase cables and is also effective technique for rejecting interference signals.
67 citations
TL;DR: In this article, a surface charge measurement system based on the Pockels effect was constructed to detect the variation of residual surface charge distribution in partial discharge (PD) sequences, and the current form (ns level) of the PD sequence was measured simultaneously.
Abstract: A surface charge measurement system based on Pockels effect was constructed to detect the variation of residual surface charge distribution in partial discharge (PD) sequences. The current form (ns level) of the PD sequence was measured simultaneously. By using this system, it is found that surface charge distribution caused by PDs appeared as several isolated charges spots similar to that in dielectric barrier discharges (DBD). The result also agrees with the previous models, suggesting that charge distribution is not uniform and that it plays an important role in the stochastic behavior of PDs. As the applied voltage increased, the number of charge spots increased and the hetero-discharge occurred. Besides, a charge ring along the void edge was observed after aging due to PD. An approximate linear relationship existed between PD magnitude and the corresponding accumulated surface charges. In the PD sequence, the discharges tended to take place at the sites having heterocharges at dielectric surface after voltage polarity reversed. Moreover, there were no homodischarges observed at the decreasing part of applied voltage even at the area without surface charges existing. This could not be explained by the accumulation of surface charges. It was also observed that more than one charge spot in one PD could occur. This was named simultaneous discharge in our paper, and may be attributed to the effects of photoionization and time lag.
65 citations
TL;DR: In this article, the dominant modes of single water droplet oscillation on hydrophobic surfaces were investigated in a wide range of droplet volume and frequency of applied electric field using a high speed camera.
Abstract: Water droplets on hydrophobic surfaces of polymeric insulators oscillate under applied high voltage electric field stress. Deformation of the droplets increases local electric field stress in the triple zones, causing lower partial discharge inception voltage and consequently affecting the ageing performance of the insulator. For this contribution dominant modes of single water droplet oscillation on hydrophobic surfaces were investigated in a wide range of droplet volume and frequency of applied electric field using a high speed camera. 3D frame analysis showed for all volumes an increasing trend of mode number with frequency in the range of 20 to 100 Hz. Experimentally found resonance frequencies for water droplets on a hydrophobic surface approximately correlate with published frequencies of free water droplets. Conductivity showed no effect on the pattern of water droplet oscillation. Partial discharge inception voltages on two different hydrophobic surfaces (silicone rubber and epoxy resin) with conductive and non-conductive (distilled) water droplets were measured. These measurements showed that inception voltage makes a step whenever the oscillation mode of water droplet changes. Conductivity of the water droplets was found to have no effect on the inception voltage on silicone rubber surfaces having a high degree of hydrophobicity, whereas conductive droplets on epoxy resin with lower hydrophobicity lead to lower inception voltages.
64 citations
TL;DR: In this article, the authors proposed a method based on comparing the differences in the arrival times, to antennas in the transformer, of EM waves emitted from the PD source, and factoring in the influence of the transformer active part on the EM wave propagation.
Abstract: Nowadays, the localization of partial discharge (PD) in power transformers by measurement of ultra-high-frequency (UHF) electromagnetic (EM) waves from a PD source is receiving more attention. This method is based on comparing the differences in the arrival times, to antennas in the transformer, of EM waves emitted from the PD source. From the measured UHF signal, and factoring in the influence of the transformer active part on the EM wave propagation, the correct determination of an EM wave arrival time in the localization algorithm is a critical task that influences the accuracy of the UHF PD localization method. Nearly all weak points in the dielectric system of power transformers generate PD. These discharges gradually degrade the insulation, leading to transformer failure. It is possible to detect these defects in the early stages of PD generation by measuring and analyzing the PD data. Suitable maintenance and repair strategies can then be implemented.
63 citations
TL;DR: In this article, a new indicator for monitoring the turn-to-turn insulation aging of ac motors is presented, measuring capacitance and Partial Discharge Inception Voltage (PDIV) on a large number of twisted pairs of enameled wires.
Abstract: The paper deals with a new indicator for monitoring the turn-to-turn insulation aging of ac motors. Measurements of capacitance and Partial Discharge Inception Voltage (PDIV) were performed on a large number of twisted pairs of enameled wires between standard thermal accelerated aging cycles. A significant increase of the capacitances and a reduction of the PDIV were noted on all the samples for three different diameters of enameled wires. The correlation of the capacitance increase with the degradation of the insulation quality opens perspectives for preventive maintenance applications.
63 citations
TL;DR: In this article, the same points that generated the John Tanaka review are used as an homage to his unforgettable contribution to the science of dielectrics and electrical insulation, as well as a summary of the main points of the review.
Abstract: This article starts from the same points that generated the John Tanaka review, as an homage to his unforgettable contribution to the science of dielectrics and electrical insulation.
TL;DR: In this paper, atmospheric pressure plasmas in open air are produced in a configuration of discharge actuators by repetitive nanosecond pulses, and electrical parameters including applied voltage, total discharge current, and transported charge are measured and analyzed.
Abstract: Nanosecond-pulse surface dielectric barrier discharge is a promising method used for airflow control application. In our letter, atmospheric-pressure plasmas in open air are produced in a configuration of discharge actuators by repetitive nanosecond pulses. The electrical parameters including applied voltage, total discharge current, and transported charge are measured and analysed, especially it is aimed at the time behaviour of the total discharge current. Experimental results show that the total discharge current pulse includes two obvious spikes during the rise time of the applied pulse voltage. According to the simulation, it is concluded that the first current spike is due to the discharge propagation in the form of wave ionization and displacement current. The second current spike is caused by the repeated re-ignition of the surface dielectric barrier discharge on the area covered previously by the wave ionization.
TL;DR: In this article, a magnetic-compression pulse generator was used to produce repetitive positive nanosecond pulses for excitation of a diffuse discharge, which had a rise time of about 25 ns and a full width at half maximum of 40 ns.
Abstract: Nanosecond pulsed discharges have various discharge modes, such as corona, diffuse discharge, spark or arc. A dense diffuse discharge is particularly desirable for various applications at atmospheric pressure. In this paper, a magnetic-compression pulse generator was used to produce repetitive positive nanosecond pulses for excitation of a diffuse discharge. The output pulse of the generator had a rise time of about 25 ns and a full width at half maximum of 40 ns. Electrical characteristics of the diffuse discharge were studied by measuring its voltage and current waveforms, as well as images of the discharge. The conduction current was calculated by the measured voltage and current, which was a true discharge current. The experimental results show that a stable diffuse discharge could be obtained at atmospheric pressure, and the conduction current was unipolar and had similar amplitude of several amperes under our experimental condition, which has the similar amplitude with the displacement current. Furthermore, the air gap spacing and pulse repetition frequency (PRF) affected the intensity and mode transition of the diffuse discharge. The conduction current increased with the PRF but decreased with the air gap spacing. Therefore, the diffuse discharge was likely available under some conditions of proper air gap, high PRF with positive pulse.
TL;DR: In this article, a new location method is proposed based on using circular array of ultrasonic sensors (CAUS) and implemented as follows: First, the fast independent component analysis (FastICA) algorithm is used to de-noise PD signal obtained by CAUS.
Abstract: Partial discharge (PD) in transformer oil is one of the major causes of electrical insulation failures in oil transformers. An accurate location of PD provides important information required for detection and elimination of insulation defects. To improve accuracy of PD location, a new location method is proposed in this paper based on using circular array of ultrasonic sensors (CAUS) and implemented as follows. First, the fast independent component analysis (FastICA) algorithm is used to de-noise PD signal obtained by CAUS. Second, the total least square (TLS) algorithm is used to transform the wide-band signal obtained by CAUS to the narrowband one. Third, the mode excitation algorithm and the fast direction of arrival (FastDOA) algorithm are combined together to find three different directions of arrival (DOA) of the signal from PD to CAUS. Next, using the azimuth and pitch angles of these three DOAs, the PD location is determined in the center of a sphere whose surface tangents to these three DOAs in three different planes. Finally, the improved genetic algorithm is used to obtain accurate coordinates of the PD source. An experimental system of PD-location has been developed, which consists of (i) CAUS made of 8 sensors evenly placed along a circle, and a single sensor placed in the center of the circle, (ii) classic three-capacitance PD model, (iii) 16-channel synchronous data collector, (iv) oil tank, and (v) computer. The preliminary experimental results show that the accuracy of PD location after denoising is better than that before de-noising.
TL;DR: In this paper, it was observed that the UHF signals generated due to partial discharges formed by particle movement in GISs are independent of operating pressure and the applied voltage.
TL;DR: In this paper, the effect of temperature, pressure, and moisture on the partial discharge inception voltage as well as the discharge characteristics was investigated and the relationship between the measured dissipated energy and the polyimide lifetime was investigated.
Abstract: Recent aircraft designs increasingly use electrical systems with higher voltages. This can lead to the occurrence of partial discharges. Testing for these phenomena is relatively poorly documented in comparison with other standardized tests available for aerospace components. After having investigated the effect of temperature, pressure, and moisture on the partial discharge inception voltage as well as the discharge characteristics, we focused on the effect of these environmental parameters on the behaviour of the energy dissipated by the discharges and on polyimide film endurance during aging under partial discharge. The results show two different behaviours for the variation of energy dissipation along aging time related to environmental conditions. In fact, when a semi-conducting layer is formed in wet conditions due to the interaction between the gaseous by-products and the water molecules, a decrease in the energy measured was revealed. In addition, the relationship between the measured dissipated energy and the polyimide lifetime was investigated and did not present constant trends for the different aging conditions. While it is clear that the material endurance was energy dependent in dry conditions, it was shown that, even when the discharge energies were higher, an increase in the endurance of the dielectric was observed when the superficial semi-conducting layer was formed.
TL;DR: In this article, the influence of voltage harmonics on partial discharge behavior and pattern evolution is analyzed and the experimental results showed that various harmonic compositions superimposed on the fundamental sinusoidal waveform have a significant impact on PD intensity and maximum charge.
Abstract: Typically, in laboratory and diagnostics tests focused on measuring partial discharges, a pure sinusoidal voltage waveform is assumed. However, in practice the spectral content of the applied voltage is rarely so ideal and additional spectral components have a significant impact on the discharge behavior in electrical insulation systems. In this paper the influence of voltage harmonics on partial discharge behavior and pattern evolution is analyzed. The presented experiments were conducted on a transformer installed in a municipal network and on specimens representing defects in a transformer insulation system, in the form of a micro blade protrusion on a winding conductor and an embedded gas inclusion. The experimental results showed that various harmonic compositions superimposed on the fundamental sinusoidal waveform have a significant impact on PD intensity and maximum charge. In consequence, PD pattern phase and amplitude distributions are distorted and calculated statistical parameters are changed. The rough parameters reflecting the waveform spectral quality, such as THD, are rather superficial and do not provide a unique and reliable signature of the applied voltage in terms of phase angle variations. In certain environments, neglecting harmonic content in the voltage may lead to a misleading interpretation and assessment of partial discharge severity. A complete knowledge of harmonic content is essential and critical in conducting a proper assessment of the impact of PD, including acceptability criteria and compatibility with the standards.
TL;DR: In this paper, the intrinsic characteristics of the typical defects in GIS, such as the amplitude of the time-domain signal and frequency spectrum characteristics, are investigated for calibrating the intensity of the partial discharge.
Abstract: Partial discharge (PD) monitoring plays an important role in the maintenance of the high voltage (HV) apparatus, such as transformer and gas-insulated substation (GIS) In recent years, the ultra high frequency (UHF) method for PD detection arouses great interest of many researchers because of its high sensitivity and anti-interference capability The coupling of UHF signal and process of the signal constitute the UHF detection method There are three key components for the coupling of UHF signal in GIS, including the frequency spectrum characteristics of the PD source, the propagation characteristics in GIS, the coupling style and the capability of the UHF coupler Many researchers are interested in the recognition algorithm and the analysis procedure of the PD data But the intrinsic attributes of the partial discharges should attract more attentions because they are the foundation of the UHF detection method This paper focuses on the intrinsic characteristics of the typical defects in GIS, such as the amplitude of the time-domain signal and frequency spectrum characteristics Four types of typical partial discharge sources are designed and fabricated, including floating metal, protrusions, particle on the spacer, and void in solid insulation Several different structure sizes of each defect are applied to ensure the consistency of the results and discover the factors that affect the frequency spectrum characteristics The results of the study present the essential characteristics of the partial discharge It can be applied to the design of the coupler and amplifier circuit In addition, the sensitivity and anti-interference capability of the UHF method are promoted effectively, and it is valuable for calibrating the intensity of PD in GIS
TL;DR: In this article, a differential electric field (D-dot) sensor for partial discharge (PD) measurements has been introduced to detect slowly developing faults leading to internal arc using online monitoring technologies in medium-voltage switchgear.
Abstract: An electrical fault in switchgear results in interruption of power supply, damage to equipment, and poses a hazard to personnel. This paper focuses on the detection of slowly developing faults leading to internal arc, using online monitoring technologies in medium-voltage switchgear. Unconventional radio-frequency (RF) techniques for discharge measurement are highly attractive but have not been widely applied in the industry due to their ineligibility to quantify actual discharge. On the basis of various benefits, a new application of a differential electric field ( D-dot) sensor for partial-discharge (PD) measurements has been introduced in this paper. The reliability of the sensor has been confirmed through comparison with a commercial high- frequency current transformer. An attempt has been made to quantify the apparent charge of online PD measurements. The energy of signal captured by the D-dot sensor has been compared with the apparent charge quantity calculated from current pulse measured by the conventional method. A second degree polynomial relation exists between the cumulative energy and apparent charge. It has been shown that when apparent charge is plotted against the cumulative energy of the RF signal for a number of pulses, defects can be separated on the basis of cluster positions within the scatter plot.
TL;DR: In this article, the authors proposed a new method for detection and location of two simultaneous partial discharge sources in three-phase power transformer, where acoustic signals are detected by sensors first and are then denoised using a wavelet transform.
Abstract: One of the main methods for partial discharge (PD) source localisation in power transformers is acoustic emission measurements. This study describes a new method for detection and location of two simultaneous partial discharge sources in three-phase power transformer. In this method, acoustic signals are detected by sensors first and are then denoised using a wavelet transform. Finally, the two PD sources are localised using the modified binary partial swarm optimisation (MBPSO) method. To prove the efficiency of the two simultaneous PD localisations, the proposed algorithm is used to localise PD sources of the arc furnace transformer at Isfahan's Mobarakeh steel company. For this purpose, the PD localisation problem converts to an optimisation problem. To prove the efficiency of the MBPSO algorithm, its performance is compared with a genetic algorithm. The PD localisation results confirm the efficiency of the proposed method for the detection and location of PD sources.
TL;DR: In this paper, an ultraviolet imager, a partial discharge detector, a current-measuring radio-frequency interference receiver, and a sound level meter were used to observe the transition region between no corona and strong corona, and hence determine the corona inception voltages of two practical conductors, types LGJ500/35 and LGJ400/50.
TL;DR: In this article, a new dielectric breakdown measurement method for determining breakdown characteristics of polymer films has been developed and evaluated, based on measurement of multiple breakdowns per sample area beyond the weakest point of the film by utilizing low-energy self-healing breakdown of metallized polymer film.
Abstract: A new dielectric breakdown measurement method for determining breakdown characteristics of polymer films has been developed and evaluated. The method is based on measurement of multiple breakdowns per sample area beyond the weakest point of the film by utilizing low-energy self-healing breakdown of metallized polymer film. A data selection process based on the discharge energy characteristics of each measured self-healing breakdown is utilized prior to the statistical analysis in order to validate the mutual independence of the results. Even with a relatively small sample area, the method yields a large amount of breakdown data from a wide voltage spectrum, thus enabling the formation of detailed material-specific breakdown fingerprints. The measurement system and the area dependence of the breakdown results have been evaluated with capacitor-grade metallized film. For the statistical analysis, additively mixed Weibull distributions are utilized as multiple breakdown mechanisms are found to be operative in the dielectric. Defects in the dielectric volume are found to have a profound effect on the structure of the mixed distribution with increasing area.
TL;DR: In this article, the authors presented the application potential for the on-line detection of partial discharges of a new generation of piezoelectric sensors (High Temperature Ultrasonic Transducers, HTUTs).
Patent•
15 May 2013
TL;DR: In this paper, a transformer paper oil insulation experiment device integrated with electric heating combination ageing and partial discharge is presented, which can guarantee reliability of the partial discharge, and is simple in structure, convenient to operate and capable of achieving good test effects.
Abstract: The invention provides a transformer paper oil insulation experiment device integrated with electric heating combination ageing and partial discharge, and provides a corresponding experiment method. The experiment device comprises a high voltage portion, a low voltage portion and a sealing tank portion. The device can provide a platform of electric heating combination ageing and partial discharge experiments for a transformer paper oil insulation defect model, and can provide experiments of corona discharge, creeping discharge and air-gap discharge models in oil. The device has good air-tight performance, and can be isolated from external air and other influences. The whole system self cannot produce partial discharge, and the device cannot produce rust and other impurities in the partial discharge, can guarantee reliability of the partial discharge, and is simple in structure, convenient to operate, and capable of achieving good test effects.
TL;DR: In this paper, an experimental setup has been arranged in the laboratory for generation of partial discharge inside a steel tank provided with five optical sensors placed at the centre of all its five inside walls excepting the top.
TL;DR: In this paper, the discharge feature gases, such as C 2 H 2, CH 4, CO 2 and H 2 O, were measured with a tunable laser photoacoustic spectrometer at the 1530.3709nm transition line.
TL;DR: In this paper, a TJ model was used to study the characteristic of partial discharge (PD) signals under four types of impulse voltages were detected by electrical methods and the results indicated that the PD signals under impulse voltage can be detected using electrical method, the number of discharges under oscillating impulse voltage was significantly larger, which was due to the influence of source oscillation.
Abstract: Gas insulated switchgears (GIS) have been widely used due to their high reliability, low maintenance and compact size. The field experiment is an important step to ensure the safety of GIS. The AC withstand voltage test and its corresponding partial discharge (PD) measurement are inadequate for the detection of all the hidden flaws in GIS. Such inadequacy can be compensated by additional impulse withstand voltage test and its PD detection measurement. This paper reports on experiments to study surface discharge over SF6/epoxy under impulse voltage. The TJ (triple-junction) model was used to study the characteristic of partial discharge (PD). The PD signals under four types of impulse voltages were detected by electrical methods. The 50% probability PD inception voltage (PDIV50), time lags and maximum discharge magnitude were analyzed as a function of gas pressure. The PD characteristics under AC voltage were investigated for comparison. The results indicate that the PD signals under impulse voltage can be detected using electrical method, the number of discharges under oscillating impulse voltage was significantly larger, which was due to the influence of source oscillation. The oscillating lightning impulse has the lowest impulse ratio and it is recommended as the best test waveform choice for the field impulse withstand test with PD detection.
TL;DR: In this article, a large volume cold atmospheric plasma brush array was developed, which was enhanced by a dielectric barrier discharge by integrating a pair of DC glow discharge in parallel, which effectively reduced the breakdown voltage and working voltage.
Abstract: This study developed a large volume cold atmospheric plasma brush array, which was enhanced by a dielectric barrier discharge by integrating a pair of DC glow discharge in parallel. A platinum sheet electrode was placed in the middle of the discharge chamber, which effectively reduced the breakdown voltage and working voltage. Emission spectroscopy diagnosis indicated that many excited argon atoms were distributed almost symmetrically in the lateral direction of the plasma. The concentration variations of reactive species relative to the gas flow rate and discharge current were also examined.
TL;DR: In this article, the breakdown properties of oil-impregnated paper under pulsating DC voltages at different temperatures were investigated, and an electrical aging lifetime model was proposed for the paper.
Abstract: Main insulation of windings connected with valves in high voltage direct current (HVDC) convert transformers withstands pulsating DC voltages. This paper presents breakdown properties of oil-impregnated paper under pulsating DC voltages at different temperatures. Progressive stress tests were carried out to obtain breakdown voltages of oil-impregnated paper with thickness of 0.2 mm under pulsating DC voltages at different temperatures. Constant stress tests were executed to measure time to breakdown of the oil-paper specimens. Both types of the experiments were also undertaken under either AC or DC voltages. An electrical aging lifetime model was proposed for the oil-impregnated paper, and parameters of the electrical aging lifetime model were presented. Experiments and analysis results show that the breakdown voltages and time to breakdown of oil-paper insulation are influenced by temperature significantly.
TL;DR: In this paper, a self-pulsing discharge in flowing argon is investigated by means of electrical, optical and spectroscopic methods, and the dependence of the discharge self pulsing frequency on external parameters (applied negative dc voltage, gap dimensions) is determined, and high-resolution spectroscopy measurements at several wavelengths reveal the complex dynamics of the transient spark discharge: a pre-phase at the needle tip and capillary edge, propagation of positive and negative streamers, creation of a transient glow discharge structure and a longlasting afterglow.
Abstract: A self-pulsing discharge in flowing argon is investigated by means of electrical, optical and spectroscopic methods. The dependence of the discharge self-pulsing frequency on external parameters (applied negative dc voltage, gap dimensions) is determined, and optical and spectroscopic methods are used to investigate the discharge development with high spatial and temporal resolution. High-resolution spectroscopic measurements at several wavelengths reveal the complex dynamics of the transient spark discharge: a pre-phase at the needle tip and capillary edge, propagation of positive and negative streamers, creation of a transient glow discharge structure and a long-lasting afterglow. Excited plasma species necessary for the treatment of an exposed sample continue to be present even 80 µs after the breakdown of the active plasma.