Academia.edu no longer supports Internet Explorer.
To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser.
2012, IEEE Transactions on Dielectrics and Electrical Insulation
Partial discharge (PD) spectral response to variations in the supply voltage frequency was experimentally investigated through laboratory-based tests. The PD spectral content of each defect type responded uniquely to variations in the sinusoidal supply voltage frequency in the range 20 to 400 Hz. The findings are interpreted using the theory of space charge dynamics in PD mechanisms. Prospective diagnostic applications
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.
Partial discharge (PD) tests on power cables are now conducted at Very Low Frequencies (VLFs) as it is technically and economically convenient, yet power cables operate and fail at power frequency. A comparative study is conducted in accordance with IEC 60270. Surface PD parameters in air at VLF (0.02 Hz and 0.1 Hz) and at power frequency (50 Hz) sinusoidal test voltages are presented. PD measurements were performed in a fairly constant temperature and humidity environment. Six polyethylene disk samples were prepared with a diameter of 132 mm and 4.25 mm thickness for each test frequency. The sample thickness was chosen to correspond to the insulation thickness of 6.35/11 kV XLPE insulated power cables. PD inception voltage and PD magnitude increased with frequency whilst PD extinction voltage showed no peculiar trend. Repetition rate increased with frequency and statistical operators such as kurtosis and skew of mean pulse height and pulse count of PD phase resolved patterns (PDPRPs) decreased with frequency. The findings are explained using the known theory of surface PD mechanism. Knowledge obtained from this work is used to qualitatively model the behaviour of surface PD parameters with frequency. Possible practical implications of the findings are also outlined. Keywords: Surface PDs, very low frequency, power frequency, repetition rate, phase resolved patterns, kurtosis, skew
2008
Ozone is now attracting much attention worldwide as a pollutionfree oxidant for a wide range of applications, including deodorisation, decolourisation, disinfection, various bleaching processes, gas treatment and chemical synthesis. In each of these, ozone requires less energy than the alternative chlorination process [1].
2008
Most of high voltage insulators are being used in outdoor applications. Environmental pollution can cause the insulators to become progressively coated with dirt and chemicals in the long run. This pollution coating does not have a detrimental effect when the insulator is dry. The electrostatic field determines the voltage distribution of such a dry insulator and a very small capacitive leakage current (LC) flows across the entire insulator.
1995, IEEE Transactions on Dielectrics and Electrical Insulation
2000, IEEE Transactions on Dielectrics and Electrical Insulation
2000, IEEE Transactions on Instrumentation and Measurement
2015, Renewable and Sustainable Energy Reviews
Polymeric insulating materials with excellent electrical properties are widely used in electrical power equipment. These materials are degraded, however, when they are subjected to partial discharge (PD) with different polymeric materials possessing different levels of PD resistance. In this study the PD characteristics and degradation caused by PD are analysed and compared for four different polymers – poly(ether sulphone) (PES), poly(ethylene terephthalate) (PET), poly(propylene) (PP) and low-density poly(ethylene) (LDPE). An artificial void is created in each of the polymer samples and electrically stressed above PD inception voltage (PDIV) for 4 h. The simulated electric field distribution inside the void for each of the polymer materials at the respective PDIVs is modelled using COMSOL to validate the experimental results. Little work has correlated void PD characteristics with material degradation induced by PD across a range of different polymers and subsequently categorised them according to their PD resistances. This study therefore presents a comparative study of the N– Q patterns of PD pulses (a plot of the number of discharges against the measure of apparent charge), PD repetition rate and the chemical and morphological changes occurring on the void surfaces for each type of polymer. The results show that the PD resistance of these four polymers can be categorised in a decreasing order according to the following sequence: LDPE, PP, PET and PES with LDPE being most resistant to PD and PES the least resistant.
2012, 2012 IEEE International Conference on Power and Energy (PECon)
2004, IEEE Transactions on Instrumentation and Measurement
2000, IEEE Transactions on Dielectrics and Electrical Insulation
2000, IEEE Transactions on Dielectrics and Electrical Insulation
The classification of medium voltage cable defects is the most important tool to avoid the inaccurate Partial Discharge (PD) measurements. This paper presents a proposal methodology based on pattern recognition technique to classify the PD occurred in cables into two distinct groups internal and external. The Artificial Neural Networks (ANNs) with different input schemes have been built to obtain the optimal classification. Many statistical features, which extracted by different techniques from measured, have established the input schemes 3D-pattern PD to improve the performance and classification speed of ANN. In order to obtain the effective statistical features, the study and comparison between all ANN has been finished by evaluating the classification through two parameters the mean square error (MSE), and the accuracy of neural network. As the result, the proposed approach provides high recognition rate of classification between internal and external PD within Cross-Linked Polyethylene (XLPE) insulated medium voltage cable.
2012, International Transactions on Electrical Energy Systems
1995, IEEE Transactions on Dielectrics and Electrical Insulation
At the applied voltage a disc-shaped cavity with partial discharges are measured at variable frequency (0.01-50 Hz). By varying the frequency it was observed that measured PD phase, magnitude of distributions and number of PDs per voltage cycles are varied. In the cavity, sequence of Partial discharge is simulated dynamically. For that purpose a model is presented with charge consistent. Simulated results shows that cavity surface and emission properties are effected by varying the magnitude of applied frequency, mainly conductivity of surface. This paper is illustrating the frequency dependence of PD in a cavity. The paper illustrates how the applied voltage amplitude and the cavity size can influence the frequency dependence PD activity.
1982, Electrical Insulation, IEEE Transactions …
2013, Journal of Electrostatics
—To improve the reliability of Medium Voltage (MV) power cables in distribution electricity companies networks, Partial Discharge (PD) measurements are performed on-site using Very Low Frequency (VLF) as energizing source. Several different VLF waveforms are utilized with the most common being sinusoidal and cosine-rectangular. Using of VLF-PD as a diagnostic technique to investigate the condition of power cables requires understanding the nature of dependency of the PD activity on the frequency and wave shape of applied voltage. Many of works investigated the behaviour of PD activity due to an artificial cavity within XLPE power cables at 50 Hz of sinusoidal applied voltage practically and theoretically, but it is still not so much work in this scope under different wave shapes and frequencies of testing voltage. This paper is introduced to participate in understanding the impact of these two factors on PD behaviour experimentally through performing of PD measurements on XLPE cable sample 12/20 kV-1400 mm 2 with an artificial cavity as well as theoretically using COMSOL and MATLAB software to carry out the simulation based on the Finite Element Method (FEM). The practical and theoretical results are compared together and show good agreement between them.
2003
The used of polymeric insulators (PIs) are well accepted worldwide for replacing the traditional insulators such as glass and porcelain. The main advantages of using polymeric materials are low surface energy, higher mechanical strength to weight ratio, lightweight, resistance to vandalism and better performance in the present of wet contaminated conditions [1-2]. Most polymer outdoor insulators may suffer from surface discharge phenomenon due to the surface contamination from the polluted environment.
Partial Discharge (PD) monitoring and analysis has become imperative for utilities as well as for equipment manufacturers as it causes deterioration of insulation systems in high voltage (HV) electrical equipment. The analysis of PD includes detection, recognition & classification of PD using various advanced mathematical tools & techniques. In the artificial intelligence, Neural network methodology is one of the most popular and widely used for the analysis of PD. This work represents the generation of the partial discharge like signal using the MATLAB 7.9 software and the recognition of generated signals by artificial neural network technique. The obtained PD pattern represents the characteristics of Partial discharge signal and the discrete spectrum interference signal with it. The variants of these signals are taken as samples for the training of the neural network. The offline recognition of the PD signal has been done.
2005, IEEE Transactions on Instrumentation and Measurement
2008
Surface discharge is a common electrical discharge phenomenon that occurs on the insulator surface under high voltage stress. This phenomenon, which is normally known as dry-band discharge, exists due to the flowing of leakage current (LC) under the presence of wet and contaminated conditions. When the insulator is wetted, a resistive surface LC flows, which is generally many orders of magnitude higher than the capacitive current in the case of dry insulators.
2000, IEEE Transactions on Dielectrics and Electrical Insulation
2014, TELKOMNIKA Indonesian Journal of Electrical Engineering
The reliability of low-voltage inverter-fed motors is highly dependent on the inception of partial discharges. The effect of impulsive waveform parameters must be investigated to predict the repetitive partial discharge inception voltage (RPDIV) and define test procedures that can indicate properly the behavior in service of the insulation system. This paper focuses on the RPDIV of magnet wires using twisted pairs subjected to repetitive unipolar impulsive voltage waveforms. The effects of supply frequency (5 to 200 kHz) at pressure levels that are typical for aircraft (20 to 100 kPa) is examined. Results show that RPDIV steadily decreases with frequency up to 100 kHz where it reaches a plateau. This behavior is explained as an effect of the oscillations that inevitably exist in the applied voltage waveform. Therefore, a conservative estimate of the RPDIV could be achieved by raising the supply frequency well above the operation frequency. In the experiments, the RPDIV is decreasing linearly with pressure. If this behavior could be confirmed for other insulation systems, the design of systems working at pressures typical of aircraft would result relatively easy.
One of the common causes of cross-linked polyethylene (XLPE) insulation ageing and finally cable failure is the presence of a cavity within cable insulation. Gas filled cavities can be initiated in XLPE cables during its manufacturing, installing and operating conditions. Once the size of the cavity reaches the critical limit, noticeable partial discharge (PD) activity develops. Therefore, the size of the cavity is one of the important factors that considered when investigating the PD activity in power cable. This work studies the effect of cavity size on PD behaviour within insulation layer of an 18/30 kV XLPE cable specimen; the changing in an artificial spherical cavity depths and diameters is investigated in the laboratory. In addition, 2D model geometry of a cable insulation having an artificial cavity is also developed using COMSOL software and MATLAB program to simulate the PD measurements from the laboratory experiments to imitate the conditions found during measurements, hence interpreting the obtained experimental results and determining the significant parameters influencing PD activity; hence, more a fuller understanding of PD phenomena within a cavity. The results show good coincidence between experimental and simulated data, in terms of PD magnitude and PD inception voltage.
2007, C.L. Wadhwa High voltage engineering, second edition.
“High Voltage Engineering” has been written for the undergraduate students in Electrical Engineering of Indian and foreign Universities as well as the practising electrical engineers.
2010, 2010 IEEE International Symposium on Electrical Insulation, ISEI 2010
Partial discharge (PD) is a discharge phenomenon that does not bridge the whole electrodes within a dielectric insulation under high field stress. The measurement of PD activity is used in the insulation diagnosis of high voltage components. A better understanding of PD may be gained from modeling of the discharge process. This paper is an extension from previous works by the same authors which have considered the modeling of PD activity in a spherical cavity within a dielectric material by using Finite Element Analysis (FEA) method to study the influence of applied frequency. However, in this paper, simulation results are compared with measurement results as a function of frequency. From this, the parameters that influence PD frequency dependent behavior have been identified through comparison between experimental measurement and simulation results. © 2010 IEEE. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5549733
2000, IEEE Transactions on Dielectrics and Electrical Insulation
2005
standard and correct methods for tests to power cables implementing the method of injection of high potential at very low frequency for measurements of leakage current
2000, IEEE Transactions on Instrumentation and Measurement