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Gas insulated substations (GIS) are finding wide use on account of environmental and operational advantages. Faults undermining reliability in a GIS can be analyzed by detecting and locating partial discharges (PD) arising in GIS. These PD pulses in GIS, however, are extremely small and prone to noise corruption. To remove noise effectively wavelet transform (WT) based methods are better suited than...
Dielectric barrier discharge (DBD) tests were carried out in an air gap with flowing helium. Through photos taken from discharges between transparent water electrodes, influence of some test conditions on characteristics of DBD was invested. The conditions included amplitude and frequency of applied voltage, velocity of gas flow, distance of gas gap, and thickness of barriers. The results show that...
The treeing phenomena are well known as an initiation process of electrical breakdown in the electric power cables. It is discussed that the charge injection from electrode is related to the growth of the tree. The space charge measurement technique by the pulsed electro acoustic (PEA) method is widely used. However, the measurement in the non-uniform electric field has not been realized in PEA method...
All-Dielectric Self-Supporting (ADSS) fiber-optic cables have been widely used in communications of power system. As ADSS optical cables are installed on power tower with high-voltage transmission lines, it may be affected by electrical field of electrical lines. So electro-corrosion may be damaged ADSS optical cables. Therefore, it is necessary to get the best location for the installation of ADSS...
This paper investigated the influence of varied additives/sintering condition on the performance of ZnO based on the space charge distribution measurements. Four kinds of ZnO based varistor samples have been tested. According to the experimental results, the space charge distributions are varied with different samples which were made from different formulas and varied sintering temperatures. The experimental...
This article analyses the fluctuation rule of insulation natural contaminant deposit of insulators and the shortages of the existing contaminant flashover theory. The relation of weather statistics and natural contaminant deposit and contaminant flashover are discussed.
Polybutylene naphthalate (PBN) was employed as test sample which was previously irradiated in air up to 100 kGy and then up to 1000 kGy with dosage rate of 10 kGy / h by using a 60Co gamma-source. The experiment was carried out on sample surface under a negative dc stress between two parallel electrodes. An electrostatic probe was designed to measure the surface charge density during charging period...
Patch antennae suitable for partial discharge detection in power cables have been characterized through laboratory experiments carried out in the time and frequency domain, as well as through PD testing. The results reported in this paper show that helicoidal antennae wrapped around the cable at a distance of few meters from the defect site can provide sensitivities and bandwidth that can allow effective...
This paper shows the benefits of synchronous multichannel PD measurements. Different methods of evaluation as 3PARD, multi-site PD decoupling and multi-frequency PD decoupling are presented in theory and supported by application examples as PD measurements on power transformers and high voltage XLPE cable systems. These advanced evaluation techniques require a fully synchronized multi-channel PD measuring...
The pulsed electroacoustic (PEA) technique was used to perform space charge measurements in polymeric power cables. However, for a practical dc power cable the electric field is affected by conductivity of the material, which is a function of both temperature and electric field. The coupled problems inflict difficulties to identify the electric field distribution in high voltage (HV) cables, which...
An important parameter for the expansion of the plasma bases at the electrodes is the expansion of plasma channel and gas bubble of the spark erosion. Simulations for the expansions on the basis of two different models are presented. The initial size of the discharge channel diameter is determined by the breakdown conditions in the narrow working gap (streamer entry). The expansion of the discharge...
Investigations about the effect of roughness on the surface flashover voltages were made with different materials under different ambient conditions. The tendency of the investigations appear to be contradictory to the results exhibited in other publications, where only roughness values up to 10 micrometers were investigated and different directions of the roughness in respect to the electrical field...
Films of poly(ethylene naphthalate), polyethylene (either low density or cross-linked) and epoxy resins have been irradiated with electrons having kinetic energies of up to 10 keV, i.e. able to break bonds of the polymeric chains (featuring therefore hot electrons effects). The so-called cathodo-luminescence spectrum has been acquired for different electron energies. With the various materials tested,...
High-voltage storage capacitor is the key device in weapon system, high reliability is required. In the process of storage and application, effective measurements are needed to ensure the insulation capability of capacitors. Usually, partial discharge (PD) is used to detect the insulation status of capacitors. Under DC there does not exist fundamental parameter Phi , so a new parameter delta (t) is...
In this paper, we focused on the breakdown lifetime characteristics under repetitive surge voltage application for nanocomposite enameled wires. Experimental results revealed that the nanocomposite enameled wires exhibited the longer breakdown lifetime as high as 1000 times of conventional enameled wires under surge voltage application. The relationship between the surge breakdown voltage V and the...
Whenever a polymeric material is subjected to an electrical stress, imperfections such as protrusions, contaminants and microvoids, will all act as points where the field is enhanced, causing the degradation processes to be initiated. However, as manufacturing technology improves, insulation systems are of higher quality and their interfaces smoother. The reduction in concentration and size of impurities...
The paper describes the procedure for the reduction of the breakdown appearance in HV apparatus by automatic geometry optimization. Such procedure consists basically of three main steps: field analysis, breakdown criteria evaluation and geometry optimization. The evaluation of the breakdown criteria is briefly elaborated and illustrated at some well-known "two-sphere" examples. As the accurate...
Online monitoring of partial discharges (PD) can reduce the risk of catastrophic failure of power apparatus. Acoustic emission technique is advantageous for online PD measurement and is adopted here. Partial discharges are classified according to the origin of discharges and their effects on insulation deterioration are also different. This paper reports experimental results and analysis for classification...
This paper confronts the practical problems associated with ester fluids, due to their higher viscosities, for the impregnation of cellulosic insulation systems used in power transformers. The impregnation mechanism by an insulating fluid was studied using an analytical model and then laboratory tests were carried out to investigate the impregnation process of cellulosic materials in the forms of...
In this paper, we have investigated the dielectric properties (losses, conductivity) of a modified rape-seed oil (RS50). Dielectric spectroscopy has been done over a wide frequency range (10-2-106Hz) and conductivity measurements according to CEI 61620 standard. The parameters investigated are temperature (-20degC to 120degC) and water content. Frequency spectra of the dissipation factor tgzeta at...
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