Propagation Characteristics of High-Frequency Partial Discharge Current in Gas Insulated Equipment
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P262 Effects of Strain Amplitude on Relaxation Spectra of Wave Attenuation in Rock E.I. Mashinskii* (Institute of Petroleum Geology and Geophysics RAS) SUMMARY The laboratory study of wave attenuation in sandstone and the “atomic” elastic solid states (quartz and duralumin) under confining pressure of 20MPa has been performed using the reflection method on pulse frequency of 1 MHz in the strain amplitude range ~ (0.3 - 2.0) * 10-6. The experiments have shown the unusual results in the behavior of the relaxation spectra of wave attenuation in dependence on strain amplitude. The attenuation nonlinearly decreases with increasing strain amplitude. In
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GIS partial discharge detection is a scientific and effective way for insulation condition monitoring.A GIS model and the detection system based on UHF method has been set up.Several typical GIS partial discharge is studied and using power phase analysis a detailed analysis of characteristics under different voltage is made;Combined with conventional partial discharge detection method,the partial discharge quantity estimation of UHF signal is also made.All of these lay a foundation for the study of partial discharge intelligent recognition and the relationship between UHF signal and partial discharge quantity to improve the engineering utility of UHF partial discharge detection.
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Partial discharge monitoring and location system at substation receives radio frequency (RF) signals emitted by partial discharge to position partial discharge using a set of omni-directional RF antenna array. As it is possible for the entire substation to have several partial discharge sources simultaneously, the basic requirement of partial discharge detection at the substation is to judge whether there are multi-source partial discharge signals, and then identify and isolate them. Based on different time domain and frequency characteristics of ultrahigh frequency (UHF) partial discharge signals generated by different partial discharge sources, we perform time-frequency analysis and fuzzy clustering over RF pulse waveforms generated by partial discharge which are continuously acquired and stored, and isolate partial discharge signals from different partial discharge sources or interferences. By this method, we can effectively isolate and accurately position multiple partial discharge sources. Our study lays the foundation for identification of partial discharge types. The feasibility of this method has been proved by field test.
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In order to improve the accurate judgment and location level of partial discharge defects in GIS equipment, it is important to carry out the identification and determination of partial discharge types for GIS equipment running status evaluation. The types and reason of partial discharge in GIS equipment are analyzed, discusses the advantages and disadvantages of different partial discharge detection method. The amplitude, characteristics, types and empirical criterion of typical partial discharge defects are researched by employed the ultrasonic detection method (AE) and ultra-high frequency detection method (UHF) according to the five typical defect types in the field testing. It is indicate that the two methods can play their respective advantages to ensure the reliability of partial discharge detection and location accuracy. The study on the characteristics of partial discharge under the different detection methods provides important parameters and basis for the condition-based maintenance of GIS equipment and judgment data for the field tester.
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Investigation of teleseismic P-wave recordings at a temporary network in the Eastern Carpathians, equipped with predominantly short-period sensors, is compared with synthetic modelling of anelastic attenuation of teleseismic waves in the upper mantle. Using the t* approach, we examine variations of amplitude decrease over frequency for teleseismic recordings in the frequency band 0.5–1.5 Hz. The results reveal a consistent pattern of increased t* values in the centre of the network, in the Vrancea region at the bend of the Carpathian Arc, although the magnitude of the observed variation in t* is much higher than expected. Synthetic t* parameter computations for the same event-receiver configurations reproduce the observed pattern in terms of relative variations. However, the amplitude of the synthetic t* values explains only 10–20 per cent of the observed variation in t*. t* is not a direct measure for anelastic attenuation but rather for a combination of anelastic and other attenuating effects such as scattering and amplitude fluctuation related to velocity inhomogeneities. If regional amplitude variations are solely attributed to anelastic attenuation, all other effects are mapped into Q. We discuss the role of anelastic attenuation and other effects in the case of the Eastern Carpathians and conclude that t* is an unsuitable parameter to characterize anelastic attenuation in the Eastern Carpathians.
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The partial discharge measurements have been widely used in the field of insulation diagnostics. The presence of partial discharges inside the cable indicates the degradation of insulation material. This paper deals with the development of insulation diagnostic method based on the partial discharge (PD) measurements. The useful information about the partial discharge activity and insulation defects is extracted by the experimental results. Artificial cavity was introduced inside the medium voltage XLPE cable by using the traditional needleplane configuration. The statistical characteristics formulated with the help of PRPDA technique and ultra-wideband discharge characteristics by using HFCT sensor was studied and analyzed. Paper is related to study about the partial discharge phenomenon in detail. The aim is to interpret the variations in the partial discharge characteristics over the insulation ageing period in terms of physical phenomenon's taking place in PD sources. The results of this work are based on the partial discharge measurements for lifetime tests conducted over the medium voltage (MV) XLPE cable samples at high voltage laboratory.
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Optical signal at Stokes frequency producing the attenuation of the signal at higher frequency is studied in this paper.By simulating the couple power differential equations,the relations of the signal's attenuation with pump power and distance are analyzed numerically and theoretically.The good accordance between our solutions and the former researcher's experimental observations proves the feasibility that signal processing can be realized by pure optical method.The advantages and broad applications are also illustrated.
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Intermittent partial discharge has become an essential threat to the safety and stability of high voltage electrical equipment. In order to reduce the sudden insulation breakdown failure due to the intermittent and latent partial discharge of the operating equipment, this paper analyzes the discharge characteristics of the intermittent partial discharge in the constant voltage mode. The UHF partial discharge spectrum of typical intermittent partial discharges is obtained, and the intermittent discharges are divided into low-risk and high-risk categories by adopting PCA and FCM cluster algorithms. Aiming at the characteristics of intermittent partial discharge and the on-line monitoring method of partial discharge, a partial discharge signal collection method based on dynamic frequency is proposed. An intelligent monitoring system of intermittent partial discharge is designed to acquire partial discharge signals initially locate defects. Then the BP neural network method is applied to automatically evaluate and early warn the internal insulation status. The test concluded that the designed monitoring system for intermittent partial discharge could dynamically track and warn the low-risk and high-risk, and evaluate the insulation status of the equipment.
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The authors present the emission spectra of four types of partial discharges. The purpose was to develop a partial discharge (PD) light detector. PDs in SF/sub 6/ gas-insulated systems (GIS) often indicate a fault in the electrical insulation. Four cases of PD in SF/sub 6/ gas were measured using a needle point discharge, a floating-electrode discharge, and a metallic-particle discharge, which are likely to occur inside a GIS. Spectral measurements have also made of spark discharge caused by glass discharge tubes. The results indicated by the different spectral patterns are discussed.< >
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The lifetime of high voltage equipment is very dependent on the condition of insulation, poor insulation means the life span of high voltage equipment is getting shorter. Partial Discharge is one of the causes of deterioration of high voltage equipment insulation. The ability to know the phenomenon of partial discharge in equipment becomes very important and adds value to the maintenance of high voltage equipment. Many explanations regarding partial discharge, partial discharge is the lack of uniformity of the electric field in the isolation or dielectric media which will result in the phenomenon of Partial Discharge where this will lead to the failure of the isolation media. Partial Discharge that occurs continuously can cause damage (breakdown) on a high voltage equipment. Therefore, before a high voltage device is used, Partial Discharge detection is necessary. Partial Discharge Detection can use the Partial Discharge measurement circuit. In testing partial discharges can be tested using a sensor with various circuits including High Frequency Current Transformers (HFCT) so that this research will discuss one part of the Partial Discharge measurement circuit, the HFCT detector. Hopefully, the HFCT detector can be further developed and can be used for better partial discharge detection.
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