Wyniki 1-10 spośród 10 dla zapytania: authorDesc:"Xiuchen JIANG"

Statistical Parameters Applied to the Analysis of Partial Discharge Signals in Power Cables

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To analyze the partial discharge signals in power cables, statistics method is investigated according to the experiment data of defect models. Phase resolved partial discharge graphics and associated pulse distributions are acquired to show the characteristics of defect PD events. 28 statistical parameters are extracted and employed to find the different representation of the defect models in power cables. The results show that statistics method and are useful and effective in the partial discharge signals analysis. Streszczenie. Do analzy sygnału częściowego wyładowania w kablach użyto metod statystycznych. Rozkład statystyczny impulsu wyładowania pozwala na określenie defektu. 28 parametrów statystycznych zostało wydobytych i wykorzystanych do określania rodzaju defektu w kablu. Wyn[...]

Time-frequency Representation to the Analysis of Partial Discharges in Power Cables Using Novel Transform Method

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Partial discharge is induced by the defect or failure inside high voltage power cables. The non-stable property of pulse signals requires both time and frequency domain information to indicate the characteristics. This paper introduces the application of the newly developed timefrequency representation, i.e. S-transform, to the analysis of partial discharge signals. Through simulation and on-site experiment, S-transform presents its effectivity of extracting partial discharge signal information. Abstract. Wyładowanie niezupełne może być powodowane przez defekty lub uszkodzenia wewnątrz kabli wysokiego napięcia. Analiza sygnałów impulsowych wymaga zastosowania analizy zarówno czasowej jak i częstotliwościowej aby można było uzyskać pełną informację o zjawisku. W artykule przedstawiono nowe metody takiej analizy, jak na przykład transformatę S. Na podstawie symulacji i eksperymentów można stwierdzić że transformata S jest efektywnym narzędziem do wydobycia informacji o wyładowaniach. (Czasowo-częstotliwościowa reprezentacja w analizie wyładowań niezupełnych przy zastosowaniu nowych metod transformacji) Keywords: partial discharge, power cables, time-frequency representation, S-transform Słowa kluczowe: wyładowania niezupełne, kable, reprezentacja czasowo-częstotliwościowa Introduction Nowadays, cross-linked polyethene (XLPE) power cables are widely populated in power grids. However, the defects and failure of power cables and cable accessories, which includes cable joints and cable terminations, are becoming one of the main problems affecting power system stability. Thus monitoring these high voltage devices is definitely essential which can supply with the operation status information for doing maintenance decisions. Partial discharge (PD) detection is a proved effective method to reflect the insulation characteristics of power cables and cable accessories in [1] and [2], and contributes to the condition based maintenance (CBM) of hig[...]

Partial discharge signal analysis using Reassigned Time Frequency Transform for GIS

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Partial discharge signal of gas insulated switchgear is a typical non-stationary signal, using the time or frequency domain simply is not enough to describe the time-varying information of PD. Based on the reason above, this paper introduces a joint time-frequency analysis method according to the reassignment theory for analyzing the PD of GIS. After the processing of the PD signals simulated and on field, we conclude that this method provides a higher concentration in the time-frequency plane and reduces the most influence of the cross-interference terms. Abstract. Wyładowania niezupełne w wyłącznikach z izolacja gazową są typowym przykładem sygnału niestacjonarnego, kiedy czasowa lub częstotliwościowa analiza nie daje dobrych wyników. Dlatego przedstawiono metodę czasowo-częstotliwościową zgodną z teorią przyporządkowania. Przeprowadzone symulacje wskazują że metoda redukuje wpływ składowej interferencji krzyżowej. (Analiza sygnału wyładowań niezupełnych w wyłącznikach przy zastosowaniu transformaty czasowo-częstotliwościowej). Keywords: gas insulated switchgear (GIS), partial discharge (PD), time-frequency (TF) analysis, reassignment theory Słowa kluczowe: wyłączniki z izolacją gazową, wyładowanie niezupełne, analiza czasowo-częstotliwościowa. Introduction In recent years, gas insulated switchgear (GIS) has been proven to be very reliable. However, the moving particles, particles on the insulators and protrusions on the conductors can be very dangerous to the insulation conditions of the GIS during the process of manufacturing and assembling. Partial discharge (PD) gives an indication of the degradation on the insulation system. Therefore, the detection of insulation changes at early stages plays an important rule in increasing the service life of power equipment [1, 2, 3]. According to the non-stationary statistical properties of PD, it is not enough to describe the time varying information using time-domain or frequency-domain s[...]

Application of Gustafson-Kessel clustering algorithm in the pattern recognition for GIS

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This paper simulates four typical defects in GIS for PD detection, and uses the pulse, amplitude, phase and number of PD to form the three-dimensional PQN matrix. Based on the PQN, three two-dimensional distributions of Hqmax~Phi, Hqmean~Phi and Hn~Phi can be achieved. Then the new G-K clustering method is introduced to separate the four different defects according to the parameters of Sk, Ku, Pe, Q and CC. At last the comparison with different clustering methods is achieved based on the evaluation criterions which are PC, CE, PI and SI. Streszczenie. W artykule zasymulowano cztery typowe defekty w łącznikach gazowych wynikające z wyładowań niezupełnych oraz wykorzystano amplitudę, fazę i liczbę impulsów do sformowania trzywymiarowej macierzy PQN. Następnie wykorzystano nową metodę klastrową do rozdzielenia różnych defektów na podstawie parametrów Sk, Ku, Pe,Q i CC. Nas™epnie przeprowadzono porównanie różnych metod. (Zastosowanie algorytmu klastrów Gustafsona-Kessela do rozpoznawania wzoru przy analizie rozdzielnic gazowych). Keywords: gas insulated switchgear (GIS), partial discharge (PD), Gustafson-Kessel (G-K) method, pattern recognition Słowa kluczowe: rozdzielnice gazowe, wyładowanie niezupełne, rozpoznawanie znaków. Introduction Measurement of partial discharge (PD) for gas insulated switchgear (GIS) is an important tool for evaluating the insulating system constructions. Because of the high reliability, low maintenance, and compact size have made the GIS an attractive option in many substations. Although the reason above, it is well known that GIS breakdown is preceded by PD activity inside the GIS chamber, caused by defects such as: (i) protrusion on the high voltage conductor or enclosure; (ii) free moving particles; (iii) floating electrode; (iv) void in the resin spacer and etcetera[1-3]. Thus, it is highly desirable not only to detect the PD but also to identify the pattern of the harmful defects before GIS failure.[...]

Research on Partial Discharge Localization in XLPE Cable Accessories Using Multi-Sensor Joint Detection Technology

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A multi-sensor joint detection technology was proposed based on the theory of the high frequency current transformer (HFCT) method, Ultra-high frequency (UHF) method and acoustic emission (AE) method. An experimental partial discharge (PD) testing was applied on XLPE cable with artificial defect signals. The experimental results show that the multi-sensor joint detection technology will help to identify the PD signals from the interference noises and improve the localization accuracy. Streszczenie. Zastosowano wielosensorową metodę badania wyładowania niezupełnego: wysokoczęstotliwościowy transformator prądu oraz metodę emisji akustycznej. Badania przeprowadzono na kablu ze sztucznym sygnałem defektu. Umożliwiło to wydzielenie sygnału z szumów i poprawe dokładności pomiaru lokalizacji. (Badania lokalizacji wyładowania niezupełnego w kablu XLPE przy użyciu techniki multiczujnikowej) Keywords: XLPE cable; partial discharge; Multi-Sensor; HFCT; UHF; AE Słowa kluczowe: kabel XLPE, wyładowanie niezupełne. Introduction As the extensive application of Cross-linked Polyethylene (XLPE) cable in power grid, power accidents caused by insulation faults in cable equipments are increasing constantly. Meanwhile, the cable laying method is mainly concerned with underground, which brings problems on state testing and fault localization in cable systems. Therefore, how to judge the cable insulation situation effectively and locate the fault site accurately is of great practical significance [1]. Insulation faults occur more often in cable accessories. And the existence of insulation faults, can lead internal partial discharge (PD) to occur. Through the partial discharge testing in XLPE cable accessories, we can indirectly access the XLPE cable insulation status. In this paper, we proposed a XLPE cable on-line testing method which based on multi-sensor joint detection technology, in order to realize the partial discharge localization in XLPE cable[...]

A Traveling Wave Fault Location Method for Earth Faults Based on Mode Propagation Time Delays of Multi-measuring Points

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A new traveling wave fault location method for earth faults is proposed based on propagation time delays between aerial mode and earth mode acquired by multi-measuring points on transmission line. Using phase-mode transformation theory and the theory of wavelet singularity detection to achieve the algorithm of propagation time difference detection. The JMarti model is used to build the system simulation model in the EMTP. The final results show that the method has high reliability and precision. Streszczenie. Przedstawiono nową metodę wykrywania I lokalizacji błędu w linii transmisyjnej bazującą na analizie propagacji fali. Do tego celu wykorzystano transformatę falkową. (Lokalizacja błędu w linii transmisyjnej na podstawie analizy propagacji fali) Keywords: transmission line;traveling wave;mode propagation time delays;fault location Słowa kluczowe: linia transmisyjna, fala wędrująca, lokalizacja błędu. Introduction Earth faults in power network have a very high probability of occurrence,up to 90%. The accurate and fast location of earth faults can not only reduce outage losses but also guarantee the safe and stable operation of the power system. After earth faults occur to the transmission line, the transient traveling wave resulting from fault points includes not only aerial mode component but also earth mode component. Fault location is conducted through judgment of the approximate entropy of transient earth mode current of adjacent measuring points in literature [1]. However, this method is only capable of determining fault section, but can't determine the position of fault points. Another method is the single ended method which uses time delay of the initial wave head (hereinafter referred to as mode propagation time delays), the earth-mode and aerial-mode wave velocity to range. Although the method was put forward earlier, its location range is very limited due to the attenuation of earth mode an[...]

Output Characteristics and MPPT Research for PV Array under Partially Shaded Conditions

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MPPT(maximum power point tracking) has been one of the hot issues in PV power system all the time. At present, most of MPPT methods are very efficient only under uniform irradiance. However, the output power-voltage curve presents multi-peak characteristics under PSCs (partially shaded conditions), which is one challenge of the MPPT technology. In this paper, the segment characteristics of PV array, which is made by PV modules in series-parallel (SP) connection, was analyzed in details under PSCs. And then a GMPPT (global maximum power point tracking) algorithm was proposed based on the segment model. The MPPT controller using this algorithm can rapidly locate the segment where the GMPP(Global Maximum Power Point) is in and then converges the working point to GMPP using an improved InC (Incremental Conductance) method. A Matlab/SIMULINK model verifies that the proposed algorithm is efficient under both uniform irradiance and PSCs. Streszczenie. System śledzenia warunków maksymalnej mocy MPPT jest powszechnie stosowany w systemach fotowoltaicznych. Systemy te w większości działają w warunkach jednorodnego nasłonecznienia. W artykule zaproponowano system śledzenia mocy w warunkach częściowego nasłonecznienia. (System śledzenia mocy MPPT dla układów fotowoltaicznych w warunkach częściowego zacienienia). Keywords: Partially Shaded Condition(PSC), Global Maximum Power Point Tracking(GMPP), Attracting Region, Segment Model Słowa kluczowe: układy fotowoltaiczne, system śledzenia maksymalnej mocy MPPT 0. Introduction Solar PV power generation is one of the most important directions in the field of new energy development. In PV power generation system, the working point has considerable impact on the conversion efficiency of PV systems, and thus the research on maximum power point tracking (MPPT) algorithm has been one of the hot issues all the time. In actual PV power generation system, high voltage and power output is required, so PV array wi[...]

Research of the GIS Structure Influence on Propagation Characteristic of Partial Discharge Electromagnetic Waves

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Partial discharge process caused by Gas Insulatd Switchgear (GIS) typical insulation defect is mainly analyzed in this study, and propagation properties of electromagnetic waves in actual GIS structure are investigated by applying FDTD algorithm and using real PD current signal as excitation source. The results show that great difference occurs between electromagnetic waves excited by PD actual current signal and that by ideal Gaussian pulse excitation and basin type insulator, shielding electrodes and three-phase common enclosure can affect the amplitude, frequency component and propagation mode of electromagnetic waves. The electromagnetic waves signal intensity is not necessarily proportional to its distance from discharge source; the proportion of frequency components is proportional to the diameter of GIS shell when it propagate in breakers . Streszczenie. Zaprezentowano stadium wyładowania niezupełnego przy typowych defektach łączników gazowych. Zastosowano metodę różnic skończonych. Zaobserwowano istotne różnice fali elektromagnetycznej przy rzeczywistym wyładowaniu w stosunku do modelu teoretycznego. Sygnał fali elektromagnetycznej jest proporcjonalny do średnicy powłoki wyłącznika. (Badania wpływu struktury wyłącznika gazowego na propagację fali elektromagnetycznej przy wyładowaniu niezupełnym) Keywords: PD; propagation of electromagnetic Waves; Gas Insulatd Switchgear(GIS); basin type insulator ; shielding electrode ; breaker Słowa kluczowe: wyładowanie niezupełne, wyłącznik gazowy. Introduction Partial discharge(PD) current pulse in Gas Insulatd Switchgear(GIS) possesses steep rising edge, with the rising time of ns order[1-2], and the electromagnetic waves with the frequency of GHz excited propagates in the coaxial structure formed by GIS cavity. Due to the coaxial structure of GIS, the electromagnetic wave not only propagates in the form of transverse electromagnetic wave (e.g. TEM wave), but also in the form of high-order [...]

A Multi-parameter Comprehensive Analytical Method for Online Assessing Power Transformer Condition

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The effective assessment on the operation condition of power transformer is an important means to conduct the condition maintenance for transformer and to improve the reliability of power system. Based on the amount of information of all kinds of online monitoring conditions obtained from the transformer intelligent components, the assessment model for comprehensive condition of transformer is established in this study through the introduction of extension theory. First, with respect to the disadvantage that there is considerable subjectivity in constructing judgment matrix by the traditional analytic hierarchy process (AHP), a new method is adopted to construct the judgment matrix. The orthogonal experimental design method, finite element simulation as well as AHP are adopted to determine the weighting of condition information index with scientific and objective attitude; next, the framework for comprehensive assessment of transformer condition is established with the extension-based comprehensive assessment method to achieve the qualitative and quantitative assessment on the transformer condition. The method is proved to be correct and valid through analysis of examples. Streszczenie. W artykule przedstawiono wyniki badań dotyczących opracowania modelu szacowania warunków pracy transformatora. W pierwszym kroku stworzono metodę budowy macierzy orzeczeń, z uwzględnieniem pewnych subiektywności tradycyjnej metody tworzenia tej macierzy (ang. Analytic Hierarchy Process). Do oszacowania wagi wskaźnika informacji o warunkach pracy, wykorzystano metodę eksperymentalną, symulację elementów skończonych oraz AHP. Wykonane badania wykazały poprawność działania metody. (Wszechstronna, wieloparametrowa metoda analizy do dynamicznego szacowania warunków pracy transformatora). Keywords: Power Transformer; condition assessment; index weighting; online monitoring Słowa kluczowe: transformator energetyczny, szacowanie warunków, waga wskaźnika, monitoring o[...]

Development of Distributed On-line Monitoring System for Dielectric Loss Tangent of High Voltage Capacitive Apparatus

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This paper presents a distributed measuring system for on-line monitoring of dielectric loss factor tan δ, and capacitance of HV apparatus. The method employs the Discrete Fourier Transform (DFT) which is performed on the scaled down analog voltage and current signals obtained using digital signal processing (DSP) technology. The measuring unit of the on-line monitoring system takes a series of measures in the hardware circuit design to improve the effectiveness of the DFT algorithm. The lab test results of measuring unit show that the measuring unit has high precision of measurement based on the DFT method. Field tests at a regional substation to evaluate the insulation of two groups of 220kV current transformer units using the developed system. Streszczenie. W artykule opisano system pomiaru rozproszonego do monitorowania on-line współczynnika strat dielektrycznych i pojemności w aparatach HV. W metodzie wykorzystano Dyskretną Transformatę Fouriera. W celu poprawy dokładności i skuteczności DFT, dokonywana jest seria pomiarów. Wyniki badań laboratoryjnych oraz w rzeczywistej podstacji, wykazały wysoką precyzję rozwiązania. (Budowa systemu rozproszonego monitorowania on-line współczynnika strat dielektrycznych w wysokonapięciowych aparatach pojemnościowych). Keywords: dielectric loss factor;discrete Fourier Transform; distributed measuring system;DSP;on-line monitoring Słowa kluczowe: współczynnik strat dielektrycznych, Dyskretna Transformata Fourier’a, system pomiaru rozproszonego, DSP, monitorowanie on-line. Introduction To ensure the safe and reliable operation of a power system it is necessary to monitor periodically the insulation condition of HV apparatus. This may be accomplished by measuring partial discharge levels and/or dielectric loss factor and capacitance using conventional well-established time based maintenance. However, the implementation of these routine tests requires removal of[...]

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