Wyniki wyszukiwania - Biblioteka Nauki

1

Time-frequency analysis on pulse current of partial discharge

100%

Wenrong S. , Junhao L. , Yongfen L. , Yanming L.

Przegląd Elektrotechniczny

|

2009

|

tom R. 85, nr 7

40-44

EN

This paper introduces a time-frequency analysis (TFA) method of Wigner-Ville distribution (WVD) to analyze partial discharge (PD) pulse current signals with wideband detection for fundamental studies. The mathematical model of WVD is described, and its application in an analysis of PD pulse current signals at DC voltage shows its great advantage.

PL

W artykule zastosowano czasowo-częstotliwościową metodę rozkładu Wignera-Ville (WVD) do analizy prądu impulsowego wyładowania niezupełnego. Przedstawiono model matematyczny WVD oraz przykłady analizy prądu wyładowania.

2

The study of phased-ultrasonic receiving-planar array transducer for PD location in power transformer

100%

Jisheng L. , Yongfen L. , Junhao L. , Yanming L.

Przegląd Elektrotechniczny

|

2011

|

tom R. 87, nr 3

324-328

EN

Partial discharge (PD) is the main cause of electric equipment degradation. PD location can provide the scientific direction and analysis for equipment condition monitoring. The phased-ultrasonic receiving-planar array transducer for PO location in transformer is studied in this peper. The operation environment and material properties of transducer are analyzed. The center frequency of transducer is 150 kHz and its bandwidth is 100 kHz. The piezoelectric source and oil interstitial defect are used to detect the transducer's performance in lab. Experimental results show the transducer has perfect ultrasonic receiving characteristics. The successful developments of this sensor provide a good foundation for PD location in transformer using phased-ultrasonic receiving-planar array transducer.

PL

Wyładowania niezupełne są częstą przyczyną uszkodzeń urządzeń elektrycznych. W artykule przedstawiono ultradźwiękowy przetwomik o czestotliwości 150 kHz zaprojektowany do lokalizacji wyładowań nie zupełnych. Preprowadzne eksperymenty dowiodły przydatności takiego przetwornika.

3

Simulation of Cross-shaped Ultrasonic Array Applied to Partial Discharge Location in Oil

88%

Haiying J. , Yongfen L. , Shengqiang J. , Jisheng L. , Yanming L.

Przegląd Elektrotechniczny

|

2012

|

tom R. 88, nr 1b

245-249

EN

A study on a combined sensor was made for partial discharge(PD) location in oil. The sensor includes a cross-shaped ultrasonic phased array of 13 elements and an ultra-high frequency (UHF) electromagnetic conformal array of 4 elements. The ultrasonic array can achieve the array performance of 61 elements with high-order cumulant processing technology. It can improve the array aperture and direction sharpness of the sensor and greatly reduce the following circuit and manufacturing costs. The method of PD location which use expanded ultrasonic array accompanied with UHF electromagnetic array has better location performance. The spatial spectrum comparing with MUSIC(multiple signal classification�jmethod shows that virtual expanding array of the fewer number array elements with high-order cumulant processing technology has strong ability to suppress colored Gaussian noise interference. This provides the possibility for the practical application of array technology in power equipment.

PL

Zaprezentowano czujnik do badania wyładowania niezupełnego w oleju. Czujnik składał się z matrycy 13 czujników ultradźwiękowych I 4 wysokoczęstotliwościowych czujników elektromagnetycznych. Matryca czujników może spełniać rolę wirtualnej matrycy złożonej z 61 elementów.

4

Chaotic characteristics of time series of partial discharges in oilpaper insulation and their applications in pattern recognition

88%

Yongfen L. , Junhao L. , Ping H. , Shengchang J. , Yanming L.

Przegląd Elektrotechniczny

|

2011

|

tom R. 87, nr 7

219-224

EN

In order to recognize partial discharges (PD), five kinds of typical defects in oil-paper insulation are built and measured with current pulse method, and chaos method is used to research the time series of PD signals. The results revealed that the PD is of obvious chaotic characteristic, and the PD process is chaotic one. The PD patterns can be qualitatively analyzed and recognized by using the chaotic time series of PD and their chaotic attractors. Phase space reconstruction parameters and post-reconstruction chaotic characteristic quantities can be selected to quantify the PD's chaotic characteristics. Verification and comparison on pattern recognition effects of PRPD and CAPD were performed respectively by adopting the neural network of radial basis function (RBF), and the result showed that the effects of both were good and had their own advantages. Besides, statistical operators in PRPD mode and chaotic characteristic quantities in CAPD mode were comprehensively selected as the input vectors of neural network, and the average recognition rate can reach 95%, this result showed that the recognition on PD was improved by a relatively large scale.

PL

Przeprowadzono badania pięciu typowych przypadków defektów izolacji papierowo-olejowej. Sygnały wyładowań niezupełnych przetworzono w szeregi czasowe. Stwierdzono że process ma character chaotyczny. Wykorzystano teorię przebiegów chaotycznych do analizy sygnału i klasyfikacji wad.

5

Application of Time Series Used on Recognition of Partial Discharge in Oil-Paper Insulation

75%

Shengqiang J. , Yongfen L. , Haiying J. , Rui C. , Haicang L. , Yanming L.

Przegląd Elektrotechniczny

|

2012

|

tom R. 88, nr 5b

202-205

EN

Five typical partial discharge (PD) models of oil-paper insulation are made in the article, time series of PD’s amplitude are fetched from the results measured, after being pre-processed, they are fitted by auto regressive (AR) model, the coefficients of the AR model are used as feature vector to recognize the five typical partial discharges by BP Neural Network. In this article, different order AR models are used to fit the time series, the result shows that under the 4-order or 6-order AR model, the recognition accuracy rates of the five models are all as high as over 80%.

PL

Zbadano pięć typowych modeli wyładowania niezupełnego w izolacji z papieru olejowego. Rezultaty pomiarów były przetworzone numerycznie tworząc model auto-regresywny AR. Współczynniki tego modelu mogą być używane do rozpoznawania rodzaju wyładowania. Do rozpoznawania użyto sieci neuronowych.

6

Study on The Key Technologies of On-line Monitoring of Transformer Winding Deformation Based on Short-circuit Reactance Analysis

75%

Rui C. , Yongfen L. , Yanming L. , Yu S. , Ling R. , Wei L.

Przegląd Elektrotechniczny

|

2013

|

tom R. 89, nr 9

302-305

EN

The research about on-line monitoring of transformer winding deformation based on Short-Circuit Reactance is studied, then a method is put forward to calculate the leakage reactance of power transformer quickly. The equivalent resistance can be got from the ratio of voltage difference and current at the peak of current. Also, the equivalent inductance can be got from the ratio of voltage difference and current differential when current is zero. At the same time, it is helpful for improving the resolution of the algorithm to the maximum precision of AD acquisition card by magnifying the voltage difference of primary and secondary voltage before being gathered to AD card. The system designed by the two technologies above is tested on the laboratory platform and a criterion is proposed to help to judge the state of winding. The article provides an effective method to monitor on-line monitor the winding deformation of transformer.

PL

W artykule przedstawiono metodę monitorowania w trybie on-line deformacji uzwojeń transformatora. Do analizy wykorzystano pomiar reaktancji w stanie krótkotrwałego zwarcia. Określana jest też zastępcza rezystancja i indukcyjność uzwojenia. Badania eksperymentalne potwierdziły skuteczność metody.