Impulse voltage distribution and frequency response of intershield windings

The Frequency Response Analysis approach (FRA) is useful in the fault diagnosis of transformers. However, its usefulness in diagnosing any potential sources of Partial Discharge (PD) in transformers has not been thoroughly investigated so far. In this work, the use of Impulse voltage-based FRA (IFRA) in diagnosing inter-turn shorts and potential sources of PD were investigated on a 315 kVA, 11 kV/433 V transformer. Inter-turn shorts and PD sources were emulated and the usefulness of IFRA in their diagnosis was investigated while using switching impulse voltage at different magnitude levels as the test signals. For emulating the inter-turn shorts and the PDs, special tappings were provided on one of the 11 kV windings through the low capacitance bushings. Low voltage impulse was successful in diagnosing the inter-turn shorts, but unsuccessful in identifying the sources of PDs. During the test condition, the test voltage was adjusted with the presence of artificially created PD sources. The frequency response of the transformer before and after the inception of PD was observed and analyzed in this article. The FRA results demonstrated that the switching impulse voltage based IFRA approach at moderate voltages could be useful in diagnosing the presence of the potential sources of PDs.

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Estimation of Transformer Winding Capacitances through Frequency Response Analysis – An Experimental Investigation

International Journal of Emerging Electric Power Systems ◽

10.1515/ijeeps-2013-0098 ◽

2013 ◽

Vol 14 (6) ◽

pp. 549-559 ◽

Cited By ~ 3

Author(s):

Krupa Shah ◽

K. Ragavan

Keyword(s):

Frequency Response ◽

Wide Frequency Range ◽

Response Analysis ◽

Voltage Distribution ◽

Response Data ◽

Non Invasive ◽

Transformer Winding ◽

Invasive Method ◽

Ladder Network ◽

Good Agreement

Abstract This article focuses on developing a non-invasive method for determining capacitances using frequency response data. The proposed methodology involves acquiring driving-point impedance of the winding under consideration over wide frequency range. With certain terminal conditions and using the terminal impedance measured at specific frequencies, input and shunt capacitances are determined. For the purpose of estimating series capacitance of the winding, an algorithm is proposed. To demonstrate the capability of the method, initially model coils that have provisions for connecting external capacitances are considered. Then, it is found that the estimated values of capacitances are nearly same as those of connected capacitances. The method is, then, extended to transformer winding, and a capacitive ladder network is constructed. To assess the accuracy of estimation, capacitive voltage distribution is utilized. That is, the voltage distribution in the winding is compared with that of synthesized circuit. A good agreement between those data reveals that the estimated capacitance values are accurate.

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A method of analysis of transformer impulse voltage distribution using a digital computer

Proceedings of the IEE Part A Power Engineering ◽

10.1049/pi-a.1958.0080 ◽

1958 ◽

Vol 105 (23) ◽

pp. 445 ◽

Cited By ~ 15

Author(s):

Beryl M. Dent ◽

E.R. Hartill ◽

J.G. Miles

Keyword(s):

Digital Computer ◽

Voltage Distribution ◽

Impulse Voltage

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New approach to the analysis of impulse voltage distribution in transformer windings

IEE Proceedings C Generation Transmission and Distribution ◽

10.1049/ip-c.1990.0038 ◽

1990 ◽

Vol 137 (4) ◽

pp. 283 ◽

Cited By ~ 7

Author(s):

O. Honorati ◽

E. Santini

Keyword(s):

Voltage Distribution ◽

New Approach ◽

Impulse Voltage

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Power Transformer Constants Affecting its Impulse Voltage Distribution

International Journal of Electrical Engineering Education ◽

10.1177/002072097701400112 ◽

1977 ◽

Vol 14 (1) ◽

pp. 53-63

Author(s):

A. M. El-Arabaty ◽

Ezzat A. A. Mansour ◽

Osama A. M. Said

Keyword(s):

Power Transformer ◽

Power Transformers ◽

Stress Distributions ◽

Voltage Distribution ◽

Impulse Voltage ◽

The Difference ◽

Theoretical Results

This work deals with the modification of the known calculating formulae for power transformer constants used for impulse voltage distribution, presents the effect of transformer constants and their modifications on impulse voltage and stress distributions in power transformers, and compares experimental and theoretical results considering measures taken to minimize the difference between them.

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