A New Approach for Power Transformer Internal Faults Analysis Based on Magnetic Potential Balance Principle Calculation

In determining the severity of power transformer faults, several approaches have been previously proposed; however, most published studies do not accommodate gas level, gas rate, and Dissolved Gas Analysis (DGA) interpretation in a single approach. To increase the reliability of the faults’ severity assessment of power transformers, a novel approach in the form of fuzzy logic has been proposed as a new solution to determine faults’ severity using the combination of gas level, gas rate, and DGA interpretation from the Duval Pentagon Method (DPM). A four-level typical concentration and rate were established based on the local population. To simplify the assessment of hundreds of power transformer data, a Support Vector Machine (SVM)-based DPM with high agreements to the graphical DPM has been developed. The proposed approach has been implemented to 448 power transformers and further implementation was done to evaluate faults’ severity of power transformers from historical DGA data. This new approach yields in high agreement with the previous methods, but with better sensitivity due to the incorporation of gas level, gas rate, and DGA interpretation results in one approach.

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A New Adaptive Differential Protection Scheme for Tap Changing Power Transformer

International Journal of Emerging Electric Power Systems ◽

10.1515/ijeeps-2015-0005 ◽

2015 ◽

Vol 16 (4) ◽

pp. 339-348 ◽

Cited By ~ 2

Author(s):

Ashesh Mukeshbhai Shah ◽

Bhavesh Bhalja

Keyword(s):

Power Transformer ◽

Detection Sensitivity ◽

Power Transformers ◽

Test Cases ◽

Differential Protection ◽

Protection Scheme ◽

Differential Characteristic ◽

Numerous Test ◽

Internal Faults ◽

Conventional Scheme

Abstract This paper presents a new adaptive differential protection scheme which efficiently adapts the change in tap position of a power transformer. The proposed scheme is based on analytical derivation of pick-up and slope of the differential relay characteristic. By acquiring information such as rating & connection of CTs and present tap position as input, the proposed scheme enhances sensitivity of differential relay during internal faults. This is accomplished either by decreasing pick-up and/or adjusting slope of the differential characteristic of the relay in case of change in tap position. Numerous test cases consisting of various types of internal and external faults have been simulated for an existing power transformer of Gujarat Energy Transmission Corporation Limited (GETCO), Gujarat, India using PSCAD/EMTDC software package. The proposed scheme increases percentage of winding to be protected during internal faults for power transformers having different ratings and connections compared to the conventional differential protection scheme. Furthermore, it has been observed that the detection sensitivity during special types of turn-to-turn and inter-winding faults with varying fault resistances is also enhanced compared to the conventional scheme. Moreover, it equally maintains stability during CT saturation condition. At the end, comparative evaluation of the proposed scheme with the existing schemes clearly indicates superiority of the proposed adaptive scheme.

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A New Approach of Determination of Comprehensive Weight in Condition Assessment of Power Transformer

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.273.365 ◽

2013 ◽

Vol 273 ◽

pp. 365-370 ◽

Cited By ~ 1

Author(s):

Bao Guang Zhao ◽

Xin Hua Zhao ◽

Cheng Zhang Wang ◽

Chun Tian ◽

Xiang Lei Zhao ◽

...

Keyword(s):

Power Transformer ◽

Condition Assessment ◽

Specific Form ◽

Evaluation Index ◽

New Approach ◽

Empirical Results ◽

Subjective Weight

The weight of evaluation index plays a key role in condition assessment and maintenance control of power transformer. A new approach of determination of comprehensive weight is proposed in this paper. The approach combines the entropy objective weight with the expert subjective weight together in a specific form, which not only avoids the situation that single weight determines the overall weight, but considers the primary and secondary problem between the two weights. The comprehensive weight calculated by this approach can reflect the place of every index in condition assessment of power transformer well. Empirical results show that the approach is reasonable and available.

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A Novel Approach for Classifying Transient Phenomena in Power Transformers

International Journal of Emerging Electric Power Systems ◽

10.2202/1553-779x.1013 ◽

2004 ◽

Vol 1 (2) ◽

Author(s):

El Sayed M. Tag Eldin

Keyword(s):

Fuzzy Logic ◽

Wavelet Transforms ◽

Power Transformer ◽

Current Transformer ◽

Transient Phenomena ◽

Protective Relay ◽

Novel Approach ◽

Inrush Currents ◽

Internal Faults ◽

External Faults

The role of a power transformer protective relay is to rapidly operate the tripping during internal faults and block the tripping during magnetizing inrush. This paper presents a new approach for classifying transient phenomena in power transformer, which may be implemented in digital relaying for transformer differential protection. Discrimination between internal faults, external faults with current transformer saturation and magnetizing inrush currents is achieved by combining wavelet transforms and fuzzy logic. The wavelet transform is applied for the analysis of the power transformer transient phenomena because of its ability to extract information from the transient signals in both time and frequency domain. Fuzzy logic is used because of the uncertainty in the differential current signals and relay settings. MATLAB power system toolbox is used to generate current signals at both sides of a power transformer in a typical system with various conditions. The simulation results obtained show that the new algorithm provides a high operating sensitivity for internal faults and remains stable for external faults and inrush currents.

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