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- A permeance-based transformer model and its application to winding interturn arcing fault studiesPublication . Oliveira, L. M. R.; Cardoso, A. J. MarquesThis paper investigates the behavior of power transformers under the occurrence of permanent or intermittent winding insulation faults.
- Application of Park's power components to the differential protection of three-phase transformersPublication . Oliveira, L. M. R.; Cardoso, A. J. MarquesThis paper presents a new scheme for power transformers differential protection, in which the concept of the Park's instantaneous differential powers is introduced. The proposed method is able to detect winding insulation failures and to distinguish them from magnetizing inrush current transients. Experimental and simulation results are presented and discussed.
- Power transformers behavior under the occurrence of inrush currents and turn-to-turn winding insulation faultsPublication . Oliveira, L. M. R.; Cardoso, A. J. MarquesThis paper intends to provide a detailed characterization of the transformer behavior under the influence of inrush currents and/or incipient winding faults. Experimental and simulation results are presented and discussed. Finally, a promising new method to identify inrush currents, and to distinguish them from internal faults, is suggested.
- Power transformers' fault diagnostics by Park’s Vector ApproachPublication . Cardoso, A. J. Marques; Oliveira, L. M. R.The electricity market was, for a long time, dominated by national or regional monopolies. During the last decades, this picture has changed drastically, particularly in Europe and in the United States. The trend toward free competition and privatization with the related demands on return on investments results in a cost consciousness among utilities. In this context, monitoring and on-site diagnostics are seen as a possible way of optimizing existing assets. The main driving forces are to reduce maintenance costs, to prevent forced outages with the related consequential costs, and to work existing equipment harder and longer [1]. Transformers constitute the largest single component of the transmission and distribution equipment market.
- An EPVA-Based strategy for power transformers differential protectionPublication . Oliveira, Luís Manuel Ramos De; Cardoso, A. J. MarquesThis paper presents a new scheme for power transformers protection, which is based on the analysis of the harmonic content of the differential current Park's Vector modulus. The proposed method is able to detect winding insulation failures, and to distinguish them from magnetizing inrush current transients. Experimental and simulation results are presented and discussed.
- Extended Park's vector approach-based differential protection of three-phase power transformersPublication . Oliveira, L. M. R.; Cardoso, A. J. MarquesThis study presents a new scheme for power transformers protection, which is based on the analysis of the harmonic content of the differential current Park's vector modulus. The proposed method is able to detect turn-to-turn winding insulation failures, and to distinguish them from magnetising inrush current transients. Experimental and simulation results are presented and discussed.
- Power transformers differential protection using the p-q power theoryPublication . Oliveira, L. M. R.; Cardoso, A. J. MarquesThis paper describes the application of the p-q power theory to the differential protection of power transformers. The information provided by the harmonic content of the differential active and reactive power components is used to detect winding insulation failures and to distinguish them from magnetizing inrush current transients. A variety of test cases is presented in the paper, demonstrating the effectiveness of the protection strategy.
- Power transformers winding fault diagnosis by the on-load exciting current extended Park's vector approachPublication . Oliveira, L. M. R.; Cardoso, A. J. Marques; Cruz, S. M. A.This paper presents the application of the on-load exciting current Extended Park's Vector Approach to diagnose incipient turn-to-turn winding faults in operating power transformers. Experimental and simulation test results demonstrate the effectiveness of the proposed technique, which is based on the spectral analysis of the AC component of the on-load exciting current Park's Vector modulus.
- Comparing Power Transformer Turn-to-Turn Faults Protection Methods: Negative Sequence Component Versus Space-Vector AlgorithmsPublication . Oliveira, Luís; Marques Cardoso, Antonio J.This paper presents a comparison of two of the most sensitive methods to detect low-level turn-to-turn faults in the windings of three-phase transformers. The performance of the negative sequence component and of the space-vector protection algorithms is tested under several internal and/or external fault conditions. The results indicate that the space-vector approach is slightly more sensitive for detecting low-level turn-to-turn winding faults. For more severe defects, the fault detection sensitivity of both methods is similar.