Loading...
12 results
Search Results
Now showing 1 - 10 of 12
- Condition monitoring and diagnostics of power transformersPublication . Cardoso, A. J. Marques; Oliveira, L. M. R.This paper addresses the subject of condition monitoring and diagnostics of power transformers. The main results of two reliability surveys, carried out under the auspices of CIGRE and IEEE in order to assemble objective data on the performance of transformers in service, are presented, providing useful information on the main causes of transformer failures, the most likely affected components and the related outages times. A survey of the most important methods, actually in use, for condition monitoring and diagnostics of power transformers is also given, which stresses the need for the development of new diagnostic methods, that can be applied without taking the transformers out of service, and that can also provide a fault severity criteria, in particular for determining transformers windings integrity. Preliminary results, concerning the on-going research activity on the development of a new approach for inter-turn winding fault diagnosis in three-phase transformers, are also reported in the paper.
- A coupled electromagnetic transformer model for the analysis of winding inter-turn short-circuitsPublication . Oliveira, L. M. R.; Cardoso, A. J. MarquesThis paper presents the development and implementation of a coupled electromagnetic transformer model for the simulation of three-phase power and distribution transformers affected by the presence of winding inter-turn short-circuits. Generically, the coupled electromagnetic transformer model is based on the simultaneous consideration of both magnetic and electric equivalent circuits. To incorporate the internal faults in this model a suitable equivalent circuit of the faulty winding is proposed. Both simulation and laboratory tests results are presented in the paper, which demonstrate the adequacy of the proposed model.
- Incipient turn-to-turn winding fault diagnosis of power transformers by the on-load exciting current Extended Park`s Vector ApproachPublication . Oliveira, L. M. R.; Cardoso, A. J. MarquesThis paper presents the application of the on-load exciting current Extended Park's Vector Approach for diagnosing incipient turn-to-turn winding faults in operating power transformers. Experimental and simulated 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.
- 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.
- 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.
- Condition monitoring and diagnostics of power transformersPublication . Cardoso, A. J. Marques; Oliveira, L. M. R.This paper addresses the subject of condition monitoring and diagnostics of power transformers. The main results of two reliability surveys, carried out under the auspices of CIGRE and IEEE in order to assemble objective data on the performance of transformers in service, are presented, providing useful information on the main causes of transformer failures, the most likely affected components and the related outages times. A survey of the most important methods, actually in use, for condition monitoring and diagnostics of power transformers is also given, which stresses the need for the development of new diagnostic methods, that can be applied without taking the transformers out of service, and that can also provide a fault severity criteria, in particular for determining transformers windings integrity. Preliminary results, concerning the on-going research activity on the development of a new approach for inter-turn winding fault diagnosis in three-phase transformers, are also reported in the paper.
- Detection of trasformer intermittent winding faults by the on-load exciting current Park`s vector approachPublication . Oliveira, L. M. R.; Cardoso, A. J. MarquesThis paper presents the application of the on-load exciting current Park's Vector Approach for diagnosing permanent and intermittent turn-to-turn winding faults in operating power transformers. First, an experimental investigation of the behaviour of the transformer under the occurrence of both permanent and intermittent winding faults is presented. Finally, experimental test results demonstrate the effectiveness of the proposed diagnostic technique, which is based on the on-line monitoring of the on-load exciting current Park's Vector patterns.
- 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.