الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
Power transfonners are a very expensive class of electrical devices. They represent a very important link between generating utilities, transmission systems and load centers. It is important that the faulted power transfonner be isolated as quickly as possible after the fault has occurred, not only to limit the damage to the transfonner, but also to minimize the length of time the system voltage is depressed. As a result the operation oftransfonner protection must be reliable, selective, sensitive, accurate and of quick response. The differential protection is actually considered the main protection of power transfonners. Discrimination between the internal faults .... ~ transfonner inrush current must be rapid and accurate in decision.
The main objective of this work is to discriminate between differential currents due to iintemal faults and those due to power transfonner magnetizing inrush current to make the proper
. Udge and take the correct action. This thesis introduces a novel method for recognizing the .)
’fferent natures of power transfonner currents. The proposed technique is based on discrete
velet transfonn. The algorithm is based on evaluating the DWT coefficients of the third and level details. The diagnosis criterion for discrimination is evaluated for each sliding
ow. The resulting wave shape and its time locations represent the needed signatures to ify the type of the investigated currents. Many study cases were used for testing the sed algorithm and it showed to be effective and reliable for assessment.
The simulation study cases introduced in the thesis are generated using the IEMTDC software. Then the simulation output currents are transferred via an interface to the MATLAB software. Wavelet transfonn is then applied to extract the discriminating . All the simulation results showed fast, accurate, discriminative and reliable capabilities DWT statistical robust algorithm to identify different natures of currents flowing in a ,transformer under different operating conditions .
• ,Different fault resistance conditions were examined and tested and the DWT developed has showed to be an effective tool with high selectivity. The developed technique, cd to other methods, showed to be more accurate, fast and selective.