| The differential protection technique is very popular for protecting power transformers of various ratings and configurations and is based on the differences between the primary side and secondary side currents. The difference currents contain information when adequately processed and provide a clear picture about the transformer operating conditions. Among several approaches developed to process differential currents, harmonic analysis is widely employed for several utilities, industrial, commercial and residential applications.;The extraction of certain harmonic components present in the differential currents can be critical in distinguishing between the magnetizing inrush current and any internal fault current. The discrete Fourier transform can be the preferred choice in the analysis that leads to an improvement in the protection of power transformers. The implementation of a digital filtering approach is usually accomplished using microprocessor platforms, which offer accuracy, speed, reliability and simplicity for protection of distribution transformers.;This thesis implements, for the first time, harmonic analysis of differential currents for protection of power transformers in a microcontroller. The analysis is based on a discrete Fourier transform and is realized using a c-code for testing the 3-phase laboratory transformer. Performances of the microprocessor digital relay show simple implementation, reliability, speed and accuracy for distribution type transformers. |
