• Patil Bhushan Prataprao
• Dr. Shah Paresh Jaychand

This paper introduces a harmonic analysis in power transformer having differential protection scheme. As due to transients with high frequency components it poses significant challenges to power quality. These transients occur due to sudden changes such as switching operations, where the resulting frequencies are often the system natural frequencies, not harmonics related to the fundamental frequency. Harmonics are integral multiples of the fundamental frequency, arising during steady-state operation and persisting for longer durations. Transients typically dissipate within a few cycles, but transformer energization represents an ambiguous case where transient conditions cause prolonged waveform distortion, potentially leading to false differential relay operations. The power transformer is modeled using the MATLAB Simulink software environment for differential current data collection. In this article simulations under varied operational conditions of a power transformer based on a Fast Fourier Transform approach are conducted in phyton script to identify harmonic components in differential current signal during transient phases. The conventional differential protection schemes, based on the second harmonic restraint principle, assume higher second harmonic content in inrush currents, functioning effectively if relay operation exceeds 20 milliseconds. However, modern smart power systems demand fault detection within the first half-cycle, where traditional harmonic restraint relays prove inadequate. It is shown that in all cases the ranges of variation of higher harmonics overlap which makes it difficult to create an effective differential protection that recognizes emergency and normal operation conditions operation only by harmonic analysis of the operating signal.

Power transformer, Differential protection, mathematical simulation, Fast Fourier Transform, higher harmonics.

"Harmonic Analysis of the Currents in the Power Transformer Differential Protection Circuits in the Event of Internal Faults and Other Disturbances", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.6, Issue 5, page no.207-214, May-2019, Available :http://www.jetir.org/papers/JETIR1905Z27.pdf

"Harmonic Analysis of the Currents in the Power Transformer Differential Protection Circuits in the Event of Internal Faults and Other Disturbances", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.6, Issue 5, page no. pp207-214, May-2019, Available at : http://www.jetir.org/papers/JETIR1905Z27.pdf