Comparison of Rationalised Haar Transform and Block Pulse Function based algorithms for Transformer Protection

摘要

This paper describes application of Rationalized Haar Transform and Block Pulse Function for digital protection of power transformers. Digital relay algorithms are developed to extract fundamental, second harmonic and fifth harmonic components. These components are then used for harmonic restraint differential protection of power transformers. The Block Pulse Function based method is computationally simple and flexible to use with any sampling frequency with respect to Rationalized Haar Transform. In Rationalized Haar Transform method one extra step of computation of Haar co-efficient is involved. Different graphs of Rationalized Haar Transform and Block Pulse Function based methods for Inrush, Over-excitation and Internal fault conditions have been plotted and compared. Off-line testing of the method with simulated inrush, over-excitation and internal fault current data clearly indicate that the Block Pulse Function method can provide fast and reliable trip decision