Certain investigations on power Transformer protection using Soft computing techniques

Abstract

Power transformers are one of the most essential and expensive components newlinein the operation of electric power system When an internal fault occurs in a newlinetransformer immediate disconnection of the faulty transformer is necessary to protect newlinethe power system Differential protection is commonly employed for transformer newlineprotection When an unloaded transformer is energized high magnetizing inrush current newlineflows only on the energised side of the transformer it ends up as spill current and the newlinedifferential relay possibly maloperates which is not desirable Thus the differential newlinerelay is expected to operate only for internal faults and not for inrush current external newlinefault normal and overexcitation conditions Fundamentally inrush current contains second harmonic component which is atleast 15 of the fundamental component whereas the internal fault contains only negligible amount of second harmonic component when compared to the fundamental component of the differential current Conventional transformer protection schemes use the percentage of second harmonics as criteria to discriminate internal fault from inrush newlinecurrent But due to the improvement in the core steel material the second harmonic newlinecomponent has been reduced considerably to as low as 7 in inrush current and no newlinelonger harmonics based protective relays are reliable and dependable for transformer newlineprotection newline newline